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1. Global patterns and drivers of influenza decline during the COVID-19 pandemic

Author: Vittoria Colizza, Pierre-Yves Boelle, Chiara Poletto, Olivier Lopez, Francesco Bonacina, Maud Thomas, Surveillance et modélisation des maladies transmissibles [iPLesp] (SUMO), Institut Pierre Louis d'Epidémiologie et de Santé Publique (iPLESP), Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU), Laboratoire de Probabilités, Statistique et Modélisation (LPSM (UMR_8001)), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU), Tokyo Institute of Technology [Tokyo] (TITECH), Department of Molecular Medicine, University of Padova, Padova, Italy, and BONACINA, Francesco
Subjects: Microbiology (medical), [STAT]Statistics [stat], [SDV] Life Sciences [q-bio], Infectious Diseases, COVID-19 pandemic, Global analysis, Influenza, Regression trees, [SDV]Life Sciences [q-bio], General Medicine, [STAT] Statistics [stat]
Abstract: Influenza circulation declined during the COVID-19 pandemic. The timing and extent of decline and its association with interventions against COVID-19 were described for some regions. Here, we provide a global analysis of the influenza decline between March 2020 and September 2021 and investigate its potential drivers. We computed influenza change by country and trimester relative to the 2014-2019 period using the number of samples in the FluNet database. We used random forests to determine important predictors in a list of 20 covariates including demography, weather, pandemic preparedness, COVID-19 incidence, and COVID-19 pandemic response. With a regression tree we then classified observations according to these predictors. We found that influenza circulation decreased globally, with COVID-19 incidence and pandemic preparedness being the two most important predictors of this decrease. The regression tree showed interpretable groups of observations by country and trimester: Europe and North America clustered together in spring 2020, with limited influenza decline despite strong COVID-19 restrictions; in the period afterwards countries of temperate regions, with high pandemic preparedness, high COVID-19 incidence and stringent social restrictions grouped together having strong influenza decline. Conversely, countries in the tropics, with altogether low pandemic preparedness, low reported COVID-19 incidence and low strength of COVID-19 response showed low influenza decline overall. A final group singled out four “zero-Covid” countries, with the lowest residual influenza levels. The spatiotemporal decline of influenza during the COVID-19 pandemic was global, yet heterogeneous. The sociodemographic context and stage of the COVID-19 pandemic showed non-linear associations with this decline. Zero-Covid countries maintained the lowest levels of reduction with strict border controls and despite close-to-normal social activity. These results suggest that the resurgence of influenza could take equally diverse paths. It also emphasises the importance of influenza reseeding in driving countries’ seasonal influenza epidemics.
Published: 2023
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2. An accurate and robust metrological network for coherent optical frequency dissemination

Author: Anne Amy-Klein, Mads Tonnes, Paul-Eric Pottie, Olivier Lopez, Rodolphe Le Targat, Etienne Cantin, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord, Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ANR-10-LABX-0048,FIRST-TF,Network of Facilities for Innovation, Research, Services and Training in Time & Frequency(2010), ANR-11-EQPX-0039,REFIMEVE+,RESEAU FIBRE METROLOGIQUE A VOCATION EUROPEENNE +(2011), ANR-10-IDEX-0001,PSL,Paris Sciences et Lettres(2010), European Project: 15SIB05, Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord, Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: Time delay and integration, Repeater, Physics, [PHYS]Physics [physics], Fibre optic links, Optical fiber, Frequency transfer, interferometer, General Physics and Astronomy, Laser optics, Multi-user, Metrology, 01 natural sciences, Noise floor, Stability (probability), 010305 fluids & plasmas, law.invention, Interferometry, law, Robustness (computer science), 0103 physical sciences, Electronic engineering, 010306 general physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We introduce multi-branch repeater laser stations (MLSs) for the dissemination of an ultra-stable signal from one point to multiple users and the simultaneous evaluation of the stability and accuracy of multiple links. We perform the study of the noise floor of this new instrument. We present then an optical fiber network of 4800 km built with three MLSs and 13 repeater laser stations (RLSs). We show the multi-user optical frequency dissemination on four links totalizing 2198 km with uncertainties below 1.1 × 10−19. The robustness of the network over two years is presented and stability and accuracy at 107 seconds integration time are finally showed.
Published: 2021
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3. Propagation of cyber incidents in an insurance portfolio: counting processes combined with compartmental epidemiological models

Author: Olivier Lopez, Caroline Hillairet, Centre de Mathématiques Appliquées - Ecole Polytechnique (CMAP), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Probabilités, Statistiques et Modélisations (LPSM (UMR_8001)), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire de Statistique Théorique et Appliquée (LSTA), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Statistics and Probability, Economics and Econometrics, emerging risks, Computer science, risk theory, compartmental epidemiological models, [QFIN.RM]Quantitative Finance [q-fin]/Risk Management [q-fin.RM], 01 natural sciences, 010104 statistics & probability, compartmental epi- demiological models, Response strategy, [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], 0502 economics and business, Confidence bounds, Cyber-Insurance, Cyber insurance, 0101 mathematics, Event (probability theory), 050208 finance, 05 social sciences, Gaussian approximation, [MATH.MATH-PR]Mathematics [math]/Probability [math.PR], Risk analysis (engineering), Cyber-attack, Portfolio, Statistics, Probability and Uncertainty, Insurance portfolio, counting processes
Abstract: In this paper, we propose a general framework to design accumulation scenarios that can be used to anticipate the impact of a massive cyber attack on an insurance portfolio. The aim is also to emphasize the role of countermeasures in stopping the spread of the attack over the portfolio, and to quantify the benefits of implementing such strategies of response. Our approach consists of separating the global dynamic of the cyber event (that can be described through compartmental epidemiological models), the effect on the portfolio, and the response strategy. This general framework allows us to obtain Gaussian approximations for the corresponding processes, and sharp confidence bounds for the losses. A detailed simulation study, which mimics the effects of a Wannacry scenario, illustrates the practical implementation of the method.
Published: 2020

4. The impact of churn on client value in health insurance, evaluation using a random forest under various censoring mechanisms

Author: Yohann Le Faou, Michael Trupin, Guillaume Gerber, Olivier Lopez, Laboratoire de Probabilités, Statistiques et Modélisations (LPSM (UMR_8001)), and Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: Statistics and Probability, Actuarial science, business.industry, 05 social sciences, Mathematical statistics, 01 natural sciences, Profit (economics), Random forest, Applications and case studies, [STAT]Statistics [stat], 010104 statistics & probability, Insurance broker, Customer value, 0502 economics and business, Health insurance, Lifetime and survival analysis, 0101 mathematics, Statistics, Probability and Uncertainty, business, Algorithms, 050205 econometrics
Abstract: International audience; In the insurance broker market, commissions received by brokers are closely related to so-called "customer value": the longer a policyholder keeps their contract, the more profit there is for the company and therefore the broker. Hence, predicting the time at which a potential policyholder will surrender their contract is essential in order to optimize a commercial process and define a prospect scoring. In this paper, we propose a weighted random forest model to address this problem. Our model is designed to compensate for the impact of random censoring. We investigate different types of assumptions on the censor-ing, studying both the cases where it is independent or not from the covariates. We compare our approach with other standard methods which apply in our setting, using simulated and real data analysis. We show that our approach is very competitive in terms of quadratic error in addressing the given problem.
Published: 2020
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5. Automatic analysis of insurance reports through deep neural networks to identify severe claims

Author: Yann Mercuzot, Isaac Cohen Sabban, Olivier Lopez, Laboratoire de Probabilités, Statistiques et Modélisations (LPSM (UMR_8001)), and Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Statistics and Probability, Economics and Econometrics, business.industry, Computer science, Convolutional Neural Networks, 02 engineering and technology, Text analysis, Machine learning, computer.software_genre, 01 natural sciences, 010104 statistics & probability, Insurance mathematics, [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], Deep neural networks, 0202 electrical engineering, electronic engineering, information engineering, 020201 artificial intelligence & image processing, Artificial intelligence, 0101 mathematics, Statistics, Probability and Uncertainty, business, computer, Long Short Term Memory
Abstract: In this paper, we develop a methodology to automatically classify claims using the information contained in text reports (redacted at their opening). From this automatic analysis, the aim is to predict if a claim is expected to be particularly severe or not. The difficulty is the rarity of such extreme claims in the database, and hence the difficulty, for classical prediction techniques like logistic regression to accurately predict the outcome. Since data is unbalanced (too few observations are associated with a positive label), we propose different rebalance algorithm to deal with this issue. We discuss the use of different embedding methodologies used to process text data, and the role of the architectures of the networks.
Published: 2020

6. Individual reserving and nonparametric estimation of claim amounts subject to large reporting delays

Author: Xavier Milhaud, Olivier Lopez, Laboratoire de Probabilités, Statistiques et Modélisations (LPSM (UMR_8001)), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire de Finance et d'Assurance, Centre de Recherche en Economie et en Statistique (CREST-INSEE), and Institut national de la statistique et des études économiques (INSEE)-Institut national de la statistique et des études économiques (INSEE)
Subjects: Statistics and Probability, Estimation, Economics and Econometrics, 050208 finance, truncation, Computer science, 05 social sciences, Nonparametric statistics, Estimator, Subject (documents), 01 natural sciences, Censoring (statistics), 010104 statistics & probability, censoring, [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], 0502 economics and business, reporting delay, Econometrics, reserving, CART, Truncation (statistics), 0101 mathematics, Statistics, Probability and Uncertainty
Abstract: Thanks to nonparametric estimators coming from machine learning, microlevel reserving has become more and more popular for actuaries. Recent research focused on how to integrate the whole information one can have on claims to predict individual reserves, with varying success due to incomplete observations. Using the CART algorithm, we develop new results that allow us to deal with large reporting delays and partially observed explanatory variables. Statistically speaking, we extend CART to take into account truncation of the data, and introduce plug-in estimators. Our applications are based on real-life insurance portfolios embedding Income Protection and Third-Party Liability guarantees. The full knowledge of the claim lifetime is shown to be crucial to predict the individual reserves efficiently.
Published: 2020

7. Bridging the Li-Carter's gap: a locally coherent mortality forecast approach

Author: Quentin Guibert, Stéphane Loisel, Olivier Lopez, Pierrick Piette, Laboratoire de Sciences Actuarielle et Financière (SAF), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, CEntre de REcherches en MAthématiques de la DEcision (CEREMADE), Centre National de la Recherche Scientifique (CNRS)-Université Paris Dauphine-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Prim'Act, Laboratoire de Probabilités, Statistiques et Modélisations (LPSM (UMR_8001)), Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Seyna, Piette, Pierrick, Université Paris Dauphine-PSL-Centre National de la Recherche Scientifique (CNRS), and Laboratoire de Probabilités, Statistique et Modélisation (LPSM (UMR_8001))
Subjects: [STAT.AP]Statistics [stat]/Applications [stat.AP], [SHS.DEMO] Humanities and Social Sciences/Demography, [STAT.AP] Statistics [stat]/Applications [stat.AP], Basis risk, Multi-population, [SHS.DEMO]Humanities and Social Sciences/Demography, Coherent mortality forecasting, Vector Autoregression, Elastic-Net
Abstract: Countries with common features in terms of social, economic and health systems generally have mortality trends which evolve in a similar manner. Drawing on this, many multi-population models are built on a coherence assumption which inhibits the divergence of mortality rates between two populations, or more, on the long run. However, this assumption may prove to be too strong in a general context, especially when it is imposed to a large collection of countries. We also note that the coherence hypothesis significantly reduces the spectrum of achievable mortality dispersion forecasts for a collection of populations when comparing to the historical observations. This may distort the longevity risk assessment of an insurer. In this paper, we propose a new model to forecast multiple populations assuming that the long-run coherent principle is verified by subgroups of countries that we call the "locally coherence" property. Thus, our specification is built on a trade-off between the Lee-Carter's diversification and Li-Lee's concentration features and allows to fit the model to a large number of populations simultaneously. A penalized vector autoregressive (VAR) model, based on the elastic-net regularization, is considered for modeling the dynamics of common trends between subgroups. Furthermore, we apply our methodology on 32 European populations mortality data and discuss the behavior of our model in terms of simulated mortality dispersion. Within the Solvency II directive, we quantify the impact on the longevity risk solvency capital requirement of an insurer for a simplified pension product. Finally, we extend our model by allowing populations to switch from one coherence group to another. We then analyze its incidence on longevity hedges basis risk assessment. JEL Classification: C18, C32, C53, J11.
Published: 2020

8. Unidirectional two-way optical frequency comparison and its fundamental limitations

Author: Paul-Eric Pottie, Dan Xu, Olivier Lopez, Anne Amy-Klein, Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Optical amplifier, Time delay and integration, [PHYS]Physics [physics], Fiber (mathematics), business.industry, Computer science, Scale (descriptive set theory), 01 natural sciences, Instability, Atomic and Molecular Physics, and Optics, 010309 optics, Optics, Transfer (computing), 0103 physical sciences, Electronic engineering, Satellite, 010306 general physics, business, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Microwave, ComputingMilieux_MISCELLANEOUS
Abstract: High-quality frequency transfer based on existing telecommunication fiber links allows state-of-the-art microwave and optical clocks to be compared on a continental and potentially even intercontinental scale. We present a half-a-year-long data set of unidirectional optical frequency transfer over a 2 × 43 k m urban fiber link. We observe a relative frequency instability of 8.0 × 10 − 16 at 1 s and at best 6.0 × 10 − 18 at 10 6 s integration time. Our results show that the unidirectional two-way method gives the possibility to perform comparisons of international primary standards over fiber links faster than over satellite links. Moreover, we investigate the major limiting factors of such a unidirectional setup.
Published: 2020
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9. Reciprocity of propagation in optical fiber links demonstrated to 10−21

Author: Anne Amy-Klein, Dan Xu, Olivier Lopez, P. Delva, Paul-Eric Pottie, Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Lasers (LPL), Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord, PN GRAM, ANR-10-LABX-0048,FIRST-TF,Network of Facilities for Innovation, Research, Services and Training in Time & Frequency(2010), ANR-11-EQPX-0039,REFIMEVE+,RESEAU FIBRE METROLOGIQUE A VOCATION EUROPEENNE +(2011), European Project, European Project: 15SIB05, and Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord
Subjects: Physics, Optical fiber, Global temperature, business.industry, Michelson interferometer, 02 engineering and technology, Propagation delay, 021001 nanoscience & nanotechnology, Residual, Topology, 01 natural sciences, Atomic and Molecular Physics, and Optics, law.invention, 010309 optics, Interferometry, Optics, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, Reciprocity (electromagnetism), 0103 physical sciences, Frequency offset, 0210 nano-technology, business
Abstract: International audience; We present a study of the fundamental limit of fiber links using dedicated link architecture. We use an experimental arrangement that enables us to detect the forward and backward propagation noise independently and simultaneously in optical fiber and where the optical phase evolution is expected to be driven by the only contribution of the reference arms of the Michelson interferometer ensemble. In this article, we demonstrate indeed the high correlation between the optical phase evolution and the temperature variation of the interferometer ensemble, leading to a frequency offset of (4.4 ± 2.3) × 10 −21. Using a simple temperature model and a Bayesian analysis to evaluate the model parameters, we show that the temperature effect can be compensated with post-processing, removing the frequency offset down to (0.5 ± 2.0) × 10 −21. The residual slope of the optical phase evolution over 33 days is 350 yoctosecond/s. Using a global temperature parameter, we divide these 33 days dataset in four subsets and analyse their uncertainties. We show that they are self-consistent when the temperature is taken into account. This provides an alternative method to evaluate the accuracy of a fiber link, especially when the dataset includes large dead times. The result is finally interpreted as a test of the reciprocity of the propagation delay in an optical fiber. This unprecedented transfer capability could enable the comparisons of future optical clocks with expected performance at 10 −20 level and open new possibilities for stringent tests of special and general relativity.
Published: 2019
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10. Forecasting mortality rate improvements with a high-dimensional VAR

Author: Olivier Lopez, Pierrick Piette, Quentin Guibert, CEntre de REcherches en MAthématiques de la DEcision (CEREMADE), Centre National de la Recherche Scientifique (CNRS)-Université Paris Dauphine-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Laboratoire de Sciences Actuarielle et Financière (SAF), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, Prim'Act, Laboratoire de Probabilités, Statistiques et Modélisations (LPSM (UMR_8001)), Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Sinalys, Laboratoire de Statistique Théorique et Appliquée (LSTA), Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), ANR-13-BS01-0011,LoLitA,Modèles dynamiques pour la longévité humaine avec ajustements de style de vie(2013), Université Paris Dauphine-PSL-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Probabilités, Statistique et Modélisation (LPSM (UMR_8001)), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Piette, Pierrick, and Blanc 2013 - Modèles dynamiques pour la longévité humaine avec ajustements de style de vie - - LoLitA2013 - ANR-13-BS01-0011 - Blanc 2013 - VALID
Subjects: Statistics and Probability, Elastic net regularization, Economics and Econometrics, Population, Feature selection, 01 natural sciences, Vector autoregression, Elastic-Net, 010104 statistics & probability, Modeling multiple populations, [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], 0502 economics and business, Econometrics, 050207 economics, 0101 mathematics, [MATH]Mathematics [math], education, [MATH.MATH-ST] Mathematics [math]/Statistics [math.ST], Variance-covariance estimation, ComputingMilieux_MISCELLANEOUS, Mathematics, Estimation, education.field_of_study, High-dimensional time series, 05 social sciences, Contrast (statistics), Mortality forecasting, Autoregressive model, Sample size determination, Statistics, Probability and Uncertainty, Vector Autoregression
Abstract: Forecasting mortality rates is a problem which involves the analysis of high-dimensional time series. Most of usual mortality models propose to decompose the mortality rates into several latent factors to reduce this complexity. These approaches, in particular those using cohort factors, have a good fit, but they are less reliable for forecasting purposes. One of the major challenges is to determine the spatial–temporal dependence structure between mortality rates given a relatively moderate sample size. This paper proposes a large vector autoregressive (VAR) model fitted on the differences in the log-mortality rates, ensuring the existence of long-run relationships between mortality rate improvements. Our contribution is threefold. First, sparsity, when fitting the model, is ensured by using high-dimensional variable selection techniques without imposing arbitrary constraints on the dependence structure. The main interest is that the structure of the model is directly driven by the data, in contrast to the main factor-based mortality forecasting models. Hence, this approach is more versatile and would provide good forecasting performance for any considered population. Additionally, our estimation allows a one-step procedure, as we do not need to estimate hyper-parameters. The variance–covariance matrix of residuals is then estimated through a parametric form. Secondly, our approach can be used to detect nonintuitive age dependence in the data, beyond the cohort and the period effects which are implicitly captured by our model. Third, our approach can be extended to model the several populations in long run perspectives, without raising issue in the estimation process. Finally, in an out-of-sample forecasting study for mortality rates, we obtain rather good performances and more relevant forecasts compared to classical mortality models using the French, US and UK data. We also show that our results enlighten the so-called cohort and period effects for these populations.
Published: 2019
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11. A tree-based algorithm adapted to microlevel reserving and long development claims

Author: Xavier Milhaud, Olivier Lopez, Pierre-Emmanuel Thérond, Sorbonne Université (SU), Laboratoire de Finance et d'Assurance, Centre de Recherche en Economie et en Statistique (CREST-INSEE), Institut national de la statistique et des études économiques (INSEE)-Institut national de la statistique et des études économiques (INSEE), and Galea & Associés
Subjects: Economics and Econometrics, [STAT.AP]Statistics [stat]/Applications [stat.AP], 050208 finance, Computer science, 05 social sciences, Decision tree, Context (language use), 01 natural sciences, long-tail, 010104 statistics & probability, Tree (data structure), Development (topology), censoring, disability, [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], Accounting, Censoring (clinical trials), 0502 economics and business, Sustainability, reserving, regression tree, Tree based, 0101 mathematics, Algorithm, Finance
Abstract: In non-life insurance, business sustainability requires accurate and robust predictions of reserves related to unpaid claims. To this aim, two different approaches have historically been developed: aggregated loss triangles and individual claim reserving. The former has reached operational great success in the past decades, whereas the use of the latter still remains limited. Through two illustrative examples and introducing an appropriate tree-based algorithm, we show that individual claim reserving can be really promising, especially in the context of long-term risks.
Published: 2019
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12. Search for transient variations of the fine structure constant and dark matter using fiber-linked optical atomic clocks

Author: Roman Schwarz, Olivier Lopez, R. M. Godun, J E Calvert, Dan Xu, L De Sarlo, C. Baerentsen, R. Le Targat, Ian R. Hill, Thomas Legero, Jérôme Lodewyck, Nicolas Quintin, Erik Benkler, Guy Vallet, Benjamin Roberts, S. Dörscher, Helen S. Margolis, P. Delva, Alissa Silva, Uwe Sterr, Christine C. Guo, Ch. Lisdat, C. F. A. Baynham, Ekkehard Peik, A. Al-Masoudi, Nils Huntemann, Peter Wolf, Sébastien Bize, H. Alvarez-Martinez, Christian Sanner, Aurélien Hees, T. Waterholter, William B. Bowden, Philip Tuckey, Sebastian Koke, F. Ozimek, R. Lange, Gesine Grosche, Anne Amy-Klein, V. Cambier, Etienne Cantin, F. Meynadier, Chr. Tamm, Maxime Favier, Paul-Eric Pottie, Florian Frank, S. Bilicki, A. Kuhl, J. Kronjäger, Richard Hobson, Burghard Lipphardt, Marco Schioppo, E. A. Curtis, Patrick Gill, Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Bureau International des Poids et Mesures (BIPM), Laboratoire Photonique, Numérique et Nanosciences (LP2N), Université Sciences et Technologies - Bordeaux 1-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS), Physikalisch-Technische Bundesanstalt [Braunschweig] (PTB), Instituto de Plasmas e Fusão Nuclear [Lisboa] (IPFN), Instituto Superior Técnico, Universidade Técnica de Lisboa (IST), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord, and HEP, INSPIRE
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), [PHYS.PHYS.PHYS-GEN-PH] Physics [physics]/Physics [physics]/General Physics [physics.gen-ph], Atomic Physics (physics.atom-ph), Dark matter, Clock rate, defect: topological, General Physics and Astronomy, FOS: Physical sciences, 01 natural sciences, dark matter: parametrization, 010305 fluids & plasmas, Physics - Atomic Physics, High Energy Physics - Phenomenology (hep-ph), 0103 physical sciences, optical, Sensitivity (control systems), 010306 general physics, matter: density, ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], fundamental constant: fine structure, [PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph], Quantum sensor, Fine-structure constant, sensitivity, Atomic clock, [PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph], Computational physics, coherence, [PHYS.HPHE] Physics [physics]/High Energy Physics - Phenomenology [hep-ph], High Energy Physics - Phenomenology, [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph], network, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], Transient (oscillation), galaxy, [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Coherence (physics), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We search for transient variations of the fine structure constant using data from a European network of fiber-linked optical atomic clocks. By searching for coherent variations in the recorded clock frequency comparisons across the network, we significantly improve the constraints on transient variations of the fine structure constant. For example, we constrain the variation to |δα/α| < 5 × 10−17 for transients of duration 103 s. This analysis also presents a possibility to search for dark matter, the mysterious substance hypothesised to explain galaxy dynamics and other astrophysical phenomena that is thought to dominate the matter density of the universe. At the current sensitivity level, we find no evidence for dark matter in the form of topological defects (or, more generally, any macroscopic objects), and we thus place constraints on certain potential couplings between the dark matter and standard model particles, substantially improving upon the existing constraints, particularly for large (≳104 km) objects.
Published: 2019
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13. Two-Branch Fiber Link for International Clock Networks

Author: Olivier Lopez, Philip Tuckey, Nicolas Quintin, Paul-Eric Pottie, Etienne Cantin, Dan Xu, F. Meynadier, Anne Amy-Klein, Florian Frank, Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), RENATER, MMTF, Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), ANR-10-LABX-0048,FIRST-TF,Network of Facilities for Innovation, Research, Services and Training in Time & Frequency(2010), ANR-11-EQPX-0039,REFIMEVE+,RESEAU FIBRE METROLOGIQUE A VOCATION EUROPEENNE +(2011), ANR-10-IDEX-0001,PSL,Paris Sciences et Lettres(2010), and European Project: 15SIB05
Subjects: Repeater, Quantum Physics, Physics - Instrumentation and Detectors, Computer science, Fiber (mathematics), 020208 electrical & electronic engineering, FOS: Physical sciences, 02 engineering and technology, Instrumentation and Detectors (physics.ins-det), Laser, Topology, Stability (probability), Frequency, law.invention, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, Transfer (computing), 0202 electrical engineering, electronic engineering, information engineering, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Electrical and Electronic Engineering, Link (knot theory), Quantum Physics (quant-ph), Instrumentation
Abstract: International audience; We present our work on realizing two-branch fiber links enabling multiple-partner clock comparisons in Europe. We report in detail on the setup connecting two long haul links, and report for the relative frequency stability and accuracy. We report on a combined uptime of 90% for our dual-branch link during almost one month. We finally discuss the combined uncertainty contribution of the ensemble of the link architecture to a clock comparison. We show that the frequency transfer uncertainty is 2 × 10 −19 .
Published: 2019
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14. High-precision methanol spectroscopy with a widely tunable SI-traceable frequency-comb-based mid-infrared QCL

Author: Dan Xu, Andrey Goncharov, H. Mouhamad, R. Santagata, Fabrice Wiotte, Paul-Eric Pottie, Benoît Darquié, Anne Amy-Klein, Y. Le Coq, Olivier Lopez, R. Le Targat, Dang Tran, B. Argence, H. Alvarez-Martinez, Won-Kyu Lee, M. Abgrall, Sean Tokunaga, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Faculty of Physics Ho Chi Minh City University of Education, Laboratoire Kastler Brossel (LKB (Jussieu)), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Institute of Laser Physics of SB RAS (ILP), Siberian Branch of the Russian Academy of Sciences (SB RAS), Real Instituto y Observatorio de la Armada (ROA), Korea Research Institute of Standards and Science [Daejon] (KRISS), and KRISS
Subjects: Materials science, Physics - Instrumentation and Detectors, Saturated absorption spectroscopy, Physics::Optics, Molecular spectroscopy, 01 natural sciences, 7. Clean energy, Spectral line, law.invention, Physics - Atomic Physics, 010309 optics, Frequency comb, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, 0103 physical sciences, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], 010306 general physics, Spectroscopy, Quantum Physics, Spectrometer, business.industry, Laser, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, Optoelectronics, business, Quantum cascade laser
Abstract: International audience; There is an increasing demand for precise molecular spectroscopy, in particular in the mid-infrared fingerprint window that hosts a considerable number of vibrational signatures, whether it be for modeling our atmosphere, interpreting astrophysical spectra or testing fundamental physics. We present a high-resolution mid-infrared spectrometer traceable to primary frequency standards. It combines a widely tunable ultra-narrow Quantum Cascade Laser (QCL), an optical frequency comb and a compact multipass cell. The QCL frequency is stabilized onto a comb controlled with a remote near-infrared ultra-stable laser, transferred through a fiber link. The resulting QCL frequency stability is below 10-15 from 0.1 to 10s and its frequency uncertainty of 4×10-14 is given by the remote frequency standards. Continuous tuning over ~400 MHz is reported. We use the apparatus to perform saturated absorption spectroscopy of methanol in the low-pressure multipass cell and demonstrate a statistical uncertainty at the kHz level on transition center frequencies, confirming its potential for driving the next generation technology required for precise spectroscopic measurements.
Published: 2019
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15. A new experiment to test parity symmetry in cold chiral molecules using vibrational spectroscopy

Author: Won-Kyu Lee, Benoît Darquié, Dan Xu, Olivier Lopez, Anne Cournol, Andrei Goncharov, R. Le Targat, M. Abgrall, Mathieu Manceau, Ben Sauer, Dang Tran, Sean Tokunaga, M. R. Tarbutt, T. E. Wall, Paul-Eric Pottie, Matthieu Pierens, Anne Amy-Klein, B. Argence, H Alvarez Martinez, Y. Le Coq, Richard Hendricks, R. Santagata, J M Bieniewska, Louis Lecordier, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Faculty of Physics, Ho Chi Minh City University of Education, Ho Chi Minh City, DPHY, ONERA, Université Paris Saclay (COmUE) [Palaiseau], ONERA-Université Paris Saclay (COmUE), Laboratoire Kastler Brossel (LKB (Jussieu)), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, (CCM), Imperial College London, and National Physical Laboratory [Teddington] (NPL)
Subjects: Atomic Physics (physics.atom-ph), molecular beams, FOS: Physical sciences, Infrared spectroscopy, quantum cascade laser, mid-infrared precise laser spectroscopy, 01 natural sciences, Physics - Atomic Physics, law.invention, 010309 optics, Ramsey interferometry, law, Physics - Chemical Physics, 0103 physical sciences, Molecule, chiral molecules, Electrical and Electronic Engineering, Quantum, parity violation, Chemical Physics (physics.chem-ph), 010302 applied physics, Physics, [PHYS]Physics [physics], [PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph], Polyatomic ion, Statistical and Nonlinear Physics, Parity (physics), Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, frequency metrology, Cascade, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Atomic physics, Quantum cascade laser, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], buffer-gas cooling
Abstract: International audience; We present a brief review of our progress towards measuring parity violation in heavy-metal chiral complexes using mid-infrared Ramsey interferometry. We discuss our progress addressing the main challenges, including the development of buffer-gas sources of slow, cold polyatomic molecules, and the frequency-stabilisation of quantum cascade lasers calibrated using primary frequency standards. We report investigations on achiral test species of which promising chiral derivatives have been synthesized.
Published: 2019
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16. High-Precision Mid-IR Molecular Spectroscopy with Traceability to Primary Standards

Author: Michel Abgrall, Sean Tokunaga, Olivier Lopez, R. Santagata, R. Le Targat, Dan Xu, Y. Le Coq, Paul-Eric Pottie, Dang Bao An Tran, Anne Amy-Klein, Won-Kyu Lee, Benoît Darquié, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Materials science, Spectrometer, [PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph], business.industry, Optical link, Saturated absorption spectroscopy, Laser, 01 natural sciences, Signal, law.invention, 010309 optics, law, Cascade, 0103 physical sciences, Optoelectronics, Measurement uncertainty, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], business, Spectroscopy, 010301 acoustics, ComputingMilieux_MISCELLANEOUS
Abstract: We are stabilizing the frequency of a mid-infrared quantum cascade lasers (QCLs) to an optical frequency comb itself stabilized to an ultra-stable near-infrared reference signal at $\pmb{1.5\mu} \mathbf{m}$ transferred from SYRTE to LPL using an optical link. The reference stability is copied to the QCL and we benefit from the traceability to the primary standards of SYRTE. The stabilized QCL can be scanned by scanning the near-IR reference with an electro-optic modulator. We use this ultrastable spectrometer to carry out saturated absorption spectroscopy of methanol. A detailed analysis of the frequency measurement uncertainty will be presented.
Published: 2018
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17. Studying fundamental limit of optical fiber links to 10 −21 level

Author: Dan Xu, Won-Kyu Lee, Fabio Stefani, Olivier Lopez, Anne Amy-Klein, Paul-Eric POTTIE, Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Korea Research Institute of Standards and Science [Daejon] (KRISS), KRISS, University of Science and Technology, Yuseong, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Conseil Régional Ile-de-France (DIM Nano’K), CNRS with Action Spécifique GRAM, ANR-10-LABX-0048,FIRST-TF,Network of Facilities for Innovation, Research, Services and Training in Time & Frequency(2010), ANR-11-EQPX-0039,REFIMEVE+,RESEAU FIBRE METROLOGIQUE A VOCATION EUROPEENNE +(2011), European Project: SIB02, European Project: 15SIB05, Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace ( LNE - SYRTE ), Systèmes de Référence Temps Espace ( SYRTE ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Centre National de la Recherche Scientifique ( CNRS ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Centre National de la Recherche Scientifique ( CNRS ), Korea Research Institute of Standards and Science [Daejon] ( KRISS ), Laboratoire de Physique des Lasers ( LPL ), Université Paris 13 ( UP13 ) -Université Sorbonne Paris Cité ( USPC ) -Institut Galilée-Centre National de la Recherche Scientifique ( CNRS ), Amy-Klein, Anne, Laboratoires d'excellence - Network of Facilities for Innovation, Research, Services and Training in Time & Frequency - - FIRST-TF2010 - ANR-10-LABX-0048 - LABX - VALID, RESEAU FIBRE METROLOGIQUE A VOCATION EUROPEENNE + - - REFIMEVE+2011 - ANR-11-EQPX-0039 - EQPX - VALID, Neat-FT - SIB02 - INCOMING, and OFTEN - 15SIB05 - INCOMING
Subjects: [ PHYS.QPHY ] Physics [physics]/Quantum Physics [quant-ph], [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], (1203930) Metrological instrumentation, (1205050) Phase measurement, [PHYS.QPHY] Physics [physics]/Quantum Physics [quant-ph], (1203940) Metrology, OCIS codes: (0602360) Fiber optics links and subsystems
Abstract: International audience; We present an hybrid fiber link combining effective optical frequency transfer and evaluation of performances with a self-synchronized two-way comparison. It enables us to detect the round-trip fiber noise and each of the forward and backward one-way fiber noises simultaneously. The various signals acquired with this setup allow us to study quantitatively several properties of optical fiber links. We check the reciprocity of the accumulated noise forth and back over a bi-directional fiber to the level of 3.1(±3.9) × 10 −20. We also analyze the noise correlation between two adjacent fibers and show the first experimental evidence of interferometric noise at very low Fourier frequency. We estimate redundantly and consistently the stability and accuracy of the transferred optical frequency over 43 km at 4 × 10 −21 level after 16 days of integration and demonstrate that frequency comparison with resolution as low as 8 × 10 −18 would be achievable with uni-directional fibers in urban area.
Published: 2018

18. Relativistic geodesy with a transportable optical clock

Author: Grotti, J., Koller, S., Herbers, S., Vogt, S., Al-Masoudi, A., Doerscher, S., Schwarz, R., Haefner, S., Uwe Sterr, Erik Benkler, Koke, S., Kuhl, A., Waterholter, T., Gesine Grosche, Rodolphe Le Targat, Jérôme Lodewyck, Héctor Alvarez Martinez, Michel Abgrall, Etienne Cantin, Dan Xu, Olivier Lopez, Anne Amy-Klein, Paul-Eric POTTIE, Denker, H., Christian Lisdat, and Henry, Florence
Subjects: [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph]
Published: 2018

19. Agence du ministère des Affaires étrangères à Marseille

Author: Mathieu Grenet, Olivier Lopez, France, Amériques, Espagne – Sociétés, pouvoirs, acteurs (FRAMESPA), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Temps, espaces, langages Europe méridionale-Méditerranée (TELEMME), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Jean-Baptiste Bruneau, Christophe Cérino, Gérard Le Bouëdec, Jörg Ulbert, Grenet, Mathieu, and Université Toulouse - Jean Jaurès (UT2J)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SHS.HIST] Humanities and Social Sciences/History, [SHS.HIST]Humanities and Social Sciences/History, ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2018

20. Hybrid fiber links for accurate optical frequency comparisons

Author: Won-Kyu Lee, Anthony Bercy, Paul-Eric Pottie, Anne Amy-Klein, Olivier Lopez, Fabio Stefani, Laboratoire National de Métrologie et d’Essais–Système de Références Temps-Espace [Paris], Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Korea Research Institute of Standards and Science [Daejon] (KRISS), KRISS, University of Science and Technology, Yuseong, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), AS GRAM INSU, Korea Research Institute of Standards and Science (KR) (16011007), National Research council of Science and Technology (CAP-15-08-KRISS), European Project, European Project: 605243,GN3plus, Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and University of Science and Technology [Daejeon] (UST)
Subjects: Physics and Astronomy (miscellaneous), Frequency transfer, Acoustics, General Physics and Astronomy, FOS: Physical sciences, Physics and Astronomy (all), 01 natural sciences, Signal, Instability, Measure (mathematics), law.invention, Compensation (engineering), 010309 optics, Synchronization (alternating current), [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, 0103 physical sciences, 11. Sustainability, Phase noise, Optical link, Astronomical interferometer, 010306 general physics, ComputingMilieux_MISCELLANEOUS, Physics, Quantum Physics, Laser stabilization, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], General Engineering, Time and frequency metrology, Laser, [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, Quantum Physics (quant-ph), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, Optics (physics.optics), Physics - Optics
Abstract: We present the first experimental demonstration over a 43-km-long urban fiber network of a local two-way optical frequency comparison, which does not require any synchronization of the measurements. It was combined with a regular active-noise compensation on another parallel fiber leading to a very reliable and robust frequency transfer. This hybrid scheme enables us to investigate the major limiting factors of the local two-way comparison. We analyze the contribution to the phase noise of the recovered signal by the interferometers at local and remote places. By using the ability of this set up to be injected by a single laser or two independent lasers, we measure the contribution to the long-term instability by the demodulated laser instabilities. We show that a fractional frequency instability level of $1\times10^{-20}$ at 10 000 s can be obtained with this simple setup after 43-km-long propagation in an urban area.
Published: 2017
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21. Ultra-stable optical frequency dissemination on a multi-access fibre network

Author: Paul-Eric Pottie, Anthony Bercy, Anne Amy-Klein, Olivier Lopez, Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Agence nationale de la Recherche, IFRAF, conseil régional d'Ile de France, CNRS, Université Paris 13, ANR-11-BS04-0009,LIOM,Lien optique multiplexé pour la métrologie et la physique fondamentale(2011), ANR-10-LABX-0048,FIRST-TF,Network of Facilities for Innovation, Research, Services and Training in Time & Frequency(2010), Laboratoire National de Métrologie et d’Essais–Système de Références Temps-Espace [Paris], Centre National de la Recherche Scientifique (CNRS)-Université Paris sciences et lettres (PSL)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris
Subjects: Time delay and integration, Physics and Astronomy (miscellaneous), Computer science, Optical link, General Physics and Astronomy, FOS: Physical sciences, Physics and Astronomy(all), 01 natural sciences, Instability, law.invention, 010309 optics, Laser linewidth, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, Optical frequencies, 0103 physical sciences, Phase noise, Electronic engineering, 010306 general physics, Quantum optics, [PHYS]Physics [physics], Quantum Physics, Laser diode, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], General Engineering, [SDU]Sciences of the Universe [physics], Quantum Physics (quant-ph), Optics (physics.optics), Physics - Optics
Abstract: International audience; We report a laboratory demonstration of the dissemination of an ultrastable optical frequency signal to two distant users simultaneously using a branching network. The ultrastable signal is extracted along a main fibre link; it is optically tracked by a narrow linewidth laser diode, which light is injected in a secondary link. The propagation noise of both links is actively compensated. We implement this scheme with two links of 50-km fibre spools, the extraction being set up at the mid-point of the main link. We show that the extracted signal at the end of the secondary link exhibits a fractional frequency instability of 1.4 × 10−15 at 1-s measurement time, almost equal to the 1.3 × 10−15 instability of the main link output end. The long-term instabilities are also very similar, at a level of 3–5 × 10−20 at 3 × 104-s integration time. We also show that the setting up of this extraction device, or of a simpler one, at the main link input, can test the proper functioning of the noise rejection on this main link. This work is a significant step towards a robust and flexible ultrastable network for multi-users dissemination.
Published: 2016
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22. International strontium optical lattice clocks comparisons with an optical fiber link

Author: Christian Lisdat, Gesine Grosche, Nicolas Quintin, Chunyan Shi, Raupach, S. M. F., Grebing, C., Daniele Nicolodi, Fabio Stefani, Al-Masoudi, A., Dörscher, S., Sebastian Häfner, Jean-Luc Robyr, Nicola Chiodo, Slawomir Bilicki, Eva Bookjans, Koczwara, A., Koke, S., Kuhl, A., Fabrice Wiotte, Frédéric Meynadier, Emilie Camisard, Michel Abgrall, Michel Lours, Thomas Legero, Harald Schnatz, Uwe Sterr, Denker, H., Christian Chardonnet, Yann Le Coq, Giorgio Santarelli, Anne Amy-Klein, Rodolphe Le Targat, Jérôme Lodewyck, Olivier Lopez, Paul-Eric POTTIE, Henry, Florence, Physikalisch-Technische Bundesanstalt (PTB), RENATER, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Métrologie des fréquences optiques, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Références micro-ondes et échelles de temps, Théorie et métrologie, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord, Institut für Erdmessung, Leibniz Universität Hannover, Laboratoire Photonique, Numérique et Nanosciences (LP2N), and Université de Bordeaux (UB)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience
Published: 2016

23. Cascaded optical fiber link using the internet network for remote clocks comparison

Author: Nicolas Quintin, Anne Amy-Klein, Paul-Eric Pottie, Giorgio Santarelli, Nicola Chiodo, Christian Chardonnet, Fabrice Wiotte, Emilie Camisard, Fabio Stefani, Olivier Lopez, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), RENATER, Laboratoire Photonique, Numérique et Nanosciences (LP2N), Université Sciences et Technologies - Bordeaux 1-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS), funding support from the Agence Nationale de la Recherche the Agence Nationale de la Recherche (ANR blanc LIOM 2011-BS04-009-01, Labex First-TF ANR 10 LABX 48 01, Equipex REFIMEVE+ ANR-11-EQPX-0039), the European Metrology Research Programm (contract SIB-02 NEAT-FT), IFRAF-Conseil Régional Ile-de-France, CNRS with Action Spécifique Gravitation, Références, Astronomie, Métrologie (GRAM), ANR-11-BS04-0009,LIOM,Lien optique multiplexé pour la métrologie et la physique fondamentale(2011), ANR-10-LABX-0048,FIRST-TF,Network of Facilities for Innovation, Research, Services and Training in Time & Frequency(2010), ANR-11-EQPX-0039,REFIMEVE+,RESEAU FIBRE METROLOGIQUE A VOCATION EUROPEENNE +(2011), European Project, and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Optical fiber, Physics - Instrumentation and Detectors, Atomic Physics (physics.atom-ph), Computer science, Optical link, Physics::Optics, 01 natural sciences, law.invention, Physics - Atomic Physics, law, Optical frequencies, Locks (fasteners), [PHYS]Physics [physics], Signal processing, Quantum Physics, Internet, Laser mode locking, Locks (fasteners), Optical fibers, Comparison networks, Continuous operation, Fractional frequencies, Noise compensation, Optical interferometer, Optical phase locking, Optical-fiber links, Stable frequencies, Wide area networks, Fractional frequencies, Optical-fiber links, Laser diode, Instrumentation and Detectors (physics.ins-det), Optical interferometer, Atomic and Molecular Physics, and Optics, Noise compensation, OCIS codes: (120.3930) Metrological instrumentation, (060.2360) Fiber optics links and subsystems, (140.0140) Lasers and laser optics, (120.5050) Phase measurement, Stable frequencies, Physics - Optics, Heterodyne, Continuous operation, FOS: Physical sciences, Fiber network, Laser mode locking, 010309 optics, Optics, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Wavelength-division multiplexing, 0103 physical sciences, Phase noise, Electronic engineering, Optical fibers, 010306 general physics, Internet, business.industry, Optical phase locking, Comparison networks, Laser, Wide area networks, Polarization mode dispersion, Quantum Physics (quant-ph), business, Optics (physics.optics)
Abstract: International audience; We report a cascaded optical link of 1100 km for ultra-stable frequency distribution over an Internet fiber network. The link is composed of four spans for which the propagation noise is actively compensated. The robustness and the performance of the link are ensured by five fully automated optoelectronic stations, two of them at the link ends, and three deployed on the field and connecting the spans. This device coherently regenerates the optical signal with the heterodyne optical phase locking of a low-noise laser diode. Optical detection of the beat-note signals for the laser lock and the link noise compensation are obtained with stable and low-noise fibered optical interferometer. We show 3.5 days of continuous operation of the noise-compensated 4-span cascaded link leading to fractional frequency instability of 4x10 −16 at 1-s measurement time and 1x10 −19 at 2000 s. This cascaded link was extended to 1480-km with the same performance. This work is a significant step towards a sustainable wide area ultra-stable optical frequency distribution and comparison network at a very high level of performance.
Published: 2015
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24. Quantum cascade laser frequency stabilisation at the sub-Hz level

Author: Christophe Daussy, Daniele Nicolodi, Christian Chardonnet, Bruno Chanteau, B. Argence, Michel Abgrall, Yann Le Coq, Anne Amy-Klein, Benoît Darquié, Olivier Lopez, MMTF, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), CNRS, Agence Nationale de la Recherche (ANR BLANC LIOM 2011 BS04 009 01, ANR QUIGARDE 2012 ANR-12-ASTR-0028-03 and ANR NCPCHEM 2010 BLAN 724 3), Labex First-TF (ANR 10 LABX 48 01), AS GRAM and Université Paris 13., ANR-11-BS04-0009,LIOM,Lien optique multiplexé pour la métrologie et la physique fondamentale(2011), ANR-10-BLAN-0724,NCPCHEM,Non-Conservation de la Parité dans les Systèmes Moléculaires(2010), and ANR-12-ASTR-0028,QUIGARDE,Lasers à cascade quantiques émettant autour de 10 µm pour la détection à distance de composés gazeux(2012)
Subjects: Optical fiber, Atomic Physics (physics.atom-ph), FOS: Physical sciences, 01 natural sciences, Signal, law.invention, Physics - Atomic Physics, 010309 optics, Frequency comb, Optics, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, 0103 physical sciences, Quantum metrology, frequency comb, 010306 general physics, Absorption (electromagnetic radiation), Physics, Quantum Physics, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], [PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph], business.industry, Laser, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, frequency stabilisation, Cascade, QCL, business, Quantum cascade laser, Quantum Physics (quant-ph), Optics (physics.optics), Physics - Optics
Abstract: International audience; Quantum Cascade Lasers (QCL) are increasingly being used to probe the mid-infrared “molecular fingerprint” region. This prompted efforts towards improving their spectral performance, in order to reach ever-higher resolution and precision. Here, we report the stabilisation of a QCL onto an optical frequency comb. We demonstrate a relative stability and accuracy of 2x10-15 and 10-14, respectively. The comb is stabilised to a remote near-infrared ultra-stable laser referenced to frequency primary standards, whose signal is transferred via an optical fibre link. The stability and frequency traceability of our QCL exceed those demonstrated so far by two orders of magnitude. As a demonstration of its capability, we then use it to perform high-resolution molecular spectroscopy. We measure absorption frequencies with an 8x10-13 relative uncertainty. This confirms the potential of this setup for ultra-high precision measurements with molecules, such as our ongoing effort towards testing the parity symmetry by probing chiral species.
Published: 2015
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25. Tackling the Limits of Optical Fiber Links

Author: Anthony Bercy, Won-Kyu Lee, Giorgio Santarelli, Paul-Eric Pottie, Christian Chardonnet, Anne Amy-Klein, Olivier Lopez, Fabio Stefani, MMTF, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), This work is supported by the European Metrology Research Programme (EMRP) under SIB-02 NEAT-FT, the Labex FIRST-TF, the french spatial agency CNES, IFRAF-Conseil Régional Ile-de-France and Agence Nationale de la Recherche (ANR BLANC 2011-BS04-009-01 and REFIMEVE+)., ANR-11-BS04-0009,LIOM,Lien optique multiplexé pour la métrologie et la physique fondamentale(2011), and European Project
Subjects: Optical fiber, Optical engineering, Frequency Stabiliezd Lasers, FOS: Physical sciences, Polarization-maintaining optical fiber, Fiber Optics, law.invention, Optics, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, Atomic and Molecular Physics, Physics, [PHYS]Physics [physics], Sagnac effect, Mode volume, Multi-mode optical fiber, Statistical and Nonlinear Physics, Atomic and Molecular Physics, and Optics, Optical Links, business.industry, Interferometers, Interferometry, Fiber optic sensor, Time and Frequency Metrology, and Optics, business, Optics (physics.optics), Physics - Optics
Abstract: International audience; We theoretically and experimentally investigate relevant noise processes arising in optical fiber links, which fundamentally limit their relative stability. We derive the unsuppressed delay noise for three configurations of optical links: two-way method, Sagnac interferometry, and actively compensated link, respectively designed for frequency comparison, rotation sensing, and frequency transfer. We also consider an alternative two-way setup allowing real-time frequency comparison and demonstrate its effectiveness on a proof-of-principle experiment with a 25-km fiber spool. For these three configurations, we analyze the noise arising from uncommon fiber paths in the interferometric ensemble and design optimized interferometers. We demonstrate interferometers with very low temperature sensitivity of respectively -2.2, -0.03 and 1 fs/K. We use one of these optimized interferometers on a long haul compensated fiber link of 540 km. We obtain a relative frequency stability of 3x10^-20 after 10,000 s of integration time.
Published: 2015
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26. Coral Fishermen in Barbary in the Eighteenth Century: Between Norms and Practices

Author: Olivier Lopez, Temps, espaces, langages Europe méridionale-Méditerranée (TELEMME), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU), Maria Fusaro, Bernard Allaire, Richard Blakemore & Tijl Vanneste (eds), Lopez, Olivier, and Maria Fusaro, Bernard Allaire, Richard Blakemore & Tijl Vanneste (eds)
Subjects: Politics, Geography, State (polity), Economy, Multinational corporation, media_common.quotation_subject, [SHS.HIST] Humanities and Social Sciences/History, Professional environment, North african, Monopoly, [SHS.HIST]Humanities and Social Sciences/History, Archaeology, media_common
Abstract: As itinerant, multinational labourers, seamen fully deserve the analytical attention they have received throughout this volume. This is not to say, however, that they (in addition to merchants and political personnel such as consuls) were the only relevant actors in the development of connections in the early modern Mediterranean. Other groups of workers were active in occupations linked to the same commercial activities which provided employment for sailors, and promoted interaction between physically and culturally distant communities. Fishermen, coming from different backgrounds and working for some of the French companies trading in coral from the waters of the North African coast, provide but one example of this. This chapter will investigate their professional environment, arguing that these fishermen were at the same time agents promoting French imperial interests in the Mediterranean, as well as sometimes challenging the very monopoly underlying such state efforts.
Published: 2015

27. Semiparametric inference for the recurrent event process by means of a single-index model

Author: Olivier Bouaziz, Ségolen Geffray, Olivier Lopez, Mathématiques Appliquées Paris 5 (MAP5 - UMR 8145), Université Paris Descartes - Paris 5 (UPD5)-Institut National des Sciences Mathématiques et de leurs Interactions (INSMI)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche Mathématique Avancée (IRMA), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche en Économie et Statistique (CREST), Ecole Nationale de la Statistique et de l'Analyse de l'Information [Bruz] (ENSAI)-École polytechnique (X)-École Nationale de la Statistique et de l'Administration Économique (ENSAE ParisTech )-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Statistique Théorique et Appliquée (LSTA), Université Pierre et Marie Curie - Paris 6 (UPMC), Mathématiques Appliquées à Paris 5 ( MAP5 - UMR 8145 ), Université Paris Descartes - Paris 5 ( UPD5 ) -Institut National des Sciences Mathématiques et de leurs Interactions-Centre National de la Recherche Scientifique ( CNRS ), Institut de Recherche Mathématique Avancée ( IRMA ), Université de Strasbourg ( UNISTRA ) -Centre National de la Recherche Scientifique ( CNRS ), Centre de Recherche en Économie et Statistique ( CREST ), Ecole Nationale de la Statistique et de l'Analyse de l'Information [Bruz] ( ENSAI ) -École polytechnique ( X ) -École Nationale de la Statistique et de l'Administration Économique ( ENSAE ParisTech ), Laboratoire de Statistique Théorique et Appliquée ( LSTA ), Université Pierre et Marie Curie - Paris 6 ( UPMC ), Ecole Nationale de la Statistique et de l'Analyse de l'Information [Bruz] (ENSAI)-École polytechnique (X)-École Nationale de la Statistique et de l'Administration Économique (ENSAE Paris)-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Statistics and Probability, Statistics::Theory, dimension reduction, asymptotic normality, Asymptotic distribution, Mathematics - Statistics Theory, Statistics Theory (math.ST), [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], single-index model, Econometrics, FOS: Mathematics, Statistics::Methodology, Semiparametric regression, [ MATH.MATH-ST ] Mathematics [math]/Statistics [math.ST], Parametric statistics, Mathematics, empirical processes, Dimensionality reduction, Nonparametric statistics, Estimator, [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], [ STAT.TH ] Statistics [stat]/Statistics Theory [stat.TH], right-censoring, Semiparametric model, recurrent events, Statistics, Probability and Uncertainty, Curse of dimensionality
Abstract: International audience; In this paper, we introduce new parametric and semiparametric regression techniques for a recurrent event process subject to random right censoring. We develop models for the cumula- tive mean function and provide asymptotically normal estimators. Our semiparametric model which relies on a single-index assumption can be seen as a dimension reduction technique that, contrary to a fully nonparametric approach, is not stroke by the curse of dimensional- ity when the number of covariates is high. We discuss data-driven techniques to choose the parameters involved in the estimation procedures and provide a simulation study to support our theoretical results.
Published: 2015
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28. Quantum Cascade Laser at Hz-Level by Use of a Frequency Comb and an Optical Link

Author: Bruno Chanteau, C. Chardonnet, Olivier Lopez, M. Abgrall, B. Argence, Anne Amy-Klein, Christophe Daussy, Daniele Nicolodi, Benoît Darquié, Y. Le Coq, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Métrologie des fréquences optiques, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Distributed feedback laser, Materials science, business.industry, Optical link, Far-infrared laser, Laser, Signal, law.invention, Frequency comb, Optics, law, Quantum cascade laser, business, Spectroscopy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience; We present a frequency chain which enables to transfer coherently the stability and the accuracy of an ultrastable laser emitting at 1.54 mu m to the mid-infrared region. It includes an optical frequency comb and an ultrastable 1.54 mu m frequency signal, referenced to primary standards and transferred from LNE-SYRTE to LPL through an optical link. This system gives us the ability to transfer frequency stability in the range of 10(-15) and accuracy in the range of 10(-14) from 1.54 mu m to a wide spectral range in the mid-infrared domain. With this set-up, we stabilized a Quantum Cascade Laser emitting at 10.3 mu m at an unprecedented Hz-level.
Published: 2014
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29. Non-Parametric Estimation of Linear Functionals of a Multivariate Distribution Under Multivariate Censoring with Applications

Author: Philippe Saint-Pierre, Olivier Lopez, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Statistique Théorique et Appliquée (LSTA), Université Pierre et Marie Curie - Paris 6 (UPMC), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Multivariate statistics, 05 social sciences, Inverse-Wishart distribution, Matrix t-distribution, [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], 01 natural sciences, Multivariate kernel density estimation, Normal-Wishart distribution, 010104 statistics & probability, 0502 economics and business, Statistics, Matrix normal distribution, Multivariate t-distribution, 0101 mathematics, [STAT.ME]Statistics [stat]/Methodology [stat.ME], ComputingMilieux_MISCELLANEOUS, 050205 econometrics, Mathematics, Multivariate stable distribution
Abstract: International audience
Published: 2014

30. Towards large scale metrological fibre network

Author: Anthony Bercy, Giorgio Santarelli, Paul-Eric Pottie, Fabio Stefani, Anne Amy-Klein, Olivier Lopez, Christian Chardonnet, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Métrologie des fréquences optiques, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Engineering, business.industry, Scale (chemistry), Optical link, Frame (networking), Fiber network, Metrology, frequency transfert, ultrastable laser, Control and Systems Engineering, Optical frequencies, Systems engineering, Electronic engineering, business, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: In the frame of the REFIMEVE+ project, aiming at disseminating an optical frequency standard to more than 20 laboratories in France, we present the progress made towards a metrological fibre wide-area network.
Published: 2013
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31. Ultra-stable long distance optical frequency distribution using the Internet fiber network and application to high-precision molecular spectroscopy

Author: Michel Abgrall, Bruno Chanteau, Paul-Eric Pottie, Anthony Bercy, Daniele Rovera, B. Argence, Daniele Nicolodi, C. Chardonnet, Joseph Achkar, Amale Kanj, Benoît Darquié, Y. Le Coq, Wei Zhang, A. Haboucha, Giorgio Santarelli, Olivier Lopez, Anne Amy-Klein, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Métrologie des fréquences optiques, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Références micro-ondes et échelles de temps, Laboratoire Photonique, Numérique et Nanosciences (LP2N), and Université de Bordeaux (UB)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, History, business.industry, Optical link, Bandwidth (signal processing), Rotational–vibrational spectroscopy, Laser, Computer Science Applications, Education, law.invention, Optics, law, Electronic engineering, Time transfer, The Internet, business, Spectroscopy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Order of magnitude
Abstract: International audience; We report an optical link of 540 km for ultrastable frequency distribution over the Internet fiber network. The phase-noise compensated link shows a fractional frequency instability in full bandwidth of 3×10-14 at one second measurement time and 2×10-18 at 30 000 s. This work is a significant step towards a sustainable wide area ultrastable optical frequency distribution and comparison network. Time transfer was demonstrated simultaneously on the same link and led to an absolute time accuracy (250 ps) and long-term timing stability (20 ps) which outperform the conventional satellite transfer methods by one order of magnitude. Current development addresses the question of multiple users distribution in the same metropolitan area. We demonstrate on-line extraction and first results show frequency stability at the same level as with conventional link. We also report an application to coherent frequency transfer to the mid-infrared. We demonstrate the frequency stabilisation of a mid-infrared laser to the near-infrared frequency reference transferred through the optical link. Fractional stability better than 4×10-14 at 1 s averaging time was obtained, opening the way to ultrahigh resolution spectroscopy of molecular rovibrational transitions.
Published: 2013
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32. Ultra-stable Long Distance Optical Frequency/Time Distribution Using the Internet Network

Author: Giorgio Santarelli, Olivier Lopez, Paul-Eric POTTIE, Rovera, Giovanni D., Joseph Achkar, Anne Amy, Christian Chardonnet, Santarelli, Giorgio, lp2n-06,lp2n-14, Laboratoire Photonique, Numérique et Nanosciences (LP2N), Université Sciences et Technologies - Bordeaux 1-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS), MMTF, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], ComputingMilieux_MISCELLANEOUS, [PHYS.QPHY] Physics [physics]/Quantum Physics [quant-ph]
Abstract: International audience
Published: 2013

33. Simultaneous remote transfer of accurate timing and optical frequency over a public fiber network

Author: Anne Amy-Klein, Christian Chardonnet, Paul-Eric Pottie, Daniele Rovera, Amale Kanj, Joseph Achkar, Giorgio Santarelli, Olivier Lopez, MMTF, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), lp2n-06,lp2n-14, Laboratoire Photonique, Numérique et Nanosciences (LP2N), Université Sciences et Technologies - Bordeaux 1-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS), ANR BLANC 2011-BS04-009-01, Université Sciences et Technologies - Bordeaux 1 (UB)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord, Références micro-ondes et échelles de temps, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Optical fiber, Physics - Instrumentation and Detectors, Physics and Astronomy (miscellaneous), Computer science, Optical link, General Physics and Astronomy, FOS: Physical sciences, Satellite system, Physics and Astronomy(all), Optical time-domain reflectometer, 01 natural sciences, law.invention, time transfer, 010309 optics, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, Optical Carrier transmission rates, 0103 physical sciences, Fiber optic splitter, Electronic engineering, Time transfer, 010306 general physics, frequency transfer, Quantum Physics, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Multi-mode optical fiber, Optical cross-connect, General Engineering, time and frequency metrology, Instrumentation and Detectors (physics.ins-det), (120.3930) Metrological instrumentation, (060.2360) Fiber optics links and subsystems, (120.5050) Phase measurement, Fiber-optic communication, Spread spectrum, Fiber optic sensor, Geostationary orbit, optical link, Timestamp, Quantum Physics (quant-ph), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Phase modulation, Physics - Optics, Optics (physics.optics)
Abstract: In this work we demonstrate for the first time that it is possible to transfer simultaneously an ultra-stable optical frequency and a precise and accurate timing over 540 km using a public telecommunication optical fiber networks with Internet data. The optical phase is used to carry both the frequency information and the timestamps by modulating a very narrow optical carrier at 1.55 $\mu$m with spread spectrum signals using two-way satellite time transfer modems. The results in term of absolute time accuracy (250 ps) and long-term timing stability (20 ps) well outperform the conventional Global Navigation Satellite System or geostationary transfer methods.
Published: 2013
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34. Ultra-stable long distance optical frequency distribution using the Internet fiber network

Author: Olivier Lopez, Christian Chardonnet, A. Haboucha, Bruno Chanteau, Giorgio Santarelli, Anne Amy-Klein, MMTF, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), lp2n-06,lp2n-14, Laboratoire Photonique, Numérique et Nanosciences (LP2N), Université Sciences et Technologies - Bordeaux 1-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS), ANR BLANC 2011-BS04-009-01 et Université Paris 13 et IFRAF-Conseil Régional Ile-de-France, and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Optical link, Beat (acoustics), FOS: Physical sciences, Metrological instrumentation, (120.3930) (060.2360) (140.0140) (120.5050), 01 natural sciences, Lasers and laser optics, law.invention, 010309 optics, Optics, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Robustness (computer science), law, 0103 physical sciences, 010306 general physics, Optical Fibers, Physics, Internet, Quantum Physics, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Laser diode, business.industry, Bandwidth (signal processing), Equipment Design, Phase measurement, Polarization (waves), Atomic and Molecular Physics, and Optics, Equipment Failure Analysis, Amplitude, The Internet, Fiber optics links and subsystems, Lasers, Semiconductor, business, Quantum Physics (quant-ph), Optics (physics.optics), Physics - Optics
Abstract: International audience; We report an optical link of 540 km for ultrastable frequency distribution over the Internet fiber network. The stable frequency optical signal is processed enabling uninterrupted propagation on both directions. The robustness and the performance of the link are enhanced by a cost effective fully automated optoelectronic station. This device is able to coherently regenerate the return optical signal with a heterodyne optical phase locking of a low noise laser diode. Moreover the incoming signal polarization variation are tracked and processed in order to maintain beat note amplitudes within the operation range. Stable fibered optical interferometer enables optical detection of the link round trip phase signal. The phase-noise compensated link shows a fractional frequency instability in 10 Hz bandwidth of 5x10-15 at one second measurement time and 2x10-19 at 30 000 s. This work is a significant step towards a sustainable wide area ultrastable optical frequency distribution and comparison network.
Published: 2012

35. A simplified model for studying bivariate mortality under right-censoring

Author: Philippe Saint-Pierre, Olivier Lopez, Svetlana Gribkova, Laboratoire de Statistique Théorique et Appliquée (LSTA), Université Pierre et Marie Curie - Paris 6 (UPMC), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Statistics and Probability, Statistics::Theory, mortality analysis, Bivariate analysis, 01 natural sciences, Copula (probability theory), 010104 statistics & probability, [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], 0502 economics and business, Statistics, Econometrics, Statistics::Methodology, 0101 mathematics, bivariate censoring, bootstrap, Kaplan–Meier estimator, Survival analysis, 050205 econometrics, Mathematics, Numerical Analysis, Nonparametric estimator, Age differences, Kaplan-Meier estimator, 05 social sciences, Estimator, copula models, nonparametric estimation, [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], Censoring (statistics), Statistics, Probability and Uncertainty
Abstract: In this paper, we provide a nonparametric estimator of the distribution of bivariate censored lifetimes, in a model where the two censoring variables differ only through an additional observed variable. This situation is motivated by a particular application to insurance, where the supplementary variable corresponds to the age difference between two individuals. Asymptotic results for our estimator are provided. The new tools that we develop are used to perform goodness-of-fit tests for survival copula models. The practical performance is illustrated through simulations and a real data analysis.
Published: 2012

36. Bivariate censored regression relying on a new estimator of the joint distribution function

Author: Philippe Saint-Pierre, Olivier Lopez, Laboratoire de Statistique Théorique et Appliquée (LSTA), Université Pierre et Marie Curie - Paris 6 (UPMC), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Statistics and Probability, Bivariate censoring, Statistics::Theory, 0211 other engineering and technologies, 02 engineering and technology, Bivariate analysis, Statistics::Other Statistics, 01 natural sciences, Copula (probability theory), 010104 statistics & probability, [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], Regression modeling, Econometrics, Statistics::Methodology, Joint distribution function, 0101 mathematics, Kaplan–Meier estimator, $M-$estimation, Mathematics, Censored regression model, 021103 operations research, Kaplan-Meier estimator, Applied Mathematics, Estimator, i.i.d. representations, Regression analysis, [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], Statistics::Computation, Censoring (clinical trials), Statistics, Probability and Uncertainty, Copula functions
Abstract: In this paper we study a class of M-estimators in a regression model under bivariate random censoring and provide a set of sufficient conditions that ensure asymptotic n 1 / 2 - convergence . The cornerstone of our approach is a new estimator of the joint distribution function of the censored lifetimes. A copula approach is used to modelize the dependence structure between the bivariate censoring times. The resulting estimators present the advantage of being easily computable. A simulation study enlighten the finite sample behavior of this technique.
Published: 2011

37. Alpha-particle condensation in excited 12C

Author: Raduta, Ad R., Borderie, B., Geraci, E., Neindre, N. Le, Napolitani, P., Rivet, M. F., Alba, R., Amorini, F., Cardella, G., Chatterjee, M., Filippo, E., Guinet, D., Lautesse, P., La Guidara, E., Lanzalone, G., Lanzano, G., Lombardo, I., Olivier Lopez, Maiolino, C., Pagano, A., Pirrone, S., Politi, G., Porto, F., Rizzo, F., Russotto, P., Wieleczko, J. P., Institut de Physique Nucléaire d'Orsay (IPNO), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Institut de Physique Nucléaire de Lyon (IPNL), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Grand Accélérateur National d'Ions Lourds (GANIL), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Nuclear Theory, FOS: Physical sciences, Nuclear Experiment (nucl-ex), [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract: The fragmentation of quasi-projectiles from the nuclear reaction $^{40}Ca$+$^{12}C$ at 25 MeV/nucleon was used to produce excited states candidates to $\alpha$-particle condensation. The methodology relies on high granularity 4$\pi$ detection coupled to correlation function techniques. Under the assumption that the equality among the kinetic energies of the emitted $\alpha$-particles and the emission simultaneity constitutes a reliable fingerprint of $\alpha$ condensation, we identify several tens of events corresponding to the deexcitation of the Hoyle state of $^{12}$C which fulfill the condition., Comment: 5 pages, 3 figures
Published: 2010

38. High-resolution optical frequency dissemination on a telecommunication network with data traffic

Author: Olivier Lopez, Fabien Kéfélian, Haifeng Jiang, Anne Amy-Klein, Christian Chardonnet, Georgio Santarelli, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), ANR Alpha+, Lien optique, and ANR-06-BLAN-0143,ALPHA+,Test de stabilité des constantes fondamentales par conparaisons à longue distance d'horloges optiques ultra-stables(2006)
Subjects: Computer science, Optical communication, FOS: Physical sciences, transfert de fréquence, 01 natural sciences, Signal, Multiplexer, law.invention, 010309 optics, OADM, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, Optical frequencies, Wavelength-division multiplexing, 0103 physical sciences, Phase noise, OCIS 060.2360, 120.3930, Fiber, Allan variance, 010306 general physics, Quantum Physics, business.industry, lien optique, Electrical engineering, Laser, Telecommunications network, Atomic and Molecular Physics, and Optics, Interferometry, réseaux optiques, Quantum Physics (quant-ph), business
Abstract: International audience; We transferred the frequency of an ultra-stable laser over a 108 km urban fiber link comprising 22 km of optical communications network fiber simultaneously carrying Internet data traffic. The metrological signal and the digital data signal are transferred on two different frequency channels in a dense wavelength division multiplexing scheme. The metrological signal is inserted into and extracted from the communications network by using bidirectional off-the-shelf optical add-drop multiplexers. The link-induced phase noise is measured and cancelled with round-trip technique using an all-fiber-based interferometer. The compensated link shows an Allan deviation of a few 10-16 at one second and below 10-19 at 10,000 seconds. This opens the way to a wide dissemination of ultra stable optical clock signals between distant laboratories via the Internet network.
Published: 2009

39. Conditional density estimation in a censored single-index regression model

Author: Olivier Lopez, Olivier Bouaziz, Laboratoire de Statistique Théorique et Appliquée (LSTA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)
Subjects: Statistics and Probability, Statistics::Theory, Single-index model, asymptotic normality, 62N01,62N02, Asymptotic distribution, Mathematics - Statistics Theory, Statistics Theory (math.ST), 01 natural sciences, 010104 statistics & probability, censoring, [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], single-index model, 0502 economics and business, FOS: Mathematics, Applied mathematics, Statistics::Methodology, 0101 mathematics, 050205 econometrics, Mathematics, martingales for counting processes, empirical processes, 05 social sciences, Estimator, Regression analysis, Conditional probability distribution, [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], Regression, Censoring (clinical trials), pseudo-maximum likelihood, Smoothing
Abstract: Under a single-index regression assumption, we introduce a new semiparametric procedure to estimate a conditional density of a censored response. The regression model can be seen as a generalization of the Cox regression model and also as a profitable tool for performing dimension reduction under censoring. This technique extends the results of Delecroix et al. [J. Multivariate Anal. 86 (2003) 213–226]. We derive consistency and asymptotic normality of our estimator of the index parameter by proving its asymptotic equivalence with the (uncomputable) maximum likelihood estimator, using martingales results for counting processes and arguments from empirical processes theory. Furthermore, we provide a new adaptive procedure which allows us both to choose the smoothing parameter involved in our approach and to circumvent the weak performances of the Kaplan–Meier estimator [Amer. Statist. Assoc. 53 (1958) 457–481] in the right-tail of the distribution. By means of a simulation study, we study the behavior of our estimator for small samples.
Published: 2009

40. On the estimation of the joint distribution in regression models with censored responses

Author: Olivier Lopez, Institut de Recherche Mathématique de Rennes ( IRMAR ), Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -AGROCAMPUS OUEST-École normale supérieure - Rennes ( ENS Rennes ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -Institut National des Sciences Appliquées ( INSA ) -Université de Rennes 2 ( UR2 ), Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ), Centre de Recherche en Économie et Statistique ( CREST ), Ecole Nationale de la Statistique et de l'Analyse de l'Information [Bruz] ( ENSAI ) -École polytechnique ( X ) -École Nationale de la Statistique et de l'Administration Économique ( ENSAE ParisTech ), Institut de Recherche Mathématique de Rennes (IRMAR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École normale supérieure - Rennes (ENS Rennes)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-INSTITUT AGRO Agrocampus Ouest, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Centre de Recherche en Économie et Statistique (CREST), Ecole Nationale de la Statistique et de l'Analyse de l'Information [Bruz] (ENSAI)-École polytechnique (X)-École Nationale de la Statistique et de l'Administration Économique (ENSAE Paris)-Centre National de la Recherche Scientifique (CNRS), AGROCAMPUS OUEST, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)
Subjects: right censored regression, [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], asymptotic normality, MSC2000 : 62N01, 62G30, 60F05, law of large numbers, Statistics::Methodology, [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], kernel estimators, [ MATH.MATH-ST ] Mathematics [math]/Statistics [math.ST], distribution function, [ STAT.TH ] Statistics [stat]/Statistics Theory [stat.TH]
Abstract: In a regression model with univariate censored responses, a new estimator of the joint distribution function of the covariates and response is proposed, under the assumption that the response and the censoring variable are independent conditionally to the covariates. This estimator is an extension of the multivariate empirical function used in the uncensored case. Furthermore, under some simple additional identifiability assumption, this estimator is not sensible to the "curse of dimensionality", so that it allows to infer on models with multidimensional covariates. Integrals with respect to this empirical measure are considered. Consistency and asymptotic normality of these integrals over a class of functions is obtained, by deriving asymptotic i.i.d. representations. Several applications of the new estimator are proposed.
Published: 2008

41. Nonlinear censored regression using synthetic data

Author: Olivier Lopez, Michel Delecroix, Valentin Patilea, Laboratoire de Statistique Théorique et Appliquée (LSTA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche Mathématique de Rennes (IRMAR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École normale supérieure - Rennes (ENS Rennes)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-INSTITUT AGRO Agrocampus Ouest, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Université Pierre et Marie Curie - Paris 6 (UPMC), AGROCAMPUS OUEST, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)
Subjects: Statistics and Probability, asymptotic normality, Kaplan-Meier integral, Asymptotic distribution, 01 natural sciences, Least squares, Synthetic data, 010104 statistics & probability, Consistency (statistics), [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], 0502 economics and business, Statistics, 0101 mathematics, 050205 econometrics, Mathematics, Censored regression model, consistency, 05 social sciences, 62J02, 62N01, Estimator, Regression analysis, synthetic data, nonlinear regression, right censoring, Statistics, Probability and Uncertainty, Nonlinear regression
Abstract: The problem of estimating a nonlinear regression model when the dependent variableis randomly censored is considered. The parameter of the model is estimated by leastsquares using synthetic data, that is a suitable transformation of the response variablesthat preserves the conditional expectation. Two such transformations are considered.Consistency and asymptotic normality of the least squares estimators are derived. Theproofs are based on a novel approach that uses i.i.d. representation of synthetic datathrough Kaplan-Meier integrals. The asymptotic results are completed by a small com-parative simulation study.
Published: 2008
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42. 86-km optical link with a resolution of 2.10-18 for RF frequency transfer

Author: Anne Amy-Klein, Michel Lours, Olivier Lopez, Christian Chardonnet, F. Narbonneau, Christophe Daussy, Georgio Santarelli, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), and Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord
Subjects: Materials science, Optical link, FOS: Physical sciences, 01 natural sciences, Scrambling, 010309 optics, Optics, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], 0103 physical sciences, Dispersion (optics), 010306 general physics, Optical amplifier, frequency transfer, Quantum Physics, business.industry, Resolution (electron density), Mode (statistics), Atomic and Molecular Physics, and Optics, metrology, PACS : 42.62.Eh, 06.30.Ft, 42.81.Uv, 42.81.Gs, optical link, Radio frequency, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], business, Quantum Physics (quant-ph), Sensitivity (electronics)
Abstract: International audience; RF frequency transfer over an urban 86 km fibre has been demonstrated with a resolution of 2×10-18 at one day measuring time using an optical compensator. This result is obtained with a reference carrier frequency of 1 GHz, and a rapid scrambling of the polarisation state of the input light in order to reduce the sensitivity to the polarisation mode dispersion in the fibre. The limitation due to the fibre chromatic dispersion associated with the laser frequency fluctuations is highlighted and analyzed. A preliminary test of an extended compensated link over 186 km using optical amplifiers gives a resolution below 10-17 at 1 day.
Published: 2008
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43. Synthetic data based nonparametric testing of parametric mean-regression models with censored data

Author: Olivier Lopez, Valentin Patilea, Laboratoire de Statistique Théorique et Appliquée (LSTA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche Mathématique de Rennes (IRMAR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École normale supérieure - Rennes (ENS Rennes)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-INSTITUT AGRO Agrocampus Ouest, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Université Pierre et Marie Curie - Paris 6 (UPMC), AGROCAMPUS OUEST, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), and Guillemer, Marie-Annick
Subjects: Statistics::Theory, [STAT.TH] Statistics [stat]/Statistics Theory [stat.TH], Nonparametric statistics, 020206 networking & telecommunications, Regression analysis, 02 engineering and technology, [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], 01 natural sciences, Censoring (statistics), 62-06, 010104 statistics & probability, [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], Linear regression, Statistics, 0202 electrical engineering, electronic engineering, information engineering, Test statistic, Kernel smoother, Statistics::Methodology, 0101 mathematics, [MATH.MATH-ST] Mathematics [math]/Statistics [math.ST], ComputingMilieux_MISCELLANEOUS, Quantile, Parametric statistics, Mathematics
Abstract: We develop a kernel smoothing based test of a parametric mean-regression model against a nonparametric alternative when the response variable is rightcensored. The new test statistic is inspired by the synthetic data approach for estimating the parameters of a (non)linear regression model under censoring. The asymptotic critical values of our tests are given by the quantiles of the standard normal law. The test is consistent against any fixed alternative, against local Pitman alternatives and uniformly over alternatives in Holder classes of functions of known regularity.
Published: 2007

44. Frequency dissemination with a 86-km optical fibre for fundamental tests of physics

Author: Anne Amy-Klein, C. Chardonnet, Olivier Lopez, Giorgio Santarelli, Christophe Daussy, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Métrologie des fréquences optiques, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Optical fiber, business.industry, Optical link, Resolution (electron density), General Physics and Astronomy, Electron, Propagation delay, Stability (probability), law.invention, Optics, law, Phase noise, business, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Line (formation)
Abstract: International audience; A 43-km optical link has been developed between LPL and LNE-SYRTE, to transfer a primary reference frequency in the RF or microwave range. The phase noise introduced by the fluctuations of the propagation delay is compensated using a delay line. The resolution has been improved by increasing the transferred frequency up to 9 GHz. This link was used to compare a molecular optical clock in LPL to a primary reference in SYRTE, which leads to a test of the stability of electron to proton mass ratio.
Published: 2007
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45. Absolute frequency measurements for hyperfine structure determination of the R(26) 62-0 transition at 501.7 nm in molecular iodine

Author: Andrei Goncharov, Frédéric Du Burck, Anne Amy-Klein, Olivier Lopez, Institute of Laser Physics of SB RAS (ILP), Siberian Branch of the Russian Academy of Sciences (SB RAS), Laboratoire de Physique des Lasers (LPL), and Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord
Subjects: Materials science, Atomic Physics (physics.atom-ph), Absolute frequency, iodine spectroscopy, FOS: Physical sciences, chemistry.chemical_element, Comb generator, 02 engineering and technology, Iodine, 01 natural sciences, law.invention, Physics - Atomic Physics, 010309 optics, Laser linewidth, 06.20.-f, 06.20.F, 06.30.Bp, 06.30.Ft, 33.20.-t, optical frequency measurement, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Hyperfine structure, femtosecond comb, [PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph], 020208 electrical & electronic engineering, General Engineering, Laser, hyperfine interaction, chemistry, Femtosecond, Atomic physics, Laser frequency
Abstract: International audience; The absolute frequencies of the hyperfine components of the R(26) 62-0 transition in molecular iodine at 501.7 nm are measured for the first time with an optical clockwork based on a femtosecond laser frequency comb generator. The set-up is composed of an Ar+ laser locked to a hyperfine component of the R(26) 62-0 transition detected in a continuously pumped low-pressure cell (0.33 Pa). The detected resonances show a linewidth of 45 kHz (half-width at half-maximum). The uncertainty of the frequency measurement is estimated to be 250 Hz.
Published: 2007

46. Calcite surface renewal caused by fluid inclusions mobility: An AFM study

Author: Pierpaolo Zuddas, Olivier Lopez, Dynamique et thermodynamique nucléaire, Institut de Physique du Globe de Paris (IPGP), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Calcite, Surface (mathematics), 010504 meteorology & atmospheric sciences, Atomic force microscopy, Geochemistry, Mineralogy, 010502 geochemistry & geophysics, 01 natural sciences, chemistry.chemical_compound, chemistry, Geochemistry and Petrology, Fluid inclusions, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Geology, 0105 earth and related environmental sciences
Published: 2006
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47. High resolution frequency standard dissemination via optical fiber metropolitan network

Author: Sébastien Bize, Ch. Daussy, Ch. Chardonnet, Anne Amy-Klein, Giorgio Santarelli, André Clairon, Olivier Lopez, F. Narbonneau, M. Lours, Laboratoire national de métrologie et d'essais - Systèmes de Référence Temps-Espace (LNE - SYRTE), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Lasers (LPL), and Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord
Subjects: Time delay and integration, Optical fiber, business.industry, Computer science, Optical link, Frequency standard, 01 natural sciences, Signal, Noise (electronics), law.invention, 010309 optics, Amplitude modulation, Optics, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, Optical Carrier transmission rates, 0103 physical sciences, Electronic engineering, 010306 general physics, business, Instrumentation
Abstract: International audience; We present in this article results on a new dissemination system of an ultrastable reference signal at 100 MHz on a standard fiber network. The 100 MHz signal is simply transferred by amplitude modulation of an optical carrier. Two different approaches for compensating the noise introduced by the link have been implemented. The limits of the two systems are analyzed and several solutions are suggested in order to improve the frequency stability and to further extend the distribution distance. Nevertheless, our system is a good tool for the best cold atom fountains comparison between laboratories, up to 100 km, with a relative frequency resolution of 10 −14 at 1 s integration time and 10 −17 for 1 day of measurement. The distribution system may be upgraded to fulfill the stringent distribution requirements for the future optical clocks.
Published: 2006
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48. Phase-space methods in nuclear reactions around the Fermi energy

Author: Lacroix, Denis, Durand, Dominique, Lehaut, Gregory, Olivier Lopez, Vient, Emmanuel, Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), R. Bougault, A. Pagano, S. Pirrone, M-F. Rivet, F. Rizzo, Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Guesnon, Sandrine, and R. Bougault, A. Pagano, S. Pirrone, M-F. Rivet, F. Rizzo
Subjects: Nuclear Theory (nucl-th), [PHYS.NUCL] Physics [physics]/Nuclear Theory [nucl-th], Nuclear Theory, [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], [PHYS.NEXP] Physics [physics]/Nuclear Experiment [nucl-ex], FOS: Physical sciences, Nuclear Experiment (nucl-ex), [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract: Some prescriptions for in-medium complex particle production in nuclear reactions are proposed. They have been implemented in two models to simulate nucleon-nucleus (nIPSE) and nucleus-nucleus (HIPSE) reactions around the Fermi energy \cite{Lac04,Lac05}. Our work emphasizes the effect of randomness in cluster formation, the importance of the nucleonic Fermi motion as well as the role of conservation laws. The key role of the phase-space exploration before and after secondary decay is underlined. This is illustrated in the case of two debated issues: the memory loss of the entrance channel in central collisions and the $(N,Z)$ partitions after the pre-equilibrium stage., Comment: Proceedings of the IWM2005 workshop, Catane (Italy), Nov. 2005. DOWNLOAD HIPSE program at: http://caeinfo.in2p3.fr/theorie/theory_lacroix.html
Published: 2005

49. Long-distance frequency dissemination with a resolution of 10-17

Author: Andrei Goncharov, Olivier Lopez, Andre N. Luiten, Sébastien Bize, Christophe Daussy, Christian Chardonnet, M. Guinet, Anne Amy-Klein, F. Narbonneau, Georgio Santarelli, Michael E. Tobar, André Clairon, D. Chambon, Michel Lours, Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), School of physics, University of Western Australia (UWA), and The University of Western Australia (UWA)
Subjects: 06.20.-f, 42.62.Eh, 06.30.Ft, FOS: Physical sciences, General Physics and Astronomy, Physics::Optics, Frequency standard, 01 natural sciences, law.invention, 010309 optics, Optics, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, Frequency resolution, 0103 physical sciences, 010306 general physics, horloge moléculaire, Physics, Quantum Physics, business.industry, métrologie des fréquences, lien optique, Resolution (electron density), Laser, Femtosecond, Atomic physics, Laser frequency, dissémination du temps, Quantum Physics (quant-ph), business, Microwave
Abstract: We use a new technique to disseminate microwave reference signals along ordinary optical fiber. The fractional frequency resolution of a link of 86 km in length is ${10}^{\ensuremath{-}17}$ for a one day integration time, a resolution higher than the stability of the best microwave or optical clocks. We use the link to compare the microwave reference and a ${\mathrm{CO}}_{2}/{\mathrm{OsO}}_{4}$ frequency standard that stabilizes a femtosecond laser frequency comb. This demonstrates a resolution of $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}$ at 1 s. An upper value of the instability introduced by the femtosecond laser-based synthesizer is estimated as $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}$ at 1 s.
Published: 2005

50. Morphology of nanomagnetite crystals: Implications for formation conditions

Author: Damien Faivre, Menguy, N., François Guyot, Olivier Lopez, Pierpaolo Zuddas, Institut de Physique du Globe de Paris (IPGP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Institut de minéralogie et de physique des milieux condensés (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Physique des géomatériaux (PG), IPG PARIS-Centre National de la Recherche Scientifique (CNRS), PaleoEnvironnements et PaleobioSphere (PEPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Abstract: A series of controlled abiotic syntheses of magnetite nanocrystals were carried out to explore the possibility of using morphological criteria, crystal size distributions, and shape ratio as tools for identifying nanocrystals that would be speciÞ cally produced by magnetotactic bacteria. High-quality magnetite crystals synthesized with various controlled total iron concentrations were shown to have cubo-octahedral shapes and sizes varying from 4 to 24 nm. The mean particle size of the population was found to be 10.5 ± 0.7 nm and no signiÞ cant effect of the total iron concentration on the particle size was observed. Systematical analyses of size and morphology also allowed for the determination of crystal size and shape ratio distributions. Crystal sizes were observed to follow log-normal distribu- tions. Shape factors are bounded by one, with maxima between 0.80 to 1.00. Their distributions are asymmetric, with a cut off toward the high values. Crystal morphologies and shape factors appear not to be a powerful diagnostic tool for the differentiation of abiotic vs. biotic particles. However, crystal size distributions of abiotic crystals are signiÞ cantly different from those of biotic populations. Indeed, opposite asymmetry of the size distributions from biogenic and non biogenic crystals was observed, with cut off toward larger sizes for biogenic nanocrystals and with cut off toward smaller sizes for abiogenic nanocrystals. This therefore constitutes a potential diagnostic tool for deciphering magnetite origin.
Published: 2005

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