Search

Understanding the fundamental mechanisms of optoelectronic excitation and relaxation pathways on the single-molecule level has only recently been started by combining scanning tunneling microscopy (STM) and spectroscopy (STS) with STM-induced luminescence (STML). In this paper, we investigate cationic and anionic fluorescence of individual zinc phthalocyanine (ZnPc) molecules adsorbed on ultrathin NaCl films on Ag(111) by using STML. They depend on the tip-sample bias polarity and appear at threshold voltages that are correlated with the onset energies of particular molecular orbitals, as identified by STS. We also find that the fluorescence is caused by a single-electron tunneling process. Comparing with results from density functional theory calculations, we propose an alternative many-body picture to describe the charging and electroluminescence mechanism. In this paper, we provide aspects toward well-defined voltage selectivity of bipolar electrofluorochromism as well as fundamental insights regarding the role of transiently charged states of emitter molecules within organic light-emitting diode devices.

©2016 American Physical Society. This paper has been financially supported through of the Spanish Ministry of Economy and Competitiveness (MINECO), MAT2015-66888-C3-3-R. We thank “CAI Difracción de rayos-X” of Universidad Complutense de Madrid for the x-ray diffractometry measurements and Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM) for the use of some of its facilities. We also thank BM25-SpLine, the Spanish CRG at ESRF for providing beam time., In this paper we analyze the structure of Fe-Ga layers with a Ga content of ∼30 at.% deposited by the sputtering technique under two different regimes. We also studied the correlation between the structure and magnetic behavior of the samples. Keeping the Ar pressure fixed, we modified the flow regime from ballistic to diffusive by increasing the distance between the target and the substrate. X-ray diffraction measurements have shown a lower structural quality when growing in the diffusive flow. We investigated the impact of the growth regime by means of x-ray absorption fine structure (XAFS) measurements and obtained signs of its influence on the local atomic order. Full multiple scattering and finite difference calculations based on XAFS measurements point to a more relevant presence of a disordered A2 phase and of orthorhombic Ga clusters on the Fe-Ga alloy deposited under a diffusive regime; however, in the ballistic sample, a higher presence of D0_3/B2 phases is evidenced. Structural characteristics, from local to long range, seem to determine the magnetic behavior of the layers. Whereas a clear in-plane magnetic anisotropy is observed in the film deposited under ballistic flow, the diffusive sample is magnetically isotropic. Therefore, our experimental results provide evidence of a correlation between flow regime and structural properties and its impact on the magnetic behavior of a rather unexplored compositional region of Fe-Ga compounds., Ministerio de Economía y Competitividad (MINECO), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Symmetry defects, e.g., vortices in conventional superfluids, play a critical role in a complete description of symmetry breaking phases. In this paper, we develop the theory of symmetry defects in fractonic superfluids, i.e., spontaneously higher-rank symmetry (HRS) breaking phases initially proposed by Yuan et al. [Phys. Rev. Res. 2, 023267 (2020)] and by Chen et al. [Phys. Rev. Res. 3, 013226 (2021)]. By Noether's theorem, HRS is associated with the conservation law of higher moments, e.g., dipoles, quadrupoles, and angular moments. We establish finite-temperature phase diagrams by identifying a series of topological phase transitions via the renormalization group flow equations and Debye-Hückel approximation. Accordingly, a series of Kosterlitz-Thouless topological transitions are found to occur successively at different temperatures, which are triggered by proliferation of defects, defect bound states, and so on. Such a hierarchical proliferation brings rich phase structures. Meanwhile, a screening effect from sufficiently high density of defect bound states leads to instability and collapse of the intermediate temperature phases, which further enriches the phase diagrams. For concreteness, we consider a fractonic superfluid in which “angular moments” are conserved. We then present the general theory, in which other types of HRS can be analyzed in a similar manner. Further directions are present at the end of the paper.

This paper presents a first experimental demonstration of a new nondestructive method for aperture measurements based on ac dipoles. In high intensity particle colliders, such as the CERN Large Hadron Collider (LHC), aperture measurements are crucial for a safe operation while optimizing the optics in order to reduce the size of the colliding beams and hence increase the luminosity. In the LHC, this type of measurements became mandatory during beam commissioning and the current method used is based on the destructive blowup of bunches using a transverse damper. The new method presented in this paper uses the ac-dipole excitation to generate adiabatic forced oscillations of the beam in order to create losses to identify the smallest aperture in the machine without blowing up the beam emittance. A precise and tuneable control of the oscillation amplitude enables the beams to be reused for several aperture measurements, as well as for other subsequent commissioning activities. Measurements performed with the new method are presented and compared with the current LHC transverse damper method for two different beam energies and two different operational optics.

A search for events with two displaced vertices from long-lived particle (LLP) pairs using data collected by the ATLAS detector at the LHC is presented. This analysis uses 139 fb-1 of proton-proton collision data at s=13 TeV recorded in 2015-2018. The search employs techniques for reconstructing vertices of LLPs decaying to jets in the muon spectrometer displaced between 3 and 14 m with respect to the primary interaction vertex. The observed numbers of events are consistent with the expected background and limits for several benchmark signals are determined. For the Higgs boson with a mass of 125 GeV, the paper reports the first exclusion limits for branching fractions into neutral long-lived particles below 0.1%, while branching fractions above 10% are excluded at 95% confidence level for LLP proper lifetimes ranging from 4 cm to 72.4 m. In addition, the paper present the first results for the decay of LLPs into tt¯ in the ATLAS muon spectrometer. © 2022 CERN.

Accurately describing the lattice dynamics and microscopic mechanism of thermal transport in materials with low-lying flat phonon modes remains an outstanding challenge due to the intrinsic strong anharmonicity. In this paper, we investigate the lattice dynamics and thermal transport in skutterudite YbFe4Sb12 using a state-of-the-art first-principles-based anharmonic phonon renormalization technique and a unified theory of lattice thermal transport. In contrast to the previous phenomenological models that introduce additional resonant scattering terms or hopping channels, we show that the unusual total lattice thermal conductivity in YbFe4Sb12 can be accurately predicted by considering anharmonic phonon renormalization and coherence contributions from the off-diagonal terms of heat flux operators. Both the cubic and quartic anharmonicities are essential for precisely predicting the significant shift in phonon energies. Specifically, the anharmonicity-induced phonon stiffening of the low-lying flat modes significantly enhances the thermal conductivity of particlelike phonons, e.g., by up to a factor of 1.6 at 300 K, by suppressing the cubic coupling strength and altering the scattering phase space, resulting in much-improved agreement with experiments. By further including the coherence contributions, the predicted total thermal conductivity increases by ∼22% throughout the entire temperature range, reproducing well the experimental values in both magnitude and temperature dependence. In this paper, we highlight the strong impact of higher-order anharmonicity on lattice dynamics and thermal transport in the filled skutterudite YbFe4Sb12. The insights gained in this paper will be helpful for manipulating the thermal properties of skutterudites and potentially other complex materials with strong anharmonicity, which can improve their performance in applications such as thermoelectrics, ferroelectrics, and photovoltaics. © 2022 American Physical Society.

Canonical discrete quantum error correction (DQEC) schemes use projective von Neumann measurements on stabilizers to discretize the error syndromes into a finite set, and fast unitary gates are applied to recover the corrupted information. Quantum error correction (QEC) based on continuous measurement, known as continuous quantum error correction (CQEC), in principle, can be executed faster than DQEC and can also be resource efficient. However, CQEC requires meticulous filtering of noisy continuous measurement data to reliably extract error syndromes on the basis of which errors could be detected. In this paper, we show that by constructing a measurement-based estimator (MBE) of the logical qubit to be protected, which is driven by the noisy continuous measurement currents of the stabilizers, it is possible to accurately track the errors occurring on the physical qubits in real time. We use this MBE to develop a continuous quantum error correction (MBE-CQEC) scheme that can protect the logical qubit to a high degree, surpassing the performance of DQEC, and also allows QEC to be conducted either immediately or in delayed time with instantaneous feedbacks., source:https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.4.033207

The 77Se(n,¿) reaction is of importance for 77Se abundance during the slow neutron capture process in massive stars. We have performed a new measurement of the 77Se radiative neutron capture cross section at the Neutron Time-of-Flight facility at CERN. Resonance capture kernels were derived up to 51 keV and cross sections up to 200 keV. Maxwellian-averaged cross sections were calculated for stellar temperatures between kT=5keV and kT=100keV, with uncertainties between 4.2% and 5.7%. Our results lead to substantial decreases of 14% and 19% in 77Se abundances produced through the slow neutron capture process in selected stellar models of 15M¿ and 2M¿, respectively, compared to using previous recommendation of the cross section., This work was supported by the UK Science and Facilities Council (ST/M006085/1), the MSMT of the Czech Republic, the Charles University UNCE/SCI/013 project, the European Research Council ERC-2015-StG No. 677497, and by the funding agencies of the participating institutes. In line with the principles that apply to scientific publishing and the CERN policy in matters of scientific publications, the n_TOF Col- laboration recognizes the work of Y. Kopatch and V. Furman (JINR, Russia), who have contributed to the experiment used to obtain the results described in this paper., Article signat per 131 autors/es: N. V. Sosnin , C. Lederer-Woods, M. Krtiˇcka, R. Garg, M. Dietz, M. Bacak, M. Barbagallo, U. Battino, S. Cristallo, L. A. Damone, M. Diakaki, S. Heinitz, D. Macina, M. Mastromarco, F. Mingrone, A. St. J. Murphy, G. Tagliente, S. Valenta, D. Vescovi, O. Aberle, V. Alcayne, S. Amaducci, J. Andrzejewski, L. Audouin, V. Bécares, V. Babiano-Suarez, F. Beˇcváˇr, G. Bellia, E. Berthoumieux, J. Billowes, D. Bosnar, A. Brown, M. Busso, M. Caamaño, L. Caballero, F. Calviño, M. Calviani, D. Cano-Ott, A. Casanovas, F. Cerutti, Y. H. Chen, E. Chiaveri, N. Colonna, G. Cortés, M. A. Cortés-Giraldo, L. Cosentino, C. Domingo-Pardo, R. Dressler, E. Dupont, I. Durán, Z. Eleme, B. Fernández-Domínguez, A. Ferrari, P. Finocchiaro, K. Göbel, A. Gawlik-Rami˛ega, S. Gilardoni, T. Glodariu, I. F. Gonçalves, E. González-Romero, C. Guerrero, F. Gunsing, H. Harada, J. Heyse, D. G. Jenkins, E. Jericha, F. Käppeler, Y. Kadi, A. Kimura, N. Kivel, M. Kokkoris, D. Kurtulgil, I. Ladarescu, H. Leeb, J. Lerendegui-Marco, S. Lo Meo, S. J. Lonsdale, A. Manna, T. Martínez, A. Masi, C. Massimi, P. Mastinu, F. Matteucci, E. A. Maugeri, A. Mazzone, E. Mendoza, A. Mengoni, V. Michalopoulou, P. M. Milazzo, A. Musumarra, A. Negret, R. Nolte, F. Ogállar, A. Oprea, N. Patronis, A. Pavlik, J. Perkowski, L. Piersanti, I. Porras, J. Praena, J. M. Quesada, D. Radeck, D. Ramos-Doval, T. Rauscher, R. Reifarth, D. Rochman, C. Rubbia, M. Sabaté-Gilarte, A. Saxena, P. Schillebeeckx, D. Schumann, A. G. Smith, A. Stamatopoulos, J. L. Tain, T. Talip, A. Tarifeño-Saldivia, L. Tassan-Got, P. Torres-Sánchez, A. Tsinganis, J. Ulrich, S. Urlass, G. Vannini, V. Variale, P. Vaz, A. Ventura, V. Vlachoudis, R. Vlastou, A. Wallner, P. J. Woods,T. Wright, and P. Žugec., Postprint (published version)

The dynamics of perturbed nonrotating black holes (BHs) can be described in terms of master equations of the wave type with a potential. In the frequency domain, the master equations become time-independent Schrödinger equations with no discrete spectrum. It has been recently shown that these wave equations possess an infinite number of symmetries that correspond to the flow of the infinite hierarchy of Korteweg–de Vries (KdV) equations. As a consequence, the infinite set of associated conserved quantities, the KdV integrals, are the same for all the different master equations that we can consider. In this paper we show that the BH scattering reflection and transmission coefficients characterizing the continuous spectrum can be fully determined via a moment problem, in such a way that the KdV integrals provide the momenta of a distribution function depending only on the reflection coefficient. We also discuss the existence and uniqueness of solutions, strategies to solve the moment problem, and finally show the case of the Pöschl-Teller potential where all the steps can be carried out analytically.

It has recently been shown that the dynamics of perturbed nonrotating black holes (BHs) admits an infinite number of symmetries that are generated by the flow of the Korteweg-de Vries (KdV) equation. These symmetries lead to an infinite number of conserved quantities that can be obtained as integrals of differential polynomials in the potential appearing in the gauge-invariant master equations describing the BH perturbations, the KdV integrals. These conserved quantities are the same for all the possible potentials, which means that they are invariant under Darboux transformations, and they fully determine the BHs transmission amplitudes, or greybody factors, via a moment problem. In this paper we introduce a new semianalytical method to obtain the greybody factors associated with BH scattering processes by solving the moment problem using only the KdV integrals. The method is based on the use of Padé approximants and we check it first by comparing with results from the case of a Pöschl-Teller potential, for which we have analytical expressions for the greybody factors. Then, we apply it to the case of a Schwarzschild BH and compare with results from computations based on the Wentzel–Kramers–Brillouin (WKB) approximation. It turns out that the new method provides accurate results for the BH greybody factors for all frequencies. The method is also computationally very efficient.

In this paper, we consider the possibility of generating the observed baryon asymmetry of the Universe via leptogenesis in the context of a triplet fermion-mediated type-III seesaw model of neutrino mass. With a hierarchical spectrum of the additional fermions, the lower bound on the lightest triplet mass is ∼1010 GeV for successful leptogenesis, a couple of orders higher than that of the type-I case. We investigate the possibility of lowering this bound in the framework of two-Higgs-doublet models. We find that the bounds can be lowered down to 107 GeV for a hierarchical spectrum. If we include the flavor effects, then a further lowering by one order of magnitude is possible. We also discuss if such lowering can be compatible with the naturalness bounds on the triplet mass.

The gauge bosons of the Pati-Salam model do not mediate proton decay at the renormalizable level, and for this reason it is possible to construct scenarios in which SU(4)⊗SU(2)R is broken at relatively low scales. In this paper we show that such low-scale models generate dimension-five operators that can give rise to nucleon decays at unacceptably large rates, even if the operators are suppressed by the Planck scale. We find an interesting complementarity between the nucleon-decay limits and the usual meson-decay constraints. Furthermore, we argue that these operators are generically present when the model is embedded into SO(10), lowering the suppression scale. Under reasonable assumptions, the lower limit on the breaking scale can be constrained to be as high as O(108) GeV.

In this paper, we analyze the quantum vacuum in a radiation-dominated and CPT-invariant universe by further imposing the quantum states to be ultraviolet regular i.e., satisfying the Hadamard/adiabatic condition. For scalar fields, this is enforced by constructing the vacuum via the states of low-energy proposal. For spin-12 fields, we extend this proposal for a FLRW spacetime and apply it for the radiation-dominated and CPT-invariant universe. We focus on minimizing the smeared energy density around the big bang and give strong evidence that the resulting states satisfy the Hadamard/adiabatic condition. These states are then self-consistent candidates as effective big bang quantum vacuum from the field theory perspective.

Many quantum speed limits for isolated systems can be generalized to also apply to closed systems. This is, for example, the case with the well-known Mandelstam-Tamm quantum speed limit. Margolus and Levitin derived an equally well-known and ostensibly related quantum speed limit, and it seems to be widely believed that the Margolus-Levitin quantum speed limit can be similarly generalized to closed systems. However, a recent geometrical examination of this limit reveals that it differs significantly from most known quantum speed limits. In this paper, we show that, contrary to the common belief, the Margolus-Levitin quantum speed limit does not extend to closed systems in an obvious way. More precisely, we show that for every hypothetical bound of Margolus-Levitin type, there are closed systems that evolve with a conserved normalized expected energy between states with any given fidelity in a time shorter than the bound. We also show that for isolated systems, the Mandelstam-Tamm quantum speed limit and a slightly weakened version of this limit that we call the Bhatia-Davies quantum speed limit always saturate simultaneously. Both of these evolution time estimates extend straightforwardly to closed systems. We demonstrate that there are closed systems that saturate the Mandelstam-Tamm but not the Bhatia-Davies quantum speed limit.

Many quantum speed limits for isolated systems can be generalized to also apply to closed systems. This is, for example, the case with the well-known Mandelstam-Tamm quantum speed limit. Margolus and Levitin derived an equally well-known and ostensibly related quantum speed limit, and it seems to be widely believed that the Margolus-Levitin quantum speed limit can be similarly generalized to closed systems. However, a recent geometrical examination of this limit reveals that it differs significantly from most known quantum speed limits. In this paper, we show that, contrary to the common belief, the Margolus-Levitin quantum speed limit does not extend to closed systems in an obvious way. More precisely, we show that for every hypothetical bound of Margolus-Levitin type, there are closed systems that evolve with a conserved normalized expected energy between states with any given fidelity in a time shorter than the bound. We also show that for isolated systems, the Mandelstam-Tamm quantum speed limit and a slightly weakened version of this limit that we call the Bhatia-Davies quantum speed limit always saturate simultaneously. Both of these evolution time estimates extend straightforwardly to closed systems. We demonstrate that there are closed systems that saturate the Mandelstam-Tamm but not the Bhatia-Davies quantum speed limit.

©2005 The American Physical Society. M.H.E. is supported by Secretaría de Estado de Educación y Universidades (Spain), and R.B. by the Universidad Complutense (Profesores en el Extranjero). This work is financed by the research project FIS2004-271 (Spain)., We present a generalization of the Green-Kubo expressions for thermal transport coefficients mu in complex fluids of the generic form mu=mu(infinity)+integral(infinity)(0) dtV(-1)< J(epsilon)exp(tL)J >(0), i.e. a sum of an instantaneous transport coefficient mu(infinity), and a time integral over a time correlation function in a state of thermal equilibrium between a current J and its conjugate current J(epsilon). The streaming operator exp(tL) generates the trajectory of a dynamical variable J(t)=exp(tL)J when used inside the thermal average <(...)>(0). These formulas are valid for conservative, impulsive (hard spheres), stochastic, and dissipative forces (Langevin fluids), provided the system approaches a thermal equilibrium state. In general mu(infinity)not equal 0 and J(epsilon)not equal J, except for the case of conservative forces, where the equality signs apply. The most important application in the present paper is the hard sphere fluid., Secretaría de Estado de Educación y Universidades (Spain), Universidad Complutense (Profesores en el Extranjero), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 1980 The American Physical Society. We are very indebted to Dr. M. Ramón, Dr. M.A. Rodríguez, and Dr. J. Usón for discussions. This paper was partly supported by Junta de Energía Nuclear, Madrid., It is shown that the noncausality of the Rarita-Schwinger equation in an external electromagnetic field can be avoided by the substitution of a subsidiary constraint by a subsidiary differential equation. As the number of degrees of freedom increases, the theory represents two kinds of articles with spin l/2 and spin 3/2. Some consequences are studied., Junta de Energía Nuclear, Madrid, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 1994 The American Physical Society. It is with great pleasure that we thank collaboration and illuminating conversations with Enrique Maciá. A.S. is also thankful to Alan Bishop for warm hospital ityat Los Alamos National Laboratory where this paper was written in part. Work at Leganes is supported by the Direccion General de Investigacion Cientifica y Tecnica (Spain) through project PB92-0248, and by the European Union Human Capital and Mobility Programme through Contract No. ERBCHRXCT930413. Work at Madrid is supported by Universidad Complutense through Project No. PR161/93-4811., We study how the in8uence of structural correlations in disordered systems manifests itself in experimentally measurable magnitudes, focusing on dc conductance of semiconductor superlattices with general potential pro6les. We show that the existence of bands of extended states in these structures gives rise to very noticeable peaks in the 6nite-temperature dc conductance as the chem ical potential is moved through the bands or as the temperature is increased from zero. On the basis of these results we discuss how dc conductance measurements can provide information on the location and width of the bands of extended states. Our predictions can be used to demonstrate experimentally that structural correlations inhibit the localization eKects of disorder., Direccion General de Investigacion Cientifica y Tecnica (Spain), Universidad Complutense, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

©2015 American Physical Society. We gratefully acknowledge Elena Beltrán de Heredia Rodríguez for checking the results and the equations in the paper. This work was supported by Ministerio de Ciencia e Innovación (Spain) through Grants No. FIS2010-17440 (F.J.C.), No. FIS2012-35723 (F.M.), and No. CSD2007-0010 (F.M.) (the last one as part of the Consolider Ingenio en Nanociencia Molecular Grant); Ministerio de Economía y Competitividad (Spain) Grant No. FIS2009-14650-C02-01 (F.M); and Comunidad Autónoma de Madrid (Spain) Grant No. S2009MAT-1507 (F.M.).V.G.A.-V. acknowledges support from Ministerio de Educación Cultura y Deporte (Spain) through the Becas de Colaboración program., Analytical expressions are obtained for the main magnitudes of a symmetrically constricted vesicle. These equations provide an easy and compact way to predict minimal requirements for successful constriction and its main magnitudes. Thus, they can be useful for the design of synthetic divisomes and give good predictions for magnitudes including constriction energy, length of the constriction zone, volume and area of the vesicle, and the stability coefficient for symmetric constriction. The analytical expressions are derived combining a perturbative expansion in the Lagrangian for small deformations with a cosine ansatz in the constriction region. Already the simple fourth-order (or sixth-order) approximation provides a good approximation to the values of the main physical magnitudes during constriction, as we show through comparison with numerical results. Results are for vesicles with negligible effects from spontaneous curvature, surface tension, and pressure differences. This is the case when membrane components generating spontaneous curvature are scarce, membrane trafficking is present with low energetic cost, and the external medium is isotonic, Comunidad de Madrid, Ministerio de Ciencia e Innovación (Spain), Ministerio de Economía y Competitividad (Spain), Ministerio de Educacion Cultura y Deporte (Spain) through the Becas de Colaboracion program, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 1980 The American Physical Society. We are very indebted to Dr. L. Vázquez and Dr. J. Usón for discussions. This paper was partly supported by Junta de Energía Nuclear, Madrid., A characterization of the noncausal behavior of a covariant wave equation is given in terms of the invariance of the hyperbolicity conditions. Some examples in which the Dirac field is not causal are studied., Junta de Energía Nuclear, Madrid., Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

©2003 The American Physical Society. The authors acknowledge financial support from the Dirección General de Enseñanza Superior e Investigación Científica (DGESCYT) under Grant Nos. PB 98-0673-C02-02 and BFM-2001-1017-C03 (E.L., G.R., and C.F.T.)., In a recent paper [Phys. Rev. Lett. 86, 2038 (2001)] a simple fluid with a particular density-dependent pair potential was shown to exhibit, together with the vapor-liquid transition, a liquid-liquid phase separation and it was evidenced that, in order to adequately define the correct boundaries of stability, a simulation procedure based on the use of local densities had to be devised. It was found that for certain thermodynamic states the potential drives the system toward a phase separation that is otherwise frustrated by the change in the interactions induced by density fluctuations. Therefore, when integral equations or global density simulations are used, the critical points estimated from the thermodynamics are not associated with divergent correlations and vice versa. Here, we will explore in depth this fluid and introduce a detailed account of the proposed local density simulation technique. The results presented bear general significance for density-dependent potentials, like those of liquid metals or charge-stabilized colloids., Dirección General de Enseñanza Superior e Investigación Científica (DGESCYT), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

©2009 The American Physical Society. We are indebted to Frans T. M. Nieuwstadt, who called our attention to the problem addressed in this research. We are indebted to the Spanish Ministerio de Educacion y Ciencia for supporting J. V. S. during a sabbatical leave at the Universidad Complutense de Madrid where this work was initiated and for continued support through Research Project No. FIS2008-03801., In this paper we investigate intrinsic thermally excited nonequilibrium velocity fluctuations in laminar planar Couette flow. For this purpose we have complemented the solution of the stochastic Orr-Sommerfeld equation for the intensity of the fluctuations of the wall-normal velocity, presented in a previous publication, with a solution of the stochastic Squire equation for the intensity of the fluctuations of the wall-normal vorticity. We have obtained exact solutions of these equations without boundary conditions and solutions in a Galerkin approximation when appropriate boundary conditions are included. These results enable us to make a quantitative assessment of the intensity of these nonequilibrium fluctuations, as well as of the related energy amplification, which are always present, even in the absence of any externally imposed noise., Spanish Ministerio de Educación y Ciencia, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2016 American Physical Society. A. V. thanks Victor Svensson for helpful discussions. M. G. E. is supported by the “Stichting voor Fundamenteel Onderzoek der Materie” (FOM), which is financially supported by the “Nederlandse Organisatie voor Wetenschappelijk Onderzoek” (NWO). I. S. is supported by the Spanish MECD Grants No. FPA2011-27853-CO2- 02 and No. FPA2014-53375-C2-2-P., All (un)polarized transverse momentum dependent functions (TMDs), both distribution and fragmentation functions, are defined with the same universal soft function, which cancels spurious rapidity divergences within an individual TMD and renders them well-defined hadronic quantities. Moreover, it is independent of the kinematics, whether it is Drell-Yan, deep inelastic scattering, or e^+e^−→2 hadrons. In this paper, we provide this soft function at next-to-next-to-leading order (NNLO), necessary for the calculation of all TMDs at the same order, and to perform the resummation of large logarithms at next-to-next-to-next-to-leading-logarithmic accuracy. From the results we obtain the D function at NNLO, which governs the evolution of all TMDs. This work represents the first independent and direct calculation of this quantity. Given the all-order relation through a Casimir scaling between the soft function relevant for gluon TMDs and the one for quark TMDs, we also obtain the first at NNLO. The used regularization method to deal with the rapidity divergences is discussed as well., Nederlandse Organisatie voor Wetenschappelijk Onderzoek” (NWO), Holanda, Ministerio de Educación, Cultura y Deporte (MECD), España, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 1985 The American Physical Society. We acknowledge the partial financial support from Comisión Asesora de Investigación Científica y Técnica (Spain)., In this paper, a previously published method to deal with proton decay in nuclear rnatter is generalized in order to account for eA'ects coming from the nuclear surface. The treatment is applied to nucleon decay in 16^O and 56^Fe., Comisión Asesora de Investigación Científica y Técnica (CAICYT), España, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©2010 The American Physical Society. This work was supported in part by the MICINN and the UCM–Banco Santander under Grants No. FIS2008-00209 and No. GR58/08-910556. The authors would also like to thank Gabriel Álvarez for some useful discussions, and the anonymous referees of a previous version of this paper for their helpful suggestions., We provide a rigorous proof of the fact that the level density of all known su (m) spin chains of Haldane-Shastry type associated with the A(N-1) root system approaches a Gaussian distribution as the number of spins N tends to infinity. Our approach is based on the study of the large-N limit of the characteristic function of the level density, using the description of the spectrum in terms of motifs and the asymptotic behavior of the transfer matrix., MICINN, UCM–Banco Santander, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 American Physical Society. We are extremely grateful to R. Woodard for his advice and guidance and to Tessa Baker, Joe Conlon, and Johannes Noller for discussions. P. G. F. acknowledges support from Leverhulme, STFC, BIPAC, and the Oxford Martin School and the hospitality of the Higgs Centre in Edinburgh while this paper was being completed. A. L. M. acknowledges support from MICINN (Spain) Projects No. FIS2011-23000 and Consolider-Ingenio MULTIDARK No. CSD2009-00064, the Salvador de Madariaga program, and the hospitality of Oxford BIPAC., We consider nonlocal gravity theories that include tensor nonlocalities. We show that in the cosmological context, the tensor nonlocalities, unlike scalar ones, generically give rise to growing modes. An explicit example with quadratic curvature terms is studied in detail. Possible consequences for recent nonlocal cosmological models proposed in the literature are also discussed., MICINN (Spain), Consolider-Ingenio MULTIDARK, Leverhulme, STFC, Oxford Martin School, BIPAC, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©2002 The American Physical Society. This work has been supported in part by the Spanish Ministerio de Ciencia y Tecnología under projects CICYT FPA 2000-0980, CICYT AEN 97-1693 and PB98-0782., In this paper we study the Yukawa Higgs-quark-quark interactions that are generated from radiative corrections of squarks and gluinos, in the minimal supersymmetric standard model. We compute the corrections to the effective action for Higgs and quark fields that are produced by explicit integration in the path integral formalism of all the squarks and gluinos at the one-loop level and order alpha(s). In addition, we consider the limit of nearly degenerate heavy squarks and gluinos, with masses much larger than the electroweak scale, and we derive the effective Lagrangian containing all the relevant new local Higgs-quark-quark interactions. We show that these new interactions do remain nonvanishing, even in the case of infinitely heavy supersymmetric particles and, therefore, we demonstrate explicitly the nondecoupling behavior of squarks and gluinos in Higgs bosons physics. We present the set of new Yukawa couplings and finally derive the corresponding one-loop, order alpha(s), corrections to the Higgs bosons partial decay widths into quarks., Spanish Ministerio de Ciencia y Tecnología, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 1974 The American Physical Society. We wish to express our appreciation to Dr. B. Carreras for carefully reading our manuscript and for very useful discussions and suggestions during the completion of this paper., The classical electromagnetic interactions of a nonlinear spinor field are studied in perturbation theory. When Pauli terms are included, the model describes with reasonable accuracy (within the assumed approximations) such properties of the nucleons as spin, charge, magnetic moment, and the proton mass. With no other information one can calculate the proton-neutron mass difference, which comes out of the wrong sign and of the same size as in quantum electrodynamics., Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2014 American Physical Society. Financial support was provided by the Spanish MICINN through Projects No. FIS2011-30145-C03-01 and No. FIS2011-30145-C03-02 (with FEDER contribution), and by the Junta de Andalucía through Project No. FQM219. R. C-R. acknowledges support from CSIC through the JAE-predoc program, cofunded by FSE., It is commonly accepted that general relativity is the only solution to the consistency problem that appears when trying to build a theory of interacting gravitons (massless spin-2 particles). Padmanabhan’s 2008 thought-provoking analysis raised some concerns that are having resonance in the community. In this paper we present the self-coupling problem in detail and explicitly solve the infinite-iterations scheme associated with it for the simplest theory of a graviton field, which corresponds to an irreducible spin-2 representation of the Poincaré group. We make explicit the nonuniqueness problem by finding an entire family of solutions to the self-coupling problem. Then we show that the only resulting theory which implements a deformation of the original gauge symmetry happens to have essentially the structure of unimodular gravity. This makes plausible the possibility of a natural solution to the first cosmological constant problem in theories of emergent gravity. Later on, we change for the sake of completeness the starting free-field theory to Fierz-Pauli theory, an equivalent theory but with a larger gauge symmetry. We indicate how to carry out the infinite summation procedure in a similar way. Overall, we conclude that as long as one requires the (deformed) preservation of internal gauge invariance, one naturally recovers the structure of unimodular gravity or general relativity but in a version that explicitly shows the underlying Minkowski spacetime, in the spirit of Rosen’s flat-background bimetric theory., Spanish MICINN, Junta de Andalucía, CSIC, FSE, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2002 American Physical Society. We thank P. A. Algarabel, J. Blasco, J. García, R. Ibarra, J. M. de Teresa, and especially Domingo González, for discussions. The authors acknowledge financial support from CICyT (Spain) through Grant Nos. PB96-0875, AEN99- 0990, FPA2000-0956, and FPA2000-1252. V.M.-M. was supported by E.C. Contract No. HPMF-CT-2000-00450., Considering the disorder caused in manganites by the substitution Mn→Fe or Ga, we accomplish a systematic study of doped manganites begun in previous papers. To this end, a disordered model is formulated and solved using the variational mean-field technique. The subtle interplay between double exchange, superexchange, and disorder causes similar effects on the dependence of T_(C) on the percentage of Mn substitution in the cases considered. Yet, in La_(2/3)Ca_(1/3)Mn_(1-y)Ga_(y)O_(3) our results suggest a quantum critical point (QCP) for y ≈ 0.1–0.2, associated to the localization of the electronic states of the conduction band. In the case of La_(x)Ca_(x)Mn_(1-y)Fe_(y)O_(3) (with x = 1/3,3/8) no such QCP is expected., CICyT (Spain), E.C., Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 1994 The American Physical Society. A.S. is thankful to Alan Bishop for warm hospitality at Los Alamos National Laboratory where this paper was written in part. Work at Madrid was supported by UCM through Project No. PR161/93-4811. Work at Leganes was supported by the DGICyT (Spain) through Project No. PB92-0248, and by the European Union Human Capital and Mobility Programrne through Contract No. ERBCHRXCT930413., We theoretically study electron transport in disordered, quantum-well-based, semiconductor superlattices with structural short-range correlations. Our system consists of equal-width square barriers and quantum wells with two different thicknesses. The two kinds of quantum wells are randomly distributed along the growth direction. Structural correlations are introduced by adding the constraint that one of the wells always appears in pairs. We show that such correlated disordered superlattices exhibit a strong enhancement of their dc conductance as compared to usual random ones, giving rise to quasi-ballistic-electron transport. Interestingly, this phenomenon is also detected in superlattices with random fluctuations of the well thicknesses. Our predictions can be used to demonstrate experimentally that structural correlations inhibit the localization effects of disorder and, most important, that it should be clearly observed even in the presence of imperfections., UCM, DGICyT (Spain), European Union, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1998 The American Physical Society. E.D. thanks Antti-Pekka Jauho for illuminating conversations and his warm hospitality at Mikroelektronik Centret where this paper was written in part. Work at Leganés and Madrid was supported by CICYT (Spain) under Projects Nos. MAT95-0325 and PB96-0199. E.D. gratefully acknowledges partial support from Fundación Universidad Carlos III de Madrid. G.P.B. gratefully acknowledges partial support by the Defense Advanced Research Projects Agency., We investigate the dynamics of a semiconductor superlattice driven by an ac electric field by solving numerically the one-dimensional time-dependent Schrodinger equation including interface roughness effects. Rabi oscillations between minibands are clearly identified under resonant conditions, but we show that their lifetime is controlled by a characteristic time that depends on the superlattice deviation from perfection and is independent of the electric field. Experiments for the observation of the predicted effects are proposed. [[S0163-1829(98)01327-7]., CICYT, Fundación Universidad Carlos III de Madrid, Defense Advanced Research Projects Agency, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2006 The American Physical Society., In this paper we evaluate the enhancement of nonequilibrium concentration fluctuations induced by the Soret effect when a binary fluid layer is subjected to a stationary temperature gradient. Starting from the fluctuating Boussinesq equations for a binary fluid in the large-Lewis-number approximation, we show how one can obtain an exact expression for the nonequilibrium structure factor in the long-wavelength limit for a fluid layer with realistic impermeable and no-slip boundary conditions. A numerical calculation of the wave-number dependence of the nonequilibrium enhancement and of the corresponding decay rate of the concentration fluctuations is also presented. Some physical consequences of our results are briefly discussed., Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2014 American Physical Society. A. A.-S. is grateful to A. Ashtekar, M. Fernández Méndez, and P. Martín Moruno for conversations. The authors acknowledge financial support from MICINN/ MINECO Grant No. FIS2011-30145-C03-02 from Spain., Different spacetime regions separated by horizons are not related to each other. We know that this statement holds for classical spacetimes. In this paper we carry out a canonical quantization of a Kantowski-Sachs minisuperspace model whose classical solutions exhibit both an event horizon and a cosmological horizon in order to check whether the above statement also holds from the quantum gravitational point of view. Our analysis shows that in fact this is not the case: Quantum gravitational states with support in spacetime configurations that exclusively describe either the region between horizons or outside them are not consistent in the sense that there exist unitary operators describing a natural notion of evolution that connect them. In other words, unitarity is only preserved in this quantization when dealing with the whole spacetime and not in each region separately., MICINN/ MINECO (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©2015 American Physical Society. Project TEC2014-57394-P (Spain) and CNPq 311741/2014-2 (Brazil) are acknowledged., In this paper, a meaningful classification of optical caustic beams in two dimensions is presented. It is demonstrated that the phase symmetry of the beam's angular spectrum governs the optical catastrophe, which describes the wave properties of ray singularities, for cusp (symmetric phase) and fold (antisymmetric phase) caustics. In contrast to the established idea, the caustic classification arises from the phase symmetry rather than from the phase power, thus breaking the commonly accepted concept that fold and cusp caustics are related to the Airy and Pearcey functions, respectively. Nevertheless, the role played by the spectral phase power is to control the degree of caustic curvature. These findings provide straightforward engineering of caustic beams by addressing the spectral phase into a spatial light modulator or glass plate., Ministerio de Economía y Competitividad (MINECO), España, Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brasil, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub