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We study the inverse problem of determining a time-dependent globally hyperbolic Lorentzian metric from the scattering operator for semilinear wave equations., Comment: 62 pages

Modern imaging technologies are widely based on classical principles of light or electromagnetic wave propagation. They can be remarkably sophisticated, with recent successes ranging from single molecule microscopy to imaging far-distant galaxies. However, new imaging technologies based on quantum principles are gradually emerging. They can either surpass classical approaches or provide novel imaging capabilities that would not otherwise be possible. {Here }we provide an overview {of the most recently developed quantum imaging systems, highlighting the non-classical properties of sources such as bright squeezed light, entangled photons, and single-photon emitters that enable their functionality.} We outline potential upcoming trends and the associated challenges, all driven by a central inquiry, which is to understand whether quantum light can make visible the invisible.

Despite the recent improvements in supporting Persistent Hardware Transactions (PHTs) on emerging persistent memories (PM), the poor performance of Read-Only (RO) transactions remains largely overlooked. We propose DUMBO, a new design for PHT that eliminates the two most crucial bottlenecks that hinder RO transactions in state-of-the-art PHT. At its core, DUMBO exploits advanced instructions that some contemporary HTMs provide to suspend (and resume) transactional access tracking. Our experimental evaluation with an IBM POWER9 system using the TPC-C benchmark shows that DUMBO can outperform the state of the art designs for persistent hardware (SPHT) and software memory transactions (Pisces), by up to 4.0x.

This paper is motivated by studies in neuroscience experiments to understand interactions between nodes in a brain network using different types of data modalities that capture different distinct facets of brain activity. To assess Granger-causality, we introduce a flexible framework through a general class of models that accommodates mixed types of data (binary, count, continuous, and positive components) formulated in a generalized linear model (GLM) fashion. Statistical inference for causality is performed based on both frequentist and Bayesian approaches, with a focus on the latter. Here, we develop a procedure for conducting inference through the proposed Bayesian mixed time series model. By introducing spike and slab priors for some parameters in the model, our inferential approach guides causality order selection and provides proper uncertainty quantification. The proposed methods are then utilized to study the rat spike train and local field potentials (LFP) data recorded during the olfaction working memory task. The proposed methodology provides critical insights into the causal relationship between the rat spiking activity and LFP spectral power. Specifically, power in the LFP beta band is predictive of spiking activity 300 milliseconds later, providing a novel analytical tool for this area of emerging interest in neuroscience and demonstrating its usefulness and flexibility in the study of causality in general., Comment: Paper submitted for publication

We discuss how to extract numerically the expected lowest quasi-normal mode (QNM) associated with the pressure anisotropy for a Bjorken flux evolution to equilibrium. This QNM was easily decoded subtracting the hydrodynamical attractors and was compared with other authors calculations. After evolutions with transients close to the expected lowest QNM the system goes to a tail (pure imaginary frequency) for late times. We analyze the relevance of Navier-Stokes, second order and Borel attractors at each stage of the evolution, which begins far-from-equilibrium and ends close to equilibrium., Comment: 7 pages, 6 figures; revised version; title, abstract and keywords added in Portuguese

We present an experiment investigating the rotational Doppler effect using a single trapped ion excited by two copropagating vortex laser beams. The setup isolates the azimuthal gradients of the fields, eliminating longitudinal and curvature effects. We provide a detailed characterization of the phenomenon by deterministically positioning a single ion across the beams, achieving a signal which depends on the angular velocity of the ion and the difference of optical orbital angular momentum between the two beams. The interpretation of the measurements is supported by numerical simulations and by a simplified analytical model. Our results reveal key properties of the rotational Doppler effect, showing that it increases approaching the center of the beam and that it is independent of the waist of the beam. This offers insights into the feasibility of super-kicks or super-Doppler shifts for sensing and manipulating atomic motion transverse to the beams' propagation direction., Comment: 5+6 pages, 2+4 figures

We study how to optimally segment a monopolistic market given a redistributive objective. Optimal redistributive segmentations (i) induce the seller to price progressively, i.e., richer consumers pay higher prices than poorer ones, and (ii) may require giving a higher profit than uniform pricing if the redistributive motive is strong. We further show that optimal redistributive segmentations are implementable via price-based regulation.

In tissue engineering, 3D scaffolds and chemical treatments are often used for providing a cell-friendly surface for improving cell adhesion and tissue growth. Indeed, the cell adhesion degree can be controlled by physical-chemical changes in the surface of substrates, such as wettability, surface charges and roughness. In this work, we describe the synthesis, characterization and cytocompatibility of photoresins useful for construction of cell scaffolds via two-photon polymerization. Additionally, we have demonstrated a simple surface treatment method that promotes cell adhesion. This method alters the surface charge of the polymer and enhances the adhesion of epithelial cells. Our results indicate an efficient approach for modifying the surface of biocompatible polymer scaffolds with the purpose of enhances the performance of cell functions suitable for tissue engineering and regenerative medicine.

Cosmic rays (CRs) interact with turbulent magnetic fields in the intestellar medium, generating nonthermal emission. After many decades of studies, the theoretical understanding of their diffusion in the ISM continues to pose a challenge. This study numerically explores a recent prediction termed "mirror diffusion" and its synergy with traditional diffusion mechanism based on gyroresonant scattering. Our study combines 3D MHD simulations of star-forming regions with test particle simulations to analyze CR diffusion. We demonstrate the significance of mirror diffusion in CR diffusion parallel to the magnetic field, when the mirroring condition is satisfied. Our results support the theoretical expectation that the resulting particle propagation arising from mirror diffusion in combination with much faster diffusion induced by gyroresonant scattering resembles a Levy-flight-like propagation. Our study highlights the necessity to reevaluate the diffusion coefficients traditionally adopeted in the ISM based on gyroresonant scattering alone. For instance, our simulations imply a diffusion coefficient $\sim10^{27}cm^2/s$ for particles with a few hundred TeV within regions spanning a few parsecs around the source. This estimate is in agreement with gamma-ray observations, which shows the relevance of our results for understanding of diffuse gamma-ray emission in star-forming regions.

Bug fixing is a crucial task in software maintenance to hold user trust. Although various automated fault localization techniques exist, they often require specific conditions to be effective. For example, Spectrum-Based Fault Localization (SBFL) techniques need at least one failing test to identify bugs, which may not always be available. Bug reports, particularly those with stack traces, provide detailed information on system execution failures and are invaluable for developers. This study focuses on utilizing stack traces from crash reports as fault-triggering tests for SBFL. Our findings indicate that only 3.33% of bugs have fault-triggering tests, limiting traditional SBFL efficiency. However, 98.3% of bugfix intentions align directly with exceptions in stack traces, and 78.3% of buggy methods are reachable within an average of 0.34 method calls, proving stack traces as a reliable source for locating bugs. We introduce a new approach, SBEST, that integrates stack trace data with test coverage to enhance fault localization. Our approach shows a significant improvement, increasing Mean Average Precision (MAP) by 32.22% and Mean Reciprocal Rank (MRR) by 17.43% over traditional stack trace ranking methods.

Samples of the monolithic silicon pixel ASIC prototype produced in 2022 within the framework of the Horizon 2020 MONOLITH ERC Advanced project were irradiated with 70 MeV protons up to a fluence of 1 x 1016 neq/cm2, and then tested using a beam of 120 GeV/c pions. The ASIC contains a matrix of 100 \mu m pitch hexagonal pixels, readout out by low noise and very fast frontend electronics produced in a 130 nm SiGe BiCMOS technology process. The dependence on the proton fluence of the efficiency and the time resolution of this prototype was measured with the frontend electronics operated at a power density between 0.13 and 0.9 W/cm2. The testbeam data show that the detection efficiency of 99.96% measured at sensor bias voltage of 200 V before irradiation becomes 96.2% after a fluence of 1 x 1016 neq/cm2. An increase of the sensor bias voltage to 300 V provides an efficiency to 99.7% at that proton fluence. The timing resolution of 20 ps measured before irradiation rises for a proton fluence of 1 x 1016 neq/cm2 to 53 and 45 ps at HV = 200 and 300 V, respectively.

Photonic Integrated Circuits (PIC)s are a promising contender for quantum information technologies. The spectral purity of photons is one of the key attributes of PIC photon-pair sources. The dual-pulse pump manipulation technique [1] showed >99% purity in ring-resonator photon-pair sources. Here, we have developed a PIC to shape a pulse into dual, triple and quadruple pulses and investigated the effect of these pump pulse configurations on the purity. Our results show that more complex configurations over dual-pulse do not result in comparatively higher purity but allow accurate control over choosing arbitrary values of the purity.

Here we show photon pair generation from ring resonator and waveguide structures in a hybrid silicon-BTO on insulator platform with a pulsed pump. Our analysis of single photon and coincidence generation rates show that Spontaneous Four-Wave Mixing is comparable to that expected from SOI devices of similar characteristics and find a $\gamma_{eff}$ of (14.7 $\pm$ 1.3) and (2.0 $\pm$ 0.3) MHz/mW$^{2}$ for ring resonator and waveguide structures respectively.

This paper establishes the optimal sub-Gaussian variance proxy for truncated Gaussian and truncated exponential random variables. The proofs rely on first characterizing the optimal variance proxy as the unique solution to a set of two equations and then observing that for these two truncated distributions, one may find explicit solutions to this set of equations. Moreover, we establish the conditions under which the optimal variance proxy coincides with the variance, thereby characterizing the strict sub-Gaussianity of the truncated random variables. Specifically, we demonstrate that truncated Gaussian variables exhibit strict sub-Gaussian behavior if and only if they are symmetric, meaning their truncation is symmetric with respect to the mean. Conversely, truncated exponential variables are shown to never exhibit strict sub-Gaussian properties. These findings contribute to the understanding of these prevalent probability distributions in statistics and machine learning, providing a valuable foundation for improved and optimal modeling and decision-making processes., Comment: 30 pages, 4 figures