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Le spectromètre de neutrons à focalisation temporelle SHARP
No full textInternational audienceSHARP (Spectromètre Hybride Alpes Région Parisienne) is a new-generation time-of-flight neutron spectrometer installed at the Institut Laue-Langevin (ILL). It is designed to investigate dynamical processes in condensed matter with high energy resolution and broad experimental versatility. Developed as a complete upgrade of the former IN6 instrument, SHARP addresses key scientific challenges in soft matter, biology, energy materials, and solid-state physics, where precise measurements of atomic and molecular motions are essential. The main design objective is to achieve a higher counting rate while maintaining the IN6 strong neutron flux, by providing wide angular and energy coverage through multiple take-off angle geometries. Notable features include a fully vacuum-compatible secondary spectrometer, a retractable sample window allowing the detector tank to remain under vacuum while enabling experiments requiring controlled sample environments, and a bank of 240 position-sensitive 3 He detectors operating at 5 bar, ensuring enhanced spectral spatial definition. Compared to IN6, SHARP delivers a twofold increase in counting rate in the elastic region and a lower background. This paper outlines the scientific motivations behind the SHARP project, describes the main instrumental innovations, and demonstrates the instrument's performance through initial scientific results on molecular diffusion in zeolite, determinant of the selectivity of these materials for use in membrane-based gas separations.SHARP (Spectromètre Hybride Alpes Région Parisienne) est un spectromètre de neutrons à temps de vol de nouvelle génération installé à l’Institut Laue-Langevin (ILL). Il est conçu pour étudier les processus dynamiques dans la matière condensée avec une haute résolution en énergie et une grande polyvalence expérimentale. Développé comme une mise à niveau complète de l’ancien instrument IN6, SHARP répond à des défis scientifiques majeurs en matière de matière molle, biologie, matériaux pour l’énergie et physique du solide, où des mesures précises des mouvements atomiques et moléculaires sont essentielles.L’objectif principal de conception est d’obtenir un taux de comptage plus élevé tout en maintenant le fort flux de neutrons d’IN6, grâce à une large couverture angulaire et énergétique permise par plusieurs géométries d’angles de réflexion. Parmi les caractéristiques notables figurent un spectromètre secondaire entièrement compatible avec le vide, une fenêtre d’échantillon rétractable permettant de maintenir la cuve des détecteurs sous vide tout en réalisant des expériences nécessitant un environnement contrôlé autour de l’échantillon, ainsi qu’un ensemble de 240 détecteurs ³He sensibles à la position opérant à 5 bars, offrant une meilleure définition spatiale du spectre.Comparé à IN6, SHARP fournit un taux de comptage doublé dans la région élastique et un bruit de fond réduit. Cet article expose les motivations scientifiques du projet SHARP, décrit les principales innovations instrumentales, et démontre les performances de l’instrument à travers des premiers résultats scientifiques sur la diffusion moléculaire dans une zéolithe, déterminante pour la sélectivité de ces matériaux utilisés dans les séparations de gaz par membranes
AdapTT: Functoriality for Dependent Type Casts
No full textInternational audienceThe ability to cast values between related types is a leitmotiv of many flavors of dependent type theory, such as observational type theories, subtyping, or cast calculi for gradual typing. These casts all exhibit a common structural behavior that boils down to the pervasive functoriality of type formers. We propose and extensively study a type theory, called AdapTT, which makes systematic and precise this idea of functorial type formers, with respect to an abstract notion of adapters relating types. Leveraging descriptions for functorial inductive types in AdapTT, we derive structural laws for type casts on general inductive type formers
Optimizing the Viability of Interacting Systems with Evolutionary Algorithms
No full textInternational audienceViability theory studies the behavior of dynamical systems, with the aim of keeping them viable, or in other terms, keep their trajectories within desired constraints in the state space. Finding strategies to keep a dynamical system viable is already a challenge for optimization algorithms, but this task becomes even harder for multi-agent systems, where agents’ individual decision can influence the dynamics of the whole system. In this paper, we consider a multi-agent dynamic system and introduce an evolutionary approach for optimizing agents’ interaction behaviour, delimited by some a priori agreements, in the form of a set of commitments, with the objective of keeping the system viable. This approach is tested on the case-study of a collective project grouping several agritouristic activities on a shared place. Experimental results show that it is possible to find a set of agents’ commitments that can maintain system viability, supporting the proposed framework’s effectiveness
Normal Rank E-Order Interval Observer Design for Continuous Linear Time-Invariant Systems With Unknown Input and Bounded Disturbances
No full textInternational audienceIn this paper, an interval observer for continuous linear time‐invariant systems with unknown input and bounded disturbances is proposed. Usually, the design of such observers is based on the cooperative property of the considered system dynamics, which is hard to satisfy in many cases. To overcome this issue, in a recent work, it has been shown that under some assumptions, the cooperativity of the studied system can be ensured by means of a time‐varying change of coordinates. However, a constructive method for the design of the observer gain, making the observation error dynamics simultaneously positive and stable, is still missing and remains an open problem, especially in the context of unknown input. In this paper, a constructive approach is provided to obtain not only the observer gain but also a new gain that cancels the unknown input of the system and reduces the effect of the bounded disturbances. The proposed approach also allows for estimating the bounds of the unknown input. The efficiency of the proposed methodology is shown through numerical simulations and is compared with simulations resulting from a new method proposed in a recent work
Foreground removal in HI 21 cm intensity mapping under frequency-dependent beam distortions
No full textInternational audienceNeutral hydrogen (HI) intensity mapping with single-dish experiments is a powerful approach for probing cosmology in the post-reionization epoch. However, the presence of bright foregrounds over four orders of magnitude stronger than the HI signal makes its extraction highly challenging. While all methods perform well when assuming a Gaussian beam degraded to the worst resolution, most of them degrade significantly in the presence of a more realistic beam model. In this work, we investigate the performance of SDecGMCA. This method extends DecGMCA to spherical data, combining sparse component separation with beam deconvolution. Our goal is to evaluate this method in comparison with established foreground removal techniques, assessing its ability to recover the cosmological HI signal from single-dish intensity mapping observations under varying beam conditions. We use simulated HI signal and foregrounds, covering the frequency ranges relevant to MeerKAT and SKA-Mid. The foreground removal techniques tested fall into two main categories: model-fitting methods (polynomial and parametric) and blind source separation methods (PCA, ICA, GMCA, and SDecGMCA). Their effectiveness is evaluated based on the recovery of the HI angular and frequency power spectra under progressively more realistic beam conditions. While all methods perform adequately under a uniform degraded beam, SDecGMCA remains robust when frequency-dependent beam distortions are introduced. In the oscillating beam case, SDecGMCA suppresses the spurious spectral peak at and achieves accuracy at intermediate angular scales (), outperforming other methods. Beam inversion, however, remains intrinsically unstable beyond , setting a practical limit on the method
Fractal dimensions of complex networks: advocating for a topological approach
No full textTopological Data Analysis (TDA) uses insights from topology to create representations of data able to capture global and local geometric and topologicalproperties. Its methods have successfully been used to develop estimations of fractal dimensions for metric spaces that have been shown to outperform existingtechniques. In a parallel line of work, networks are ubiquitously used to model a variety of complex systems. Higher-order interactions, i.e., simultaneous interactions between more than two nodes, are wide-spread in social and biological systems, and simplicial complexes, used in TDA, can capture important structural and topological properties of networks by modelling such higher-order interactions. In this position paper, we advocate for methods from TDA to be used to estimate fractal dimensions of complex networks, we discuss the possible advantages of such an approach and outline some of the challenges to be addressed
Search for charged Higgs bosons decaying into top and bottom quarks in lepton+jets final states in proton-proton collisions at = 13 TeV
No full textInternational audienceA search is presented for charged Higgs bosons (H) in proton-proton (pp) collision events via the pp (b)H processes, with H decaying into top (t) and bottom (b) quarks. The search targets final states with one lepton, missing transverse momentum, and two or more b jets. The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb. We search for charged Higgs bosons in the 200 GeV to 1 TeV mass range. The results are interpreted within the generalized two-Higgs-doublet model (g2HDM). This model predicts additional Yukawa couplings of the Higgs bosons to the top quark , the top and charm quark , and the top and up quark . This search focuses on the real components of and , which are probed up to values of unity. An excess is observed with respect to the standard model expectation with a local significance of 2.4 standard deviations for a signal with an H boson mass () of 600 GeV. Limits are derived on the product of the cross section (pp (b)H) and branching fraction (H tb, t b), where = e, . The values of 0.150.5 are excluded at 95% confidence level, depending on the and assumptions. The results represent the first search for charged Higgs bosons within the g2HDM framework and complement the existing results on additional neutral Higgs bosons
Superfluid fraction in the crystal phase of the inner crust of neutron stars
No full textInternational audienceIn the most extended layer of the inner crust of neutron stars, nuclear matter is believed to form a crystal of clusters immersed in a superfluid neutron gas. Here we analyze this phase of matter within fully self-consistent Hartree-Fock-Bogoliubov calculations using Skyrme-type energy density functionals for the mean field and a separable interaction in the pairing channel. The periodicity of the lattice is taken into account using Bloch boundary conditions, in order to describe the interplay between band structure and superfluidity. A relative flow between the clusters and the surrounding neutron gas is introduced in a time-independent way. As a consequence, the complex order parameter develops a phase, and in the rest frame of the superfluid one finds a counterflow between neutrons inside and outside the clusters. The neutron superfluid fraction is computed from the resulting current. Our results indicate that at densities above 0.03 fm, more than 90% of the neutrons are effectively superfluid, independently of the detailed choice of the interaction, cluster charge, and lattice geometry. This fraction is only slightly lower than the one obtained recently within linear response theory on top of the Bardeen-Cooper-Schrieffer approximation, and it approaches the hydrodynamic limit for strong pairing. As a consequence, it is likely that the inner crust alone can provide a sufficient superfluid angular momentum reservoir to explain pulsar glitches
Search for heavy neutral leptons in B-meson decays
No full textInternational audienceA search for long-lived heavy neutral leptons produced in B-meson decays and decaying to a final state is performed with data collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of . The results are interpreted in both lepton-number-conserving and lepton-number-violating scenarios. No significant excess is observed. Constraints are placed on the squared mixing element to the active muon neutrino, under the assumption that couplings to other lepton flavours are negligible, in the mass range of - GeV
Investigating the Effects of Augmented Reality on Message Credibility When Visualizing Environmental Impacts
No full textInternational audienceAugmented reality (AR) has increasingly been used to communicate environmental impacts, offering greater engagement than conventional displays. However, its effect on message credibility—how much people believe in the content of the communication—remains unclear. In a preregistered study, we compared the perceived credibility of environmental information presented via visualizations on an AR headset or a desktop display. We created display-specific visual encodings (3D concrete for AR, 2D bar charts for desktop) and added two control conditions to cross display and encoding. We found no difference in message credibility between AR and desktop, though concrete AR was rated most engaging. Supplementary material is available at https://osf.io/n4p5c/