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Constraints on gravitational waves from the 2024 Vela pulsar glitch
No full textInternational audienceAmong known neutron stars, the Vela pulsar is one of the best targets for gravitational-wave searches. It is also one of the most prolific in terms of glitches, sudden frequency changes in a pulsar's rotation. Such glitches could cause a variety of transient gravitational-wave signals. Here we search for signals associated with a Vela glitch on 29 April 2024 in data of the two LIGO detectors from the fourth LIGO--Virgo--KAGRA observing run. We search both for seconds-scale burst-like emission, primarily from fundamental (f-)mode oscillations, and for longer quasi-monochromatic transients up to four months in duration, primarily from quasi-static quadrupolar deformations. We find no significant detection candidates, but for the first time we set direct observational upper limits on gravitational strain amplitude that are stricter than what can be indirectly inferred from the overall glitch energy scale. We discuss the short- and long-duration observational constraints in the context of specific emission models. These results demonstrate the potential of gravitational-wave probes of glitching pulsars as detector sensitivity continues to improve
Cosmological and High Energy Physics implications from gravitational-wave background searches in LIGO-Virgo-KAGRA's O1-O4a runs
No full textInternational audienceWe search for gravitational-wave background signals produced by various early Universe processes in the Advanced LIGO O4a dataset, combined with the data from the earlier O1, O2, and O3 (LIGO-Virgo) runs. The absence of detectable signals enables powerful constraints on fundamental physics. We derive gravitational-wave background energy density upper limits from the O1-O4a data to constrain parameters associated with various possible processes in the early Universe: first-order phase transitions, cosmic strings, domain walls, stiff equation of state, axion inflation, second-order scalar perturbations, primordial black hole binaries, and parity violation. In our analyses, the presence of an astrophysical background produced by compact (black hole and neutron star) binary coalescences throughout the Universe is also considered. We address the implications for various cosmological and high energy physics models based on the obtained parameter constraints. We conclude that LIGO-Virgo data already yield significant constraints on numerous early Universe scenarios
GWTC-4.0: Population Properties of Merging Compact Binaries
No full textInternational audienceWe detail the population properties of merging compact objects using 158 mergers from the cumulative Gravitational-Wave Transient Catalog 4.0, which includes three types of binary mergers: binary neutron star, neutron star--black hole binary, and binary black hole mergers. We resolve multiple over- and under-densities in the black hole mass distribution: features persist at primary masses of and with a possible third feature at . These are departures from an otherwise power-law-like continuum that steepens above . Binary black holes with primary masses near are more likely to have less massive secondaries, with a mass ratio distribution peaking at , potentially a signature of stable mass transfer during binary evolution. Black hole spins are inferred to be non-extremal, with 90% of black holes having , and preferentially aligned with binary orbits, implying many merging binaries form in isolation. However, we find a significant fraction, 0.24-0.42, of binaries have negative effective inspiral spins, suggesting many could be formed dynamically in gas-free environments. We find evidence for correlation between effective inspiral spin and mass ratio, though it is unclear if this is driven by variation in the mode of the distribution or the width. (Abridged
A Dynamic Cartographic Tool Suite for Coastal Flooding Vulnerability Assessment
No full textInternational audienceIn this article we propose a generic cartographic toolkit for vulnerability assessment to hazard based on multi-criteria analysis, enabling the most vulnerable areas to be accurately mapped. To achieve this, we designed an adaptive cartographic grid, with cell size being adapted to the geographical features. We also created a synthetic map relying on an innovative method based on the Choquet integral and the MACBETH method, in collaboration with the emergency services of the Pays de la Loire region (France). Finally our toolkit includes a dynamic decision-making tool for firefighters working in these sensible areas, which might help the emergency services to intervene with a spatial resolution of 25m/25m, including interactive maps to ease decision making. In this way, this methodology provides a global view and knowledge of the issues and vulnerability upstream of the crisis. To illustrate the use of our toolkit, we use it on the coastal flooding hazard in a Batz-sur-mer, a city in Pays de la Loire. This tool will be transferable and adaptable to other study areas and other risks following this work
Presque vingt ans après la loi Pécresse, les universités de plus en plus surveillées au nom de l’autonomie
No full textThis article examines the evolution of university autonomy in France since the 2007 Law on the Liberties and Responsibilities of Universities (LRU). Initially presented as a reform aimed at strengthening institutional freedom and strategic governance, university autonomy has gradually been accompanied by an increasing number of evaluation procedures, reporting requirements, and contractual controls. While universities have assumed greater responsibility for their budgets and internal organization, many key decisions remain strongly regulated by the central state. In a context of widespread financial pressure and growing student numbers, this situation results in a constrained form of autonomy, where institutions bear financial risks without having sufficient room for strategic action. The article argues for a renewed balance between autonomy and public responsibility, including the reinforcement of core public funding, simplified governance mechanisms, and evaluation processes based on long-term academic development.Cet article analyse les transformations de l’autonomie universitaire en France depuis la loi relative aux libertés et responsabilités des universités (LRU) de 2007. Présentée initialement comme un levier de liberté stratégique et de modernisation de la gouvernance, cette autonomie s’est progressivement accompagnée d’une multiplication des dispositifs de contrôle, d’évaluation et de contractualisation. Les universités ont vu leurs responsabilités budgétaires et organisationnelles augmenter, tandis que de nombreuses décisions structurantes demeurent fortement encadrées par l’État. Dans un contexte de tension financière généralisée et de croissance des effectifs étudiants, cette évolution conduit à une autonomie sous contrainte, où les établissements assument le risque sans disposer de marges d’action suffisantes. L’article plaide pour une revalorisation de la subvention pour charges de service public, un pilotage simplifié et une évaluation inscrite dans le temps long afin de redonner aux universités de véritables capacités stratégiques
Compact segmented meta-liners for enhanced acoustic absorption with grazing flow
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: contributions du droit, du français, de la géographie, de l'histoire, des arts, des SVT et des mathématiques aux compétences citoyennes
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Toward More Reliable Artificial Intelligence: Reducing Hallucinations in Vision-Language Models
No full textInternational audienceVision-language models (VLMs) frequently generate hallucinated content plausible but incorrect claims about image content. We propose a training-free self-correction framework enabling VLMs to iteratively refine responses through uncertainty-guided visual re-attention. Our method combines multi-dimensional uncertainty quantification (token entropy, attention dispersion, semantic consistency, claim confidence) with attention-guided cropping of under-explored regions. Operating entirely with frozen, pretrained VLMs, our framework requires no gradient updates. We validate our approach on the POPE and MMHAL-BENCH benchmarks using the Qwen2.5-VL-7B [23] architecture. Experimental results demonstrate that our method reduces hallucination rates by 9.8 percentage points compared to the baseline, while improving object existence accuracy by 4.7 points on adversarial splits. Furthermore, qualitative analysis confirms that uncertainty-guided re-attention successfully grounds corrections in visual evidence where standard decoding fails. We validate our approach on Qwen2.5-VL-7B [23], with plans to extend validation across diverse architectures in future versions. We release our code and methodology to facilitate future research in trustworthy multimodal systems.1 illustrate this process on a real parking lot counting task, showing progressive uncertainty reduction from 0.52 to 0.27 and accuracy improvement from 12 to 21 cars. MotivationExisting approaches to hallucination mitigation in VLMs fall into three categories. Trainingbased methods [22, 11] use reinforcement learning from human feedback (RLHF) or specialized datasets to reduce hallucination rates during model development, but require extensive computational resources and may not generalize to new domains. External verification methods [25, 12] employ object detectors or knowledge bases to validate generated content, introducing dependencies on additional models and computational overhead. Decoding strategies [17, 4] modify the generation process through contrastive decoding or beam search variants, yet they operate without an explicit mechanism to localize where hallucinations originate.</div
Bronze Age copper supply in Mediterranean France: first results from lead isotope and chemical analyses of hoarded metalwork
No full textInternational audienceCopper supply networks in southern France are analysed on the basis of a study of five hoards of metal objects dating from the end of the Early Bronze Age (c. 17th-16th BCE) to the end of the Late Bronze Age (c. 9th BCE). A total of 73 inductively coupled plasma-optical emission spectroscopy elemental analyses were performed and 48 objects belonging to the different groups that could be identified from the elemental compositions were targeted for lead isotope analysis (multicollector-inductively coupled plasma mass spectrometry). The results clearly show that the same source was used for the various objects in each hoard, but that copper from different origins was used depending on the period. This reveals evolving supply networks that can be linked to the cultural interactions observed during this period. Towards the end of the Early Bronze Age or the beginning of the Middle Bronze Age (c. 17th-16th BCE), axe-ingots were imported into southern France along the Rhone corridor. The origin of the copper from which they are made could potentially be the Vosges massif. On the other hand, one of the major contributions of this study is to have demonstrated the use of copper originating from the Southeastern Alps during a late phase of the Middle Bronze Age and up to the Late Bronze Age (c. 14th-11th BCE). A form of packaging for this Alpine copper was as pick-ingots, and it was probably in this form that it arrived in southern France. This network was interrupted around the 9th century BCE and the populations of southern France returned to the exploitation of local minerals (Cabrières-Péret district). This research highlights the link between trade networks and cultural dynamics, showing that the circulation of raw materials also helps strengthen relations between communities