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Mega-Hertz Gravitational Waves from Neutron Star Mergers
No full textInternational audienceNeutron star mergers provide a unique laboratory for the study of strong-field gravity coupled to Quantum Chromodynamics in extreme conditions. The frequencies and amplitudes of the resulting gravitational waves encode invaluable information about the merger. Simulations to date have shown that these frequencies lie in the kilo-Hertz range. They have also shown that, if Quantum Chromodynamics possesses a first-order phase transition at high baryon density, then this is likely to be accessed during the merger dynamics. Here we show that this would result in the nucleation of superheated and/or supercompressed bubbles whose subsequent dynamics would produce gravitational waves in the Mega-Hertz range. We estimate the amplitude of this signal and show that it may fall within the expected sensitivity of future superconducting radio-frequency cavity detectors for mergers at distances up to tens of Mega-parsecs
Sensitivity of the Hyper-Kamiokande experiment to neutrino oscillation parameters using acceleration neutrinos
No full textInternational audienceThis paper describes the analysis to estimate the sensitivity of the Hyper-Kamiokande experiment to long-baseline neutrino oscillation parameters using accelerator (anti)neutrinos. Results are presented for the CPV discovery sensitivity and precision measurements of the oscillation parameters , , and . With the assumed Hyper-Kamiokande running plan, a CPV discovery is possible in less than three years in the case of maximal CPV and known MO.In the absence of external constraints on the MO, considering the MO sensitivity of the Hyper-Kamiokande measurement using atmospheric neutrinos, the time for a CPV discovery could be estimated to be around six years. Using the nominal final exposure of protons on target, corresponding to 10 years, with a ratio of 1:3 in neutrino to antineutrino beam mode, we expect to select approximately 10000 charged current, quasi-elastic-like, muon neutrino events, and a similar number of muon anti-neutrino events. In the electron (anti)neutrino appearance channels, we expect approximately 2000 charged current, quasi-elastic-like electron neutrino events and 800 electron antineutrino events. These larges event samples will allow Hyper-Kamiokande to exclude CP conservation at the significance level for over 60% of the possible true values of
Certified Per-Instance Unlearning Using Individual Sensitivity Bounds
No full textCertified machine unlearning can be achieved via noise injection leading to differential privacy guarantees, where noise is calibrated to worst-case sensitivity. Such conservative calibration often results in performance degradation, limiting practical applicability. In this work, we investigate an alternative approach based on adaptive per-instance noise calibration tailored to the individual contribution of each data point to the learned solution. This raises the following challenge: how can one establish formal unlearning guarantees when the mechanism depends on the specific point to be removed? To define individual data point sensitivities in noisy gradient dynamics, we consider the use of per-instance differential privacy. For ridge regression trained via Langevin dynamics, we derive high-probability per-instance sensitivity bounds, yielding certified unlearning with substantially less noise injection. We corroborate our theoretical findings through experiments in linear settings and provide further empirical evidence on the relevance of the approach in deep learning settings
From path integral quantization to stochastic quantization: a pedestrian's journey
No full textInternational audienceWe give two novel proofs that the path integral and stochastic quantizations of generic scalar Euclidean quantum field theories are equivalent. Our proofs rely on Taylor interpolations indexed by forests, in the fashion of constructive field theory. The first proof works at the level of individual terms in the Feynman expansion, with the forests appearing as spanning forests in Feynman graphs. The second one works at the level of the path integral and avoids the full expansion of the Feynman perturbation series
QUANTUM COHOMOLOGY AND IRRATIONALITY OF GUSHEL-MUKAI FOURFOLDS
No full textWe compute the small quantum cohomology of Gushel-Mukai fourfolds. Following [13], our computations imply that the very general ones are not rational. Following [8], and thanks to a suitable deformation of the small quantum cohomology ring, we also deduce that a rational Gushel-Mukai fourfold has the same rational cohomology as some K3 surface
A stochastic SIR model for cyber contagion: application to granular growth of firms and to insurance portfolio
No full textThis work evaluates the impact of contagious cyber-events, over a finite horizon, on firms' financial health and on a cyber insurance portfolio. Our approach builds on key empirical findings from economics and cybersecurity. In economics, firm size and growth-rate distributions are non-Gaussian and exhibit heavy tails. In cybersecurity, contagion dynamics strongly depend on firm size and environmental conditions. To capture these features, we propose a stochastic multi-group SIR model coupled with a granular model of firm growth. This framework allows us to quantify the financial impact of cyber-attacks on firms' revenues and on the insurer's portfolio. In the model, the arrival time and duration of cyber-attacks are driven by a combination of a Cox process and a Bernoulli random variable. The Cox process represents external contagion, with an intensity given by the force of infection derived from the stochastic SIR dynamics. The Bernoulli component captures contagion originating from an infected sister or subsidiary firm. Environmental variability enables stochastic scenario generation and the computation of aggregate exceedance probabilities, a standard metric in catastrophe modeling that provides insurers with immediate insight into the financial severity of an event. We apply the framework to the LockBit ransomware attacks observed between May and July 2024. For a portfolio of 2,929 firms located in Île-de-France, the model predicts that, with 50% probability, the insurer will need to compensate losses equivalent to up to two days of revenue over a 100-day cyber incident.</div
Validation du simulateur ICI de propagation d'épidémies à l'aide des données publiques recueillies pendant la première vague de la pandémie de COVID-19
No full textCe rapport a pour premier objectif de présenter le simulateur ICI de propagation d'épidémies fondé sur des jumeaux numériques de territoires géographiques,de populations synthétiques statistiquement conformes aux populations réelles, et à la simulation numérique des agendas horaires et des interactionssociales des individus, ainsi que des contaminations entre individus. Par méthode de Monte-Carlo ICI fournit des informations statistiques précises, différenciéespar zones géographiques et par catégories de population, sur les évolutions d'épidémies. Ces informations permettent de comparer quantitativement les impacts attendus de politiques sanitaires variées.Le second objectif est de dresser le bilan de nos tests sur la capacité d’ICI à reproduire quantitativement la dynamique épidémiologique et hospitalière observée lors de la première vague de Covid-19 à Paris, et d'analyser les capacités et les limites d'ICI pour des analyses contrefactuelles. Nos résultats montrent que d'ores et déjà ICI est un outil numérique opérationnel d'aide à la décision préalable aux interventions publiques contre les épidémies futures, prêt à être déployé sur des territoires multiples et pour des types variés d'épidémies
Accounting for exposure in 3D spatiotemporally contiguous heatwaves in Europe 1975-2024
No full textHeatwaves are becoming more common, intense, and widespread as climate change accelerates, increasing their effects on infrastructure, economies, and health. However, heatwaves' material and human effects cannot be adequately captured by their meteorological characteristics alone. In order to address this challenge, we propose a new heatwave index (HWMId_pop), which combines population exposure and meteorological data to provide a more accurate representation of heatwave impacts. Heatwaves are detected using a 3D-event framework, which considers heatwaves as spatiotemporal events that transcend conventional, spatially limited definitions. We validate this new index by comparing it to the impacts of heatwaves recorded in the EM-DAT disaster database for Europe from 1975 to 2021. Our results show that HWMId_pop outperforms traditional heatwave indices by correlating more closely with mortality data and demonstrating a superior ability to identify significant heatwave events. We also examine trends in several commonly used heatwave indices between 1975 and 2024, finding that our proposed index shows a significant increasing trend. We highlight that the increasing affected population, driven by the expanding spatial extent of heatwaves and the rising European population, poses growing health risks. Additionally, we argue that this index can be used as a guide to carry out gap-filling in heatwaves impacts database such as EM-DAT
Why should I comply with taxes if others don’t?: Social information and behavioral convergence: An experimental study
No full textInternational audienceThis experimental study investigates the impact of social information about others’ tax behavior on individuals’ subsequent tax decisions. Two types of social information are introduced: (i) the average income reported within the subject’s entire group, and (ii) the average income reported within a reference subgroup made of either peers or non-peers and chosen by the subject. Our results show that social information significantly affects subsequent tax decisions, with a change in reported income ranging from 15% to 30% of total income on average. Moreover, the influence of whole-group information on tax behavior appears to be stronger than that of chosen-group information. Quite strikingly, a majority of subjects show more interest in the tax behavior of non-peers than in that of peers. Finally, our data provide strong evidence of behavioral convergence towards the average tax behavior of others
Measurement of the Z production cross section and search for anomalous neutral triple gauge couplings in pp collisions at = 13 TeV
No full textInternational audienceA measurement of the fiducial cross section of the associated production of a Z boson and a high- photon, where the Z decays to two neutrinos, and a search for anomalous triple gauge couplings are reported. The results are based on data collected by the CMS experiment at the LHC in proton-proton collisions at = 13 TeV during 20162018, corresponding to an integrated luminosity of 138 fb. The fiducial Z cross section, where a photon with a greater than 225 GeV is produced in association with a Z, and the Z decays to a pair (Z()), is measured to be 23.3 fb, in agreement, within uncertainties, with the standard model prediction. The differential cross section as a function of the photon has been measured and compared with standard model predictions computed at next-to-leading and at next-to-next-to-leading order in perturbative quantum chromodynamics. Constraints have been placed on the presence of anomalous couplings that affect the ZZ and Z vertex using the spectrum of the photons. The observed 95% confidence level intervals for -conserving and are determined to be (3.4, 3.5) 10 and (6.8, 6.8) 10, and for and they are (2.2, 2.2) 10 and (4.1, 4.2) 10, respectively. These are the strictest limits to date on , and