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First detection of ultra-high energy emission from gamma-ray binary LS I +61 303
No full textInternational audienceWe report the first detection of gamma-ray emission up to ultra-high-energy (UHE; 100 TeV) emission from the prototypical gamma-ray binary system LS I +61 303 using data from the Large High Altitude Air Shower Observatory (LHAASO). It is detected with significances of 9.2 in WCDA (1.4--30.5 TeV) and 6.2 in KM2A (25--267 TeV); in KM2A alone we identify 16 photon-like events above 100 TeV against an estimated 5.1 background events, corresponding to a 3.8 detection. These results provide compelling evidence of extreme particle acceleration in LS I +61 303. Furthermore, we observe orbital modulation at 4.0 confidence between 25 and 100 TeV, and a hint of energy-dependent orbital modulation. These features can be understood in a composite scenario in which leptonic and hadronic processes jointly contribute
Digging deeper: deep joint species distribution modeling reveals environmental drivers of Earthworm Communities
No full textInternational audienceEarthworms are key drivers of soil function, influencing organic matter turnover, nutrient cycling, and soil structure. Understanding the environmental controls on their distribution is essential for predicting the impacts of land use and climate change on soil ecosystems. While local studies have identified abiotic drivers of earthworm communities, broad-scale spatial patterns remain underexplored. We developed a multi-species, multi-task deep learning model to jointly predict the distribution of 77 earthworm species across metropolitan France, using historical (1960–1970) and contemporary (1990–2020) records. The model integrates climate, soil, and land cover variables to estimate habitat suitability. We applied SHapley Additive exPlanations (SHAP) to identify key environmental drivers and used species clustering to reveal ecological response groups. The joint model achieved high predictive performance (TSS >0.7) and improved predictions for rare species compared to traditional species distribution models. Shared feature extraction across species allowed for more robust identification of common and contrasting environmental responses. Precipitation variability, temperature seasonality, and land cover emerged as dominant predictors of earthworm distribution but differed in ranking across species and functional groups. Species clustering into response groups to climatic, land use and soil revealed distinct ecological strategies including a gradient of sensitivity to precipitation seasonality, differential habitat preferences in terms of vegetation cover and wetness and trade-offs between soil acidity and organic matter quality. Our study advances both the methodological and ecological understanding of soil biodiversity. We demonstrate the utility of interpretable deep learning approaches for large-scale soil fauna modeling and provide new insights into earthworm habitat specialization. These findings highlight land cover and seasonal climate variability as efficient proxies for soil biodiversity, providing actionable indicators for global monitoring initiatives and helping to identify habitat requirements of earthworm species to guide emerging earthworm conservation strategies in the face of global environmental change
Estimation in linear high dimensional Hawkes processes: a Bayesian approach
No full textInternational audienceIn this paper we study the frequentist properties of Bayesian approaches in linear high dimensional Hawkes processes in a sparse regime where the number of interaction functions acting on each component of the Hawkes process is much smaller than the dimension. We consider two types of loss function: the empirical L 1 distance between the intensity functions of the process and the L 1 norm on the parameters (background rates and interaction functions). Our results are the first results to control the L 1 norm on the parameters under such a framework. They are also the first results to study Bayesian procedures in high dimensional Hawkes processes
Les Quatre préceptes (al-aḥkām al-arba‘a). Le droit shi’ite imamite à l’épreuvede l’Occultation
No full textInternational audienceRésumé Le shi’isme est avant tout la religion de la figure sainte du Guide divin, de l’Imam. L’imamisme duodécimain (à douze imams), branche principale et de loin majoritaire du shi’isme (actuellement plus de 200 millions de fidèles) et religion d’Etat en Iran depuis le X/XVIe siècle, porte ce nom car sa lignée d’Imams se termine avec le douzième. D’après la tradition, celui-ci s’est occulté dans la première moitié du IV/Xe siècle, devenant ainsi « l’Imam caché », pour revenir à la Fin des temps en tant que Sauveur eschatologique. Or, sur le plan juridique, l’absence de l’Imam rend problématiques un certain nombre de pratiques religieuses. En l’occurrence, c’est le cas de ce qu’on appelle en droit imamite « les Quatre Préceptes » (al-aḥkām al-arba‘a). Il s’agit de : 1) la guerre sainte, le jihād, plus particulièrement le jihād offensif. 2) La collecte et la distribution de certaines taxes religieuses, plus précisément le Cinquième (al-khums), l’aumône (al-zakāt) et dans certains cas l’impôt foncier (al-kharāj). 3) Les peines légales (ḥadd, pluriel ḥudūd), c’est-à-dire les peines prévues par le Coran pour punir certaines fautes comme couper la main du voleur ou fouetter l’adultère. 4) Enfin, les prières collectives et plus singulièrement la prière collective du vendredi (ṣalāt al-jumu‘a). C’est que selon le droit imamite ancien, consigné dans le corpus des enseignements attribués aux Imams historiques et compilé dans les plus anciens ouvrages de Hadith tout le long des III-IV/IX-Xe siècles, ces prescriptions, pour être pratiquées et mises en application de manière adéquate, doivent être directement dirigées par la personne de l’Imam infaillible ou le représentant de l’Imam, explicitement et nommément désigné par ce dernier. Dans la période de l’Occultation qui, selon l’imamisme duodécimain, dure encore et durera jusqu’à la Fin des temps, l’Imam étant lui-même physiquement absent et n’étant pas capable de désigner nommément un représentant, l’application de ces Quatre Préceptes devient problématique. La thèse est l’étude de l’évolution des théories juridiques autour de ces Quatre Préceptes, les débats voire les conflits entre différents courants à leur sujet ainsi que la présentation des sources les concernant depuis l’avènement de l’Occultation au IV/Xe siècle jusqu’à nos jours. Une attention particulière y est accordée à l’époque safavide (X/XVIe au XII/XVIIIe siècle), époque de la déclaration de l’imamisme comme religion d’Etat dans l’empire iranien et celle de la naissance de ce qui est conventionnellement appelé « le clergé shi’ite ». A travers l’examen historique des différentes théories sur la légalité ou l’illégalité de la pratique des Quatre Préceptes pendant l’Occultation, on peut se rendre compte d’un phénomène historique majeur : le remplacement progressif de la figure de l’Imam et de son autorité spirituelle par celle du Docteur de la Loi, juriste-théologien mujtahid, et son autorité théologico-politique. Ce phénomène, commencé il y a plus d’un millénaire dans la Bagdad des Bouyides avec la rationalisation du shi’isme, atteint son apogée dans l’Iran révolutionnaire du XXe siècle et l’arrivée au pouvoir, pour la première fois, du clergé « rationaliste » à la tête d’un grand Etat.
Understanding Degradation Mechanisms in Water‐In‐Salt Electrolyte: Part 1—In Depth Soaking Investigation by Means of Multiprobe Techniques of LiFePO 4 versus TiS 2
No full textInternational audienceWater‐based liquid electrolytes for Li‐ion batteries offer the promise of improved safety and lower cost, but the energy density remains too low due to the narrow electrochemical stability window of water. Switching to the water‐in‐salt electrolyte approach appears to be an ideal solution as the electrochemical stability window of water is extended, thereby increasing the overall energy density. To date, despite an increase in electrochemical stability window, hydrogen evolution reaction (HER) and oxygen evolution reaction still occur during cycling, resulting in poor electrochemical performance. Most articles report that this phenomenon is intrinsically related to the change in potential within the cell. In the present work, we carry out a complete surface‐to‐bulk investigation of two well‐known electroactive materials used in the water‐in‐salt system, LiFePO 4 and TiS 2 . The aim in this first part is to understand the role of soaking the composite electrode in the water‐in‐salt electrolyte and to see if degradation occurs prior to any electrochemical measurement. We show that LiFePO 4 is a robust material that develops a surface layer rich in LiF, whereas TiS 2 decomposes at the top surface into a mixture of TiO 2 /TiS 2 or oxysulfide byproduct
Quenched properties of the Spectral Form Factor
No full textInternational audienceThe Spectral Form Factor (SFF) is defined as the modulus squared of the partition function in complex temperature for hermitian matrices and a suitable generalisation has been given in the non hermitian case. In this work we compute the properties of the quenched SFF for hermitian and non hermitian random matrices. Despite the fact that the (annealed) SFF is not self-averaging the quenched SFF is self-averaging but these two averages coincide up to subleading constants (at least for high enough temperatures). The fluctuations of are deep and one encounters thin spikes when moving close to a zero of the partition function. We study the partition function at late times by considering a suitable change of variable which turns out to be compatible with a Gumbel distribution. We note that the exponential tails of this distribution can be obtained by the deep spikes in the , namely the zeros of the partition function. We compare with the results obtained in isolated many-body systems and we show that same results hold at late times also for non-hermitian Hamiltonains and non-hermitian random matrices
Inverse Monoid Topological Quantum Field Theories and Open-Closed Grand Canonical Symmetric Orbifolds
No full textInternational audienceWe present an open-closed topological quantum field theory for inverse monoids which generalizes the theory of principle fiber bundles with finite gauge group over Riemann surfaces with boundary. The theory is constructed using the isomorphism between the semisimple inverse monoid algebra and a matrix algebra which lies at the heart of monoid structure and representation theory. An example that we study in detail is the Ivanov-Kerov monoid of partial permutations. We review motivations from string theory for the resulting grand canonical theory of covers with boundaries
