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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250204T110000
DTEND;TZID=Europe/Paris:20250204T120000
DTSTAMP:20260415T035204
CREATED:20250127T214628Z
LAST-MODIFIED:20250207T111921Z
UID:13615-1738666800-1738670400@lmv.math.cnrs.fr
SUMMARY:CRYPTO: Antonio Flórez-Gutiérrez - Design and Analysis of ZIP-AES
DESCRIPTION:Based on « General Practical Cryptanalysis of the Sum of Round-Reduced Block Ciphers and ZIP-AES »: Antonio Flórez-Gutiérrez\, Lorenzo Grassi\, Gregor Leander\, Ferdinand Sybleyras and Yosuke Todo\, presented at ASIACRYPT 2024.\n\nIn recent years\, there has been an increased interest in the desgin of pseudorandom functions (PRFs)\, as they provide better security than block ciphers when used in some modes of operations. In this talk\, I will present a low-latency PRF called ZIP-AES and its associated ZIP construction. ZIP-AES consists of two branches\, one of which is 5-round AES\, and the other of which is inverse 5-round AES\, which are XORed to obtain the output. The main feature of ZIP-AES is that\, as it uses the AES round function and has a very short critical path\, a great software performance with exceptionally low latency can be achieved due to the existence of AES-specific instructions in most modern microprocessors. Furthermore\, it is designed so that its resistance to many cryptanalysis families can be deduced from existing cryptanalysis of AES. For differential and linear cryptanalysis\, it is possible to prove that any trail of ZIP-AES has an equivalent counterpart for full 10-round AES. For other cryptanalysis families\, we can recycle known attacks on reduced-round AES to quickly assess its resistance\, as is shown with integral cryptanalysis. The construction is also quite resistant to several kinds of key recovery attacks. This intermediate approach between security reduction of modes and dedicated cryptanalysis\, which we call general practical cryptanalysis\, can provide an effective and efficient way of assessing the security of new constructions\, as well as guide the design of cryptanalysis-friendly primitives in the future.
URL:https://lmv.math.cnrs.fr/evenenement/crypto-antonio-florez-gutierrez-design-and-analysis-of-zip-aes/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire CRYPTO
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250204T163000
DTEND;TZID=Europe/Paris:20250204T173000
DTSTAMP:20260415T035204
CREATED:20250120T104925Z
LAST-MODIFIED:20250207T111928Z
UID:13595-1738686600-1738690200@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Danil Gubarevich (LMV) : Generalised wheel conditions for reductive groups
DESCRIPTION:Consider the variety Comm_n of pairs of commuting n by n matrices\, it is invariant under the action of GL_n on the space of pairs of all matrices\, by simultaneous conjunction. The natural algebraic structure to associate with is equivariant Borel-Moore homology (or K-theory) of the variety. It turns out the direct sum by n of homologies of varieties Comm_n is equipped with an associative multiplication\, given by convolution. The conjugation action has a fixed point (0\,0)\, it’s embedding induces the pullback map of the algebra in hand into the direct sum of algebras of symmetric polynomials\, equipped itself with a shuffle multiplication for which the map is an algebra homomorphism. In the paper (arXiv: 2108.08779)\, where one considers arbitrary finite quiver\, Neguţ proves the image of the morphism is given by polynomials satisfying certain vanishing conditions. In this talk I’ll give the overview of the subject and announce the computation made for general reductive groups. This is a work in progress.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250206T140000
DTEND;TZID=Europe/Paris:20250206T153000
DTSTAMP:20260415T035204
CREATED:20250130T142424Z
LAST-MODIFIED:20250207T111934Z
UID:13649-1738850400-1738855800@lmv.math.cnrs.fr
SUMMARY:GT-Cluster : Pierre-Guy Plamondon : The category of Cohen-Macaulay modules over the algebra A of [JKS]
DESCRIPTION:First of a series of lectures on \nBernt Tore Jensen\, Alastair King\, Xiuping Su\, A categorification of Grassmannian cluster algebras\, arXiv:1309.7301
URL:https://lmv.math.cnrs.fr/evenenement/pierre-guy-plamondon-the-category-of-cohen-macaulay-modules-over-the-algebra-a-of-jks/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:GT-clusters
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250206T143000
DTEND;TZID=Europe/Paris:20250206T170000
DTSTAMP:20260415T035204
CREATED:20250131T104519Z
LAST-MODIFIED:20250207T111944Z
UID:13658-1738852200-1738861200@lmv.math.cnrs.fr
SUMMARY:Soutenance HDR de Yann Rotella : Éléments de Cryptanalyse
DESCRIPTION:Résumé : La cryptanalyse est un domaine de recherche consistant en l’étude approfondie du niveau de sécurité apporté par les constructions cryptographiques. Au travers d’exemples détaillés ou de points de vue plus génériques\, nous voyagerons au pays des techniques de cryptanalyse\, afin de comprendre un peu plus d’où vient la sécurité de constructions cryptographiques.\nUne première partie sera consacrée à l’étude de deux chiffrements (GEA-1 et Subterranean) et deux fonctions de hachage (Subterranean-XOF et Keccak). Nous verrons comment une représentation polynomiale des composants permet d’améliorer les attaques existantes.\nEnsuite\, nous présenterons un peu plus en détail ce qui est réalisable du point de vue d’un.e attaquant.e lorsque l’on connaît tout ou partie de la forme algébrique normale d’une fonction cryptographique. Nous partirons d’un exemple pratique\, le chiffrement Pyjamask\, et nous détaillerons des améliorations potentielles ainsi que les limitations actuelles des attaques intégrales.\nEnfin\, une dernière partie prendra un peu plus de hauteur en présentant des cryptanalyses génériques sur le mode duplex et sur des fonctions de compression.
URL:https://lmv.math.cnrs.fr/evenenement/soutenance-hdr-de-yann-rotella-elements-de-cryptanalyse/
LOCATION:Bâtiment Descartes\, amphi E
CATEGORIES:Soutenance HDR
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250211T133000
DTEND;TZID=Europe/Paris:20250211T153000
DTSTAMP:20260415T035204
CREATED:20250109T130736Z
LAST-MODIFIED:20250214T125151Z
UID:13548-1739280600-1739287800@lmv.math.cnrs.fr
SUMMARY:AG : Johannes Girsch (University of Sheffield) : Representations of GL_n over a p-adic field
DESCRIPTION:Abstract: I will give a basic introduction to the representation theory of \(GL_n(\mathbb{Q}_p) \) and describe some phenomena that do not appear in the complex representation theory of finite groups. In particular\, I will introduce the so-called Bernstein block decomposition. In the second half I will explain how one can use the theory of Bernstein-Zelevinsky derivatives and the notion of « highest derivative partition » to study Bernstein blocks. This is joint work with David Helm.
URL:https://lmv.math.cnrs.fr/evenenement/ag-johannes-girsch-university-of-sheffield/
CATEGORIES:Séminaire AG
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250213T140000
DTEND;TZID=Europe/Paris:20250213T150000
DTSTAMP:20260415T035204
CREATED:20241209T100852Z
LAST-MODIFIED:20250214T125158Z
UID:13456-1739455200-1739458800@lmv.math.cnrs.fr
SUMMARY:EDP : Annabelle Collin (Université de Nantes) : Sequential Data Assimilation for Oncology: Theory & Practice illustrations.
DESCRIPTION:Abstract: The development of PDE models capable of describing tumor growth may help to monitor disease progression or predict the efficacy of different therapeutic strategies. However\, to be truly informative or predictive\, these models need to be corrected and/or parameterized with available observations. The aim of this talk is to present some sequential data assimilation strategies that address these types of problems. A first\, rather simple example will be presented to introduce the concepts\, followed by two parts. More specifically\, in the first part\, we focus on a Luenberger observer that can handle 3D tumor front data. In the second part\, we focus on the combination of a Luenberger observer with a population-based Kalman observer\, which allows the use of repeated measurements in configurations with common priors (e.g.\, multiple subjects in a clinical trial or repeated biological measurements) when data are sparse or corrupted by noise. Theoretical results and numerical illustrations with synthetic and real data are presented for both parts.
URL:https://lmv.math.cnrs.fr/evenenement/edp-annabelle-collin-universite-de-nantes/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire EDP
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250213T153000
DTEND;TZID=Europe/Paris:20250213T163000
DTSTAMP:20260415T035204
CREATED:20241209T101000Z
LAST-MODIFIED:20250214T125204Z
UID:13458-1739460600-1739464200@lmv.math.cnrs.fr
SUMMARY:EDP : Simão Correia (Instituto Superior Técnico\, Lisbonne) : Blow-up stability of self-similar solutions to the modified Korteweg-de Vries equation
DESCRIPTION:Abstract : Self-similar solutions for the modified Korteweg-de Vries equation are of both physical and mathematical interest. On the physical side\, among several applications\, they model the formation of sharp corners in planar vortex patches. Mathematically\, they describe the asymptotic behavior of solutions for large times and present a blow-up behavior at the initial time. Due to their scaling invariance\, these solutions display several critical features (time decay\, spatial decay and regularity)\, which means that the existing theory is not applicable. In this talk\, I will show that the blow-up structure is stable under subcritical perturbations of any size. The proof relies on new a priori estimates for the modified KdV at critical regularity and on an infinite normal form reduction. This is joint work with R. Côte.
URL:https://lmv.math.cnrs.fr/evenenement/edp-simao-correia-instituto-superior-tecnico-lisbonne/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire EDP
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250214T100000
DTEND;TZID=Europe/Paris:20250214T110000
DTSTAMP:20260415T035204
CREATED:20240904T164342Z
LAST-MODIFIED:20250214T125212Z
UID:13094-1739527200-1739530800@lmv.math.cnrs.fr
SUMMARY:PS : Benjamin Dupuis (INRIA et ENS Paris) : Data-dependent Uniform Generalization Bounds
DESCRIPTION:We study data-dependent uniform generalization bounds by approaching the problem from a PAC-Bayesian perspective. We first apply the PAC-Bayesian framework on « random sets » in a rigorous way\, where the training algorithm is assumed to output a data-dependent hypothesis set after observing the training data. This approach allows us to prove data-dependent bounds\, which can be applicable in numerous contexts. To highlight the power of our approach\, we consider several applications of these new techniques.\nFirst\, we prove uniform bounds over the trajectories of continuous Langevin dynamics and stochastic gradient Langevin dynamics. These results provide novel information about the generalization properties of noisy algorithms.\nSecond\, we focus on the geometric terms appearing in our generalization bounds and use it to (1) simplify and recover existing fractal-based generalization bounds and (2) develop new topological bounds that are better adapted to discrete-time stochastic optimizers compared to the previous fractal approach. \nLinks to the papers:\n– https://arxiv.org/abs/2404.17442\n– https://arxiv.org/abs/2407.08723\n– https://arxiv.org/abs/2302.02766
URL:https://lmv.math.cnrs.fr/evenenement/ps-benjamin-dupuis-inria-et-ens-paris/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire PS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250214T113000
DTEND;TZID=Europe/Paris:20250214T123000
DTSTAMP:20260415T035204
CREATED:20240904T164618Z
LAST-MODIFIED:20250207T112138Z
UID:13098-1739532600-1739536200@lmv.math.cnrs.fr
SUMMARY:PS : Umut Simsekli (INRIA et ENS Paris) : Implicit Compressibility of Overparametrized Neural Networks Trained with Heavy-Tailed SGD
DESCRIPTION:Neural network compression has been an increasingly important subject\, not only due to its practical relevance\, but also due to its theoretical implications\, as there is an explicit connection between compressibility and generalization error. In this talk\, I will present a simple modification for SGD\, such that the outputs of the algorithm will be provably compressible without making any nontrivial assumptions. We will consider a one-hidden-layer neural network trained with SGD\, and show that if we inject additive heavy-tailed noise to the iterates at each iteration\, for any compression rate\, there exists a level of overparametrization such that the output of the algorithm will be compressible with high probability. To achieve this result\, we make two main technical contributions: (i) we prove a “propagation of chaos” result for a class of heavy-tailed stochastic differential equations\, and (ii) we derive error estimates for their Euler discretization. Our experiments suggest that the proposed approach not only achieves increased compressibility with various models and datasets\, but also leads to robust test performance under pruning\, even in more realistic architectures that lie beyond our theoretical setting. The talk is based on the following article: https://arxiv.org/pdf/2306.08125.pdf
URL:https://lmv.math.cnrs.fr/evenenement/ps-umut-simsekli-inria-et-ens-paris/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire PS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250218T133000
DTEND;TZID=Europe/Paris:20250218T153000
DTSTAMP:20260415T035204
CREATED:20250130T124657Z
LAST-MODIFIED:20250221T084814Z
UID:13632-1739885400-1739892600@lmv.math.cnrs.fr
SUMMARY:AG : Pierre-Guy Plamondon (LMV) : Représentations de carquois\, éventails et polytopes
DESCRIPTION:Résumé : Dans une première partie\, je ferai une introduction à quelques méthodes de calcul en théorie des représentations des carquois. Je choisirai des exemples où l’on peut tout faire à la main par une combinatoire des chemins dans un graphe. \nDans la deuxième partie\, je montrerai des exemples d’éventails et polytopes que l’on peut définir à partir de représentations de carquois. On retrouvera des polytopes connus (comme l’associaèdre et le permutoèdre). Si le temps le permet\, je parlerai d’une nouvelle construction de ces polytopes comme ensemble de solutions réelles positives d’un ensemble d’équations polynomiales. Dans certains cas particuliers\, cette construction est analogue à celle de variétés amassées (cluster varieties) au sens de Fock et Goncharov.
URL:https://lmv.math.cnrs.fr/evenenement/ag-pierre-guy-plamondon-lmv/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire AG
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250218T163000
DTEND;TZID=Europe/Paris:20250218T173000
DTSTAMP:20260415T035204
CREATED:20250214T154946Z
LAST-MODIFIED:20250221T084820Z
UID:13739-1739896200-1739899800@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Ricardo Canesin (Université Paris Cité) : Quiver Representations and Lie Theory
DESCRIPTION:Quiver representation theory is a fundamental tool in modern representation theory of associative algebras. A cornerstone of this field is Gabriel’s theorem\, which characterizes quivers with finitely many indecomposable representations as precisely those arising from Dynkin diagrams of type ADE. This result provided an early glimpse into a profound connection between quiver representations and Lie theory\, one that has since led to remarkable developments\, including Lusztig’s theory of canonical bases in quantum groups and Nakajima’s quiver varieties in geometric representation theory. In this talk\, we will give an accessible introduction to this interplay\, starting with the theorems of Gabriel and Kac and culminating in Ringel’s realization of the positive half of quantum groups through Ringel-Hall algebras.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-ricardo-canesin-universite-paris-cite-quiver-representations-and-lie-theory/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250220T140000
DTEND;TZID=Europe/Paris:20250220T153000
DTSTAMP:20260415T035204
CREATED:20250305T133937Z
LAST-MODIFIED:20250305T134750Z
UID:13810-1740060000-1740065400@lmv.math.cnrs.fr
SUMMARY:GT-Cluster: Esha Gupta: Rank one CM modules and profiles of grades modules
DESCRIPTION:
URL:https://lmv.math.cnrs.fr/evenenement/esha-gupta-rank-one-cm-modules-and-profiles-of-grades-modules/
CATEGORIES:GT-clusters
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250221T110000
DTEND;TZID=Europe/Paris:20250221T120000
DTSTAMP:20260415T035204
CREATED:20250127T214856Z
LAST-MODIFIED:20250221T125150Z
UID:13617-1740135600-1740139200@lmv.math.cnrs.fr
SUMMARY:CRYPTO - Jules Baudrin - L'auto-équivalence linéaire\, un point de vue unifié sur les familles connues de fonctions APN
DESCRIPTION:Les fonctions APN (Almost Perfect Nonlinear) sont les fonctions qui offrent une résistance optimale à la cryptanalyse différentielle. Étudiées depuis plus de 30 ans\, elles posent encore un grand nombre de problèmes ouverts. Le plus important est sans aucun doute le « grand problème APN » : existe-t-il une bijection APN de GF(2^n) dans lui-même quand n est pair et strictement supérieur à 6 ?\n\nIl a longtemps été conjecturé que les bijections APN n’existaient pas en dimension n paire\, jusqu’à l’identification par Dillon en 2009 d’une bijection APN de GF(2^6) dans la classe d’équivalence CCZ d’une fonction quadratique. Il s’agit cependant du seul exemple (à équivalence près) connu à ce jour.\nNaturellement\, un grand nombre de travaux a tenté de généraliser la construction de Dillon\, en cherchant de nouvelles fonctions APN en dimension paire puis en parcourant leur classe d’équivalence CCZ. Ces recherches incluent des travaux mathématiques qui définissent des familles de fonctions quadratiques APN par une forme polynomiale instantiable pour presque toutes valeurs de n\, mais aussi des travaux algorithmiques permettant de trouver un grand nombre de fonctions APN quadratiques pour de petites valeurs de n\, typiquement 8 ou 10. Parmi ces derniers\, une idée récente consiste à rechercher des fonctions APN uniquement parmi les fonctions linéairement auto-équivalentes\, i.e. pour lesquelles il existe deux bijections linéaires A\, B telles que B o F o A = F.\n\nDans un récent travail collaboratif avec Anne Canteaut et Léo Perrin\, nous avons montré que\, malgré des techniques très diverses\, l’immense majorité des familles infinies de fonctions APN connues partagent les mêmes propriétés structurelles\, puisqu’elles sont elles aussi\, (à équivalence près)\, linéairement auto-équivalentes. Après des rappels contextuels et une présentation détaillée de la boîte à outils d’analyse de fonctions booléennes\, nous aborderons donc ce point de vue unifié\, ce qu’il dit de notre compréhension actuelle des fonctions APN\, mais aussi les problèmes et perspectives ouverts (ou réouverts) par notre travail.
URL:https://lmv.math.cnrs.fr/evenenement/tba-jules-baudrin/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire CRYPTO
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250227T140000
DTEND;TZID=Europe/Paris:20250227T153000
DTSTAMP:20260415T035204
CREATED:20250305T133855Z
LAST-MODIFIED:20250305T134759Z
UID:13808-1740664800-1740670200@lmv.math.cnrs.fr
SUMMARY:GT-Cluster: Esha Gupta (LMV): Rank one CM modules and profiles of grades modules\, part 2
DESCRIPTION:
URL:https://lmv.math.cnrs.fr/evenenement/esha-gupta-lmv-rank-one-cm-modules-and-profiles-of-grades-modules-part-2/
CATEGORIES:GT-clusters
END:VEVENT
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