1,197 Works

Boundary calculus on conformally compact manifolds, and a boundary Yamabe problem

A. Rod Gover
On conformally compact manifolds of arbitrary signature I will describe a natural boundary calculus for computing the asymptotics of a class of natural boundary problems. This is applied to the non-linear problem of finding, conformally, a conformally compact constant scalar curvature metric on the interior of a manifold with boundary. This problem was studied from a different point of view by Andersson, Chrusciel, Friedrich (ACF) in 1992. They identified a conformal submanifold invariant that obstructs...

Kodaira dimension of algebraic fiber spaces over abelian varieties or projective surfaces

Junyan Cao
Let $f : X \to Y$ be a fibration between two projective manifolds. The Iitaka’s conjecture predicts that the Kodaira dimension of $X$ is larger than the sum of the Kodaira dimension of $X$ and the Kodaira dimension of the generic fiber. We explain a proof of the Iitaka conjecture for algebraic fiber spaces over abelian varieties or projective surfaces. It is a joint work with Mihai Paun.

Quantum $\mathfrak{sl}_n$ knot cohomology and the slice genus

Andrew Lobb
We will give an overview of the information about the smooth slice genus so far yielded by the quantum $\mathfrak{sl}_n$ knot cohomologies.

Efficient iterative solvers: FETI methods with multiple search directions

François-Xavier Roux
In domain decomposition methods, most of the computational cost lies in the successive solutions of the local problems in subdomains via forward-backward substitutions and in the orthogonalization of interface search directions. All these operations are performed, in the best case, via BLAS-1 or BLAS-2 routines which are inefficient on multicore systems with hierarchical memory. A way to improve the parallel efficiency of the method consists in working with several search directions, since multiple forward-backward substitutions...

Operators in ergodic theory - Lecture 2: Dilations and joinings

Markus Haase
The titles of the of the individual lectures are: 1. Operators dynamics versus base space dynamics 2. Dilations and joinings 3. Compact semigroups and splitting theorems

Uncertainty principles for discrete Schrödinger evolutions

Eugenia Malinnikova
We consider solutions of the semi-discrete Schrödinger equation (where time is continuous and spacial variable is discrete), $\partial_tu = i(\Delta_du + V u)$, where $\Delta_d$ is the standard discrete Laplacian on $\mathbb{Z}^n$ and $u : [0, 1] \times \mathbb{Z}^d \to \mathbb{C}$. Uncertainty principle states that a non-trivial solution of the free equation (without potential) cannot be sharply localized at two distinct times. We discuss different extensions of this result to equations with bounded potentials. The...

Wavelets and signal processing: a match made in heaven

Martin Vetterli
In this talk, we will briefly look at the history of wavelets, from signal processing algorithms originating in speech and image processing, and harmonic analysis constructions of orthonormal bases. We review the promises, the achievements, and some of the limitations of wavelet applications, with JPEG and JPEG2000 as examples. We then take two key insights from the wavelet and signal processing experience, namely the time-frequency-scale view of the world, and the sparsity property of wavelet...

Fractional Poisson process: long-range dependence and applications in ruin theory

Romain Biard
We study a renewal risk model in which the surplus process of the insurance company is modeled by a compound fractional Poisson process. We establish the long-range dependence property of this non-stationary process. Some results for the ruin probabilities are presented in various assumptions on the distribution of the claim sizes.

Hyperbolic triangles with no positive Neumann eigenvalues

Christopher Judge
In joint work with Luc Hillairet, we show that the Laplacian associated with the generic finite area triangle in hyperbolic plane with one vertex of angle zero has no positive Neumann eigenvalues. This is the first evidence for the Phillips-Sarnak philosophy that does not depend on a multiplicity hypothesis. The proof is based an a method that we call asymptotic separation of variables.

About mathematical modelling for microbial ecosystems with control and design perspectives

Alain Rapaport
The mathematical model of the chemostat has been extensively studied and extended from the eightees, not only as a mathematical representation of the chemostat device invented in the fifties, but also as a general model of resource/consumer dynamics in microbial ecosystems, such as in marine ecology, food fermentation, waste-water treatment, biotechnology. I will present a survey of some recent and less recent results about extensions of this model, that concern the roles of spatialization, density...

Stable rationality - Lecture 1

Alena Pirutka
Let X be a smooth and projective complex algebraic variety. Several notions, describing how close X is to projective space, have been developed: X is rational if an open subset of X is isomorphic to an open of a projective space, X is stably rational if this property holds for a product of X with some projective space, and X is unirational if X is rationally dominated by a projective space. A classical Lüroth problem...

Colouring graphs with no odd holes, and other stories

Paul D. Seymour
The chromatic number $\chi(G)$ of a graph $G$ is always at least the size of its largest clique (denoted by $\omega(G)$), and there are graphs $G$ with $\omega(G)=2$ and $\chi(G)$ arbitrarily large. On the other hand, the perfect graph theorem asserts that if neither $G$ nor its complement has an odd hole, then $\chi(G)=\omega(G)$ . (A "hole" is an induced cycle of length at least four, and "odd holes" are holes of odd length.) What...

Metamodels for uncertainty quantification and reliability analysis

Stefano Marelli
Uncertainty quantification (UQ) in the context of engineering applications aims aims at quantifying the effects of uncertainty in the input parameters of complex models on their output responses. Due to the increased availability of computational power and advanced modelling techniques, current simulation tools can provide unprecedented insight in the behaviour of complex systems. However, the associated computational costs have also increased significantly, often hindering the applicability of standard UQ techniques based on Monte-Carlo sampling. To...

Introduction to hyperbolic sigma models and Edge Reinforced Random Walk

Tom Spencer
This talk will introduce two statistical mechanics models on the lattice. The spins in these models have a hyperbolic symmetry. Correlations for these models can be expressed in terms of a random walk in a highly correlated random environment. In the SUSY hyperbolic case these walks are closely related to the vertex reinforced jump process and to the edge reinforced random walk. (Joint work with M. Disertori and M. Zirnbauer.)

Functional convergence for dependent heavy-tailed models

Adam Jakubowski
The Skorokhod space is natural for modeling trajectories of most time series with heavy tails. We give a systematic account of topologies on the Skorokhod space. The applicability of each topology is illustrated by examples of suitable dependent stationary sequences, for which the corresponding functional limit theorem holds.

Variational and non-Archimedean aspects of the Yau-Tian-Donaldson conjecture

Sébastien Boucksom
I will discuss some recent developments in the direction of the Yau-Tian-Donaldson conjecture, which relates the existence of constant scalar curvature Kähler metrics to the algebro-geometric notion of $K$-stability. The emphasis will be put on the use of pluripotential theory and the interpretation of $K$-stability in terms of non-Archimedean geometry.

Liouville's inequality for transcendental points on projective varieties

Carlo Gasbarri
Liouville inequality is a lower bound of the norm of an integral section of a line bundle on an algebraic point of a variety. It is an important tool in may proofs in diophantine geometry and in transcendence. On transcendental points an inequality as good as Liouville inequality cannot hold. We will describe similar inequalities which hold for "many" transcendental points and some applications

Interview au CIRM : David Ruelle

David Ruelle
David Ruelle est professeur honoraire de Physique Théorique à l’Institut des Hautes Études Scientifiques (IHÉS). Il a reçu la médaille Matteucci en 2004, en 2006 le Prix Henri-Poincaré et en 2014 la Médaille Max-Planck pour l'ensemble de ses travaux.

Terminologie des données encyclopédiques et politique de repérage

Irène Passeron, Alexandre Guilbaud, Marie Leca-Tsiomis & Alain Cernuschi
La richesse du contenu de l'Encyclopédie nécessite la définition d'un protocole de présentation et d'éclairage critique se déclinant à plusieurs échelles : aux textes de présentations généraux (de tel volume, de tel article ou ensemble d'articles) et notes ponctuelles classiques s'ajouteront à la fois la possibilité de mettre en valeur les nombreux éléments caractéristiques constitutifs du texte encyclopédique (les titres des articles, les désignants, les renvois vers d'autres articles, les signatures des encyclopédistes, les mentions...

Variational formulas, Busemann functions, and fluctuation exponents for the corner growth model with exponential weights - Lecture 1

Timo Seppäläinen
Variational formulas for limit shapes of directed last-passage percolation models. Connections of minimizing cocycles of the variational formulas to geodesics, Busemann functions, and stationary percolation.

Analytic torsion for locally symmetric spaces of finite volume

Werner Müller
This is joint work with Jasmin Matz. The goal is to introduce a regularized version of the analytic torsion for locally symmetric spaces of finite volume and higher rank. Currently we are able to treat quotients of the symmetric space $SL(n,\mathbb{R})/SO(n)$ by congruence subgroups of $SL(n,\mathbb{Z})$. The definition of the analytic torsion is based on the study of the renormalized trace of the corresponding heat operators. The main tool is the Arthur trace formula. I...

The compressed annotation matrix: an efficient data structure for persistent cohomology

Clément Maria
The persistent homology with coefficients in a field F coincides with the same for cohomology because of duality. We propose an implementation of a recently introduced algorithm for persistent cohomology that attaches annotation vectors with the simplices. We separate the representation of the simplicial complex from the representation of the cohomology groups, and introduce a new data structure for maintaining the annotation matrix, which is more compact and reduces substancially the amount of matrix operations....

Homotopy theory of strict $\omega$-categories and its connections with homology of monoids - Lecture 3

François Métayer
In the first part, we describe the canonical model structure on the category of strict $\omega$-categories and how it transfers to related subcategories. We then characterize the cofibrant objects as $\omega$-categories freely generated by polygraphs and introduce the key notion of polygraphic resolution. Finally, by considering a monoid as a particular $\omega$-category, this polygraphic point of view will lead us to an alternative definition of monoid homology, which happens to coincide with the usual one.

Competitive populations with vertical and horizontal transmissions

Sylvie Méléard
Horizontal transfer of information is recognized as a major process in the evolution and adaptation of population, especially micro-organisms. There is a large literature but the previous models are either based on epidemiological models or population genetics stochastic models with constant population size. We propose a general stochastic eco-evolutionary model of population dynamics with horizontal and vertical transfers, inspired by the transfer of plasmids in bacteria. The transfer rates are either density-dependent (DD) or frequency-dependent...

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