Noticias en español
Seminars appear in decreasing order in relation to date. To find an activity of your interest just go down on the list. Normally seminars are given in English. If not, they will be marked as Spanish Only.
Condiciones para la inestabilidad estructural de contracciones a trozos del intervalo.
RESUMEN: En la presente charla mostraremos que, bajo condiciones razonables, los mapas contractivos a trozos del intervalo que admiten dinámicas asintóticas no-periódicas no pueden ser estructuralmente estables. Se mencionarán algunos obstáculos y preguntas que surgieron durante este trabajo, tales como: ¿qué tipo de perturbaciones o topología deberíamos considerar? ¿cómo controlamos que las perturbaciones de contracciones a trozos sean contractivas a trozos sin exigir hipótesis adicionales? Dado que varios resultados críticos para esta...
Blow-up Analysis of Large Conformal Metrics With Prescribed Gaussian And Geodesic Curvatures
Abstract: In this talk, we consider a compact Riemannian surface (M,g) with nonempty boundary and negative Euler characteristic. Given two smooth non-constant functions f in M and h in the boundary of M with max f = max h = 0, under a suitable condition on the maximum points of f and h, we prove that for sufficiently small positive constants λ and μ, there exist at least two distinct conformal metrics g_{λ,μ}=e^{2u_{μ,λ}}g and g^{λ,μ}=e^{2u^{μ,λ}}g with prescribed sign-changing Gaussian and geodesic curvature equal to f+μ and h+λ,...
Substitutive structures on general countable groups.
RESUMEN: Symbolic dynamics has been largely used to represent dynamical systems through a coding system. This method was initially developed by M. Morse and G. A. Hedlund. One commonly used coding method involves infinite sequences of morphisms defined on finitely generated monoids, known as directive sequences or S-adic representations. Recent research has shown that understanding the underlying S-adic structures of some subshifts is valuable for studying their dynamical properties. Considering the previous studies and acknowledging the...
Powers of Hamilton cycles in directed and oriented graphs.
Abstract: The P\’osa–Seymour conjecture determines the minimum degree threshold for forcing the $k$th power of a Hamilton cycle in a graph. After numerous partial results, Koml\’os, S\’ark\”ozy and Szemer\’edi proved the conjecture for sufficiently large graphs. We focus on the analogous problem for digraphs and for oriented graphs. For digraphs, we asymptotically determine the minimum total degree threshold for forcing the square of a Hamilton cycle. We also give a conjecture on the corresponding...
Bidding problems in European deregulated electricity markets.
Abstract: In this talk, we consider a bidding problem in European deregulated electricity markets. The goal of this problem is to maximize the profit of a Generation Company (GC) by choosing the best possible bids to propose to a Market Operator (MO) whose tasks is to minimize the daily price of electricity for the retailers. This problem has many challenging features to consider such as unit commitment for the GC, a market clearing system for the MO and demand and productions capacities are subject to increasing uncertainty due to renewable...
A comparison theorem for integrated stochastic Volterra models with application to the modelling of Lagrangian intermittency in turbulence.
Resumen: We introduce a stochastic model for the Lagrangian velocity and dissipation of a turbulent flow, which takes the form of an integrated Volterra process, as already proposed in the litterature. In order to understand how to reproduce the multifractal behaviours predicted by the Kolomogorov refined theory, we propose a way to compare the effects of different Volterra kernels on the statistics of the integrated process. Since Volterra processes are not Markovian, we use the martingale approach and the functional Itô formula from...
Spectrum of the linearized Vlasov-Poisson system.
Abstract: The Vlasov-Poisson system describes a macroscopic number of particles with their mutual gravitational attraction in a mean-field approximation. Its steady-state solutions are known as “polytropes” and a popular model for galaxies in the astronomy literature. In many cases, they are known to be neutrally stable, but the question of asymptotic stability is widely open. The goal of this talk is to present some results on the linearized equation around a steady state. This is based on joint work with Matías Moreno and Paola...
Minimal configurations for Frenkel-Kontorova model on a quasicrystal.
RESUMEN: The Frenkel-Kontorova model is a physical model that is mathematically simple to describe and universal in the sense that it can be used to describe several underlying physical concepts. It was originally introduced in 1938 to represent the structure and dynamics of a crystal lattice in the vicinity of a dislocation core. It models a chain of classical particles coupled to their neighbors and subjected to an external potential. In this talk, I will present an overview of some known properties and open questions concerning equilibrium...
Tree Embedding Problem for Digraphs.
Abstract: The \textit{tree embedding problem} focuses on identifying the minimal conditions a graph $G$ must satisfy to ensure it contains all trees with $k$ edges. Here, a graph $G$ consists of a set $V$ of elements called vertices, and a set $E$ of (unordered) pairs of vertices, called edges. We say that a graph $G$ is a tree if, for any pair of vertices, there is exactly one path connecting them. Erd\H{o}s and Sós conjectured that any graph $G$ with $n$ vertices and more than $(k-1)n/2$ edges contains every tree with $k$ edges. This...
