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.
Empaquetamiento óptimo de árboles de grado máximo acotado.
Abstract: En 1976, Gyárfás y Lehel conjeturaron que si T_1,…, T_n es una secuencia de árboles tal que T_i tiene i vértices, entonces el grafo completo en n vértices K_n tiene una descomposición en T_1,…, T_n. Recientemente, Joos, Kim, Kühn y Osthus [1] probaron esta conjetura para árboles de grado máximo acotado. En este seminario vamos a estudiar las técnicas utilizadas en la demostración de este resultado. En especial, veremos una aplicación del método de absorción iterativo. [1] Felix Joos, Jaehoon Kim, Daniela Kühn, Deryk...
On Space-Time Formulations and Boundary Integral Equations for the Wave Equation.
Abstract: Space-time discretization methods are becoming increasingly popular, since they allow adaptivity in space and time simultaneously, and can use parallel iterative solution strategies for time-dependent problems. However, in order to exploit these advantages, one needs to have a complete numerical analysis of the corresponding Galerkin methods. In this talk, we consider the wave equation with on a Lipschitz bounded domain, with either Dirichlet or Neumann boundary conditions, and with zero initial conditions. The first step to build...
One-Step Estimation with Scaled Proximal Methods. & Splitting algorithms for monotone inclusions with minimal lifting.
Charla 1: Abstract: We study statistical estimators computed using iterative optimization methods that are not run until completion. Classical results on maximum likelihood estimators (MLEs) assert that a one-step estimator (OSE), in which a single Newton-Raphson iteration is performed from a starting point with certain properties, is asymptotically equivalent to the MLE. We further develop these early-stopping results by deriving properties of one-step estimators defined by a single iteration of scaled proximal methods. Our main results...
On some interacting particle systems related to random matrices.
Abstract: The talk is about two types of interacting particle systems related to the classical ensembles of random matrices. The prototypical examples are Dyson Brownian motion (also called non-intersecting Brownian motions) and Brownian TASEP (also called Brownian motions with one-sided collisions/reflections) respectively. I will discuss explicit formulae for their distributions, their correlation functions and some non-trivial connections between the two types of interacting particle systems. The bulk of the talk will be mainly focussed...
Impartial Selection with Additive Guarantees via Iterated Deletion.
Abstract: Impartial selection is the selection of an individual from a group based on nominations by other members of the group, in such a way that individuals cannot influence their own chance of selection. We give a deterministic mechanism with an additive performance guarantee of $O(n^{(1+\gamma)/2})$ in a setting with $n$ individuals where each individual casts $O(n^{\gamma})$ nominations, where $\gamma \in [0,1]$. For $\gamma=0$, i.e., when each individual casts at most a constant number of nominations, this bound is $O(\sqrt{n})$. This...
Simulations of black hole binaries and their gravitational waves.
Abstract: Our recently acquired ability to detect gravitational waves has expanded our senses and our possibilities of inquiring about the Universe. As a new era of gravitational wave detections rapidly unfolds, the importance of having accurate models for their signals becomes increasingly important. In this context, we will discuss numerical simulations of black hole binaries. In particular, we will focus on how they are made, what they help us achieve, and what are the current challenges in this research area.
Determinación de erosión costera con imágenes satelitales Sentinel-2 entre 2015 – 2022. Caso de estudio Bahía de Algarrobo, Chile Central.
Resumen: En los últimos años, la erosión costera ha aumentado a nivel mundial por la frecuencia e intensidad de eventos de tormentas, convirtiéndose en una de las principales amenazas que afectan a la zona costera a diferentes escalas. En la Bahía de Algarrobo los eventos de marejadas frecuentes e intensas en las temporadas primavera-verano y las intervenciones antrópicas en humedales costeros, sobre la playa y las dunas han intensificado los procesos erosivos. El objetivo del trabajo es determinar las tasas de erosión costera a partir del...
Grupos Nilpotentes actuando en el intervalo.
RESUMEN: En esta charla vamos a estudiar las realizaciones de los grupos Nilpotentes como subgrupos del grupo de difeomorfismos del intervalo y presentar el siguiente problema: dado un grupo Nilpotente G, ¿Cuál es el parámetro óptimo r>0 para el cual G es un subgrupo del grupo de difeomorfismos de clase C^r del intervalo?, ¿Cuál es el vínculo entre r y la estructura algebraica de G? Si bien este problema está abierto en general vamos a ver respuestas parciales a estas preguntas.
De soluciones de la ecuación de Yamabe que cambian de signo a soluciones positivas de sistemas críticos competitivos.
Abstract: En esta charla analizaremos la existencia y estructura de diferentes soluciones que cambian de signo de la ecuación de Yamabe y las usaremos para construir soluciones positivas de sistemas críticos de tipo competitivo en dimensión 4.
Structural properties in hypercubes.
Abstract: In this talk we review some structural questions on subgraphs of the hypercube of dimension n. We present a simpler proof of Huang’s 2019 result that any subgraph of $H_n$ on more than half the number of vertices has a vertex of degree at least $\sqrt{n}$. We present some strengthening of the result, and we observe a connection to an older question of Erdos who asked: how many edges of $H_n$ one should take to guarantee existence of a 4-cycle.
