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.
Popular Branchings and Their Dual Certificates.
Abstract: Let G be a digraph where every node has preferences over its incoming edges. The preferences of a node extend naturally to preferences over branchings, i.e., directed forests; a branching B is popular if B does not lose a head-to-head election (where nodes cast votes) against any branching. Such popular branchings have a natural application in liquid democracy. The popular branching problem is to decide if G admits a popular branching or not. We give a characterization of popular branchings in terms of dual certificates and use...
Observando el aula de la formación inicial docente en matemática: ¿Qué podemos aprender al visualizar las interacciones entre formadores y estudiantes?.
RESUMEN Aprender a enseñar es una de las tareas más desafiantes para los formadores de profesores de matemáticas. Implica no sólo transmitir los conocimientos y habilidades acerca de la enseñanza de un contenido, sino que también cómo los estudiantes en formación aprenden a enseñar ese contenido en el contexto escolar (Loughran, 2006). En consecuencia, las aulas de los programas de formación debiesen ser conceptualizadas como espacios de aprendizaje en donde formadores y estudiantes discuten y reflexionan acerca del razonamiento a la base de...
Kink networks for scalar fields in dimension 1+1.
Abstract: Consider a real scalar wave equation in dimension 1+1 with a positive external potential having non-degenerate isolated zeros. I will speak about the problem of construction of weakly interacting pure multi-solitons, that is solutions converging exponentially in time to a superposition of Lorentz-transformed solitons (“kinks”), in the case of distinct velocities. In a joint work with Gong Chen from the University of Toronto, we prove that these solutions form a 2K-dimensional smooth manifold in the space of solutions,...
Discovering independent sets of maximum size in large sparse random graphs.
Resumen: Finding an independent set of maximum size is a NP-hard task on fixed graphs, and can take an exponentially long-time for optimal stochastic algorithms like Glauber dynamics with high activation rates. However, simple algorithms of polynomial complexity seem to perform well in some instances. We studied the large graph characteristics of two simple algorithms in terms of functional law of large numbers and large deviations. We are especially interested in characterizing a phase transition on the “graph landscape”,...
Pressure and conformal measures on generalized countable Markov shifts.
ABSTRACT: From a generalization of the notion of countable Markov shifts developed by R. Exel and M. Laca, which includes the standard shift space, we developed its corresponding thermodynamic formalism and its connections with the standard one. This space includes extra elements that correspond to finite words. A notion of pressure introduced by M. Denker and M. Yuri for Iterated Function Systems (IFS), that considers these finite words as well, is a natural definition for the pressure in this generalized setting. We proved, for a wide class...
Condiciones de grado mínimo para particiones en ciclos monocromáticos.
Resumen: Resultados de Erdös, Gyárfás y Pyber afirman que cualquier grafo completo r-arista-coloreado tiene una partición en O(r^2 log r) ciclos monocromáticos. En esta presentación se discutirá acerca condiciones de grado mínimo que permiten afirmar la existencia de una partición en O(r^2) ciclos monocromáticos.
Deep Learning Schemes For Parabolic Nonlocal Integro-Differential Equations.
Abstract: In this work we consider the numerical approximation of nonlocal integro differential parabolic equations via neural networks. These equations appear in many recent applications, including finance, biology and others, and have been recently studied in great generality starting from the work of Caffarelli and Silvestre. Based in the work by Hure, Pham and Warin, we generalize their Euler scheme and consistency result for Backward Forward Stochastic Differential Equations to the nonlocal case. We rely on Lévy processes and a new...
Spatial behavior of solutions for a large class of non-local PDE’s arising from stratified flows.
Abstract: We propose a theoretical model of a non-local dipersive-dissipative equation which contains as a particular case a large class of non-local PDE’s arising from stratified flows. Within this fairly general framework, we study the spatial behavior of solutions proving some sharp pointwise and averaged decay properties as well as some pointwise grow properties.
Improved Approximation Algorithms for 2-Dimensional Knapsack: Packing into Multiple L-Shapes, Spirals, and More.
Abstract: In the 2-Dimensional Knapsack problem (2DK) we are given a square knapsack and a collection of n rectangular items with integer sizes and profits. Our goal is to find the most profitable subset of items that can be packed non-overlappingly into the knapsack. The currently best known polynomial-time approximation factor for 2DK is 17/9+eps<1.89 and there is a (3/2+eps)-approximation algorithm if we are allowed to rotate items by 90 degrees. In this talk, I will present a (4/3+eps)-approximation algorithms in polynomial time for...
