Seminars

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.

 

Non-intersecting paths in the plane, loop-erased walks and random matrices.

Event Date: Jun 09, 2021 in Seminario Probabilidades CMM, Seminars

Resumen:  Non-intersecting processes in one dimension have long been an integral part of random matrix theory, at least since the pioneering work of F. Dyson in the 1960s. For planar (two-dimensional) state space processes, it is not clear how to generalize these connections since the paths under consideration are allowed to have self-intersections (or loops). In this talk, we address this problem and consider systems of random walks in planar graphs constrained to a certain type of non-intersection involving their loop-erased parts (this is...

Grafos expansivos e inmersiones.

Event Date: Jun 07, 2021 in Seminario de Grafos, Seminars

Resumen: En esta charla seguiremos estudiando el uso de grafos expansivos en problemas extremales. Se estudiará cómo utilizar expansión para encontrar inmersiones de grafos completos en grafos con condiciones de grado promedio.

Separation and Interaction energy between domain walls in a nonlocal model.

Event Date: Jun 03, 2021 in Differential Equations, Seminars

Abstract: We analyse a nonconvex variational model from micromagnetics  with a nonlocal energy functional, depending on a small parameter epsilon > 0. The model gives rise to transition layers, called Néel walls, and we study their behaviour in the limit epsilon -> 0. The analysis has some similarity to the theory of Ginzburg-Landau vortices. In particular, it gives rise to a renormalised energy that determines the interaction (attraction or repulsion) between Néel walls to leading order. But while Ginzburg-Landau vortices show...

Popular Branchings and Their Dual Certificates.

Event Date: Jun 02, 2021 in ACGO, Seminars

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?.

Event Date: Jun 01, 2021 in Education, Seminars

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.

Event Date: May 27, 2021 in Differential Equations, Seminars

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.

Event Date: May 26, 2021 in Seminario Probabilidades CMM, Seminars

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.

Event Date: May 24, 2021 in Dynamical Systems, Seminars

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.

Event Date: May 24, 2021 in Seminario de Grafos, Seminars

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.

Event Date: May 20, 2021 in Differential Equations, Seminars

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...