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.

 

A VARIATIONAL APPROACH TO SECOND-ORDER OPTIMALITY

Event Date: Nov 20, 2019 in Optimization and Equilibrium, Seminars

ABSTRATC: Conditions associated with local optimality, whether necessary or sufficient, have traditionally been approached through techniques of generalized differentiation.  On the first-order level, this has been a long-standing success, although serious challenges remain for equilibrium constraints and the like.   On the second-order level, a difficulty areses with the complex concepts of generalized second derivatives and the sometimes-inadequate calculus for determining them. In fact, sufficient second-order conditions of a practical...

On the Cycle Augmentation Problem: Hardness and Approximation Algorithms.

Event Date: Nov 13, 2019 in AGCO, Seminars

Abstract: In the k-Connectivity Augmentation Problem we are given a k-edge-connected graph and a set of additional edges called links. Our goal is to find a set of links of minimum cardinality whose addition to the graph makes it (k+1)-edge-connected. There is an approximation preserving reduction from the mentioned problem to the case k=1 (a.k.a. the Tree Augmentation Problem or TAP) or k=2 (a.k.a. the Cactus Augmentation Problem or CacAP). While several better-than-2 approximation algorithms are known for TAP, nothing better is known for...

Lower bounds on the Hausdorff dimension of the Rauzy gasket

Event Date: Nov 11, 2019 in Dynamical Systems, Seminars

ABSTRACT: The Rauzy gasket is an important fractal object arising in several dynamical constructions, such as Novikov’s problem and some renormalization schemes for certain families of interval exchange maps. It was conjectured by Novikov and Maltsev in 2003 that the Hausdorff dimension D of the Rauzy gasket is strictly comprised between 1 and 2. In 2016, Avila, Hubert and Skripchenko confirmed the upper bound D<2. In this talk, I will explain how to use the thermodynamical results of Cao, Pesin and Zhao to show that D > 1.19....

REPLICATOR DYNAMICS: OLD AND NEW

Event Date: Nov 06, 2019 in AGCO, Seminars

Abstract: We introduce the unilateral version associated to the replicator dynamics and describe its connection to on-line learning procedures, in particular tomultiplicative weight algorithm. We show the interest of handling simultaneously discrete and continuous time analysis. We then survey recent results on extensions of this dynamics: regularization function and variable weights. This includes no regret algorithms, time average and link to best reply dynamics in two person games, application to equilibria and variational inequalities,...

Problemas clásicos en EDO desde un punto de vista no autónomo

Event Date: Oct 21, 2019 in Dynamical Systems, Seminars

ABSTRACT: En esta charla daremos a conocer las versiones no autónomas de los clásicos problemas de estabilidad global y linealización suave. Además haremos un link entre el problema de estabilidad global autónomo y la conjetura jacobiana.

Estabilización de una clase de ciclos heterodimensionales

Event Date: Oct 21, 2019 in Dynamical Systems, Seminars

ABSTRACT : Un difeomorfismo f tiene un ciclo (heterodimensional) si existen conjuntos hiperbólicos (transitivos) de índices diferentes (dimensión del fibrado inestable) cuyas variedades invariantes se intersectan cíclicamente. El ciclo de f es Cr-robusto si toda pequeña Cr-perturbación de f tiene un ciclo asociado a las continuaciones de estos conjuntos hiperbólicos. Si el ciclo de f es definido por un par de sillas hiperbólicas decimos que este ciclo puede ser Cr-estabilizado si toda Cr-vecindad de f contiene difeomorfismos con un ciclo...

Vortices induced by topological forcing in nematic liquid crystal layes

Event Date: Oct 16, 2019 in Differential Equations, Seminars

Abstract: Liquid crystals with negative anisotropic dielectric constant and homeotropic anchoring are a natural physical context where dissipative vortices are observed. Dissipative vortices are known in this context as \emph{umbilical defects}.Major problems arise when practical implementations are aimed at, because soft-matter defects are dissipative structures that obey a complex Ginzburg-Landau equation (CGLE) and undergo a coarsenig dynamics ruled by their mutual interaction and annhilation. Therefore, they are unstable, usually limited...

Decay in the one dimensional generalized improved Boussinesq equation.

Event Date: Oct 09, 2019 in Differential Equations, Seminars

Abstract: The purpose of this talk is to explain the decay problem for the generalized improved (or regularized)  Boussinesq model with power type nonlinearity, a modification of the originally ill-posed shallow water waves model derived by Boussinesq. The associated decay problem has been studied by Liu, and more recently by Cho-Ozawa, showing scattering in weighted spaces provided the power of the nonlinearity $p$ is sufficiently large. In this talk we remove that condition on the power $p$ and prove decay to zero in terms of the energy...

Renormalización: criterio de Masur

Event Date: Sep 30, 2019 in Dynamical Systems, Seminars

ABSTRACT En este kawin presentaré un resultado emblemático de renormalización en sistemas dinámicos conocido como criterio de Masur. Informalmente, la renormalización es una herramienta para el estudio de sistemas dinámicos cuya “forma esencial” se repite en diferentes (infinitas) escalas. Básicamente consiste en deformar, ampliar o acelerar localmente un sistema para obtener información global sobre este. En esta ocasión nos enfocaremos en flujos de translación: flujos lineales en superficies de translación. Una superficie de...