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.


On regularization/convexification of functionals including an l2-misfit term

Event Date: Mar 14, 2018 in Optimization and Equilibrium, Seminars

Abstract: A common technique for solving ill-posed inverse problems is to include some sparsity/low-rank constraint, and pose it as a convex optimization problem, as is done e.g. in compressive sensing. The corresponding functional to be minimized often includes an l2 data fidelity term plus a convex term forcing sparsity. However, for many applications a non-convex term would be more suitable, although this is usually discarded since it leads to issues with algorithm convergence, local minima etc. I will introduce a new transform...

Canonical Supermartingle Couplings

Event Date: Mar 13, 2018 in Seminars, Stochastic Modeling

ABSTRACT:   Two probability distributions in second stochastic order can be coupled by a supermartingale, and in fact by many. Is there a canonical choice? We construct and investigate two couplings which arise as optimizers for constrained Monge-Kantorovich optimal transport problems where only supermartingales are allowed as transports. Much like the Hoeffding-Frechet coupling of classical transport and its symmetric counterpart, the Antitone coupling, these can be characterized by order-theoretic minimality properties, as simultaneous...

Local rules for planar tilings

Event Date: Mar 12, 2018 in Dynamical Systems, Seminars

  ABSTRACT:  The cut and project method is one of the prominent method to define quasiperiodic tilings. In order to model quasicrystals, where energetic interactions are only short range, it is important to know which of these tilings can be characterized by local configurations (in dynamical terms: which of these tiling spaces are of finite type or sofic). In this talk we shall review known results, in particular those obtained these last years with Nicolas Bedaride and Mathieu Sablik.


Event Date: Jan 22, 2018 in Dynamical Systems, Seminars

ABSTRACT: In this work we characterize the class of continuous shift commuting maps between ultragraph shift spaces, proving a Curtis-Hedlund-Lyndon type theorem. Then we use it to characterize continuous, shift commuting, length preserving maps in terms of generalized sliding block codes. This is a joint work with Prof. Daniel Gon\c{c}alves (UFSC, Brazil)

Optimal transport and applications to Data Science

Event Date: Jan 17, 2018 in Seminario Aprendizaje de Máquinas, Seminars

Abstract: Optimal transport (OT) provides rich representations of the discrepancy between probability measures supported on geometric spaces. Recently, thanks to the development of computational techniques, OT has been used to address problems involving massive datasets, as an alternative to usual KL-divergence based approaches. In this talk I will introduce the OT problem and comment on its elementary duality properties. Then, I will present the entropy regularized problem and its (fast) solution via Sinkhorn iterations. Finally, I will...

Projected solutions of quasi-variational inequalities with application to bidding process in electricity market

Event Date: Jan 17, 2018 in Optimization and Equilibrium, Seminars

Abstract:   Quasi-variational inequalities provide perfect tools  to reformulate Generalized Nash Equilibrium Probem (GNEP), the latter being a good model to describe the day-ahead  electricity markets.   Our aim in this talk is to illustrate how some recent advances in the theory  of quasi-variational inequalities can influence the modeling of electricity market.   Talk based on: – D. Aussel, A. Sultana & V. Vetrivel, On the existence of projected solutions of quasi-variational inequalities and generalized Nash...

Physics-based Models for Uncertainty Quantification in Chemical Kinetics

Event Date: Jan 15, 2018 in Seminario Aprendizaje de Máquinas, Seminars

Abstract:   Prediction is a core element of science and engineering. Sophisticated mathematical models exist to make predictions in a variety of physical contexts including materials science, fluid mechanics, and solid mechanics. Most of these models do not have known analytical solutions. Moreover, they are generally difficult to solve numerically. In order to perform numerically tractable computations, researchers often try to develop reduced models that account for the essential physics while doing away with the complexity of the full...

Invariant measures of discrete interacting particle systems: Algebraic aspects

Event Date: Jan 09, 2018 in Núcleo Modelos Estocásticos de Sistemas Complejos y Desordenados, Seminars

Abstract: We consider a continuous time particle system on a graph L being either Z,  Z_n, a segment {1,…, n}, or Z^d, with state space Ek={0,…,k-1} for some k belonging to {infinity, 2, 3, …}. We also assume that the Markovian evolution is driven by some translation invariant local dynamics with bounded width dependence, encoded by a rate matrix T. These are standard settings, satisfied by many studied particle systems. We provide some sufficient and/or necessary conditions on the matrix T, so that this Markov process admits some...

Projected solutions for quasi-equilibrium problems.

Event Date: Dec 06, 2017 in Optimization and Equilibrium, Seminars

Abstract:   In 2016, Aussel, Sultana and Vetrivel introduced the concept of projected solutions for generalized Nash equilibrium problems (GNEPs)in the finite dimensional case. To show the existence  of such solutions they studied projected solutions for quasi-variational inequality problems. In a similar spirit, we introduce the concept of projected solution for quasi-equilibrium problems (QEPs). As a consequence of our main result we obtain an existence result for projected solutions of GNEPs, in infinite dimensional spaces....

Empoderar a grupos de trabajo en el aula: Una obligación que guía a los profesores de matemática en instituciones de acceso abierto en Chile

Event Date: Dec 06, 2017 in Education, Seminars

Resumen:   Este estudio aborda cómo las interacciones entre profesores y grupos de trabajo se relacionan con las prácticas en sala y la toma de decisiones en la enseñanza de la matemática en instituciones de acceso abierto, en educación superior. Definimos las interacciones entre profesores y grupos de estudiantes desde el momento en que el profesor visita un grupo que trabaja en una tarea matemática específica, que en nuestro caso corresponden a actividades de resolución de problemas. La metodología es mixta y basada en dos conjuntos de...