# 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.

## Experiencias de 16 años aportando al conocimiento de Chile mediante tecnología satelital

Event Date: Apr 29, 2019 in Ciclo de Seminarios quincenales de la Alianza Copernicus-Chile, Seminars

## Cost functionals for large random trees

Event Date: Apr 25, 2019 in Núcleo Modelos Estocásticos de Sistemas Complejos y Desordenados, Seminars, Stochastic Modeling

Abstract : Additive tree functionals allow to represent the cost of many divide-and-conquer algorithms. We give an invariance principle for such tree functionals for the Catalan model and for simply generated trees . In the Catalan model, this relies on the natural embedding into the Brownian excursion.  (Joint work with Jean-François Delmas and Marion Sciauveau)

## ALMOST DESCRIPTION OF DECAY FOR HAMILTONIAN ABCD SYSTEM CHULKWANG KWAK

Event Date: Apr 23, 2019 in Differential Equations, Seminars

ABSTRACT The Boussinesq abcd system was originally derived by Bona, Chen and Saut [J. Nonlinear. Sci. (2002)] as first order 2-wave approximations of the incompressible and irrotational, two dimensional water wave equations in the shallow water wave regime. Among many particular regimes, the Hamiltonian generic regime is characterized by the setting b = d > 0 and a,c < 0. It is known that the system in this regime is globally well-posed for small data in the energy space H1 × H1 by Bona, Chen and Saut [Nonlinearity (2004)]. In this...

## Finding 2-factors without triangles

Event Date: Apr 17, 2019 in AGCO, Seminars

Abstract: A 2-factor is a set of edges M of a graph G such that each vertex is incident to exactly two edges of M. Thus M determines a set of cycles in G.   One can efficiently compute minimum cost 2-factors in weighted graphs. It is open whether one can do the same, if we forbid triangles, i.e., each cycle has at least four edges. For the unweighted case, a complicated result of Hartvigsen shows that one can find such a 2-matching in polynomial time.   In the talk, we will review known results related to finding triangle free...

## Liouville dynamical percolation & The signature method

Event Date: Apr 16, 2019 in Núcleo Modelos Estocásticos de Sistemas Complejos y Desordenados, Seminars, Stochastic Modeling

Seminario doble conjunto Modelamiento Estocástico / Núcleo Milenio MESCYD Primera Sesión: 3pm Avelio Sepúlveda (U. Lyon 1) Liouville dynamical percolation A dynamical percolation is a process on black and white colourings of the vertices of a graph, in which each vertex has an independent Poissonian clock, and each time a clock rings the colour of its correspondent vertex is resampled. In this talk, we will study a dynamical percolation in the triangular grid, using clocks whose rate is defined in terms of a Liouville measure of parameter...

Event Date: Apr 15, 2019 in Ciclo de Seminarios quincenales de la Alianza Copernicus-Chile, Seminars

Seminarios de la Alianza Copernicus-Chile Titulo Sistema de Alerta RPF Expositor Roberto Tapia Servicio Agrícola y Ganadero SAG Fecha:  Lunes 15 de Abril de 2019 Hora inicio:  16:00 horas Lugar:  Sala Multimedia, Centro de Modelamiento Matemático, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile. Beauchef 851, Santiago – Edificio Norte, Piso 6 Se sugiere entrar por 7 piso y bajar por la escalera (ya que este acceso no requiere tarjeta de entrada) Participación en Linea:...

## Set-based Lagrangean decomposition methods for mathematical programming

Event Date: Apr 10, 2019 in AGCO, Seminars

Abstract: We present generic Lagrangean frameworks for primal (variable) and dual (constraint) decomposition algorithms for nonlinear mathematical programs with generalized inequalities. Akin to the Dantzig-Wolfe (DW) method and the Benders Decomposition (BD), we solve a succession of restricted problems/Lagrangean relaxations in a primal setting or relaxed problems/second stage problems in a dual standpoint.   Our approach is generic in the sense that it takes as user-defined inputs 1) a structured subset of the primal (dual)...

## A critical Poincaré-Sobolev inequality.

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

Abstract:   We study a specific Poincaré-Sobolev inequality in bounded domains, that has recently been used to prove a semi-classical bound on the kinetic energy of fermionic many-body states. The corresponding inequality in the entire space is precisely scale invariant and this gives rise to an interesting phenomenon. Optimizers exist for some (most ?) domains and do not exist for some other domains, at least for the isosceles triangle in two dimensions. In this talk, I will discuss bounds on the constant in the inequality and the...

## On subsets with no arithmetic progressions

Event Date: Apr 01, 2019 in Dynamical Systems, Seminars

ABSTRACT For $N\in \mathbb{N}$, let $\nu(N)$ be the maximal cardinality of a subset of \{1,\ldots,N\} that contains no arithmetic progression of length 3. Finding upper and lower bounds for $\nu(N)$ has been a challenging problem for decades. In this talk I will survey this problem and present a proof of a theorem by Behrend in the 40’s, that gave a surprising lower bound to $\nu(N)$.

## Counting problem on infinite periodic billiards and translation surfaces

Event Date: Apr 01, 2019 in Dynamical Systems, Seminars

ABSTRACT The Gauss circle problem consists in counting the number of integer points of bounded length in the plane. This problem is equivalent to counting the number of closed geodesics of bounded length on a flat two dimensional torus or, periodic trajectories, in a square billiard table. Many counting problems in dynamical systems have been inspired by this problem. For 30 years, the experts try to understand the asymptotic behavior of closed geodesics in translation surfaces and periodic trajectories on rational billiards. (Polygonal...