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.
Número de Ramsey orientado para árboles.
Resumen: En grafos con orientación puede hablarse del número de Ramsey orientado, el análogo al aplicado en grafos simples pero en un torneo en vez de un Kn. En esta charla se mostrarán dos de los tres resultados importantes del paper “Directed Ramsey number for trees” de Bucić, Letzter y Sudakov, publicado el año 2018, uno que entrega una cota superior para el número de Ramsey orientado k-coloreado para un árbol orientado cualquiera, y el otro que entrega cota inferior y superior del mismo número para un camino de largo n....
Automorphisms and extended symmetries of number-theoretic positive entropy subshifts.
ABSTRACT: We will discuss one- and multidimensional subshifts constructed via number-theoretically defined subsets of the integers (e.g. the visible lattice points in the plane, k-free integers, etc.), focusing our interest on their groups of automorphisms and extended symmetries, which are naturally defined conjugacy invariants. This type of shift space exhibits symmetry rigidity (that is, its group of automorphisms is essentially trivial), but is compatible with positive entropy and shows interesting variations on their extended symmetry...
An algebraic view of the smallest strictly monotonic function.
Abstract: The talk concerns with one of the most popular functions to derive nonconvex separation results. Complete characterizations for both its level sets and basic properties such as monotonicity and convexity are provided in terms of its parameters. Most of these characterizations work without considering any additional requirement or assumption. Finally, as an application, a vectorial form of the Ekeland variational principle is provided.
¿Qué, cómo y para qué medir el conocimiento matemático al inicio de la formación docente? Orientando posibilidades de las pruebas iniciales diagnósticas de Pedagogía en Educación Básica.
RESUMEN En los últimos veinte años se han desarrollado diversos tipos de mediciones sobre el conocimiento matemático del profesor, y muchas han sido desarrollas al término de la formación inicial docente. Si bien estas mediciones nos aporta mucha información de cómo ha sido el proceso formativo, nos entregan pocas herramientas de acción para tomar decisiones a tiempo durante dicha trayectoria. Así, se ha hecho necesario investigar y desarrollar herramientas para conocer el punto de partida para informar la toma de decisiones y...
Gevrey regularity for the Vlasov-Poisson system.
Abstract: The importance of understanding high regularity solutions for the Vlasov-Poisson system has been underscored by the work on Landau damping of Mouhot-Villani and several other follow ups. These works on Landau damping make use of the propagation in time of high order regularity in a perturbative regime around homogeneous stationary solutions of the Vlasov-Poisson system. In this talk, we prove a general result on propagation of Gevrey regularity for the Vlasov-Poisson system on $\T^d\times \R^d$ using a Fourier space method in...
Bounds on the unavoidability of some classes of directed trees, and algorithms for showing such embeddings.
Resumen: Decimos que un grafo dirigido H es m-inevitable si aparece como subgrafo de todo torneo en m vertices. En esta charla se presentará brevemente la historia del problema de acotar la inevitabilidad de distintas clases de arboles dirigidos. Se mostrarán resultados recientes, junto con algoritmos para realizar dichos embeddings.
On the two-dimensional knapsack problem for convex polygons.
Abstract: We study the two-dimensional geometric knapsack problem for convex polygons. Given a set of weighted convex polygons and a square knapsack, the goal is to select the most profitable subset of the given polygons that fits non-overlappingly into the knapsack. We allow rotating the polygons by arbitrary angles. In this talk we will first present: – a quasi-poly time O(1)-approximation – a poly time O(1)-approximation algorithm if all input polygons are triangles. We will then look into the setting of resource augmentation,...
Heterodimensionality of skew-products with concave fiber maps.
ABSTRACT: I will discuss examples of skew-products with concave interval fiber maps over a certain subshift. Here the subshift occurs as the projection of those orbits that stay in a given neighborhood and gives rise to a new type of symbolic space which is (essentially) coded. The fiber maps have expanding and contracting regions. As a consequence, the skew-product dynamics has pairs of horseshoes of different types of hyperbolicity. In some cases, they dynamically interact due to the superimposed effects of the (fiber) contraction...
Modified scattering for the nonlinear Schrödinger equation in an external field.
Abstract: In this talk, we consider the cubic nonlinear Schrödinger equation with an external potential. We prove the existence of modified scattering for this model, that is, linear scattering modulated by a phase. Our approach is based on the spectral theorem for the perturbed linear Schrödinger operator and a factorization technique, which allows us to control the resonant nonlinear term. This approach requires a detailed and subtle study of the low-energy properties of the scattering data. Therefore, we study the cases of generic and...
