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.
Lp-estimates for nonlocal in time heat kernels
Abstract: In [1] and [2], the authors study independently the so called fully nonlocal diffusion equation, which is of fractional order both in space and time. In both papers, the authors need several technical results about the so-called Mittag-Leffler functions and Fox H-functions to obtain Lp-estimates of the solutions. This approach seems not to be very helpful (or easy) to derive the Lp-estimates of solutions to equations with other nonlocal in time operators (for example sums of fractional derivatives). In this talk, we present a...
Multidimensional continued fractions and symbolic dynamics for toral translations
ABSTRACT: We give a dynamical, symbolic and geometric interpretation to multi-dimensional continued fractions algorithms. For some strongly convergent algorithms, the construction gives symbolic dynamics of sublinear complexity for almost all toral translations; it can be used to obtain a symbolic model of the diagonal flow on lattices in $\mathbb R^3$.
Convergence of projection algorithms: some results and counterexamples.
Abstract: Projection methods can be used for solving a range of feasibility and optimisation problems. Whenever the constraints are represented as the intersection of closed (convex) sets with readily implementable projections onto each of these sets, a projection based algorithm can be employed to force the iterates towards the feasible set. Some versions of projection methods employ approximate projections; one can also consider under- and over-relaxed iterations (such as in the Douglas-Rachford method). In this talk I will focus on...
Two-time distribution for KPZ growth in one dimension
Abstract: Consider the height fluctuations H(x,t) at spatial point x and time t of one-dimensional growth models in the Kardar-Parisi-Zhang (KPZ) class. The spatial point process at a single time is known to converge at large time to the Airy processes (depending on the initial data). The multi-time process however is less well understood. In this talk, I will discuss the result by Johansson on the two-time problem, namely the joint distribution of (H(x,t),H(x,at)) with a>0, in the case of droplet initial data. I also show how to...
Linear inviscid damping and enhanced viscous dissipation of shear flows by the conjugate operator method
Abstract: We will show how we can use the classical Mourre commutator method to study the asymptotic behavior of the linearized incompressible Euler and Navier-Stokes at small viscosity equations about shear flows. We will focus on the case of the mixing layer. Joint work with E Grenier, T. Nguyen and A. Soffer
Intertwinings and Stein’s factors for birth-death processes
Abstract: In this talk, I will present intertwinings between Markov processes and gradients, which are functional relations relative to the space-derivative of a Markov semigroup. I will recall the first-order relation , in the continuous case for diffusions and in the discrete case for birth-death processes, and introduce a new second-order relation for a discrete Laplacian. As the main application, new quantitative bounds on the Stein factors of discrete distributions are provided. Stein’s factors are a key component of Stein’s method, a...
Entropías intermedias y temperatura nula en curvatura negativa
ABSTRACT: Un problema bastante general en teoría ergódica consiste en estudiar al conjunto de entropías de un sistema dinámico respecto a sus medidas ergódicas. Katok conjeturó que dicho conjunto contiene al intervalo $[0,h_{top}(f))$ en el caso de difeomorfismos suaves en variedades compactas. Si bien la conjetura permanece abierta, muchos avances se han logrado a la fecha. Se conoce, por ejemplo, que el flujo geodésico en variedades compactas a curvatura negativa verifica esta propiedad. La demostración de esto último recae en la...
Invariant Random Subgroups of Full Groups of Bratteli diagrams
ABSTRACT: In the talk, we will classify the ergodic invariant random subgroups (IRS) of simple AF full groups. AF full groups arise as the transformation groups of Bratteli diagrams that preserve the cofinality of infinite paths in the diagram. AF full groups are complete (algebraic) invariants for the isomorphism of Bratteli diagrams. Given a simple AF full group G, we will prove that every ergodic IRS of G arises as the stabilizer distribution of a diagonal action on X^n for some n, where X is the path-space of the Bratteli diagram...
A Game Theoretic Model for Optimizing Electricity Consumers Flexibilities in the Smart Grid.
Abstract: With the evolution of electricity usages (electric vehicles, smart appliances) and the development of communication structures (smart grid), new opportunities of optimization have emerged for the actors of the electrical network. Aggregators can send signals to enrolled consumers to play on their demand flexibilities, and to optimize the providing costs and the social welfare. Game theory has been shown to be a valuable tool to study strategic electricity consumers participating in such a demand side management program. We propose a...
On the equitable Hamiltonian Cycle problem
Abstract: Kinable, Smeulders, Delcour, and Spieksma (2017) introduced the Equitable TSP (E-TSP). In the E-TSP, we are given an even number of cities and distances between each pair of these. Instead of finding a tour of minimum length, Kinable et al. (uniquely) decomposed the tour in two perfect matchings, one with “even” edges and one with “odd” edges and the goal is to minimize the difference between the costs of the two perfect matchings. Kinable et al. show that the E-TSP is strongly NP-hard by reduction from Hamiltonian Cycle. The...
