TBA

TBA

ago / 2018
07

Hard balls collisions

We will explore the behavior of systems of a large number of hard balls under elastic collisions. We prove by example that the number of elastic collisions of $n$ balls

of equal mass and equal size in $d$-dimensional space can be greater than $n^3/27$ for $n\geq 3$ and $d\geq 2$. The previously known lower bound was of order $n^2$.

jun / 2018
19

Particle systems and propagation of chaos for some kinetic models

In this talk we will make a quick historical review of some equations arising in the classical kinetic theory of gases and related models. We will start with the Boltzmann equation, which describes the evolution of the distribution of positions and velocities of infinitely many small particles of a gas in 3-dimensional space, subjected to elastic binary collisions. We consider a finite $N$-particle system and introduce the important concept of propagation of chaos: the convergence, as $N\to\infty$ and for each time $t\geq 0$, of the distribution of the particles towards the solution of the equation. We present some recent quantitative propagation of chaos results for the spatially homogeneous Boltzmann equation and Kac’s model. Lastly, we will introduce a relatively new class of one-dimensional kinetic equations modelling wealth redistribution in a population performing binary trades. When trades preserve wealth only on average, these models can exhibit an equilibrium distribution with heavy tails, as is seen in real-world economies. We focus on the corresponding finite $N$-particle system and study how the heaviness of the tails of its distribution relates to that of the limit kinetic equation. Unless wealth is preserved exactly in each trade, we find important qualitative differences between both cases.

jun / 2018
12

A non-trivial bound for the critical threshold of a percolation model with columnar disorder.

A random perturbation with a tunable parameter in a regular media can sometimes produce a disruption on macroscopic observables. In this talk, we study a percolation model on a random lattice that features such a disruption. More specifically, we show that the Bernoulli percolation in a 3D lattice with columns randomly deleted has a uniform non-trivial threshold. In the course of the proof, we have to understand some geometrical properties of the supercritical 2D cluster. Joint work with M.V Sá and M.R. Hilário.

may / 2018
29

Two-time distribution for KPZ growth in one dimension

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 adapt his approach to the flat initial case. This is based on joint work with Kurt Johansson.

may / 2018
29

Pontificia Universidad Católica de Chile (PUC-Chile)

Av. Vicuña Mackenna 4860, Macul,

Santiago – Chile

(+56 2) 2354 5779

Facultad de Ciencias Físicas y Matemáticas (FCFM)

Universidad de Chile

Beauchef 851, Edificio Norte, Piso 7,

Santiago – Chile