Homogenizations Continuum Limits and Kinetic Limits for Stochastic Models

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

An outstanding and long studied problem in statistical mechanics is to establish the connection between the microscopic world and its macroscopic behavior. The investigator's research concerns stochastic models associated with the evolution of dilute gases and the formation of solids. As the first step, one derives a partial differential equation for the macroscopic evolution of such stochastic models. Roughly speaking, one shows that after a suitable scaling, the particle density of a dilute gas (respectively, the boundary surface of a solid) converges to a solution of the Boltzmann equation (respectively, Hamilton-Jacobi equation). Probabilistically, such a convergence is a law of large numbers and its corresponding central limit theorem provides us with some vital information about the microscopic model under the study. Solids form through growth processes which take place at the surface. Imagine an already formed nucleus to which further material sticks from the ambient atmosphere. The process of the attachment is a function of a huge variety of growth mechanisms depending on the materials involved, their temperature, composition, etc. Following the tradition of statistical mechanics, one studies simplified models which nevertheless captures some of the essential physics. Such simplified models are proved to be useful in understanding the intricate formation of solids. It turns out that these models describe other phenomena such as the spread of infected cells in a tissue, the effect of impurity in the evolution of a fluid, etc. The investigator's research concerns the interplay between the microscopic growth rules and the macroscopic shape of the surface of a solid.