On a thermostated Kac model with rescaling

Abstract

We introduce a global thermostat on Kac's 1D model for the velocities of particles in a spacehomogeneous gas subjected to binary collisions, also interacting with a (local) Maxwellian thermostat. The global thermostat rescales the velocities of all the particles, thus restoring the total energy of the system, which leads to an additional drift term in the corresponding nonlinear kinetic equation. We prove ergodicity for this equation, and show that its equilibrium distribution has a density that, depending on the parameters of the model, can exhibit heavy tails, and whose behaviour at the origin can range from being analytic, to being C k , and even to blowing-up. Finally, we prove propagation of chaos for the associated N -particle system, with a uniform-in-time rate of order N −η in the squared 2-Wasserstein metric, for an explicit η ∈ (0, 1/3].