The weak solution to a Boltzmann type equation and its energy conservation

In this paper, we study the initial value problem of a Boltzmann type equation with a nonlinear degenerate damping. We prove the existence of global weak solutions with large initial data, in three dimensional space. We rely on a variant version of the Gronwall inequality and $L^p$ regularity of average velocities to derive the compactness of solutions to a suitable approximation. This allows us to recover a weak solution by passing to the limits. After the existence result, we also prove energy conservation for the weak solution under some certain condition.