In the following work, we consider the Boltzmann equation that models a diatomic gas by representing the microscopic internal energy by a continuous variable I. Under some convenient assumptions on the collision cross-section $ \mathcal{B} $, we prove that the linearized Boltzmann operator $ \mathcal{L} $ of this model is a Fredholm operator. For this, we write $ \mathcal{L} $ as a perturbation of the collision frequency multiplication operator, and we prove that the perturbation operator $ \mathcal{K} $ is compact. The result is established after inspecting the kernel form of $ \mathcal{K} $ and proving it to be $ L^2 $ integrable over its domain using elementary arguments.This implies that $ \mathcal{K} $ is a Hilbert-Schmidt operator.
Citation: Stéphane Brull, Marwa Shahine, Philippe Thieullen. Compactness property of the linearized Boltzmann operator for a diatomic single gas model[J]. Networks and Heterogeneous Media, 2022, 17(6): 847-861. doi: 10.3934/nhm.2022029
In the following work, we consider the Boltzmann equation that models a diatomic gas by representing the microscopic internal energy by a continuous variable I. Under some convenient assumptions on the collision cross-section $ \mathcal{B} $, we prove that the linearized Boltzmann operator $ \mathcal{L} $ of this model is a Fredholm operator. For this, we write $ \mathcal{L} $ as a perturbation of the collision frequency multiplication operator, and we prove that the perturbation operator $ \mathcal{K} $ is compact. The result is established after inspecting the kernel form of $ \mathcal{K} $ and proving it to be $ L^2 $ integrable over its domain using elementary arguments.This implies that $ \mathcal{K} $ is a Hilbert-Schmidt operator.