Analysis of a nonisothermal Maxwell--Stefan system with degenerate thermal conductivity

Abstract

We prove the global-in-time existence of weak solutions for the Maxwell--Stefan--Fourier system with physically motivated degenerate thermal conductivity $\kappa(\theta)=\theta^\alpha$, for $0<\alpha\leq2$. In contrast to existing nonisothermal compressible theories based on nondegenerate conductivities, the entropy inequality no longer gives control of the quantities $\nabla\theta$ and $\nabla \log\theta$. The main new ingredient is a renormalized energy estimate, which yields compactness of the temperature and allows the identification of the degenerate heat flux.