Stability and causality of Carter’s multifluid theory

Abstract Stability and causality are studied for linear perturbations about equilibrium in Carter’s multifluid theory. Our stability analysis is grounded on the requirement that entropy of multifluid, plus environment, must be maximised at equilibrium. This allows us to compute a quadratic Lyapunov functional, whose positive definiteness implies stability. Furthermore, we verify explicitly that, also multifluids, thermodynamic causality. As notable condition, find entrainment matrix always definite, confirming widespread intuition.