 Aubin–Lions lemma

If $X_0$ embeds compactly into $X$ and $X$ embeds continuously into $X_1$, then boundedness in $L^p(0,T;X_0)$ together with a suitable time-derivative bound in $L^q(0,T;X_1)$ makes a family relatively compact in $L^p(0,T;X)$. A standard case is

Aubin–Lions lemma is a result in the field of functional analysis, particularly in the study of the convergence of sequences of functions, and is often used in the context of nonlinear partial differential equations. The lemma provides conditions under which compactness can be guaranteed for a sequence of functions in certain function spaces. More specifically, it deals with the convergence properties of families of bounded sets in reflexive Banach spaces.