The $6\frac{1}{2}$-functor formalism of Cartier modules

Abstract

Let $p$ be a prime. We construct a coherent formalism of geometric operations on Cartier modules with coefficients in ind-coherent sheaves on noetherian derived $\mathbb F_p$-schemes. For such a scheme $X$, we consider the stable presentable category $\mathrm{Cart}(X)$ of ind-coherent sheaves $M$ equipped with a structural morphism $F_{*,X}M \to M$, where $F_X$ denotes the Frobenius endomorphism. We construct pushforward functors for arbitrary morphisms and exceptional pullback functors for separated morphisms almost of finite type, together with coherent composition and base-change equivalences. We single out conditions under which these functors admit further adjoints. On derived schemes separated and almost of finite type over $\mathbb F_p$, we construct compatible closed symmetric monoidal structures given by shriek tensor products, and establish which functors are symmetric monoidal. The constructions arise from a general procedure for forming functor formalisms of Cartier objects, using their description as lax limits and the universal properties of span $2$-categories developed by Cnossen--Lenz--Linskens [arXiv:2505.19192].