Divided Powers and Derived De Rham Cohomology

Abstract

We develop the formalism of derived divided power algebras, and revisit the theory of derived De Rham and crystalline cohomology in this framework. We characterize derived De Rham cohomology of a derived commutative ring $A$, together with the Hodge filtration on it, in terms of a universal property as the largest filtered divided power thickening of $A$. We show that our approach agrees with A.Raksit's. Along the way, we develop some fundamentals of square-zero extensions and derivations in derived algebraic geometry in connection with derived De Rham cohomology.