Quasi-Isomorphisms of Commutative DG Rings and Divided Power Structures

Abstract

We prove that a quasi-isomorphism $f : A \to B$ between commutative DG rings, where $B$ admits a divided power structure, can be factored as $f = \tilde{f} \circ e$, where $e : A \to \tilde{B}$ is a split injective quasi-isomorphism, and $\tilde{f} : \tilde{B} \to B$ is a surjective quasi-isomorphism. This result is used in our work on a DG approach to the cotangent complex, and our work on the derived category of commutative DG rings.