A contramodule generalization of Neeman's flat and projective module theorem

This paper builds on top of arXiv:2306.02734. We consider a complete, separated topological ring R with a countable base of neighborhoods of zero consisting of open two-sided ideals. The main result is that the homotopy category of projective left R-contramodules is equivalent to the derived category of the exact category of flat left R-contramodules. In other words, a complex of flat R-contramodules is contraacyclic in the sense of Becker if and only if it is an acyclic complex with flat R-contramodules of cocycles.