We compute the moduli of endomorphisms of the de Rham and crystalline cohomology functors, viewed as a cohomology theory on smooth schemes over truncated Witt vectors. As applications of our result, we deduce Drinfeld's refinement of the classical Deligne-Illusie decomposition result for de Rham cohomology of varieties in characteristic p > 0 that are liftable to W 2 , and prove further functorial improvements.
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