The existence of identity of periodic semigroup rings

IN ref. [1], Ponizovskiǐ raised the following problem: which semigroup rings are rings with identity? In ref. [2], Li investigated orthodox semigroup rings. In this letter we discuss periodic semigroup rings. Using the same notation as in ref. [2], we

A Theorem on the Structure of the Ring A_(cris)

In this paper, we give a new description for the structure of the p-adic period subring Acris using formal groups.