arXiv subjects
Publications and source records attributed to Harald Weber.
Let p be an odd prime. We consider the cyclotomic extension T := Z_(p)[zeta_{p^2}] of S := Z_(p), with galois group G := (Z/p^2)^*. Since this extension is wildly ramified, the SG-module T is not projective. We calculate its cohomology ring H^*(G, T; S), carrying the cup product induced by the ring structure of T. Proceeding in a somewhat greater generality, our results also apply to certain Lubin-Tate extensions.
Let n >= 1 and let p be a prime. Let t = 1 - zeta_{p^n}. Expand an integer j in [0,p^n-1], coprime to p, p-adically as j = sum_{s >= 0} a_s p^s. Denote the tensor product over Z_(p) by o . Then the #([0,j] - (p))th Z_(p)[t]-linear elementary divisor of the cyclotomic Dedekind embedding Z_(p)[t] o Z_(p)[t] --> prod_{i in (Z/p^n)^*} Z_(p)[t] has valuation -1 + sum_{s >= 0} (a_s (s+1) - a_{s+1} (s+2)) p^s at t. There is a similar result for the related cyclic Wedderburn embedding.