The Hilbert-Kunz function of rings of finite Cohen-Macaulay type

Seibert, Gerhard (1997) The Hilbert-Kunz function of rings of finite Cohen-Macaulay type. ARCHIV DER MATHEMATIK, 69 (4). pp. 286-296. ISSN 0003-889X, 1420-8938

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Abstract

Let (R, m, k) be a Noetherian local ring of prime characteristic p and d its Krull dimension. It is known that for an m-primary ideal l of R and a finitely generated R-module N the limit lim(n=infinity l?R(N/Gamma?(\n\N)/p(dn) exists where I-[n] denotes the ideal of R generated by x(Pn), x is an element of I, and I-R(M) the length of an R-module M. We will show that the ordinary generating function (n=0)Sigma(infinity)l(R)(N/(IN)-N-\n\)t(n) is an element of Q[[t]] of the Hilbert-Kunz function N --> N, n --> I-R(N/Gamma(\n\)N) is rational, i.e., an element of Q(t), if R-(1) is a finite R-module, N a maximal Cohen-Macaulay module and R is of finite Cohen-Macaulay type, i.e., the number of isomorphism classes of finite, indecomposable maximal Cohen-Macaulay modules over R is finite. From this result, we deduce that lim l(R)(N/I-(N)N)/p(dn) is an element of Q. Here R-(1) denotes R considered as an R-algebra via the Frobenius map R --> R, x --> x(P). Actually we will consider a somewhat more general situation using the Frobenius functor.

Item Type: Article
Uncontrolled Keywords: FROBENIUS
Subjects: 500 Science > 510 Mathematics
Divisions: Mathematics
Depositing User: Dr. Gernot Deinzer
Date Deposited: 28 Mar 2023 06:44
Last Modified: 28 Mar 2023 06:44
URI: https://pred.uni-regensburg.de/id/eprint/50491

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