On the rate of graded modules

Abstract

Let $K$ be a field, $R$ a standard graded $K$-algebra and $M$ be a finitely generated graded $R$-module. The rate of $M$, $rat{e}_R(M)$, is a measure of the growth of the shifts in the minimal graded free resolution of $M$. In this paper, we find upper bounds for this invariant. More precisely, let $(A,\mathfrak{n})$ be a regular local ring and $I\subseteq {\mathfrak{n}}^t$ be an ideal of $A$, where $t\ge 2$. We prove that if $(B=A/I,\mathfrak{m}=\mathfrak{n}/I)$ is a Cohen-Macaulay local ring with multiplicity $e(B)=\left(\genfrac{}{}{0ex}{}{h+t-1}{h}\right)$, where $h=embdim(B)-dimB$, then $rat(g{r}_{\mathfrak{m}}(B))=t-1$ and for every $B$-module $N$, which annihilated by a minimal reduction of $\mathfrak{m}$, $rat{e}_{g{r}_{\mathfrak{m}}(B)}(g{r}_{\mathfrak{m}}(N))\le t-1$.

This paper has been withdrawn by the author due to some changes in the paper