Bernstein-Sato polynomials and test modules in positive characteristic

Abstract

In analogy with the complex analytic case, Mustaţă constructed (a family of) Bernstein-Sato polynomials for the structure sheaf ${\mathcal{O}}_X$ and a hypersurface $(f=0)$ in $X$, where $X$ is a regular variety over an $F$-finite field of positive characteristic (see arxiv:0711.3794). He shows that the suitably interpreted zeros of his Bernstein-Sato polynomials correspond to the jumping numbers of the test ideal filtration $\tau (X,f^t)$. In the present paper we generalize Mustaţă's construction replacing ${\mathcal{O}}_X$ by an arbitrary $F$-regular Cartier module $M$ on $X$ and show an analogous correspondence of the zeros of our Bernstein-Sato polynomials with the jumping numbers of the associated filtration of test modules $\tau (M,f^t)$ provided that $f$ is a non-zero divisor on $M$.

arXiv comment13 pages; v2: Corrected a mistake in Lemma 4.1, a comparison to Stadnik's theory of $b$-functions (arXiv:1206.4039) was added; final version