An estimate for F-jumping numbers via the roots of the Bernstein-Sato polynomial

Abstract

Given a smooth complex algebraic variety $X$ and a nonzero regular function $f$ on $X$, we give an effective estimate for the difference between the jumping numbers of $f$ and the $F$-jumping numbers of a reduction $f_p$ of $f$ to characteristic $p\gg 0$, in terms of the roots of the Bernstein-Sato polynomial $b_f$ of $f$. As an application, we show that if $b_f$ has no roots of the form $-\mathrm{lct}(f)-n$, with $n$ a positive integer, then the $F$-pure threshold of $f_p$ is equal to the log canonical threshold of $f$ for $p\gg 0$ with $(p-1)\mathrm{lct}(f)\in \mathbf{Z}$.

arXiv comment10 pages; v.2: using a bound for the roots of the Bernstein-Sato polynomial, we deduce a uniform estimate only involving the dimension of the ambient variety and explain how this extends to possibly non-principal ideals. V.3: revised version, to appear in Proceedings of the AMS