Exponential sums and motivic oscillation index of arbitrary ideals and their applications

Abstract

In 2006, Budur, Musta\c{t}\v{a} and Saito introduced the notion of Bernstein-Sato polynomial of an arbitrary scheme of finite type over fields of characteristic zero. Because of the strong monodromy conjecture, it should have a corresponding picture on the arithmetic side of ideals in polynomial rings. In this paper, we try to address this problem. Motivated by the Hardy-Littlewood circle method, we introduce the notions of abstract exponential sums modulo $p^m$ and motivic oscillation index of an arbitrary ideal in polynomial rings over number fields. In the arithmetic picture, the abstract exponential sums modulo $p^m$ and the motivic oscillation index of an ideal should play the role of the Bernstein-Sato polynomial and its maximal non-trivial root of the corresponding scheme. We will provide some properties of the motivic oscillation index of ideals in this paper. On the other hand, based on Igusa's conjecture for exponential sums, we propose the averaged Igusa conjecture for exponential sums of ideals. In particular, this conjecture and the motivic oscillation index of ideals will have many interesting applications. We will introduce these applications and prove some variant version of this conjecture.