ECCC-Report TR20-092https://eccc.weizmann.ac.il/report/2020/092Comments and Revisions published for TR20-092en-usTue, 16 Jun 2020 11:32:14 +0300
Paper TR20-092
| Computing Igusa's local zeta function of univariates in deterministic polynomial-time |
Ashish Dwivedi,
Nitin Saxena
https://eccc.weizmann.ac.il/report/2020/092Igusa's local zeta function $Z_{f,p}(s)$ is the generating function that counts the number of integral roots, $N_{k}(f)$, of $f(\mathbf x) \bmod p^k$, for all $k$. It is a famous result, in analytic number theory, that $Z_{f,p}$ is a rational function in $\mathbb{Q}(p^s)$. We give an elementary proof of this fact for a univariate polynomial $f$. Our proof is constructive as it gives a closed-form expression for the number of roots $N_{k}(f)$.
Our proof, when combined with the recent root-counting algorithm of (Dwivedi, Mittal, Saxena, CCC, 2019), yields the first deterministic poly($|f|, \log p$) time algorithm to compute $Z_{f,p}(s)$. Previously, an algorithm was known only in the case when $f$ completely splits over $\mathbb{Q_p}$; it required the rational roots to use the concept of generating function of a tree (Zuniga-Galindo, J.Int.Seq., 2003).Tue, 16 Jun 2020 11:32:14 +0300https://eccc.weizmann.ac.il/report/2020/092