The Structure and Degrees of Polynomials Computing Square Roots $\mod p$

Fuente: arXiv
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Auteurs principaux: Chnaras, Foivos, Kupinsky, Noah
Format: Preprint
Publié: 2025
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author Chnaras, Foivos
Kupinsky, Noah
author_facet Chnaras, Foivos
Kupinsky, Noah
contents For an odd prime $p$, we say a polynomial $f\in \mathbb F_p[X]$ computes square roots if $f(a)^2=a$ for all nonzero, perfect squares $a\in \mathbb F_p$. When $p\equiv 3 \mod 4$, it is easy to see that $f(X)=X^{\frac{p+1}{4}}$ is the smallest such polynomial. For $p\equiv 1 \mod 4$, the situation is less clear. Tonelli-Shanks offers an algorithm for constructing polynomials that compute square roots, but the question of whether their degree is minimal remains. In this paper, we study the various degrees and structures of polynomials computing square roots.
format Preprint
id arxiv_https___arxiv_org_abs_2511_22881
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Structure and Degrees of Polynomials Computing Square Roots $\mod p$
Chnaras, Foivos
Kupinsky, Noah
Number Theory
For an odd prime $p$, we say a polynomial $f\in \mathbb F_p[X]$ computes square roots if $f(a)^2=a$ for all nonzero, perfect squares $a\in \mathbb F_p$. When $p\equiv 3 \mod 4$, it is easy to see that $f(X)=X^{\frac{p+1}{4}}$ is the smallest such polynomial. For $p\equiv 1 \mod 4$, the situation is less clear. Tonelli-Shanks offers an algorithm for constructing polynomials that compute square roots, but the question of whether their degree is minimal remains. In this paper, we study the various degrees and structures of polynomials computing square roots.
title The Structure and Degrees of Polynomials Computing Square Roots $\mod p$
topic Number Theory
url https://arxiv.org/abs/2511.22881