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Main Authors: Kim, Dohyeong, Yang, Ingyu
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2511.17095
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author Kim, Dohyeong
Yang, Ingyu
author_facet Kim, Dohyeong
Yang, Ingyu
contents For primes $p$ and $\ell$ such that $\ell$ divides $p-1$, Hirano and Morishita constructed a nonabelian Galois extension of the function field $\mathbb{F}_p(t)$ whose degree is $\ell^3$ and Galois group is of Heisenberg type. Here we analyze how primes of degree one decompose in such extensions. It amounts to investigating the decomposition of the principal ideal $(t-a)$ for $a \in \mathbb{F}_p-\{0,1\}$ and our main result determines when it decomposes completely in terms of an explicit polynomial in $a$. It is reminiscent of Euler's criterion. The proof relies on both the group structure of the mod-$\ell$ Heisenberg group and the arithmetic of field extensions.
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id arxiv_https___arxiv_org_abs_2511_17095
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publishDate 2025
record_format arxiv
spellingShingle The decomposition of primes in nonabelian extensions of Heisenberg type and an analogue of Euler's criterion
Kim, Dohyeong
Yang, Ingyu
Number Theory
For primes $p$ and $\ell$ such that $\ell$ divides $p-1$, Hirano and Morishita constructed a nonabelian Galois extension of the function field $\mathbb{F}_p(t)$ whose degree is $\ell^3$ and Galois group is of Heisenberg type. Here we analyze how primes of degree one decompose in such extensions. It amounts to investigating the decomposition of the principal ideal $(t-a)$ for $a \in \mathbb{F}_p-\{0,1\}$ and our main result determines when it decomposes completely in terms of an explicit polynomial in $a$. It is reminiscent of Euler's criterion. The proof relies on both the group structure of the mod-$\ell$ Heisenberg group and the arithmetic of field extensions.
title The decomposition of primes in nonabelian extensions of Heisenberg type and an analogue of Euler's criterion
topic Number Theory
url https://arxiv.org/abs/2511.17095