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arXiv · 2302.05165

The distribution of the multiplicative index of algebraic numbers over residue classes

Pieter Moree·Antonella Perucca·Pietro Sgobba
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Abstract

Let $K$ be a number field and $G$ a finitely generated torsion-free subgroup of $K^\times$. Given a prime $\mathfrak p$ of $K$ we denote by ${\rm ind}_{\mathfrak p}(G)$ the index of the subgroup $(G\bmod\mathfrak p)$ of the multiplicative group of the residue field at $\mathfrak p$. Under the Generalized Riemann Hypothesis we determine the natural density of primes of $K$ for which this index is in a prescribed set $S$ and has prescribed Frobenius in a finite Galois extension $F$ of $K$. We study in detail the natural density in case $S$ is an arithmetic progression, in particular its positivity.

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Pieter Moree, Antonella Perucca, Pietro Sgobba. 2023-02-10. The distribution of the multiplicative index of algebraic numbers over residue classes. https://doi.org/10.1007/s12188-024-00276-2

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