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The least prime with a given cycle type

Peter J. Cho, Robert J. Lemke Oliver, Asif Zaman

Abstract

Let $G$ be a finite group. Let $K/k$ be a Galois extension of number fields with Galois group isomorphic to $G$, and let $C \subseteq \mathrm{Gal}(K/k) \simeq G$ be a conjugacy invariant subset. It is well known that there exists an unramified prime ideal $\mathfrak{p}$ of $k$ with Frobenius element lying in $C$ and norm satisfying $\mathrm{N}\mathfrak{p} \ll |\mathrm{Disc}(K)|^α$ for some constant $α= α(G,C)$. There is a rich literature establishing unconditional admissible values for $α$, with most approaches proceeding by studying the zeros of $L$-functions. We give an alternative approach, not relying on zeros, that often substantially improves this exponent $α$ for any fixed finite group $G$, provided $C$ is a union of rational equivalence classes. As a particularly striking example, we prove that there exist absolute constants $c_1,c_2 > 0$ such that for any $n\geq 2$ and any conjugacy class $C \subset S_n$, one may take $α(S_n,C) = c_1 \exp(-c_2n)$. Our approach reduces the core problem to a question in character theory.

The least prime with a given cycle type

Abstract

Let be a finite group. Let be a Galois extension of number fields with Galois group isomorphic to , and let be a conjugacy invariant subset. It is well known that there exists an unramified prime ideal of with Frobenius element lying in and norm satisfying for some constant . There is a rich literature establishing unconditional admissible values for , with most approaches proceeding by studying the zeros of -functions. We give an alternative approach, not relying on zeros, that often substantially improves this exponent for any fixed finite group , provided is a union of rational equivalence classes. As a particularly striking example, we prove that there exist absolute constants such that for any and any conjugacy class , one may take . Our approach reduces the core problem to a question in character theory.
Paper Structure (30 sections, 42 theorems, 140 equations, 9 tables)

This paper contains 30 sections, 42 theorems, 140 equations, 9 tables.

Key Result

Theorem 1.1

Let $f$ be a monic irreducible polynomial of degree $n$ over a number field $k$. Let $K$ be its splitting field, and let $G := \mathrm{Gal}(K/k)$ be its Galois group, viewed as a subgroup of $S_n$ as described above. Let $\lambda = (\lambda_1,\dots,\lambda_r)$ be a cycle type occuring in $G$, and se where $\omega(\ell)$ denotes the number of distinct prime factors of $\ell$. The implied constant a

Theorems & Definitions (82)

  • Theorem 1.1
  • Theorem 1.2
  • Theorem 1.3
  • Theorem 2.1
  • Remark 2.1.1
  • Corollary 2.2
  • Remark 2.2.1
  • Theorem 2.3
  • Corollary 2.4
  • Theorem 2.5
  • ...and 72 more