English

Connected components of the ranges of twisted divisor functions on number fields

Number Theory 2026-05-27 v1

Abstract

Let rCr\in\mathbb{C}, let KK be a finite extension of Q\mathbb{Q}, let IKI_K be the monoid of integral ideals in the ring of integers OK\mathcal{O}_K of KK, and let χ\chi be a Dirichlet character. Then define the twisted ideal divisor function σr,K,χ:IKC\sigma_{r, K, \chi} : I_K \rightarrow \mathbb{C} by σr,K,χ(I)=JIN(J)rχ(N(J)),\sigma_{r,K,\chi}(I) = \sum_{J \mid I} N(J)^{-r}\chi(N(J)), where NN denotes the ideal norm. For real r>1,r>1, we study the number of connected components Cr,K,χC_{r, K, \chi} of the closure σr,K,χ(IK)\overline{\sigma_{r,K,\chi}(I_K)}, writing Cr,KC_{r,K} when χ\chi is the principal character modulo 1. We prove that Cr,K,χC_{r,K,\chi} is finite when χ\chi is real-valued. When K=QK = \mathbb{Q}, we show that for fixed r>1,r > 1, every sufficiently large positive integer is realized as Cr,Q,χ,C_{r,\mathbb{Q},\chi}, and if rr is sufficiently large, then every positive integer is realized as χ\chi varies. For finite Galois extensions KK over Q\mathbb{Q}, we exhibit new exponential lower bounds for Cr,K,C_{r,K}, and we prove that for every fixed integer s2s \geq 2, the values Cr,KC_{r,K} are unbounded as KK ranges over degree-ss extensions of Q\mathbb{Q}.

Keywords

Cite

@article{arxiv.2605.26482,
  title  = {Connected components of the ranges of twisted divisor functions on number fields},
  author = {Sophie Zhu},
  journal= {arXiv preprint arXiv:2605.26482},
  year   = {2026}
}