English

Small integral generators of totally complex number fields

Number Theory 2025-08-15 v6

Abstract

Let KK be an algebraic number field and HH the absolute Weil height. Write cKc_K for a certain positive constant that is an invariant of KK. We consider the question: does KK contain an algebraic integer α\alpha such that both K=Q(α)K = \mathbb{Q}(\alpha) and H(α)cKH(\alpha) \le c_K? If KK has a real embedding then a positive answer was established in previous work. Here we obtain a positive answer if Tor(K×){±1}\textrm{Tor}\bigl(K^{\times}\bigr) \not= \{\pm 1\}, and so KK has only complex embeddings. We also show that if the answer is negative, then KK is totally complex, Tor(K×)={±1}\textrm{Tor}\bigl(K^{\times}\bigr) = \{\pm 1\}, and KK is a Galois extension of its maximal totally real subfield. Further, we show that if μOK\mu \in O_K is not totally real, then there exists α\alpha in OKO_K with K=Q(α)K = \mathbb{Q}(\alpha) and H(α)H(μ)cKH(\alpha) \le H(\mu)\thinspace c_K.

Keywords

Cite

@article{arxiv.2307.11849,
  title  = {Small integral generators of totally complex number fields},
  author = {Shabnam Akhtari and Jeffrey Vaaler and Martin Widmer},
  journal= {arXiv preprint arXiv:2307.11849},
  year   = {2025}
}

Comments

previously cited as "A note on small generators of number fields, II"

R2 v1 2026-06-28T11:37:21.078Z