English

Lehmer sequence approach to the divisibility of class numbers of imaginary quadratic fields

Number Theory 2022-10-04 v1

Abstract

Let k3k\geq 3 and n3n\geq 3 be odd integers, and let m0m\geq 0 be any integer. For a prime number \ell, we prove that the class number of the imaginary quadratic field Q(2m2kn)\mathbb{Q}(\sqrt{\ell^{2m}-2k^n}) is either divisible by nn or by a specific divisor of nn. Applying this result, we construct an infinite family of certain tuples of imaginary quadratic fields of the form (Q(d),Q(d+1),Q(4d+1),Q(2d+4),Q(2d+16),,Q(2d+4t))\left(\mathbb{Q}(\sqrt{d}), \mathbb{Q}(\sqrt{d+1}), \mathbb{Q}(\sqrt{4d+1}), \mathbb{Q}(\sqrt{2d+4}), \mathbb{Q}(\sqrt{2d+16}), \cdots, \mathbb{Q}(\sqrt{2d+4^t}) \right) with dZd\in \mathbb{Z} and 14t2d1\leq 4^t\leq 2|d| whose class numbers are all divisible by nn. Our proofs use some deep results about primitive divisors of Lehmer sequences.

Keywords

Cite

@article{arxiv.2210.00561,
  title  = {Lehmer sequence approach to the divisibility of class numbers of imaginary quadratic fields},
  author = {Kalyan Chakraborty and Azizul Hoque},
  journal= {arXiv preprint arXiv:2210.00561},
  year   = {2022}
}

Comments

12 pages. To appear in 'The Ramanujan Journal'