English

Non-isogenous superelliptic jacobians II

Number Theory 2024-10-24 v4 Algebraic Geometry

Abstract

Let \ell be an odd prime and KK a field of characteristic different from \ell. Let Kˉ\bar{K} be an algebraic closure of KK. Assume that KK contains a primitive \ellth root of unity. Let nn \ne \ell be another odd prime. Let f(x)f(x) and h(x)h(x) be degree nn polynomials with coefficients in KK and without repeated roots. Let us consider superelliptic curves Cf,:y=f(x)C_{f,\ell}: y^{\ell}=f(x) and Ch,:y=h(x)C_{h,\ell}: y^{\ell}=h(x) of genus (n1)(1)/2(n-1)(\ell-1)/2, and their jacobians J(f,)J^{(f,\ell)} and J(h,)J^{(h,\ell)}, which are (n1)(1)/2(n-1)(\ell-1)/2-dimensional abelian varieties over Kˉ\bar{K}. Suppose that one of the polynomials is irreducible and the other reducible over KK. We prove that if J(f,)J^{(f,\ell)} and J(h,)J^{(h,\ell)} are isogenous over Kˉ\bar{K} then both endomorphism algebras End0(J(f,))\mathrm{End}^{0}(J^{(f,\ell)}) and End0(J(h,))\mathrm{End}^{0}(J^{(h,\ell)}) contain an invertible element of multiplicative order nn.

Keywords

Cite

@article{arxiv.2401.01365,
  title  = {Non-isogenous superelliptic jacobians II},
  author = {Yuri G. Zarhin},
  journal= {arXiv preprint arXiv:2401.01365},
  year   = {2024}
}

Comments

19 pages. arXiv admin note: substantial text overlap with arXiv:2204.10567

R2 v1 2026-06-28T14:07:12.949Z