English

Genus-correspondences respecting spinor genus

Number Theory 2016-09-13 v1

Abstract

For two positive definite integral ternary quadratic forms ff and gg and a positive integer nn, if ngn\cdot g is represented by ff and ndg=dfn\cdot dg=df, then the pair (f,g)(f,g) is called a representable pair by scaling nn. The set of all representable pairs in gen(f)×gen(g)\text{gen}(f)\times \text{gen}(g) is called a genus-correspondence. Jagy conjectured that if nn is square free and the number of spinor genera in the genus of ff equals to the number of spinor genera in the genus of gg, then such a genus-correspondence respects spinor genus in the sense that for any representable pairs (f,g),(f,g)(f,g), (f',g') by scaling nn, fspn(f)f' \in \text{spn}(f) if and only if gspn(g)g' \in \text{spn}(g). In this article, we show that by giving a counter example, Jagy's conjecture does not hold. Furthermore, we provide a necessary and sufficient condition for a genus-correspondence to respect spinor genus.

Cite

@article{arxiv.1609.03031,
  title  = {Genus-correspondences respecting spinor genus},
  author = {Jangwon Ju and Byeong-Kweon Oh},
  journal= {arXiv preprint arXiv:1609.03031},
  year   = {2016}
}

Comments

13 pages

R2 v1 2026-06-22T15:45:41.259Z