English

Quadratic Segre indices

Algebraic Geometry 2026-01-28 v2

Abstract

We prove that the local Euler class of a line on a degree 2n12n-1 hypersurface in projective n+1n+1 space is given by a product of indices of Segre involutions. Segre involutions and their associated indices were first defined by Finashin and Kharlamov over the reals. Our result is valid over any perfect field of characteristic not 2 and gives an infinite family of problems in enriched enumerative geometry with a shared geometric interpretation for the local type.

Keywords

Cite

@article{arxiv.2506.01547,
  title  = {Quadratic Segre indices},
  author = {Felipe Espreafico and Stephen McKean and Sabrina Pauli},
  journal= {arXiv preprint arXiv:2506.01547},
  year   = {2026}
}

Comments

41 pages, 2 figures. A few errors corrected, and some explanations improved. Comments welcome!

R2 v1 2026-07-01T02:54:11.426Z