English

$\mathbb{K}$-framings and $\mathbb{K}$-quadratic forms on surfaces

Geometric Topology 2026-05-01 v1 Algebraic Topology

Abstract

We introduce the notions of K\mathbb{K}-framings, based K\mathbb{K}-framings and relative K\mathbb{K}-framings of a compact connected oriented surface Σ\Sigma for any commutative ring K\mathbb{K} with unit, and a map which maps a based loop on Σ\Sigma to a homology class of its unit tangent bundle UΣU\Sigma, which recovers Johnson's lifting in the case K=Z/2\mathbb{K} = \mathbb{Z}/2. This generalizes the correspondence between a quadratic form and a spin structure established by Johnson to any commutative ring K\mathbb{K} with unit. If the genus of Σ\Sigma is positive, we have a bijection between the set of K\mathbb{K}-framings and the set of some twisted cocycles of the mapping class group of the surface Σ\Sigma. Through this bijection, in the case where the boundary Σ\partial\Sigma is non-empty and connected, we discuss some relation between K\mathbb{K}-framings and the extended first Johnson homomorphism.

Keywords

Cite

@article{arxiv.2604.27531,
  title  = {$\mathbb{K}$-framings and $\mathbb{K}$-quadratic forms on surfaces},
  author = {Nariya Kawazumi},
  journal= {arXiv preprint arXiv:2604.27531},
  year   = {2026}
}
R2 v1 2026-07-01T12:43:03.639Z