The Euler Class and Flux Homomorphisms under Non-Orientability
Geometric Topology
2025-08-19 v1
Abstract
For an orientable surface with an area form, there are two invariants of area-preserving dynamics, the flux homomorphism and the Calabi invariant. Tsuboi found a remarkable connection between the Calabi invariant on the closed disk and a topological invariant -- the Euler class. In this paper, we investigate a relationship between the Euler class and the flux homomorphism for non-orientable compact surfaces with one boundary component. Furthermore, we prove the simplicity of the kernel of the flux homomorphisms in this non-orientable setting, which implies the non-existence of invariants analogous to the Calabi invariant.
Cite
@article{arxiv.2508.12874,
title = {The Euler Class and Flux Homomorphisms under Non-Orientability},
author = {KyeongRo Kim and Shuhei Maruyama},
journal= {arXiv preprint arXiv:2508.12874},
year = {2025}
}