English

Proper actions and supported-section-valued cohomology

Group Theory 2024-11-18 v1 Algebraic Topology General Topology K-Theory and Homology

Abstract

Consider a proper action of Zd\mathbb{Z}^d on a smooth (perhaps non-paracompact) manifold MM. The pthp^{th} cohomology Hp(Zd, Γc(F))H^p(\mathbb{Z}^d,\ \Gamma_{\mathrm{c}}(\mathcal{F})) valued in the space of compactly-supported sections of a natural sheaf F\mathcal{F} on MM (such as those of smooth function germs, smooth kk-form germs, etc.) vanishes for pdp\ne d (the cohomological dimension of Zd\mathbb{Z}^d) and, at dd, equals the space of compactly-supported sections of the descent (G\mathbb{G}-invariant push-forward) F/Zd\mathcal{F}/\mathbb{Z}^d to the orbifold quotient M/ZdM/\mathbb{Z}^d. We prove this and analogous results on Zd\mathbb{Z}^d cohomology valued in Φ\Phi-supported sections of an equivariant appropriately soft sheaf F\mathcal{F} in a broader context of Zd\mathbb{Z}^d-actions proper with respect to a paracompactifying family of supports Φ\Phi, in the sense that every member of Φ\Phi has a neighborhood small with respect to the action in Palais' sense.

Keywords

Cite

@article{arxiv.2411.09857,
  title  = {Proper actions and supported-section-valued cohomology},
  author = {Alexandru Chirvasitu},
  journal= {arXiv preprint arXiv:2411.09857},
  year   = {2024}
}

Comments

20 pages + references

R2 v1 2026-06-28T20:00:37.423Z