English

The real cycle class isomorphism for linear schemes

Algebraic Geometry 2025-11-05 v1 Algebraic Topology K-Theory and Homology

Abstract

The real cycle class map Hi(X,Ij(L))Hsingi(X(R),Z(L))H^i(X,\underline{I}^j(\mathcal{L})) \rightarrow H^i_\text{sing}(X(\mathbb{R}),\mathbb{Z}(\mathcal{L})) is an isomorphism for jdim(X)+1j\geq \dim(X)+1 for any scheme XX over R\mathbb{R} by a result of Jacobson. It is also known to be an isomorphism for jij\geq i, the earliest possible case, if XX is cellular due to Hornbostel-Wendt-Xie-Zibrowius. This paper generalizes their result to linear schemes, providing (precise) intermediate bounds on the range, where the real cycle class map is an isomorphism. Moreover, we show that Lerbet's conjectured upper bound for the exponent of the cokernel of Hi(X,Ii(L))Hsingi(X(R),Z(L))H^i(X,\underline{I}^i(\mathcal{L})) \rightarrow H^i_\text{sing}(X(\mathbb{R}),\mathbb{Z}(\mathcal{L})) cannot be improved. This is part of the author's PhD thesis.

Keywords

Cite

@article{arxiv.2511.02549,
  title  = {The real cycle class isomorphism for linear schemes},
  author = {Jan Hennig},
  journal= {arXiv preprint arXiv:2511.02549},
  year   = {2025}
}

Comments

11 pages, Comments very welcome!

R2 v1 2026-07-01T07:21:10.182Z