Topology of rational equivalence closures and Lawson homology
Abstract
Rational equivalence need not be closed in the Chow topology, and its closure can have infinitely generated homotopy groups. For a connected reduced complex projective variety, we prove that this closure is locally contractible and that its quotient in the algebraically trivial cycles is a finite or countable weak product of circles. The quotient map admits a global continuous section. Consequently, the higher homotopy of the cycle space is carried by the closure and is canonically identified with Lawson homology. We describe the remaining fundamental group quotient and its integral Walker comparison. Applications include smooth projective examples with infinite rank closure homotopy throughout prescribed finite intervals and a family of abelian threefolds with four simultaneously dense, nonconstructible quotient rank strata.
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BibTeX
@misc{hu2026topology,
title = {{Topology of rational equivalence closures and Lawson homology}},
author = {Wenchuan Hu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.36913},
eprint = {2610.36913},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.36913},
}
RIS
TY - UNPB
TI - Topology of rational equivalence closures and Lawson homology
AU - Wenchuan Hu
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.36913
UR - https://arxiv.org/abs/2610.36913
AB - Rational equivalence need not be closed in the Chow topology, and its closure can have infinitely generated homotopy groups. For a connected reduced complex projective variety, we prove that this closure is locally contractible and that its quotient in the algebraically trivial cycles is a finite or countable weak product of circles. The quotient map admits a global continuous section. Consequently, the higher homotopy of the cycle space is carried by the closure and is canonically identified with Lawson homology. We describe the remaining fundamental group quotient and its integral Walker comparison. Applications include smooth projective examples with infinite rank closure homotopy throughout prescribed finite intervals and a family of abelian threefolds with four simultaneously dense, nonconstructible quotient rank strata.
ER -