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Nullhomotopic equivariant shifts and Borsuk-Ulam-compatible compact abelian groups
Abstract
We disprove the classical version of the Borsuk-Ulam-flavored conjecture, due to Baum-D{ą}browski-Hajac, that free actions X× 𝔾→ X on non-empty compact Hausdorff spaces by non-trivial compact groups admit no equivariant maps X*𝔾→ X. Specifically, among non-trivial compact abelian 𝔾, the conjecture fails precisely when 𝔾 is torsion-free profinite.
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BibTeX
@misc{chirvasitu2026nullhomotopic,
title = {{Nullhomotopic equivariant shifts and Borsuk-Ulam-compatible compact abelian groups}},
author = {Alexandru Chirvasitu and Alexander Dąbrowski},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.10111},
eprint = {2610.10111},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.10111},
}
RIS
TY - UNPB
TI - Nullhomotopic equivariant shifts and Borsuk-Ulam-compatible compact abelian groups
AU - Alexandru Chirvasitu
AU - Alexander Dąbrowski
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.10111
UR - https://arxiv.org/abs/2610.10111
AB - We disprove the classical version of the Borsuk-Ulam-flavored conjecture, due to Baum-D{ą}browski-Hajac, that free actions X× 𝔾→ X on non-empty compact Hausdorff spaces by non-trivial compact groups admit no equivariant maps X*𝔾→ X. Specifically, among non-trivial compact abelian 𝔾, the conjecture fails precisely when 𝔾 is torsion-free profinite.
ER -