Equivariantly formal 2-torus actions of complexity one

In this paper we study a specific class of actions of a 2-torus $\mathbb{Z}_{2}^{k}$ on manifolds, namely, the actions of complexity one in general position. We describe the orbit space of equivariantly formal 2-torus actions of complexity one in general position and restricted complexity one actions in the case of small covers. It is observed that the orbit spaces of such actions are topological manifolds. If the action is equivariantly formal, we prove that the orbit space is a $\mathbb{Z}_{2}$-homology sphere. We study a particular subclass of these 2-torus actions: restrictions of small covers to a subgroup of index 2 in general position. The subgroup of this form exists if and only if the small cover is orientable, and in this case we prove that the orbit space of a restricted 2-torus action is homeomorphic to a sphere.

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Publication Details

Journal
Journal of the Mathematical Society of Japan
Published
2025-03-26
DOI
https://doi.org/10.2969/jmsj/91479147
Primary Topic
Advanced Combinatorial Mathematics
Type
article
Field-Weighted Citation Impact
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article

Equivariantly formal 2-torus actions of complexity one

Vladimir Gorchakov
Journal of the Mathematical Society of Japan
Advanced Combinatorial Mathematics
article

Equivariantly formal 2-torus actions of complexity one

Vladimir Gorchakov
article en

Abstract

In this paper we study a specific class of actions of a 2-torus $\mathbb{Z}_{2}^{k}$ on manifolds, namely, the actions of complexity one in general position. We describe the orbit space of equivariantly formal 2-torus actions of complexity one in general position and restricted complexity one actions in the case of small covers. It is observed that the orbit spaces of such actions are topological manifolds. If the action is equivariantly formal, we prove that the orbit space is a $\mathbb{Z}_{2}$-homology sphere. We study a particular subclass of these 2-torus actions: restrictions of small covers to a subgroup of index 2 in general position. The subgroup of this form exists if and only if the small cover is orientable, and in this case we prove that the orbit space of a restricted 2-torus action is homeomorphic to a sphere.

Journal of the Mathematical Society of JapanVol. -1(-1)
National Research University Higher School of Economics (RU)
Openalex Percentile: Top 91%
Advanced Combinatorial Mathematics
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