$\mathbb Z_{/p}\times \mathbb Z_{/p}$ actions on $S^n\times S^n$

Fuente: arXiv
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Main Authors: Fowler, Jim, Thatcher, Courtney
Format: Preprint
Published: 2019
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author Fowler, Jim
Thatcher, Courtney
author_facet Fowler, Jim
Thatcher, Courtney
contents We determine the homotopy type of quotients of $S^n \times S^n$ by free actions of $\mathbb Z_{/p} \times \mathbb Z_{/p}$ where $2p>n+3$. Much like free $\mathbb Z_{/p}$ actions, they can be classified via the first $p$-localized $k$-invariant, but there are restrictions on the possibilities, and these restrictions are sufficient to determine every possibility in the $n=3$ case. We use this to complete the classification of free $\mathbb Z_{/p} \times \mathbb Z_{/p}$ actions on $S^3 \times S^3$, for $p>3$, by reducing the problem to the simultaneous classification of pairs of binary quadratic forms. Although the restrictions are not sufficient to determine which $k$-invariants are realizable in general, they can sometimes be used to rule out free actions by groups that contain $\mathbb Z_{/p}\times\mathbb Z_{/p}$ as a normal Abelian subgroup.
format Preprint
id arxiv_https___arxiv_org_abs_1912_12007
institution arXiv
publishDate 2019
record_format arxiv
spellingShingle $\mathbb Z_{/p}\times \mathbb Z_{/p}$ actions on $S^n\times S^n$
Fowler, Jim
Thatcher, Courtney
Geometric Topology
Algebraic Topology
We determine the homotopy type of quotients of $S^n \times S^n$ by free actions of $\mathbb Z_{/p} \times \mathbb Z_{/p}$ where $2p>n+3$. Much like free $\mathbb Z_{/p}$ actions, they can be classified via the first $p$-localized $k$-invariant, but there are restrictions on the possibilities, and these restrictions are sufficient to determine every possibility in the $n=3$ case. We use this to complete the classification of free $\mathbb Z_{/p} \times \mathbb Z_{/p}$ actions on $S^3 \times S^3$, for $p>3$, by reducing the problem to the simultaneous classification of pairs of binary quadratic forms. Although the restrictions are not sufficient to determine which $k$-invariants are realizable in general, they can sometimes be used to rule out free actions by groups that contain $\mathbb Z_{/p}\times\mathbb Z_{/p}$ as a normal Abelian subgroup.
title $\mathbb Z_{/p}\times \mathbb Z_{/p}$ actions on $S^n\times S^n$
topic Geometric Topology
Algebraic Topology
url https://arxiv.org/abs/1912.12007