English

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

Geometric Topology 2024-07-24 v3 Algebraic Topology

Abstract

We determine the homotopy type of quotients of Sn×SnS^n \times S^n by free actions of Z/p×Z/p\mathbb Z_{/p} \times \mathbb Z_{/p} where 2p>n+32p>n+3. Much like free Z/p\mathbb Z_{/p} actions, they can be classified via the first pp-localized kk-invariant, but there are restrictions on the possibilities, and these restrictions are sufficient to determine every possibility in the n=3n=3 case. We use this to complete the classification of free Z/p×Z/p\mathbb Z_{/p} \times \mathbb Z_{/p} actions on S3×S3S^3 \times S^3, for p>3p>3, by reducing the problem to the simultaneous classification of pairs of binary quadratic forms. Although the restrictions are not sufficient to determine which kk-invariants are realizable in general, they can sometimes be used to rule out free actions by groups that contain Z/p×Z/p\mathbb Z_{/p}\times\mathbb Z_{/p} as a normal Abelian subgroup.

Keywords

Cite

@article{arxiv.1912.12007,
  title  = {$\mathbb Z_{/p}\times \mathbb Z_{/p}$ actions on $S^n\times S^n$},
  author = {Jim Fowler and Courtney Thatcher},
  journal= {arXiv preprint arXiv:1912.12007},
  year   = {2024}
}

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22 pages