English

Torus actions of complexity one in non-general position

Algebraic Topology 2023-02-20 v1 Combinatorics

Abstract

Let the compact torus Tn1T^{n-1} act on a smooth compact manifold X2nX^{2n} effectively with nonempty finite set of fixed points. We pose the question: what can be said about the orbit space X2n/Tn1X^{2n}/T^{n-1} if the action is cohomologically equivariantly formal (which essentially means that Hodd(X2n;Z)=0H^{odd}(X^{2n};\mathbb{Z})=0). It happens that homology of the orbit space can be arbitrary in degrees 33 and higher. For any finite simplicial complex LL we construct an equivariantly formal manifold X2nX^{2n} such that X2n/Tn1X^{2n}/T^{n-1} is homotopy equivalent to Σ3L\Sigma^3L. The constructed manifold X2nX^{2n} is the total space of the projective line bundle over the permutohedral variety hence the action on X2nX^{2n} is Hamiltonian and cohomologically equivariantly formal. We introduce the notion of the action in jj-general position and prove that, for any simplicial complex MM, there exists an equivariantly formal action of complexity one in jj-general position such that its orbit space is homotopy equivalent to Σj+2M\Sigma^{j+2}M.

Keywords

Cite

@article{arxiv.1905.04761,
  title  = {Torus actions of complexity one in non-general position},
  author = {Anton Ayzenberg and Vladislav Cherepanov},
  journal= {arXiv preprint arXiv:1905.04761},
  year   = {2023}
}

Comments

14 pages

R2 v1 2026-06-23T09:04:08.586Z