English

Borsuk-Ulam property and Sectional Category

Algebraic Topology 2023-09-12 v4

Abstract

For a Hausdorff space XX, a free involution τ:XX\tau:X\to X and a Hausdorff space YY, we discover a connection between the sectional category of the double covers q:XX/τq:X\to X/\tau and qY:F(Y,2)D(Y,2)q^Y:F(Y,2)\to D(Y,2) from the ordered configuration space F(Y,2)F(Y,2) to its unordered quotient D(Y,2)=F(Y,2)/Σ2D(Y,2)=F(Y,2)/\Sigma_2, and the Borsuk-Ulam property (BUP) for the triple ((X,τ);Y)\left((X,\tau);Y\right). Explicitly, we demonstrate that the triple ((X,τ);Y)\left((X,\tau);Y\right) satisfies the BUP if the sectional category of qq is bigger than the sectional category of qYq^Y. This property connects a standard problem in Borsuk-Ulam theory to current research trends in sectional category. As an application of our results, we show that the index of (X,τ)(X,\tau) coincides with the sectional category of the quotient map q:XX/τq:X\to X/\tau minus 1 for any paracompact space XX. In addition, we present some new results relating Borsuk-Ulam theory and sectional category.

Keywords

Cite

@article{arxiv.2210.00205,
  title  = {Borsuk-Ulam property and Sectional Category},
  author = {Cesar A. Ipanaque Zapata and Daciberg L. Gonçalves},
  journal= {arXiv preprint arXiv:2210.00205},
  year   = {2023}
}

Comments

19 pages. We present a proof that the index of $(X,\tau)$ always coincides with the sectional category of the quotient map $q:X\to X/\tau$ minus 1 for any paracompact space $X$ (Theorem 3.39)