The Borsuk-Ulam property for homotopy classes of maps between the torus and the Klein bottle

TL;DR

This paper characterizes which homotopy classes of maps from the 2-torus to the Klein bottle satisfy the Borsuk-Ulam property relative to a specific involution, using fundamental group homomorphisms.

Contribution

It determines the homotopy classes with the Borsuk-Ulam property for maps from the torus to the Klein bottle under a particular involution, linking it to fundamental group homomorphisms.

Findings

Identifies homotopy classes with the Borsuk-Ulam property

Expresses results via fundamental group homomorphisms

Provides a classification for maps from T^2 to K^2

Abstract

Let $M$ be a topological space that admits a free involution $\tau$, and let $N$ be a topological space. A homotopy class $\beta \in [ M,N ]$ is said to have {\it the Borsuk-Ulam property with respect to $\tau$} if for every representative map $f: M \to N$ of $\beta$, there exists a point $x \in M$ such that $f(\tau(x))= f(x)$. In this paper, we determine the homotopy classes of maps from the $2$-torus $T^2$ to the Klein bottle $K^2$ that possess the Borsuk-Ulam property with respect to a free involution $\tau_1$ of $T^2$ for which the orbit space is $T^2$. Our results are given in terms of a certain family of homomorphisms involving the fundamental groups of $T^2$ and $K^2$.