The Borsuk-Ulam property for homotopy classes on bundles, parametrized braids groups and applications for surfaces bundles

Abstract

Let $M$ and $N$ be fiber bundles over the same base $B$, where $M$ is endowed with a free involution $τ$ over $B$. A homotopy class $δ\in [M,N]_{B}$ (over $B$) is said to have the Borsuk-Ulam property with respect to $τ$ if for every fiber-preserving map $f\colon M \to N$ over $B$ which represents $δ$ there exists a point $x \in M$ such that $f(τ(x)) = f(x)$. In the cases that $B$ is a $K(π,1)$-space and the fibers of the projections $M \to B$ and $N \to B$ are $K(π,1)$ closed surfaces $S_M$ and $S_N$, respectively, we show that the problem of decide if a homotopy class of a fiber-preserving map $f\colon M \to N$ over $B$ has the Borsuk-Ulam property is equivalent of an algebraic problem involving the fundamental groups of $M$, the orbit space of $M$ by $τ$ and a type of generalized braid groups of $N$ that we call parametrized braid groups. As an application, we determine the homotopy classes of self fiber-preserving maps of some 2-torus bundles over $\mathbb{S}^1$ that satisfy the Borsuk-Ulam property with respect to certain involutions $τ$ over $\mathbb{S}^1$.