$Z_2$-bordism and the Borsuk-Ulam Theorem

Abstract

The purpose of this work is to classify, for given integers $m,n\ge 1$, the bordism class of a closed smooth $m$-manifold $X$ with a free smooth involution $\tau$ with respect to the validity of the {\it Borsuk-Ulam property} that for every continuous map $\varphi :X\to R^n$ there exists a point $x\in X$ such that $\varphi (x)=\varphi (\tau (x))$. We will classify a given free $Z_2$-bordism class $\alpha$ according to the three possible cases that (a) all representatives $(X,\tau )$ of $\alpha$ satisfy the Borsuk-Ulam property; \ (b) there are representatives $(X_1,{\tau }_1)$ and $(X_2,{\tau }_2)$ of $\alpha$ such that $(X_1,{\tau }_1)$ satisfies the Borsuk-Ulam property but $(X_2,{\tau }_2)$ does not; \ (c) no representative $(X,\tau )$ of $\alpha$ satisfies the Borsuk-Ulam property.