Bisections of mass assignments by parallel hyperplanes

In this paper, we prove a result on the bisection of mass assignments by parallel hyperplanes on Euclidean vector bundles. Our methods consist of the development of a novel lifting method to define the configuration space–test map scheme, which transforms the problem to a Borsuk–Ulam-type question on equivariant fiber bundles, along with a new computation of the parametrized Fadell–Husseini index. As the primary application, we show that any $d+k+m-1$ mass assignments to linear $d$-spaces in ${\mathbb{R}}^{d+m}$ can be bisected by $k$ parallel hyperplanes in at least one $d$-space, provided that the Stirling number of the second kind $S(d+k+m-1,k)$ is odd. This generalizes all known cases of a conjecture by Soberón and Takahashi, which asserts that any $d+k-1$ measures in ${\mathbb{R}}^d$ can be bisected by $k$ parallel hyperplanes.