K"unneth Formulae in Persistent Homology

The classical K"unneth formula in algebraic topology describes the homology of a product space in terms of that of its factors. In this paper, we prove K"unneth-type theorems for the persistent homology of the categorical and tensor product of filtered spaces. That is, we describe the persistent homology of these product filtrations in terms of that of the filtered components. In addition to comparing the two products, we present two applications in the setting of Vietoris-Rips complexes: one towards more efficient algorithms for product metric spaces with the maximum metric, and the other recovering persistent homology calculations on the n-torus.