Computing 1-Periodic Persistent Homology with Finite Windows

Abstract

Let $K$ be a periodic cell complex endowed with a covering $q:K\to G$ where $G$ is a finite quotient space of equivalence classes under translations acting on $K$. We assume $G$ is embedded in a space whose homotopy type is a $d$-torus for some $d$, which introduces "toroidal cycles" in $G$ which do not lift to cycles in $K$ by $q$ . We study the behaviour of toroidal and non-toroidal cycles for the case $K$ is 1-periodic, i.e. $G=K/\mathbb{Z}$ for some free action of $\mathbb{Z}$ on $K$. We show that toroidal cycles can be entirely classified by endomorphisms on the homology of unit cells of $K$, and moreover that toroidal cycles have a sense of unimodality when studying the persistent homology of $G$.