The persistent homology of the Linial-Meshulam process

Abstract: For a fixed dimension $k\ge 1$, let us consider the randomly growing simplical complex on the vertex set ${1,2,\dots,n}$ defined as follows: We start with the empty complex, and for each $k+1$-element subset $σ$ of ${1,2,\dots,n}$, we add $σ$ and all of its subsets to the complex at some random time $t_σ$, where $(t_σ)$ are i.i.d. uniform random elements of $[0,n]$. As the complex evolves, new $k-1$-dimensional cycles are born and then at a later time they die, that is, they get filled in. The notion of persistence diagrams, which is a standard tool in topological data analysis, provides a way to record these birth and death times. In this paper, we understand the asymptotic behavior of the persistence diagrams of the above defined randomly evolving complexes as $n$ goes to infinity. As the single time marginals of the above process are variants of the Linial-Meshulam complex, our results can be viewed as extensions of the results of Linial and Peled on the Betti numbers of the Linial-Meshulam complex. Our proof relies on the notion of local weak convergence of graphs and a generalization of the results of Bordenave, Lelarge and Salez on the rank of sparse random matrices.