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arXiv · 2005.07103

Phase transition in cohomology groups of non-uniform random simplicial complexes

Oliver Cooley·Nicola Del Giudice·Mihyun Kang·Philipp Sprüssel
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Abstract

We consider a generalised model of a random simplicial complex, which arises from a random hypergraph. Our model is generated by taking the downward-closure of a non-uniform binomial random hypergraph, in which for each $k$, each set of $k+1$ vertices forms an edge with some probability $p_k$ independently. As a special case, this contains an extensively studied model of a (uniform) random simplicial complex, introduced by Meshulam and Wallach [Random Structures & Algorithms 34 (2009), no. 3, pp. 408-417]. We consider a higher-dimensional notion of connectedness on this new model according to the vanishing of cohomology groups over an arbitrary abelian group $R$. We prove that this notion of connectedness displays a phase transition and determine the threshold. We also prove a hitting time result for a natural process interpretation, in which simplices and their downward-closure are added one by one. In addition, we determine the asymptotic behaviour of cohomology groups inside the critical window around the time of the phase transition.

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Oliver Cooley, Nicola Del Giudice, Mihyun Kang, Philipp Sprüssel. 2020-05-14. Phase transition in cohomology groups of non-uniform random simplicial complexes. https://arxiv.org/abs/2005.07103

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