Idleness Functions for Ollivier-Ricci Curvature on Hypergraphs

Abstract

Let $\mathcal{H}=(V,E)$ be a locally finite simple hypergraph, equip $V$ with the hyperpath metric, and consider the equal-edges random walk \cite{CoupetteEtAl2023}. For adjacent vertices $x$ and $y$, we prove that the idleness function $\alpha \mapsto {\kappa }_{\alpha }^{\mathcal{H}}(x,y)$ is piecewise affine and with no more than three affine pieces. A separate mass-balance argument gives linearity on $[1/2,1]$ for every locally finite simple hypergraph and, consequently, a limit-free expression for the Lin--Lu--Yau curvature. In the $r$-uniform linear case, the hypergraph walk agrees exactly with the simple random walk on its 2-section. This reduction transfers the sharp endpoint intervals of Bourne, Cushing, Liu, Münch, and Peyerimhoff \cite{BourneEtAl2018}.

arXiv comment7 pages, 2 figures. Corrected the discussion and attribution of the random walk used by Tian and Zhao. The results of this preprint have subsequently been incorporated into the expanded manuscript arXiv:2608.06029