Diffusive scaling limit of the Busemann process in Last Passage Percolation

Abstract

In exponential last passage percolation, we consider the rescaled Busemann process $x\mapsto N^{-1/3}B^\rho_{0,[xN^{2/3}]e_1} \,\, (x\in\mathbb{R})$, as a process parametrized by the scaled density $\rho=1/2+\frac{\mu}{4} N^{-1/3}$, and taking values in $C(\mathbb{R})$. We show that these processes, as $N\rightarrow \infty$, have a c\`adl\`ag scaling limit $G=(G_\mu)_{\mu\in \mathbb{R}}$, parametrized by $\mu$ and taking values in $C(\mathbb{R})$. The limiting process $G$, which can be thought of as the Busemann process under the KPZ scaling, can be described as an ensemble of "sticky" lines of Brownian regularity. We believe $G$ is the universal scaling limit of Busemann processes in the KPZ universality class. Our proof provides insight into this limiting behaviour by highlighting a connection between the joint distribution of Busemann functions obtained by Fan and Sepp\"al\"ainen in arXiv:1808.09069, and a sorting algorithm of random walks introduced by O'Connell and Yor [32]