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2020 Modulus of continuity for polymer fluctuations and weight profiles in Poissonian last passage percolation
Alan Hammond, Sourav Sarkar
Electron. J. Probab. 25: 1-38 (2020). DOI: 10.1214/20-EJP430


In last passage percolation models, the energy of a path is maximized over all directed paths with given endpoints in a random environment, and the maximizing paths are called geodesics. The geodesics and their energy can be scaled so that transformed geodesics cross unit distance and have fluctuations and scaled energy of unit order. Here we consider Poissonian last passage percolation, a model lying in the KPZ universality class, and refer to scaled geodesics as polymers and their scaled energies as weights. Polymers may be viewed as random functions of the vertical coordinate and, when they are, we show that they have modulus of continuity whose order is at most $t^{2/3}\big (\log t^{-1}\big )^{1/3}$. The power of one-third in the logarithm may be expected to be sharp and in a related problem we show that it is: among polymers in the unit box whose endpoints have vertical separation $t$ (and a horizontal separation of the same order), the maximum transversal fluctuation has order $t^{2/3}\big (\log t^{-1}\big )^{1/3}$. Regarding the orthogonal direction, in which growth occurs, we show that, when one endpoint of the polymer is fixed at $(0,0)$ and the other is varied vertically over $(0,z)$, $z\in [1,2]$, the resulting random weight profile has sharp modulus of continuity of order $t^{1/3}\big (\log t^{-1}\big )^{2/3}$. In this way, we identify exponent pairs of $(2/3,1/3)$ and $(1/3,2/3)$ in power law and polylogarithmic correction, respectively for polymer fluctuation, and polymer weight under vertical endpoint perturbation. The two exponent pairs describe [9, 10, 8] the fluctuation of the boundary separating two phases in subcritical planar random cluster models.


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Alan Hammond. Sourav Sarkar. "Modulus of continuity for polymer fluctuations and weight profiles in Poissonian last passage percolation." Electron. J. Probab. 25 1 - 38, 2020.


Received: 1 November 2018; Accepted: 4 February 2020; Published: 2020
First available in Project Euclid: 24 February 2020

zbMATH: 1439.82014
MathSciNet: MR4073690
Digital Object Identifier: 10.1214/20-EJP430

Primary: 60K35, 82B23, 82C23


Vol.25 • 2020
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