Wandering Exponents and the Free Energy of the High-Dimensional Elastic Polymer

TL;DR

This paper analyzes a high-dimensional elastic polymer model in Gaussian environments, deriving explicit formulas for free energy and wandering exponents, revealing phase transitions between diffusive and superdiffusive behaviors.

Contribution

It provides explicit asymptotic formulas for free energy and characterizes phase transitions in the model based on environmental correlations, confirming physics conjectures.

Findings

Explicit asymptotic formula for free energy in high dimensions.

Characterization of low- and high-temperature phases via correlation functions.

Identification of diffusive versus superdiffusive regimes depending on correlation strength.

Abstract

We study the behavior of the elastic polymer, a model of a directed polymer in a continuous Gaussian random environment that is independent in time and correlated in space, as the dimension of the environment is taken to infinity. We give an explicit asymptotic formula for the free energy, which is given in terms of the distribution of the inner product of two sampled configurations, which we also obtain an implicit formula for. From this, we provide an explicit characterization of both the low- and high-temperature phases of this model in terms of the spatial correlation function of the environment. We find asymptotics for the wandering exponent when the spatial correlation function is either an exponential or a power-law decay. Our results show that when the correlations are either suitably weak or short ranged, the model is asymptotically diffusive. On the other hand, for suitably strong long ranged correlations, the model is asymptotically superdiffusive. Moreover, we show that this transition coincides exactly with another transition where the model goes from being one-step replica symmetry breaking to full-step replica symmetry breaking. This rigorously confirms many of the findings of Mezard and Parisi [53] in the physics literature.