Scaling for a one-dimensional directed polymer with boundary conditions

TL;DR

This paper analyzes a (1+1)-dimensional directed polymer with log-gamma weights, establishing fluctuation exponents and boundary condition effects, leveraging explicit calculations similar to classical growth models.

Contribution

It proves the conjectured fluctuation exponents for a directed polymer with boundary conditions using explicit calculations and Burke's theorem analogues.

Findings

Confirmed fluctuation exponents with boundary conditions

Established upper bounds for exponents without boundary conditions

Linked the model to last-passage percolation with explicit formulas

Abstract

We study a (1+1)-dimensional directed polymer in a random environment on the integer lattice with log-gamma distributed weights. Among directed polymers, this model is special in the same way as the last-passage percolation model with exponential or geometric weights is special among growth models, namely, both permit explicit calculations. With appropriate boundary conditions, the polymer with log-gamma weights satisfies an analogue of Burke's theorem for queues. Building on this, we prove the conjectured values for the fluctuation exponents of the free energy and the polymer path, in the case where the boundary conditions are present and both endpoints of the polymer path are fixed. For the polymer without boundary conditions and with either fixed or free endpoint, we get the expected upper bounds on the exponents.