Fluctuations of partition functions of directed polymers in weak disorder beyond the $L^2$-phase

Abstract

We study the directed polymer model in a bounded environment in weak disorder but without $L^2$-boundedness, specifically the speed of homogenization for the field $(W_n^{0,x}{)}_{x\in {\mathbb{Z}}^d}$, where $W_n^{0,x}$ denotes the associated martingale for the polymer starting from $x$. We show that a suitably re-centered spatial average over a set of diameter $n^{1/2}$ convergence to zero at rate $n^{-\xi +o(1)}$, where the exponent is an explicit function of the inverse temperature $\beta$.

v2: corrected a mistake in Theorem 1.4(i). v3: revised version with more details on the proofs. Removed an assumption in Theorem 1.1