📝 SummarXiv

Abstract

This paper is a follow-up work of arxiv.org/abs/2101.05949. We study a non-directed polymer model in random environments. The polymer is represented by a simple symmetric random walk $S$ on $\mathbb{Z}^d$ with $d\geq2$ and the random environment is represented by i.i.d. heavy-tailed random variables with their tail probability decaying polynomially. We perform a Gibbs transform to describe the interaction between polymers and random environments. Up to time $N$, the law of $S$ is tilted by $\exp(\sum_{x\in\mathcal{R}_N}(\beta\omega_x-h))$, where $\mathcal{R}_N$ is the range of $S$ up to time $N$, $\beta\geq0$ is the inverse temperature and $h\in\mathbb{R}$ is an external field. By tuning $\beta=\beta_N$ and $h=h_N$, we establish the phase diagram and study the fluctuations of $S$ under the Gibbs transform and the scaling limits of the (logarithmic) partition function. The novelty and challenge, compared to arxiv.org/abs/2101.05949, is that we also tune the external field $h$, which brings in various range penalties, unlike in arxiv.org/abs/2101.05949, where $h$ is fixed and merely playing a role of centering for the random environment.