arXiv subjects

Subhajit Goswami

Publications and source records attributed to Subhajit Goswami.

24 records · Page 2Linked to original sources

arXiv2019

Return probability and recurrence for the random walk driven by two-dimensional Gaussian free field

Given any $γ>0$ and for $η=\{η_v\}_{v\in \mathbb Z^2}$ denoting a sample of the two-dimensional discrete Gaussian free field on $\mathbb Z^2$ pinned at the origin, we consider the random walk on~$\mathbb Z^2$ among random conductances where the conductance of edge $(u, v)$ is given by $\mathrm{e}^{γ(η_u + η_v)}$. We show that, for almost every~$η$, this random walk is recurrent and that, with probability tending to~1 as $T\to \infty$, the return probability at time~$2T$ decays as $T^{-1+o(1)}$. In addition, we prove a version of subdiffusive behavior by showing that the expected exit time from a ball of radius~$N$ scales as $N^{ψ(γ)+o(1)}$ with $ψ(γ)>2$ for all~$γ>0$. Our results rely on delicate control of the effective resistance for this random network. In particular, we show that the effective resistance between two vertices at Euclidean distance~$N$ behaves as~$N^{o(1)}$.

math.PR↗

arXiv2018

Upper bounds on Liouville first passage percolation and Watabiki's prediction

Given a planar continuum Gaussian free field $h^{\mathcal U}$ in a domain $\mathcal U$ with Dirichlet boundary condition and any $δ>0$, we let $\{h_δ^{\mathcal U}(v): v\in \mathcal U\}$ be a real-valued smooth Gaussian process where $h_δ^{\mathcal U}(v)$ is the average of $h^{\mathcal U}$ along a circle of radius $δ$ with center $v$. For $γ> 0$, we study the Liouville first passage percolation (in scale $δ$), i.e., the shortest path distance in $\mathcal U$ where the weight of each path $P$ is given by $\int_P \mathrm{e}^{γh_δ^{\mathcal U}(z)} |dz|$. We show that the distance between two typical points is $O(δ^{c^* γ^{4/3}/\log γ^{-1}})$ for all sufficiently small but fixed $γ>0$ and some constant $c^* > 0$. In addition, we obtain similar upper bounds on the Liouville first passage percolation for discrete Gaussian free fields, as well as the Liouville graph distance which roughly speaking is the minimal number of Euclidean balls with comparable Liouville quantum gravity measure whose union contains a continuous path between two endpoints. Our results contradict with some reasonable interpretations of Watabiki's prediction (1993) on the random distance of Liouville quantum gravity at high temperatures.

math.PR↗

arXiv2017

First passage percolation on the exponential of two-dimensional branching random walk

We consider the branching random walk $\{\mathcal R^N_z: z\in V_N\}$ with Gaussian increments indexed over a two-dimensional box $V_N$ of side length $N$, and we study the first passage percolation where each vertex is assigned weight $e^{γ\mathcal R^N_z}$ for $γ>0$. We show that for $γ>0$ sufficiently small but fixed, the expected FPP distance between the left and right boundaries is at most $O(N^{1 - γ^2/10})$.

math.PR↗

arXiv2016

Finite size scaling of random XORSAT

We consider a "configuration model" for random XORSAT which is a random system of $n$ equations over $m$ variables in $\mathbb F_2$. Each equation is of the form $y_1 + y_2 + \cdots + y_k = b$ where $k \geq 3$ is fixed, $y_1, y_2, \cdots$ are variables (not necessarily distinct) and $b \in \mathbb F_2$. The equations are chosen independently and uniformly at random with replacement. It is known \cite{Dubois02, Dietzfelbinger10, pittel2016} that there exists $ρ_k$ such that $m / n = ρ_k$ is a sharp threshold for the satisfiability of this system. In this note we show that for the configuration model, the width of SAT-UNSAT transition window for random $k$-XORSAT is $Θ(n^{-1/2})$ and also derive the exact scaling function.

math.PR↗

arXiv2016

Liouville first passage percolation: the weight exponent is strictly less than 1 at high temperatures

Let $\{η_{N, v}: v\in V_N\}$ be a discrete Gaussian free field in a two-dimensional box $V_N$ of side length $N$ with Dirichlet boundary conditions. We study the Liouville first passage percolation, i.e., the shortest path metric where each vertex is given a weight of $e^{γη_{N, v}}$ for some $γ>0$. We show that for sufficiently small but fixed $γ>0$, the expected Liouville FPP distance between any pair of vertices is $O(N^{1-γ^2/10^3})$.

math.PR↗

arXiv2015

Percolation of averages in the stochastic mean field model: the near-supercritical regime

For a complete graph of size $n$, assign each edge an i.i.d.\ exponential variable with mean $n$. For $λ>0$, consider the length of the longest path whose average weight is at most $λ$. It was shown by Aldous (1998) that the length is of order $\log n$ for $λ< 1/\mathrm{e}$ and of order $n$ for $λ> 1/\mathrm{e}$. In this paper, we study the near-supercritical regime where $λ= \mathrm{e}^{-1} +η$ with $η>0$ a small fixed number. We show that there exist two absolute constants $c^*, C^*>0$ such that with high probability the length is in between $n \mathrm{e}^{-C^*/\sqrtη}$ and $n \mathrm{e}^{-c^*/\sqrtη}$. Our result corrects a non-rigorous prediction of Aldous (2005).

math.PR↗