Isoperimetric lower bounds for critical exponents for long-range percolation

Abstract

We study independent long-range percolation on $\mathbb{Z}^d$ where the vertices $x$ and $y$ are connected with probability $1-e^{-β\|x-y\|^{-d-α}}$ for $α> 0$. Provided the critical exponents $δ$ and $2-η$ defined by $δ= \lim_{n\to \infty} \frac{-\log(n)}{\log\left(\mathbb{P}_{β_c}\left(|K_0|\geq n\right)\right)}$ and $2-η= \lim_{x \to \infty} \frac{\log\left(\mathbb{P}_{β_c}\left(0\leftrightarrow x\right)\right)}{\log(\|x\|)} + d$ exist, where $K_0$ is the cluster containing the origin, we show that \begin{equation*} δ\geq \frac{d+(α\wedge 1)}{d-(α\wedge 1)} \ \text{ and } \ 2-η\geq α\wedge 1 \text. \end{equation*} The lower bound on $δ$ is believed to be sharp for $d = 1, α\in \left[\frac{1}{3},1\right)$ and for $d = 2, α\in \left[\frac{2}{3},1\right]$, whereas the lower bound on $2-η$ is sharp for $d=1, α\in (0,1)$, and for $α\in \left(0,1\right]$ for $d>1$, and is not believed to be sharp otherwise. Our main tool is a connection between the critical exponents and the isoperimetry of cubes inside $\mathbb{Z}^d$.