Intrinsic Contractivity of Feynman-Kac Semigroups for Symmetric Jump Processes with Infinite Range Jumps

TL;DR

This paper investigates the intrinsic contractivity properties of Feynman-Kac semigroups associated with symmetric jump processes, establishing conditions under which they exhibit hypercontractivity, supercontractivity, and ultracontractivity.

Contribution

It provides new criteria for intrinsic contractivity properties of Feynman-Kac semigroups for jump processes with infinite range jumps, including specific potential functions.

Findings

Ultracontractivity holds if and only if the potential grows faster than a certain rate.

Supercontractivity and hypercontractivity are characterized by the growth rate of the potential.

Results apply to processes with specific jump kernels and potential functions.

Abstract

Let $(X_t)_{t\ge 0}$ be a symmetric strong Markov process generated by non-local regular Dirichlet form $(D,\D(D))$ as follows \begin{equation*} \begin{split} & D(f,g)=\int_{\R^d}\int_{\R^d}\big(f(x)-f(y)\big)\big(g(x)-g(y)\big) J(x,y)\,dx\,dy, \quad f,g\in \D(D) \end{split} \end{equation*} where $J(x,y)$ is a strictly positive and symmetric measurable function on $\R^d\times \R^d$. We study the intrinsic hypercontractivity, intrinsic supercontractivity and intrinsic ultracontractivity for the Feynman-Kac semigroup $$ T^V_t(f)(x)=\Ee^x\left(\exp\Big(-\int_0^tV(X_s)\,ds\Big)f(X_t)\right),\,\, x\in\R^d, f\in L^2(\R^d;dx).$$ In particular, we prove that for $$J(x,y)\asymp|x-y|^{-d-\alpha}\I_{\{|x-y|\le 1\}}+e^{-|x-y|}\I_{\{|x-y|> 1\}}$$ with $\alpha \in (0,2)$ and $V(x)=|x|^\lambda$ with $\lambda>0$, $(T_t^V)_{t\ge 0}$ is intrinsically ultracontractive if and only if $\lambda>1$; and that for symmetric $\alpha$-stable process $(X_t)_{t\ge0}$ with $\alpha \in (0,2)$ and $V(x)=\log^\lambda(1+|x|)$ with some $\lambda>0$, $(T_t^V)_{t\ge 0}$ is intrinsically ultracontractive (or intrinsically supercontractive) if and only if $\lambda>1$, and $(T_t^V)_{t\ge 0}$ is intrinsically hypercontractive if and only if $\lambda\ge1$. Besides, we also investigate intrinsic contractivity properties of $(T_t^V)_{t \ge 0}$ for the case that $\liminf_{|x| \to \infty}V(x)<\infty$.