Intrinsic ultracontractivity for fractional Schr\"odinger operators

We establish sharp pointwise estimates for the ground states of some singular fractional Schr\"odinger operators on relatively compact Euclidean subsets. The considered operators are of the type $(-\Delta)^{\alpha/2}|_\Omega-V$, where $V\in L^1_{Loc}$ and $(-\Delta)^{\alpha/2}|_\Omega$ is the fractional-Laplacian on an open subset $\Omega$ in $\mathbb{R}^d$ with zero exterior condition . The intrinsic ultracontractivity property for such operators is discussed as well and a sharp large time asymptotic for their heat kernels is derived.