Regularity of the Optimal Stopping Problem for Jump Diffusions

The value function of an optimal stopping problem for jump diffusions is known to be a generalized solution of a variational inequality. Assuming that the diffusion component of the process is nondegenerate and a mild assumption on the singularity of the L\'{e}vy measure, this paper shows that the value function of this optimal stopping problem on an unbounded domain with finite/infinite variation jumps is in $W^{2, 1}_{p, loc}$ with $p\in(1, \infty)$. As a consequence, the smooth-fit property holds.