Principal eigenvalues of fully nonlinear integro-differential elliptic   equations with a drift term
  We study existence of principal eigenvalues of fully nonlinear integro-differential elliptic equations with a drift term via the Krein-Rutman theorem which based on regularity up to boundary of viscosity solutions. We also show the simplicity of the eigenfunctions in viscosity sense by a nonlocal version of ABP estimate. 
Alexander Quaas, Ariel Salort and Aliang Xia
math.AP