EN
The purpose of this paper is to find optimal estimates for the Green function and the Poisson kernel for a half-line and intervals of the geometric stable process with parameter α ∈ (0,2]. This process has an infinitesimal generator of the form $-log(1+(-Δ)^{α/2})$. As an application we prove the global scale invariant Harnack inequality as well as the boundary Harnack principle.