Combination theorems for geometrically finite convergence groups

Abstract: We prove combination theorems in the spirit of Klein and Maskit in the context of discrete convergence groups acting geometrically finitely on their limit sets. As special cases, we obtain combination theorems for geometrically finite groups of isometries of Hadamard manifolds with pinched negative curvature, and for relatively quasi-convex subgroups of relatively hyperbolic groups.