1Department of Mathematics, Faculty of Science, University of Qom, Qom, Iran
2Faculty of Mathematical Sciences and Computer, Kharazmi University, Tehran, Iran
In this paper we get some results and applications for duals and approximate duals of g-frames in Hilbert spaces. In particular, we consider the stability of duals and approximate duals under bounded operators and we study duals and approximate duals of g-frames in the direct sum of Hilbert spaces. We also obtain some results for perturbations of approximate duals.