In this thesis we present two applications of the AdS/CFT correspondence. The first one is the analysis of transport properties of fermionic modes in strongly coupled field theories. In particular we study the properties of the diffusion constant of the phonino in N=4 SYM at zero and finite density. We find that the diffusion constant depends on the chemical potential and therefore we conclude that it does not have a universality property analogous to the one of the shear viscosity. The second application deals with the behavior of entanglement entropy in theories with massive degrees of freedom. To identify the mass contributions to entanglement entropy we compute it in a setup with backreacted massive flavor branes and identify some of the mass dependent terms. We find that the logarithmic term has a different coefficient from the one computed in free field theory, a result that qualitatively agrees with previous holographic results. Furthermore we identify some other terms predicted in the field theory but not found before in a holographic setting.
