In this thesis we investigate the dynamics of cold atoms in optical cavities. We study how the scattering properties of laser driven atoms are modified by the presence of an optical resonator. This investigation can be divided into two parts. First, we study the scaling of the scattering properties with the number of atoms, and we show in particular how Bragg scattering by an atomic lattice is modified by the presence of the resonator. In this case, the atoms are trapped at the antinodes of the

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... cavity mode function by the mechanical potential induced by the resonator. In a second part, we show how this modification of the scattering properties can be used for efficiently cooling single atoms to the ground state of a harmonic trap. In particular, we find that the motion is critically affected by quantum correlations induced by the mechanical coupling with the resonator, which may lead to selective suppression of certain transitions for the appropriate parameters regimes, thereby increasing the cooling efficiency.