  Chaotic deterministic dynamics of a particle can give rise to diffusive
Brownian motion. In this paper, we compute analytically the diffusion
coefficient for a particular two-dimensional stochastic layer induced by the
kicked Harper map. The variations of the transport coefficient as a parameter
is varied are analyzed in terms of the underlying classical trajectories with
particular emphasis in the appearance and bifurcations of periodic orbits. When
accelerator modes are present, anomalous diffusion of the L\'evy type can
occur. The exponent characterizing the anomalous diffusion is computed
numerically and analyzed as a function of the parameter.
