Robustness and diffusion of pointer states

Classical properties of an open quantum system emerge through its interacti on with other degrees of freedom (decoherence). We treat the case where thi s interaction produces a Markovian master equation for the system. We deriv e the corresponding distinguished local basis (pointer basis) by three meth ods. The first demands that the pointer states mimic as closely as possible the local nonunitary evolution. The second demands that the local entropy production be minimal. The third imposes robustness on the inherent quantum and emerging classical uncertainties. All three methods lead to localized Gaussian pointer states, their formation and diffusion being governed by we ll-defined quantum Langevin equations.