This book presents the main techniques aimed to treat the dynamics of the quantum Brownian particle: Born-Markov master equation, Lindblad equation and Heisenberg equations formalism. Particular attention is given to the interaction between the particle and the bath depends non-linearly on the position of the former. This generalization corresponds to the case in which the bath is not homogeneous. An immediate application is the Bose polaron, specifically an impurity embedded in an ultracold gas. weiterlesen