Non-Markovian spectral broadening in interacting continuous-wave atom lasers

The non-Markovian dynamics of a continuous-wave atom laser model is studied which includes gravitational effects and interactions inside the Bose-Eins tein condensate. With the help of the time-convolutionless projection opera tor technique both the occupation number of the condensate and the spectrum of the atoms coupled out of the condensate are determined. A correct model ing of memory effects in the atom laser requires a generalization of the pr ojection operator technique which takes into account correlations in the in itial state of the combined atom-reservoir system. The non-Markovian evolut ion is shown to yield substantial deviations from results obtained in the B orn-Markov approximation.