Hi I have a question regarding the pump-term in the Hamiltonian on page 9 (equation 2.9b) of this thesis: http://mediatum2.ub.tum.de/download/652711/652711.pdf. This term is not very intuitive to me. [itex]a[/itex] is followed by a CCW phase, whereas [itex]a^\dagger[/itex] is followed by a CW phase. How does this represent pumping? I have seen many thesis presenting this term, but no one ever explains it. Best, Niles.