Nonequilibrium relaxation of Bose-Einstein condensates: Real-time equations of motion and Ward identities

Details Nonequilibrium relaxation of Bose-Einstein condensates: Real-time equations of motion and Ward identities Nonequilibrium relaxation of Bose-Einstein condensates: Real-time equations of motion and Ward identities

2001-11-20

arxiv.org/abs/cond-mat/0111375v2

Annals Phys. 300 (2002) 1-31

Physics

Condensed Matter

Latex (elsart.cls), 41 pages, 4 eps figs, to appear in Ann. Phys

Scientific paper

10.1006/aphy.2002.6275

We present a field-theoretical method to obtain consistently the equations of motion for small amplitude condensate perturbations in a homogeneous Bose-condensed gas directly in real time. It is based on linear response, and combines the Schwinger-Keldysh formulation of nonequilibrium quantum field theory with the Nambu-Gorkov formalism of quasiparticle excitations in the condensed phase and the tadpole method in quantum field theory. This method leads to causal equations of motion that allow to study the nonequilibrium evolution as an initial value problem. It also allows to extract directly the Ward identities, which are a consequence of the underlying gauge symmetry and which in equilibrium lead to the Hugenholtz-Pines theorem. An explicit one-loop calculation of the equations of motion beyond the Hartree-Fock- Bogoliubov approximation reveals that the nonlocal, absorptive contributions to the self-energies corresponding to the Beliaev and Landau damping processes are necessary to fulfill the Ward identities \emph{in} or \emph{out} of equilibrium. It is argued that a consistent implementation at low temperatures must be based on the loop expansion, which is shown to fulfill the Ward identities order by order in perturbation theory.

Affiliated with

Also associated with

No associations

Rating

Nonequilibrium relaxation of Bose-Einstein condensates: Real-time equations of motion and Ward identities does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Nonequilibrium relaxation of Bose-Einstein condensates: Real-time equations of motion and Ward identities, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nonequilibrium relaxation of Bose-Einstein condensates: Real-time equations of motion and Ward identities will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-274984