Coherent state path integral and super-symmetry for condensates composed of bosonic and fermionic atoms

Bernhard Mieck

Published 2007-02-08, updated 2007-08-26Version 4

A super-symmetric coherent state path integral on the Keldysh time contour is considered for bosonic and fermionic atoms which interact among each other with a common short-ranged two-body potential. We investigate the symmetries of Bose-Einstein condensation for the equivalent bosonic and fermionic constituents and specialize on the examination of super-symmetries for pair condensate terms. A Hubbard-Stratonovich transformation from 'Nambu'-doubled super-fields leads to a generating function with super-matrices for the self-energy whose manifold is given by the ortho-symplectic super-group Osp(S,S|2L). Effective equations are derived for anomalous terms which are related to the molecular- and BCS- condensate pairs. A change of integration measure for the coset decomposition Osp(S,S|2L)/U(L|S)xU(L|S) is performed, including a separation of density and anomalous parts of the self-energy with a gradient expansion for the Goldstone modes. The independent anomalous fields in the actions can be transformed by the inverse square root of the metric tensor of Osp(S,S|2L)/U(L|S) so that the coset integration measure with the super-Jacobi-determinant can be removed from the coherent state path integral and Gaussian-like integrations remain. The variations of the independent coset fields in the effective actions result in classical field equations for a nonlinear sigma model with the anomalous terms.