We develop a convergent variational perturbation theory for quantum-statistical density matrices which is applicable to polynomial as well as nonpolynomial interactions. We illustrate the power of the theory by calculating the temperature-dependent density of a particle in the double-well potential to second order, and of the electron in the hydrogen atom to first order.
Physical Review A
- Pub Date:
- November 1999
- Quantum statistical mechanics;
- Quantum Physics
- Author Information under http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of paper also at http://www.physik.fu-berlin.de/~kleinert/kleiner_re280/preprint.html