Application of quantum field theory to condensed systems

Lambert, Colin John

Abstract

We examine in detail the microscopic theories of Beliaev and Hugenholtz and Pines as applied to an interacting system of bosons in its ground state and demonstrate that these theories are strictly applicable to a zero density gas only. After providing a re-normalization of the time dependent perturbation theory of a many fermion system in its ground state, we reformulate the corresponding boson theory without ab initio approximations concerning the k=0 mode.

The resulting boson perturbation theory has a diagrammatic structure which is topologically identical with the corresponding fermion theory and provided the implicit assumptions concerning convergence are valid, we conclude that a finite fraction of the particles in an arbitrary interacting Bose gas at T=ok will not condense into the k=0 mode.

Citation

Lambert, C. J. (1979). Application of quantum field theory to condensed systems. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4218563

• Thesis Type: Thesis
• Deposit Date: Oct 11, 2016
• Publicly Available Date: Feb 23, 2023
• Keywords: Physics
• Public URL: https://hull-repository.worktribe.com/output/4218563
• Additional Information: Department of Physics, The University of Hull
• Award Date: Jul 1, 1979