Many-body theory for quasiparticle states in superfluid fermionic systems

Semiclassical Theory for Many-body Fermionic Systems Typeset Using Revt E X

We present a treatment of many-body Fermionic systems that facilitates an expression of the well-known quantities in a series expansion in h̄. The ensuing semiclassical result contains to a leading order of the response function the classical time correlation function of the observable followed by the WeylWigner series, on top of these terms are the periodic-orbit correction terms. The treatment...

Initial stage of quasiparticle decay in fermionic systems

Generally, the addition or removal of a single particle in a many-body system does not correspond to an exact eigenstate of the system. Thus the resulting coherent excitation evolves in time. As discussed here, the evolution at short times upon the excitation with the energy exhibits a quadratic decay [with the rate constant σ 2( )]. Later on, after some time τ ( ), the exponential decay sets i...

Many-body theory of degenerate systems

The many-body theory of degenerate systems is described in detail. More generally, this theory applies to systems with an initial state that cannot be described by a single Slater determinant. The double-source (or closed-time-path) formalism of nonequilibrium quantum field theory is used to derive an expression for the average value of a product of interacting fields when the initial state is ...

Many–body Theory of Non–equilibrium Systems

Many-body Scattering Theory of Electronic Systems

This work reviews recent advances in the analytical treatment of the continuum spectrum of correlated few-body non-relativistic Coulomb systems. The exactly solvable two-body problem serves as an introduction to the non-separable three-particle system. For the latter case we discuss the existence of an approximate separability of the long and the short-range dynamics which is exposed in an appr...