Identical Particles Second Quantization Independent-Particle Model for Fermions in Finite Systems Two-Particle States and Interactions Noninteracting Bosons and Fermions Propagators in One-Particle Quantum Mechanics Single-Particle Propagator in Many-Particle Systems Perturbation Expansion of the Single-Particle Propagator Dyson Equation and Self-consistent Green's Functions Mean-Field or Hartree-Fock Approximation Beyond the Mean-Field Approximation Interacting Boson Systems Excited States in Finite Systems Excited States in Infinite Systems Excited States in N 2 Systems and In-Medium Scattering Dynamical Treatment of the Self-energy in Infinite Systems Dynamical Treatment of the Self-energy in Finite Systems Bogoliubov Perturbation Expansion for the Bose Gas Boson Perturbation Theory Applied to Physical Systems In-Medium Interaction and Scattering of Dressed Particles Conserving Approximations and Excited States Pairing Phenomena Propagator Framework for Phenomenological Description of Many-Body Systems Finite Temperature Formalism and Applications.
We investigate the properties of the attractive polaron formed by a single impurity dressed with the particle-hole excitations in a Dirac system at zero-temperature limit. Base on the single particle-hole variational ansatz, we deduce the expressions of the pair propagator, self-energy (negative), and the non-self-consistent medium
T-matrix. Different to the self-consistent
T-matrix which contains two channels due to the many-body effect, the non-self-consistent
T-matrix discussed in this paper contains only the closed channel (i.e., the bare one) since we consider only a finite number of the majority particles. The chiral factor is also discussed within the pair propagator due to the scattering feature of the Dirac system (with a certain scattering angle
a), and we found that the fluctuation of the pair propagator is proportional to the term
cos a. Finally, we also discuss the particle spectral function of the polaron in the presence of quantum many-body effect as well as the pair-propagator at finite temperature.
Realistic nucleon-nucleon interactions induce correlations to the nuclear many-body system, which lead to a fragmentation of the single-particle strength over a wide range of energies and momenta. We address the question of how this fragmentation affects the thermodynamical properties of nuclear matter. In particular, we show that the entropy can be computed with the help of a spectral function, which can be evaluated in terms of the self-energy obtained in the self-consistent Green's function approach. Results for the density and temperature dependences of the entropy per particle for symmetric nuclear matter are presented and compared to the results of lowest order finite-temperature Brueckner-Hartree-Fock calculations. The effects of correlations on the calculated entropy are small, if the appropriate quasiparticle approximation is used. The results demonstrate the thermodynamical consistency of the self-consistent
T-matrix approximation for the evaluation of the Green's functions.