Fermi-surface instabilities from angle-correlated particle-particle propagation

Angular correlations arising from particle-particle (pp) propagation in nuclear matter are investigated. Their account follows an exact treatment of the Pauli exclusion principle on intermediate states. As a result, a correlation form factor emerges from the Cauchy principal-value of the pp propagator, while the imaginary part becomes structurally different from those in Lippmann-Schwinger-type equations. These novel features modify drastically the behavior of the mass operator near the Fermi surface, reshaping the phase-space where its imaginary part vanishes and sliding down the saturation point of symmetric nuclear matter along the Coester band. The correlation structures found here, improvement upon angle-averaged (or effective-mass type) energy denominators, may also appear in the context of other quantum many-body phenomena.