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Fermi-surface instabilities in nuclear matter 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 in the Bruekner-Bethe-Goldstone (BBG) equation. 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 behaviour 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 --which go beyond angle-averaged (or effective-mass type) energy denominators-- may impact present day model predictions for neutron stars based on the BBG equation, and for scattering and reaction observables in full folding optical model calculations