The Galitskii-Feynman $T$ matrix, which sums the ladder diagrams for both particle-particle and hole-hole scattering in a many-fermion system, is shown to have a singularity at negative values of the c.m. energy of the interacting pair. The singularity appears as a first-order pole in the $T$ matrix, the position of which is a function of both the density of the system and the total c.m. momentum of the pair, and corresponds to the formation of bound pairs in the medium. The singularity structure exists in two distinct Fermi systems (liquid ${\mathrm{He}}^{3}$ and nuclear matter), and detailed numerical results are presented using a potential appropriate to liquid ${\mathrm{He}}^{3}$ . The singularity in this case is shown to be present at all densities above a certain critical density which is lower than the physical density.The Galitskii-Feynman $T$ matrix, which sums the ladder diagrams for both particle-particle and hole-hole scattering in a many-fermion system, is shown to have a singularity at negative values of the c.m. energy of the interacting pair. The singularity appears as a first-order pole in the $T$ matrix, the position of which is a function of both the density of the system and the total c.m. momentum of the pair, and corresponds to the formation of bound pairs in the medium. The singularity structure exists in two distinct Fermi systems (liquid ${\mathrm{He}}^{3}$ and nuclear matter), and detailed numerical results are presented using a potential appropriate to liquid ${\mathrm{He}}^{3}$. The singularity in this case is shown to be present at all densities above a certain critical density which is lower than the physical density.

Physical Review ADec 1, 197426 citations

Fermi Liquid Theory

WORLD SCIENTIFIC eBooksJul 30, 20260 citations

The Galitskii-Feynman

T

matrix, which sums the ladder diagrams for both particle-particle and hole-hole scattering in a many-fermion system, is shown to have a singularity at negative values of the c.m. energy of the interacting pair. The singularity appears as a first-order pole in the

T

matrix, the position of which is a function of both the density of the system and the total c.m. momentum of the pair, and corresponds to the formation of bound pairs in the medium. The singularity structure exists in two distinct Fermi systems (liquid

{\mathrm{He}}^{3}

and nuclear matter), and detailed numerical results are presented using a potential appropriate to liquid

{\mathrm{He}}^{3}

. The singularity in this case is shown to be present at all densities above a certain critical density which is lower than the physical density.