Brueckner

In nuclear physics, the Brueckner theory is a many-body theory used to calculate the properties of nuclear matter, finite nuclei, and hypernuclei. It is based on the concept of replacing the bare nucleon-nucleon interaction with an effective interaction, often called the G-matrix, which takes into account the strong short-range correlations between nucleons. These correlations are caused by the strong repulsive core of the nuclear force, which makes perturbative calculations with the bare interaction impractical.

The central idea is to sum ladder diagrams in perturbation theory to all orders. The G-matrix satisfies a Lippmann-Schwinger-like equation, which is typically solved self-consistently. The solution involves integrating over the intermediate states of the interacting nucleons, with a Pauli exclusion operator that prevents the nucleons from scattering into occupied states below the Fermi surface. This ensures that the correlations accounted for by the G-matrix are only due to the strong interaction, and not due to Pauli blocking.

Several variants of Brueckner theory exist, including Brueckner-Hartree-Fock (BHF), which incorporates the G-matrix into a Hartree-Fock calculation. The BHF approach is commonly used to calculate the single-particle potential and the binding energy of nuclear matter. Improvements to the basic BHF approach include the inclusion of three-body forces, which are known to play an important role in nuclear structure.

The Brueckner theory has been instrumental in understanding the saturation properties of nuclear matter and the structure of finite nuclei. It continues to be an active area of research in nuclear physics.