Localized form of Fock terms in nuclear covariant density functional theory

TL;DR

This paper introduces a new method to incorporate Fock terms into local covariant density functional theories, improving the description of spin-isospin excitations without added complexity.

Contribution

A novel zero-range reduction and Fierz transformation approach to include Fock terms in local functionals, enhancing their accuracy for spin-isospin channels.

Findings

Successfully describes Gamow-Teller and spin-dipole resonances

Retains simplicity of local models while improving accuracy

Provides a more accurate treatment of Dirac effective masses

Abstract

In most of the successful versions of covariant density functional theory in nuclei, the Fock terms are not included explicitly, which leads to local functionals and forms the basis of their widespread applicability at present. However, it has serious consequences for the description of Gamow-Teller resonances (GTR) and spin-dipole resonances (SDR) which can only be cured by adding further phenomenological parameters. Relativistic Hartree-Fock models do not suffer from these problems. They can successfully describe the GTR and SDR as well as the isovector part of the Dirac effective mass without any additional parameters. However, they are non-local and require considerable numerical efforts. By the zero-range reduction and the Fierz transformation, a new method is proposed to take into account the Fock terms in local functionals, which retains the simplicity of conventional models and provides proper descriptions of the spin-isospin channels and the Dirac masses.