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Our objective is to include Fock exchange terms, and thus the pion, in a Dirac description of nuclear matter and to determine a density-dependent Dirac-Hartree-Fock meson exchange interaction that is hopefully less density-dependent than a typical Hartree one. We begin by performing extended self-consistent nuclear matter Dirac-Brueckner calculations over a wide range of densities and asymmetries. We maintain the momentum dependence of the Brueckner mean fields in the hope of fitting it with the momentum dependence of the effective Dirac-Hartree-Fock mean fields. To improve the description of the Brueckner mean fields within a Hartee-Fock approximation, we include contact terms in the interaction. [Copyright &y& Elsevier]

The REGINA code calculates the São Paulo potential version 2 (SPP2) and the Brazilian nuclear potential (BNP). The code also provides nuclear densities obtained from the Dirac-Hartree-Bogoliubov model, which are used to calculate the nuclear potentials. Elastic scattering cross sections are obtained within the context of the optical model, with different options for the real and imaginary parts of the optical potential. In this manuscript, we provide a summary of the theoretical framework and information about the use of the code. Program Title: REGINA.f CPC Library link to program files: https://doi.org/10.17632/vfkkjb8dv7.1 Licensing provisions: GPLv3 Programming language: Fortran-77 Nature of problem: We provide a code to calculate the nuclear potential between two nuclei according to two different models: the São Paulo potential version 2 (SPP2), that includes a dependence on the relative velocity between the nuclei, and the velocity independent Brazilian nuclear potential (BNP). These potentials assume the effective nuclear interactions proposed in [1,2] , and are obtained within the double-folding approach with nuclear densities calculated through the Dirac-Hartree-Bogoliubov model [3]. Solution method: The code involves two files containing previously calculated results for theoretical neutron and proton distributions and also experimental charge densities obtained from electron scattering experiments. These results are used to obtain matter densities through convolution using Fourier transforms. The Fourier transform method is also employed to obtain the double-folding potentials. Integration of the Schrödinger equation with a complex optical potential is performed using the Cowell method [4,5]. With this, for a given system and energy, we obtain the S-matrix and the elastic scattering cross sections. Additional comments including restrictions and unusual features: The maximum angular momentum supported in the optical model calculations is 2000. [ABSTRACT FROM AUTHOR]

We argue that a substantial increase in the cross section for Coulomb excitation in the region of the Double Giant Dipole Resonance should be expected from Coulomb excitation of excited states involved in the spreading of the one-phonon resonance, in a manifestation of the Brink–Axel phenomenon. This generates an additional fluctuating amplitude and a corresponding new term to be added incoherently to the usual cross section. The appropriate extension of an applicable reaction calculation is considered in order to estimate this effect.

In this work we construct a complete set of space-time/isospin of transformations U for the self-energy, , Hartree-Fock hamiltonian , and the pairing field using combinations of both the gamma and isospin matrices as generator of the transformations. [Copyright &y& Elsevier]

We study the effects of temperature on finite nuclei [1] and look at nuclear deformation and pairing correlations in a self–consistent way. We include temperature in the the Dirac–Hartree–Bogoliubov (DHB) theory using the Matsubara formalism [2]. In order to simplify the calculation we exclude the Fock term and use a zero–range approximation to the relativistic pairing tensor to obtain pure proton–proton and neutron–neutron pairing. We use the Bonche et. al [3–5] vapor subtraction procedure to account for unbound states and remove long range Coulomb repulsion between the hot nucleus and gas, i.e, remove the contributions of the external gas. [Copyright &y& Elsevier]

We derive an effective Lagrangian for pairing in nonlinear chromodielectric models (CDM), in leading order. The effective pairing coupling depends explicitly on the confinement field, χ, of the CDM. The self-consistent gap equations are constructed and solved for one example. For a quartic χ potential used in the calculations, in the chiral solution, obtained for large values of the confining field and very low quarks masses, the quarks do not pair. The chiral breaking solution, where χ is small and the quarks are massive, does show pairing. We show that the vector channel of the gap is much weaker than the scalar one. At small densities the gap increases dramatically and the corresponding quark matter collapses. However this occurs for densities where our approximation is no longer valid since pairing energy becomes of the order of magnitude of the sum of the kinetic and potential energies. [Copyright &y& Elsevier]