Nuclear Theory·nucl-th

Thursday·March 5, 2020

5 papers—3 primary·2 cross-listed

01
On collective octupole degrees of freedom -- next pieces of the formal background
L. Prochniak
The concept of an intrinsic system can be extended to the case of collective octupole degrees of freedom by exploiting the symmetry properties with respect to transformations of the octahedral group O_h. Explicit formulas for scalar invariants as polynomials of intrinsic variables are presented. A method of constructing a basis in the space of functions on the octupole intrinsic space is proposed.
nucl-thActa Phys.Polon.Supp.(2020)·0 citations
02
Parametrisations of relativistic energy density functionals with tensor couplings
Stefan Typel · Diana Alvear Terrero
The relativistic density functional with minimal density dependent nucleon-meson couplings for nuclei and nuclear matter is extended to include tensor couplings of the nucleons to the vector mesons. The dependence of the minimal couplings on either vector or scalar densities is explored. New parametrisations are obtained by a fit to nuclear observables with uncertainties that are determined self-consistently. The corresponding nuclear matter parameters at saturation are determined including their uncertainties. An improvement in the description of nuclear observables, in particular for binding energies and diffraction radii, is found when tensor couplings are considered, accompanied by an increase of the Dirac effective mass. The equations of state for symmetric nuclear matter and pure neutron matter are studied for all models. The density dependence of the nuclear symmetry energy, the Dirac effective masses and scalar densities is explored. Problems at high densities for parametrisations using a scalar density dependence of the couplings are identified due to the rearrangement contributions in the scalar self-energies that lead to vanishing Dirac effective masses.
nucl-thnucl-exEPJA(2020)·35 citations
03
Magnetic dipole excitations based on the relativistic nuclear energy density functional
G. Kruzic · T. Oishi · D. Vale · N. Paar
Magnetic dipole (M1) excitations build not only a fundamental mode of nucleonic transitions, but they are also relevant for nuclear astrophysics applications. We have established a theory framework for description of M1 transitions based on the relativistic nuclear energy density functional. For this purpose the relativistic quasiparticle random phase approximation (RQRPA) is established using density dependent point coupling interaction DD-PC1, supplemented with the isovector-pseudovector interaction channel in order to study unnatural parity transitions. The introduced framework has been validated using the M1 sum rule for core-plus-two-nucleon systems, and employed in studies of the spin, orbital, isoscalar and isovector M1 transition strengths, that relate to the electromagnetic probe, in magic nuclei $^{48}$ Ca and $^{208}$ Pb, and open shell nuclei $^{42}$ Ca and $^{50}$ Ti. In these systems, the isovector spin-flip M1 transition is dominant, mainly between one or two spin-orbit partner states. It is shown that pairing correlations have a significant impact on the centroid energy and major peak position of the M1 mode. The M1 excitations could provide an additional constraint to improve nuclear energy density functionals in the future studies.
nucl-thnucl-exPRC(2020)·28 citations
04
Thermo-magnetic spectral properties of neutral mesons in vector and axial-vector channels using NJL model
Snigdha Ghosh🇮🇳 · Arghya Mukherjee🇮🇳 · Nilanjan Chaudhuri🇮🇳 · Pradip Roy🇮🇳 · Sourav Sarkar🇮🇳
In this work the neutral meson properties have been investigated in the presence of thermo-magnetic background using two-flavor Nambu--Jona-Lasinio model. Mass, spectral function and dispersion relations are obtained in the scalar ( $σ$ ) and pseudo-scalar ( $π^{0}$ ) channels as well as in the vector ( $ρ^{0}$ ) and axial vector ( $a_{1}^{0}$ ) channels. The general Lorentz structures for the vector and axial-vector meson polarization functions have been considered in detail. The ultra-violet divergences appearing in this work have been regularized using a mixed regularization technique where the gamma functions arising in dimensional regularization are replaced with incomplete gamma functions as usually done in the proper time regularization procedure. The meson spectral functions obtained in the presence of a magnetic field possess nontrivial oscillatory structure. Similar to the scalar and pseudo-scalar channel, the spectral functions for each of the modes of $ρ^{0}$ are observed to overlap with the corresponding modes of its chiral partner $a_{1}^{0}$ mesons in the chiral symmetry restored phase. We observe discontinuities in the masses of all the mesonic excitations for a non-zero external magnetic field.
↳ hep-phnucl-thPRD(2020)·30 citations
05
Improved neutrino-nucleon interactions in dense and hot matter for numerical simulations
Micaela Oertel (LUTH (UMR\_8102))🇫🇷 · Aurélien Pascal (LUTH (UMR\_8102))🇫🇷 · Marco Mancini (LUTH (UMR\_8102))🇫🇷 · Jerome Novak (LUTH (UMR\_8102))🇫🇷
Neutrinos play an important role in compact star astrophysics: neutrino-heating is one of the main ingredients in core-collapse supernovae, neutrino-matter interactions determine the composition of matter in binary neutron star mergers and have among others a strong impact on conditions for heavy element nucleosynthesis and neutron star cooling is dominated by neutrino emission except for very old stars. Many works in the last decades have shown that in dense matter medium effects considerably change the neutrino-matter interaction rates, whereas many astrophysical simulations use analytic approximations which are often far from reproducing more complete calculations. In this work we present a scheme which allows to incorporate improved rates, for charged current interactions, into simulations and show as an example some results for core-collapse supernovae, where a noticeable difference is found in the location of the neutrinospheres of the low-energy neutrinos in the early post-bounce phase.
↳ astro-ph.HEnucl-thPRC(2020)·28 citations

Affiliations

first authorsco-authorsvia INSPIRE

On collective octupole degrees of freedom -- next pieces of the formal background

Parametrisations of relativistic energy density functionals with tensor couplings

Magnetic dipole excitations based on the relativistic nuclear energy density functional

Thermo-magnetic spectral properties of neutral mesons in vector and axial-vector channels using NJL model

Improved neutrino-nucleon interactions in dense and hot matter for numerical simulations

Affiliations