Symmetry Energy Constraints from Giant Resonances: A Theoretical Overview

Abstract

Giant resonances encapsulate the dynamic response of the nuclear ground state to external perturbations. As such, they offer a unique view of the nucleus that is often not accessible otherwise. Although interesting in their own right, giant resonances are also enormously valuable in providing stringent constraints on the equation of state of asymmetric matter. We this view in mind, we focus on two modes of excitation that are essential in reaching this goal: the isoscalar giant monopole resonance (GMR) and the isovector giant dipole resonance (GDR). GMR energies in heavy nuclei are sensitive to the symmetry energy because they probe the incompressibility of neutron-rich matter. Unfortunately, access to the symmetry energy is hindered by the relatively low neutron-proton asymmetry of stable nuclei. Thus, the measurement of GMR energies in exotic nuclei is strongly encouraged. In the case of the GDR, we find the electric dipole polarizability of paramount importance. Indeed, the electric dipole polarizability appears as one of two laboratory observables -- with the neutron-skin thickness being the other -- that are highly sensitive to the density dependence of the symmetry energy. Finally, we identify the softness of skin and the nature of the pygmy resonance as important unsolved problems in nuclear structure.

18 pages, 12 figures, submitted to EPJA "Special Issue on Symmetry Energy"

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• Electric Dipole Polarizability in ${}^{208}$Pb as a Probe of the Symmetry Energy and Neutron Matter around ${\rho }_0/3$
• Bayesian Inference of the Symmetry Energy of Super-Dense Neutron-Rich Matter from Future Radius Measurements of Massive Neutron Stars
• Electroweak Measurements of Neutron Densities in CREX and PREX at JLab, USA
• Covariant energy density functionals: nuclear matter constraints and global ground state properties
• Optimizing the relativistic energy density functional with nuclear ground state and collective excitation properties
• Constraining the density slope of nuclear symmetry energy at subsaturation densities using electric dipole polarizability in ${}^{208}$Pb
• Pygmy and core polarization dipole modes in ${}^{206}$Pb: connecting nuclear structure to stellar nucleosynthesis
• Implications of PREX-2 on the electric dipole polarizability of neutron rich nuclei
• Electric and magnetic dipole strength in 112,114,116,118,120,124Sn
• Nuclear dipole polarizability from mean-field modeling constrained by chiral effective field theory
• Sensitivity of the fusion cross section to the density dependence of the symmetry energy
• Isoscalar Giant Monopole, Dipole, and Quadrupole Resonances in ${}^{90,92}$Zr and ${}^{92}$Mo
• Evolution of the dipole polarizability in the stable tin isotope chain
• Are There Nuclear Structure Effects on the Isoscalar Giant Monopole Resonance and Nuclear Incompressibility near A~90?
• Effect of isovector scalar meson on equation of state of dense matter within relativistic mean field model
• Compressional-mode resonances in the molybdenum isotopes: Emergence of softness in open-shell nuclei near A=90
• CREX- and PREX-II-motivated relativistic interactions and their implications for the bulk properties of nuclear matter and neutron stars
• Relativistic Mean Field Model parameterizations in the light of GW170817, GW190814, and PSR J0740 + 6620
• Influence of the single-particle structure on the nuclear surface and the neutron skin
• Observational constraint from the heaviest pulsar PSR J0952-0607 on the equation of state of dense matter in relativistic mean field model
• Relativistic approach for the determination of nuclear and neutron star properties in consideration of PREX-II results
• Constraining the equation of state of nuclear matter from competition of fusion and quasi-fission in the reactions leading to production of the superheavy elements
• Nuclear Symmetry Energy and Neutron Skin Thickness of ${}^{208}Pb$ using a finite range effective interaction
• Nuclear breathing mode in neutron-rich Nickel isotopes: sensitivity to the symmetry energy and the role of the continuum
• Constraining Bag constant for Hybrid Neutron stars
• Emergence of low-energy monopole strength in the neutron-rich calcium isotopes
• Spectroscopy of ${}^{54}$Ti and the systematic behavior of low energy octupole states in Ca and Ti isotopes
• Study of nuclear matter properties for Hybrid EoS
• On the possible existence of a soft dipole mode in 8He
• Novel features of asymmetric nuclear matter from terrestrial experiments and astrophysical observations of neutron stars
• Electric dipole polarizability of neutron rich nuclei
• Implications of nuclear interaction for nuclear structure and astrophysics within the relativistic mean-field model