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Dipole Polarizability of Finite Nuclei as a Probe of Neutron Stars

P. S. Koliogiannis, E. Yuksel, T. Ghosh, N. Paar

TL;DR

This work links finite-nucleus electric dipole polarizability $\alpha_D$ to the symmetry-energy slope $L$ using a family of DD--PC relativistic energy-density functionals and relativistic QRPA calculations, deriving neutron-star EOSs from microscopic nuclear matter without truncating $S_2(\rho)$. By connecting $\alpha_D$ across multiple nuclei to $L$, and translating $L$ into neutron-star observables such as the dimensionless tidal deformability $\Lambda_{1.4}$ and radius $R_{1.4}$, the authors provide constrained NS properties that are compatible with multimessenger data. The CNSP-4 and CNSP-10 analyses yield refined ranges for $L$, $\Lambda_{1.4}$, and $R_{1.4}$, illustrating that including dipole-polarizability information reduces uncertainties in the mass-radius plane and supports a soft EOS near saturation density. The study highlights $\alpha_D$ as a robust nuclear observable that helps reconcile nuclear and astrophysical constraints and advocates expanded dipole-transition measurements across more neutron-rich nuclei and higher energies to further tighten neutron-star EOS predictions.

Abstract

Nuclear ground state and collective excitation properties provide a means to probe the nuclear matter equation of state and establish connections between observables in finite nuclei and neutron stars. Specifically, the electric dipole polarizability, measured with high precision in various neutron-rich nuclei, serves as a robust constraint on the density dependence of the symmetry energy. In this Letter, we employ a class of relativistic energy density functionals in a twofold process: first, to link the electric dipole polarizability from recent experiments to the slope of the symmetry energy, and second, to translate this information into constraints on the tidal deformability and radii of neutron stars, in connection with multimessenger astrophysical observations from pulsars and binary neutron stars. We provide compelling evidence that the electric dipole polarizability represents a key nuclear observable to probe the neutron star properties. By significantly reducing the uncertainties in the mass-radius plane, our findings also align with recent multimessenger observations.

Dipole Polarizability of Finite Nuclei as a Probe of Neutron Stars

TL;DR

This work links finite-nucleus electric dipole polarizability to the symmetry-energy slope using a family of DD--PC relativistic energy-density functionals and relativistic QRPA calculations, deriving neutron-star EOSs from microscopic nuclear matter without truncating . By connecting across multiple nuclei to , and translating into neutron-star observables such as the dimensionless tidal deformability and radius , the authors provide constrained NS properties that are compatible with multimessenger data. The CNSP-4 and CNSP-10 analyses yield refined ranges for , , and , illustrating that including dipole-polarizability information reduces uncertainties in the mass-radius plane and supports a soft EOS near saturation density. The study highlights as a robust nuclear observable that helps reconcile nuclear and astrophysical constraints and advocates expanded dipole-transition measurements across more neutron-rich nuclei and higher energies to further tighten neutron-star EOS predictions.

Abstract

Nuclear ground state and collective excitation properties provide a means to probe the nuclear matter equation of state and establish connections between observables in finite nuclei and neutron stars. Specifically, the electric dipole polarizability, measured with high precision in various neutron-rich nuclei, serves as a robust constraint on the density dependence of the symmetry energy. In this Letter, we employ a class of relativistic energy density functionals in a twofold process: first, to link the electric dipole polarizability from recent experiments to the slope of the symmetry energy, and second, to translate this information into constraints on the tidal deformability and radii of neutron stars, in connection with multimessenger astrophysical observations from pulsars and binary neutron stars. We provide compelling evidence that the electric dipole polarizability represents a key nuclear observable to probe the neutron star properties. By significantly reducing the uncertainties in the mass-radius plane, our findings also align with recent multimessenger observations.

Paper Structure

This paper contains 5 sections, 9 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Methodology
  3. Results
  4. Conclusion
  5. Dipole Polarizability and QRPA Response Function

Figures (5)

  • Figure 1: The electric dipole response $R(E1;E)$ of $^{208}$Pb as a function of the excitation energy $E$ for the DD--PC family of functionals. Darker colors indicate higher symmetry-energy values.
  • Figure 2: The dimensionless tidal deformability of a $1.4~\rm{M_{\odot}}$ neutron star $\Lambda_{1.4}$ as a function of the electric dipole polarizability $\alpha_D$ of $^{208}$Pb and the corresponding neutron star radius for DD--PC EOSs. The horizontal shaded regions mark the limits derived from GW170817 event Abbott-2019 and those obtained in the present study, while the vertical band denotes the experimental result for $\alpha_D[^{208}\text{Pb}]$ and the corresponding neutron star radius inferred in this work.
  • Figure 3: The electric dipole polarizability $\alpha_D$ as a function of the slope of the symmetry energy $L$ for the DD--PC family of functionals and various isotopes. The horizontal shaded regions represent experimental values on $\alpha_D$: (a) $^{48}$Ca Birkhan2017, (b) $^{68}$Ni PhysRevLett.111.242503, (c) $^{208}$Pb PhysRevLett.107.062502Rokamaza2015, (d) $^{120}$Sn PhysRevC.92.031305Rokamaza2015, and (e-j) $^{112-124}$Sn Bassauer2020.
  • Figure 4: The dimensionless tidal deformability of a $1.4~\rm{M_{\odot}}$ neutron star $\Lambda_{1.4}$ (left axis) and its corresponding radius $R_{1.4}$ (right axis) as a function of the slope of the symmetry energy $L$ for DD--PC EOSs. The dipole polarizability of $^{208}$Pb is also shown on the top axis for reference. The vertical shaded regions represent the $L$ values obtained from dipole polarizability for the CNSP-4 and CNSP-10 sets of nuclei, while the horizontal shaded regions denote the corresponding constraints for the $\Lambda_{1.4}~(\text{or}~R_{1.4})$, respectively. Vertical arrows indicate neutron star radii from Capano-2020, doi:10.1126/science.abb4317, and $\Lambda_{1.4}$ from the GW170817 event Abbott-2019. Horizontal arrows mark nuclei with the largest and smallest deviations of $L$ value.
  • Figure 5: Gravitational mass as a function of the radius for the DD--PC EOSs, denoted by the extended shaded region. The inner shaded region corresponds to the limits from the CNSP-4 set of nuclei. The shaded contours represent multiple observations, including HESS J1731-347 Doroshenko-2022, PSR J1231-1411 Salmi_2024, PSR J0030+0451 Raaijmakers_2019Riley_2019, PSR J0437-4715 Choudhury_2024, the GW170817 event Abbott-2019, and PSR J0740+6620 Fonseca_2021Dittmann_2024, as well as maximum neutron star masses inferred from pulsar observations Antoniadis-2013Arzoumanian-2018Romani-2022.