Nucleon effective mass and its isovector splitting

Abstract

Using an energy density functional (EDF) based on the thermodynamic Gibbs-Duhem relation, found equivalent to the standard Skyrme EDF for infinite nuclear matter, it is demonstrated that the parameters of this EDF are not uniquely determined from the fit of the empirical and theoretical data related to nuclear matter. This prevents an unambiguous determination of the nucleon effective mass ( m * 0 m ) and its isovector splitting (∆m * 0 ). Complementary information from dipole polarizability of atomic nuclei helps in removing this ambiguity and plausible values of m * 0 m and ∆m * 0 can be arrived at. Presently considered fit data on infinite nuclear matter and dipole polarizability of finite nuclei yield m * 0 m = 0.68 ± 0.04 and ∆m * 0 = (−0.20 ± 0.09)δ. This EDF is consistent with the constraint on the maximum mass of the neutron star.

Measurement of the Nuclear Symmetry Energy Parameters from Gravitational-wave Events

“…This is an important point. Previous studies connecting GW170817 to the nuclear EOS have either fixed the allowed range of L 0 or marginalized over L 0 (Malik et al 2018;Carson et al 2019), using priors from nuclear physics that we find to be in modest conflict with the values inferred from GW170817. As the LIGO/Virgo team continue to observe new gravitational wave events and further pin down the tidal deformability of neutron stars, it will become increasingly important to develop robust approaches to constrain the nuclear parameters in model-independent ways.…”

“…However, if we take the K sym (K 0 ) relationship that corresponds to the maximum likelihood in L 0 (i.e., the dark solid lines in Fig. 6), we find that the data point to smaller values of K sym , below the lower bound from the Malik et al (2018) study and on the lower end of the Carson et al (2019) constraints. This is likely a consequence of the fact that these studies both used priors that either forbade or disfavored low values of L 0 , such as those we find in this paper.…”

“…1 Already, several analyses have set initial constraints on nuclear parameters using the tidal deformability of GW170817. Malik et al (2018) found evidence of correlations between linear combinations of nuclear parameters and the neutron star radius, tidal love number, and tidal deformability, for a wide range of EOS. They used the inferred bounds on Λ 1.4 from GW170817, i.e., the tidal deformability of a 1.4 M neutron star, to constrain the symmetric nuclear parameters as well as K sym , for given choices of L 0 .…”

“…Several recent studies connecting GW170817 to the nuclear EOS have either restricted L 0 to similar priors or marginalized over them (Malik et al 2018;Carson et al 2019). While the posteriors on L 0 presented here are not exact, they do suggest that GW170817 points toward small values of L 0 that may be in tension with such priors.…”

“…Using the tidal deformability from GW170817, Malik et al (2018) found constraints of −112 < K sym < −52 MeV or −140 < K sym < 16 MeV, depending on their choice of prior for L 0 . In a similar analysis, Carson et al (2019) derived constraints of −259 ≤ K sym ≤ 32 MeV, after marginalizing over L 0 .…”