Nuclear Theory·nucl-th

Friday·October 4, 2019

9 papers—4 primary·5 cross-listed

05
Neutron stars within the Skyrme model
Carlos Naya🇮🇹
The Skyrme model is a low energy effective field theory of strong interactions where nuclei and baryons appear as collective excitations of pionic degrees of freedom. In the last years, there has been a revival of Skyrme's ideas and new related models, some of them with BPS bounds (topological lower energy bounds), have been proposed. It is the aim of this paper to review how they can be applied to the study of neutron stars allowing for a description by means of topological solitons. We will focus on different aspects as the equation of state or the mass-radius relation, where we find that high maximal masses are supported.
↳ astro-ph.HEhep-thnucl-thIJMPE(2019)·12 citations
06
Superfluid Condensate Fraction and Pairing Wave Function of the Unitary Fermi Gas
Rongzheng He🇺🇸 · Ning Li🇺🇸 · Bing-Nan Lu🇺🇸 · Dean Lee🇺🇸
The unitary Fermi gas is a many-body system of two-component fermions with zero-range interactions tuned to infinite scattering length. Despite much activity and interest in unitary Fermi gases and its universal properties, there have been great difficulties in performing accurate calculations of the superfluid condensate fraction and pairing wave function. In this work we present auxiliary-field lattice Monte Carlo simulations using a novel lattice interaction which accelerates the approach to the continuum limit, thereby allowing for robust calculations of these difficult observables. As a benchmark test we compute the ground state energy of 33 spin-up and 33 spin-down particles. As a fraction of the free Fermi gas energy $E_{F G}$ , we find $E_{0} / E_{F G} = 0.369 (2), 0.372 (2)$ , using two different definitions of the finite-system energy ratio, in agreement with the latest theoretical and experimental results. We then determine the condensate fraction by measuring off-diagonal long-range order in the two-body density matrix. We find that the fraction of condensed pairs is $α = 0.43 (2)$ . We also extract the pairing wave function and find the pair correlation length to be $ζ_{p} k_{F} = 1.8 (3) ℏ$ , where $k_{F}$ is the Fermi momentum. Provided that the simulations can be performed without severe sign oscillations, the methods we present here can be applied to superfluid neutron matter as well as more exotic P-wave and D-wave superfluids.
↳ cond-mat.quant-gashep-latnucl-thPRA(2020)·15 citations
07
Holographic Approaches to DIS on a Nucleus
Kiminad A. Mamo🇺🇸
We consider deep inelastic scattering (DIS) on a dense nucleus described as an extremal RN-AdS black hole with holographic quantum fermions in the bulk. We find that the R-ratio (the ratio of the structure function of the black hole to proton) exhibit shadowing for $x < 0.1$ , anti-shadowing for $0.1 < x < 0.3$ , EMC-like effect for $0.3 < x < 0.8$ and Fermi motion for $x > 0.8$ in a qualitative agreement with the experimental observation of the ratio for DIS on nucleus for all range of $x$ . We also take the dilute limit of the black hole and show that its R-ratio exhibits EMC-like effect for $0.2 < x < 0.8$ and the Fermi motion for $x > 0.8$ , and no shadowing is observed in the dilute limit for both bottom-up (using Thomas-Fermi approximation for the nucleon distribution inside the dilute nucleus), and top-down (considering the dilute nucleus to be a Fermi gas in AdS) approaches.
↳ hep-thhep-phnucl-th0 citations
08
Properties of heavy mesons at finite temperature
Gloria Montaña🇪🇸 · Angels Ramos🇪🇸 · Laura Tolos🇩🇪
We study the properties of heavy mesons using a unitarized approach in a hot pionic medium, based on an effective hadronic theory. The interaction between the heavy mesons and pseudoscalar Goldstone bosons is described by a chiral Lagrangian at next-to-leading order in the chiral expansion and leading order in the heavy-quark mass expansion so as to satisfy heavy-quark spin symmetry. The meson-meson scattering problem in coupled channels with finite-temperature corrections is solved in a self-consistent manner. Our results show that the masses of the ground-state charmed mesons $D (0^{-})$ and $D_{s} (1^{-})$ decrease in a pionic environment at $T \neq = 0$ and they acquire a substantial width. As a consequence, the behaviour of excited mesonic states (i.e. $D_{s 0}^{*} (2317)^{\pm}$ and $D_{0}^{*} (2300)^{0, \pm}$ ), generated dynamically in our heavy-light molecular model, is also modified at $T \neq = 0$ . The aim is to test our results against Lattice QCD calculations in the future.
↳ hep-phnucl-thSciPost Phys.Proc.(2020)·0 citations
09
Possibility of rapid neutron star cooling with the realistic equation of state
Akira Dohi🇯🇵 · Ken'ichiro Nakazato🇯🇵 · Masa-aki Hashimoto🇯🇵 · Yasuhide Matsuo🇯🇵 · Tsuneo Noda🇯🇵
Whether fast cooling processes occur or not is crucial for the thermal evolution of neutron stars. In particular, the threshold of the direct Urca process, which is one of the fast cooling processes, is determined by the interior proton fraction $Y_{p}$ , or the nuclear symmetry energy. Since recent observations indicate the small radius of neutron stars, a low value is preferred for the symmetry energy. In this study, simulations of neutron star cooling are performed adopting three models for equation of state (EoS): Togashi, Shen, and LS220 EoSs. The Togashi EoS has been recently constructed with realistic nuclear potentials under finite temperature, and found to account for the small radius of neutron stars. As a result, we find that, since the direct Urca process is forbidden, the neutron star cooling is slow with use of the Togashi EoS. This is because symmetry energy of Togashi EoS is lower than those of other EoSs. Hence, in order to account for observed age and surface temperature of isolated neutron stars (INS) with use of the Togashi EoS, other fast cooling processes are needed regardless of the surface composition.
↳ astro-ph.HEastro-ph.SRnucl-thPTEP(2019)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE

Neutron stars within the Skyrme model

Superfluid Condensate Fraction and Pairing Wave Function of the Unitary Fermi Gas

Holographic Approaches to DIS on a Nucleus

Properties of heavy mesons at finite temperature

Possibility of rapid neutron star cooling with the realistic equation of state

Affiliations