Nuclear Theory·nucl-th

Friday·April 26, 2019

11 papers—9 primary·2 cross-listed

01
Implications of the mass $M = 2.1 7_{- 0.10}^{+ 0.11}$ M $_{⊙}$ of PSR~J0740+6620 on the Equation of State of Super-Dense Neutron-Rich Nuclear Matter
Nai-Bo Zhang🇨🇳 · Bao-An Li🇺🇸
We study implications of the very recently reported mass $M = 2.1 7_{- 0.10}^{+ 0.11}$ M $_{⊙}$ of PSR~J0740+6620 on the Equation of State (EOS) of super-dense neutron-rich nuclear matter with respect to existing constraints on the EOS based on the mass $M = 2.01 \pm 0.04$ M $_{⊙}$ of PSR~J0348+0432, the maximum tidal deformability of GW170817 and earlier results of various terrestrial nuclear laboratory experiments. The lower limit of the skewness $J_{0}$ measuring the stiffness of super-dense isospin-symmetric nuclear matter is raised raised from about -220 MeV to -150 MeV, reducing significantly its current uncertainty range. The lower bound of the high-density symmetry energy also increases appreciably leading to a rise of the minimum proton fraction in neutron stars at $β$ -equilibrium from about 0 to 5\% around three times the saturation density of nuclear matter. The difficulties for some of the most widely used and previously well tested model EOSs to predict simultaneously both a maximum mass higher than 2.17 M $_{⊙}$ and a pressure consistent with that extracted from GW170817 present some interesting new challenges for nuclear theories.
nucl-thastro-ph.HEgr-qcnucl-exApJ(2019)·81 citations
02
Causal hydrodynamic fluctuations in non-static and inhomogeneous backgrounds
Koichi Murase🇯🇵
To integrate hydrodynamic fluctuations, namely thermal fluctuations of hydrodynamics, into dynamical models of high-energy nuclear collisions based on relativistic hydrodynamics, the property of the hydrodynamic fluctuations given by the fluctuation-dissipation relation should be carefully investigated. The fluctuation-dissipation relation for causal dissipative hydrodynamics with the finite relaxation time is naturally given in the integral form of the constitutive equation by the linear-response theory. While, the differential form of the constitutive equation is commonly used in analytic investigations and dynamical calculations for practical reasons. We give the fluctuation-dissipation relation for the general linear-response differential form and discuss the restrictions to the structure of the differential form, which comes from the causality and the positive semi-definiteness of the noise autocorrelation, and also the relation of those restrictions to the cutoff scale of the hydrodynamic fluctuations. We also give the fluctuation-dissipation relation for the integral form in non-static and inhomogeneous background by introducing new tensors, the pathline projectors. We find new modification terms to the fluctuation-dissipation relation for the differential form in non-static and inhomogeneous background which are particularly important in dynamical models to describe rapidly expanding systems.
nucl-thhep-phnucl-exAnnals Phys.(2019)·19 citations
03
Toroidal modes in nuclei by inelastic electron scattering
Anton Repko · Jan Kvasil
Electron scattering is a tool that can provide relatively clean view of the nuclear structure in both ground and excited states, as it depends on the well-known electromagnetic interaction. But since the common expressions for its cross section were derived with certain assumptions, in this paper we describe several nontrivial steps necessary for a proper theoretical calculation within the current density-functional framework, namely with Skyrme QRPA for axial nuclei, with aim to enable comparison of the theoretically predicted low-lying $1^{-}$ toroidal modes with future (e,e') experiments.
nucl-thActa Phys.Polon.Supp.(2019)·2 citations
04
Nuclear excitations within microscopic EDF approaches : pairing and temperature effects on the dipole response
E. Yüksel🇹🇷 · G. Colò🇮🇹 · E. Khan🇫🇷 · Y. F. Niu🇨🇳
In the present work, the isovector dipole responses, both in the resonance region and in the low-energy sector, are investigated using the microscopic nuclear Energy Density Functionals (EDFs). The self-consistent QRPA model based on Skyrme Hartree Fock BCS approach is applied to study the evolution of the isovector dipole strength by increasing neutron number and temperature. First, the isovector dipole strength and excitation energies are investigated for the Ni isotopic chain at zero temperature. The evolution of the low-energy dipole strength is studied as a function of the neutron number. In the second part, the temperature dependence of the isovector dipole excitations is studied using the self-consistent finite temperature QRPA, below and above the critical temperatures. It is shown that new excited states become possible due to the thermally occupied states above the Fermi level, and opening of the new excitations channels. In addition, temperature leads to fragmentation of the low-energy strength around the neutron separation energies, and between 9 and 12 MeV. We find that the cumulative sum of the strength below E $\leq 12$ MeV decreases in open-shell nuclei due to the vanishing of the pairing correlations as temperature increases up to T=1 MeV. The analysis of the transition densities in the low-energy region shows that the proton and neutron transition densities display a mixed pattern: both isoscalar and isovector motion of protons and neutrons are obtained inside nuclei, while the neutron transition density is dominant at the surface region.
nucl-thEPJA(2019)·15 citations
05
Neutrino-13C Cross Sections at Supernova Neutrino Energies
T. Suzuki🇯🇵 · A.B. Balantekin🇺🇸 · T. Kajino🇯🇵 · S. Chiba🇯🇵
We present neutrino capture cross sections on 13C at supernova neutrino energies, up to 50 MeV. For both charged-current and neutral-current reactions partial cross sections are calculated using statistical Hauser-Feschbach method. Coherent elastic neutrino scattering cross section for a 13C target is also provided.
nucl-thJ.Phys.G(2019)·13 citations
06
Reexamining Ginzburg-Landau theory for neutron $^{3} P_{2}$ superfluidity in neutron stars
Shigehiro Yasui🇯🇵 · Chandrasekhar Chatterjee🇯🇵 · Michikazu Kobayashi🇯🇵 · Muneto Nitta🇯🇵
The Ginzburg-Landau (GL) effective theory is a useful tool to study a superconductivity or superfluidity near the critical temperature, and usually the expansion up to the 4th order in terms of order parameters is sufficient for the description of the second-order phase transition. In this paper, we discuss the GL equation for the neutron $^{3} P_{2}$ superfluidity relevant for interior of neutron stars. We derive the GL expansion up to the 8th order in the condensates and find that this order is necessary for the system to have the unique ground state, unlike the ordinary cases. Starting from the $L S$ potential, which provides the dominant attraction between two neutrons at the high density, we derive the GL equation in the path-integral formalism, where the auxiliary field method and the Nambu-Gor'kov representation are used. We present the detailed description for the trace calculation necessary in the derivation of the GL equation. As numerical results, we show the phase diagram of the neutron $^{3} P_{2}$ superfluidity on the plane spanned by the temperature and magnetic field, and find that the 8th order terms lead to a first-order phase transition, whose existence was predicted in the Bogoliubov-de Gennes equation but has not been found thus far within the framework of the GL expansion up to the 6th order.The first-order phase transition will affect the interior structures inside the neutron stars.
nucl-thastro-ph.HEcond-mat.supr-conhep-phPRC(2019)·23 citations
07
Dense matter equation of state and neutron star properties from nuclear theory and experiment
Jeremy W. Holt🇺🇸 · Yeunhwan Lim🇺🇸
The equation of state of dense matter determines the structure of neutron stars, their typical radii, and maximum masses. Recent improvements in theoretical modeling of nuclear forces from the low-energy effective field theory of QCD has led to tighter constraints on the equation of state of neutron-rich matter at and somewhat above the densities of atomic nuclei, while the equation of state and composition of matter at high densities remains largely uncertain and open to a multitude of theoretical speculations. In the present work we review the latest advances in microscopic modeling of the nuclear equation of state and demonstrate how to consistently include also empirical nuclear data into a Bayesian posterior probability distribution for the model parameters. Derived bulk neutron star properties such as radii, moments of inertia, and tidal deformabilities are computed, and we discuss as well the limitations of our modeling.
nucl-thastro-ph.HEAIP Conf.Proc.(2019)·7 citations
08
Determining the Diffusivity for Light Quarks from Experiment
Scott Pratt🇺🇸 · Chris Plumberg🇸🇪
Charge balance functions reflect the evolution of charged pair correlations throughout the stages of pair production, dynamical diffusion, and hadronization in heavy-ion collisions. Microscopic modeling of these correlations in the full collision volume shows that the balance functions are sensitive to the diffusivity of light quarks when studied as functions of relative azimuthal angle. By restricting our analysis to K+,K- and p,pbar pairs, we find that the diffusivity of light quarks, a fundamental property not currently well understood, can be constrained by experimental measurement.
nucl-thnucl-exPRC(2020)·35 citations
09
Bulk quantities in nuclear collisions from running coupling $k_{T}$ -factorization and hybrid simulations
Andre V. Giannini🇧🇷 · Frédérique Grassi🇧🇷 · Matthew Luzum🇧🇷
Starting from a Color Glass Condensate (CGC) framework, based on a running-coupling improved $k_{T}$ -factorized formula, we calculate bulk observables in several heavy-ion collision systems. This is done in two ways: first we calculate the particle distribution directly implied from the CGC model, and we compare this to the case where it is instead used as initial conditions for a hybrid hydrodynamic simulation. In this way, we can assess the effects of hydrodynamic and hadronic evolution by quantifying how much they change the results from a pure initial state approach and, therefore, to what extent initial condition models can be directly compared to experimental data. We find that entropy production in subsequent hydrodynamic evolution can increase multiplicity by as much as 50\%. However, disregarding a single overall normalization factor, the centrality, energy, and system size dependence of charged hadron multiplicity is only affected at the $\sim$ 5\% level. Because of this, the parameter-free prediction for these dependencies gives reasonable agreement with experimental data whether or not hydrodynamic evolution is included. On the other hand, our model results are not compatible with the hypothesis that hydrodynamic evolution is present in large systems, but not small systems like p-Pb, in which case the dependence of multiplicity on system size would be stronger than seen experimentally. Moreover, we find that hydrodynamic evolution significantly changes the distribution of momentum, so that observables such as mean transverse momentum are very different from the initial particle production, and much closer to measured data. Finally, we find that a good agreement to anisotropic flow data cannot be achieved due to the large eccentricity generated by this model.
nucl-thhep-phPRC(2019)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE