Nuclear Theory·nucl-th

Thursday·March 11, 2021

11 papers—7 primary·4 cross-listed

01
[Submitted on 9 Mar 2021]
Quarkyonic Effective Field Theory, Quark-Nucleon Duality and Ghosts
Dyana C. Duarte🇺🇸 · Saul Hernandez-Ortiz🇺🇸 · Kie Sang Jeong🇺🇸 · Larry D. McLerran🇺🇸
We present a field theoretical description of quarkyonic matter consisting of quark, nucleon and ghost fields coupling to mesonic degrees of freedom. The ghosts are present to cancel over-counting of nucleon states that are Pauli blocked by the quark Fermi sea. Such a theory becomes an effective field theory of nucleons at low baryon density, and as such will reproduce nucleonic matter phenomenology. This theory can accommodate chiral symmetry restoration and the dynamical generation of a shell of nucleons at the Fermi surface. It is valid for finite temperature and density. In such a theory, quark-nucleon duality is accomplished by inclusion of ghost fields so that the nucleons extra degrees of freedom, that are beyond those of quarks, are compensated by the ghost fields.
Comments:
5 pages
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2103.05679 [pdf]
PRD(2021)·31 citations
02
[Submitted on 10 Mar 2021]
Role of the symmetry energy on the neutron-drip transition in accreting and nonaccreting neutron stars
A. F. Fantina🇧🇪 · N. Chamel🇧🇪 · Y. D. Mutafchieva🇧🇬 · Zh. K. Stoyanov🇧🇬 · L. M. Mihailov🇧🇬 · R. L. Pavlov🇧🇬
In this paper, we study the role of the symmetry energy on the neutron-drip transition in both nonaccreting and accreting neutron stars, allowing for the presence of a strong magnetic field as in magnetars. The density, pressure, and composition at the neutron-drip threshold are determined using the recent set of the Brussels-Montreal microscopic nuclear mass models, which mainly differ in their predictions for the value of the symmetry energy $J$ and its slope $L$ in infinite homogeneous nuclear matter at saturation. Although some correlations between on the one hand the neutron-drip density, the pressure, the proton fraction and on the other hand $J$ (or equivalently $L$ ) are found, these correlations are radically different in nonaccreting and accreting neutron stars. In particular, the neutron-drip density is found to increase with $L$ in the former case, but decreases in the latter case depending on the composition of ashes from x-ray bursts and superbursts. We have qualitatively explained these different behaviors using a simple mass formula. We have also shown that the details of the nuclear structure may play a more important role than the symmetry energy in accreting neutron-star crusts.
Comments:
29 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2103.05926 [pdf]
PRC(2016)·23 citations
03
[Submitted on 10 Mar 2021]
Electron exchange and polarization effects on electron captures and neutron emissions by nuclei in white dwarfs and neutron stars
Nicolas Chamel🇧🇪 · Anthea Fantina🇧🇪
In dense stellar environments, nuclei may become unstable against electron captures and/or neutron emissions. These processes are of particular importance for determining the internal constitution of white-dwarf cores and neutron-star crusts. In this paper, the role of electron exchange and polarization effects is studied. In particular, the instability condition for the onset of electron captures and neutron emissions is extended so as to account for electron exchange and polarization. Moreover, general analytical expressions for the corresponding density and pressure are derived. The corrections to the electron-capture threshold in white-dwarf cores are found to be very small. Likewise, the neutron-drip density and pressure in the crusts of accreting and nonaccreting neutron stars are only slightly shifted. Depending on the nuclear mass model employed, electron polarization may change the composition of the crust of nonaccreting neutron stars. On the other hand, the current uncertainties in the masses of neutron-rich Kr and Sr isotopes are found to be more important than electron exchange and polarization effects.
Comments:
15 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2103.05947 [pdf]
PRD(2016)·23 citations
04
[Submitted on 10 Mar 2021]
Application of an ab-initio-inspired energy density functional to nuclei: impact of the effective mass and the slope of the symmetry energy on bulk and surface properties
Stefano Burrello🇫🇷 · Jérémy Bonnard🇬🇧 · Marcella Grasso🇫🇷
The YGLO (Yang-Grasso-Lacroix-Orsay) functional is applied for the first time to investigate ground-state properties of different isotopic chains, from Oxygen to Lead. Mean-field Hartree-Fock calculations are carried out to analyze global trends for separation energies, binding energies, radii, neutron skins, and density profiles. We have three objectives: i) we study whether this functional leads to a reasonable description of ground-state properties (despite the fact that it was not adjusted on nuclei) and we discuss the associated limitations; ii) we investigate whether the correct description of the low-density nuclear gas, which is the peculiarity of this functional, has any relevant impact on predictions for nuclei; iii) we connect nuclear energies, radii and density profiles with properties of the corresponding equations of state of infinite matter. In particular, we identify a link existing between the isoscalar effective mass and spatial properties in neutron-deficient nuclei, namely proton radii and tails of proton densities. On the other side, we show that the slope of the symmetry energy is connected with spatial properties in neutron-rich nuclei: the slope computed at saturation density is related to neutron skin thicknesses, as already well known, whereas the slope calculated at lower densities is linked to the tails of neutron densities. The YGLO effective mass turns out to be quite low. Directions to improve this aspect are explored and suggested at the end of the manuscript.
Comments:
14 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.05996 [pdf]
PRC(2021)·14 citations
05
[Submitted on 10 Mar 2021]
Binary and ternary ionic compounds in the outer crust of a cold nonaccreting neutron star
Nicolas Chamel🇧🇪 · Anthea Fantina🇧🇪
The outer crust of a cold nonaccreting neutron star has been generally assumed to be stratified into different layers, each of which consists of a pure body-centered cubic ionic crystal in a charge compensating background of highly degenerate electrons. The validity of this assumption is examined by analyzing the stability of multinary ionic compounds in dense stellar matter. It is thus shown that their stability against phase separation is uniquely determined by their structure and their composition irrespective of the stellar conditions. However, equilibrium with respect to weak and strong nuclear processes imposes very stringent constraints on the composition of multinary compounds, and thereby on their formation. By examining different cubic and noncubic lattices, it is found that substitutional compounds having the same structure as cesium chloride are the most likely to exist in the outer crust of a nonaccreting neutron star. The presence of ternary compounds is also investigated. Very accurate analytical expressions are obtained for the threshold pressure, as well as for the densities of the different phases irrespective of the degree of relativity of the electron gas. Finally, numerical calculations of the ground-state structure and of the equation of state of the outer crust of a cold nonaccreting neutron star are carried out using recent experimental and microscopic nuclear mass tables.
Comments:
34 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); cond-mat.mtrl-sci (cond-mat.mtrl-sci)
arXiv:
2103.06073 [pdf]
PRC(2016)·35 citations
06
[Submitted on 10 Mar 2021]
Triaxial deformation and the loss of the N = 28 shell gap
Y. Suzuki · M. Kimura
Background: Recent accumulation of experimental data is revealing the nuclear deformation in vicinity of 42Si. This requests systematic theoretical studies to clarify more specific aspects of nuclear deformation and its causes. Purpose: The purpose of this study is to investigate the nature and cause of the nuclear deformations and its relation to the loss of the neutron magic number N = 28 in vicinity of 42Si. Method: The framework of antisymmetrized molecular dynamics with Gogny D1S density functional has been applied. The model assumes no spatial symmetry and can describe triaxial deformation. It also incorporates with the configuration mixing by the generator coordinate method. Results: We show that the shell effects and the loss of the magicity induce various nuclear deformations. In particular, the N = 26 and N = 30 isotones have triaxially deformed ground states. We also note that the erosion of the N = 28 magicity gradually occurs and has no definite boundaries. Conclusion: The present calculation predicts various nuclear deformations in vicinity of 42Si and suggests that the inter-band electric transitions are good measure for it. We also remark that the magicity is lost without the single-particle level inversion in the oblate deformed nuclei such as 42Si.
Comments:
18 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2103.06086 [pdf]
PRC(2021)·20 citations
07
[Submitted on 10 Mar 2021]
Fluctuations and phases in baryonic matter
Len Brandes🇩🇪 · Norbert Kaiser🇩🇪 · Wolfram Weise🇩🇪
The phase structure of baryonic matter is investigated with focus on the role of fluctuations beyond the mean-field approximation. The prototype test case studied is the chiral nucleon-meson model, with added comments on the chiral quark-meson model. Applications to the liquid-gas phase transition in nuclear matter and extensions to dense matter are performed. The role of vacuum fluctuations and thermal excitations is systematically explored. It is pointed out that such fluctuations tend to stabilise the hadronic phase characterised by spontaneously broken chiral symmetry, shifting the chiral restoration transition to very high densities. This stabilisation effect is shown to be further enhanced by additional dynamical fluctuations treated with functional renormalisation group methods.
Comments:
16 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.06096 [pdf]
EPJA(2021)·28 citations
08
[Submitted on 9 Mar 2021] (cross-list from hep-ph)
Bayesian nonparametric inference of neutron star equation of state via neural network
Ming-Zhe Han🇨🇳 · Jin-Liang Jiang🇨🇳 · Shao-Peng Tang🇨🇳 · Yi-Zhong Fan🇨🇳
We develop a new nonparametric method to reconstruct the Equation of State (EoS) of Neutron Star with multimessenger data. As an universal function approximator, the Feed-Forward Neural Network (FFNN) with one hidden layer and a sigmoidal activation function can approximately fit any continuous function. Thus we are able to implement the nonparametric FFNN representation of the EoSs. This new representation is validated by its capabilities of fitting the theoretical EoSs and recovering the injected parameters. Then we adopt this nonparametric method to analyze the real data, including mass-tidal deformability measurement from the Binary Neutron Star (BNS) merger Gravitational Wave (GW) event GW170817 and mass-radius measurement of PSR J0030+0451 by {\it NICER}. We take the publicly available samples to construct the likelihood and use the nested sampling to obtain the posteriors of the parameters of FFNN according to the Bayesian theorem, which in turn can be translated to the posteriors of EoS parameters. Combining all these data, for a canonical 1.4 $M_{⊙}$ neutron star, we get the radius $R_{1.4} = 11.8 3_{- 1.08}^{+ 1.25}$ km and the tidal deformability $Λ_{1.4} = 32 3_{- 165}^{+ 334}$ (90\% confidence interval).Furthermore, we find that in the high density region ( $\geq 3 ρ_{sat}$ ), the 90\% lower limits of the $c_{s}^{2} / c^{2}$ ( $c_{s}$ is the sound speed and $c$ is the velocity of light in the vacuum) are above $1/3$ , which means that the so-called conformal limit (i.e., $c_{s}^{2} / c^{2} < 1/3$ ) is not always valid in the neutron stars.
Comments:
11 pages, 3 figures, 2 tables, accepted for publication in ApJ
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2103.05408 [pdf]
ApJ(2021)·56 citations
09
[Submitted on 9 Mar 2021] (cross-list from hep-ph)
Soft interactions in cold quark matter
Tyler Gorda🇩🇪 · Aleksi Kurkela🇳🇴 · Risto Paatelainen🇫🇮 · Saga Säppi🇮🇹 · Aleksi Vuorinen🇫🇮
Accurate knowledge of the thermodynamic properties of zero-temperature, high-density quark matter plays an integral role in attempts to constrain the behavior of the dense QCD matter found inside neutron-star cores, irrespective of the phase realized inside the stars. In this Letter, we consider the weak-coupling expansion of the dense QCD equation of state and compute the next-to-next-to-next-to-leading-order contribution arising from the non-Abelian interactions among long-wavelength, dynamically screened gluonic fields. Accounting for these interactions requires an all-loop resummation, which can be performed using hard-thermal-loop (HTL) kinematic approximations. Concretely, we perform a full two-loop computation using the HTL effective theory, valid for the long-wavelength, or soft, modes. We find that the soft sector is well-behaved within cold quark matter, contrary to the case encountered at high temperatures, and find that the new contribution decreases the renormalization-scale dependence of the equation of state at high density.
Comments:
6 pages, 4 figures; Companion letter for arXiv:2103.07427. Changes from v1: references added, further discussions added, half of final figure removed for space. Version published in PRL
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2103.05658 [pdf]
PRL(2021)·166 citations
10
[Submitted on 10 Mar 2021] (cross-list from hep-ph)
Gluon PDF from Quark dressing in the Nucleon and Pion
Adam Freese🇺🇸 · Ian C. Cloët🇺🇸 · Peter C. Tandy🇺🇸
Gluon dressing of the light quarks within hadrons is very strong and extremely important in that it dynamically generates most of the observable mass through the breaking of chiral symmetry. The quark and gluon parton densities, $q (x)$ and $g (x)$ , are necessarily interrelated since any gluon emission and absorption process, especially dressing of a quark, contributes to $g (x)$ and modifies $q (x)$ . Guided by long-established results for the parton-in-parton distributions from a strict 1-loop perturbative analysis of a quark target, we extend the non-perturbative QCD approach based on the Rainbow-Ladder truncation of the Dyson-Schwinger equations to describe the interrelated valence $q_{v} (x)$ and the dressing-gluon $g (x)$ for a hadron at its intrinsic model scale. We employ the pion description from previous DSE work that accounted for the gluon-in-quark effect and introduce a simple model of the nucleon for exploratory purposes. We find typically \mbox{ $⟨ x ⟩_{g} \sim 0.20$ } for both pion and nucleon at the model scale, and the valence quark helicity contributes 52\% of nucleon spin. We deduce both $q_{v} (x)$ and $g (x)$ from 30 calculated Mellin moments, and after adopting existing data analysis results for $q_{sea} (x)$ , we find that NLO scale evolution produces $g (x)$ in good agreement with existing data analysis results for the pion at 1.3 GeV and the nucleon at 5 GeV $^{2}$ . At the scale 2 GeV typical of lattice-QCD calculations, we obtain \mbox{ $⟨ x ⟩_{g}^{N} = 0.42$ } in good agreement with 0.38 from the average of recent lattice-QCD calculations.
Comments:
8 pages, 5 figures. Removed 1 figure, added 1 figure, addded explanatory text, corrected typos, added several new references. This version to be published
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2103.05839 [pdf]
PLB(2021)·16 citations
11
[Submitted on 10 Mar 2021] (cross-list from hep-th)
Parametric resonance of complex scalar field under spacetime oscillations
Shreyansh S. Dave🇮🇳 · Sanatan Digal🇮🇳
In this proceeding, we study time evolution of a complex scalar field, in symmetry broken phase, in presence of oscillating spacetime metric background. We show that spacetime oscillations lead to parametric resonance of the field. This generates excitations in the field for a wide range of frequency of spacetime oscillations which ultimately lead to the formation of topological vortices. The lowest frequency cut-off to induce this phenomena is set by system size due to finite size effects.
Comments:
4 pages, 3 figures, Contribution to proceedings of XXIV DAE-BRNS Symposium on High Energy Physics, Dec. 14-18, 2020, Jatni, Odisha, India
Subjects:
High Energy Physics — Theory (hep-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2103.05879 [pdf]
Springer Proc.Phys.(2022)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE