Nuclear Theory·nucl-th

Wednesday·January 20, 2021

8 papers—6 primary·2 cross-listed

01
[Submitted on 19 Jan 2021]
The equation of state and radial oscillations of neutron stars
Ting-Ting Sun🇨🇳 · Zi-Yue Zheng🇨🇳 · Huan Chen🇨🇳 · G. Fiorella Burgio🇮🇹 · Hans-Josef Schulze🇮🇹
We investigate radial oscillations of pure neutron stars and hybrid stars, employing equations of state of nuclear matter from Brueckner-Hartree-Fock theory, and of quark matter from the Dyson-Schwinger quark model, performing a Gibbs construction for the mixed phase in hybrid stars. We calculate the eigenfrequencies and corresponding oscillation functions. Our results for the zero points of the first-order radial oscillation frequencies give the maximum mass of stable neutron stars, consistent with the common criterion $d M / d ρ_{c} = 0$ . Possible observations of the radial oscillation frequencies could help to learn more about the equation of state, predict the maximum mass of neutron stars more precisely, and indicate the presence of quark matter.
Comments:
9 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2101.07515 [pdf]
PRD(2021)·32 citations
02
[Submitted on 19 Jan 2021]
Role of nucleon-nucleon correlation in transport coefficients and gravitational-wave-driven $r$ -mode instability of neutron stars
X. L. Shang · P. Wang · W. Zuo · J. M. Dong
The thermal conductivity and shear viscosity of dense nuclear matter, along with the corresponding shear viscosity timescale of canonical neutron stars (NSs), are investigated, where the effect of Fermi surface depletion (i.e., the $Z$ -factor effect) induced by the nucleon-nucleon correlation are taken into account. The factors which are responsible for the transport coefficients, including the equation of state for building the stellar structure, nucleon effective masses, in-medium cross sections, and the $Z$ -factor at Fermi surfaces, are all calculated in the framework of the Brueckner theory. The Fermi surface depletion is found to enhance the transport coefficients by several times at high densities, which is more favorable to damping the gravitational-wave-driven $r$ -mode instability of NSs. Yet, the onset of the $Z$ -factor-quenched neutron triplet superfluidity provides the opposite effects, which can be much more significant than the above mentioned $Z$ -factor effect itself. Therefore, different from the previous understanding, the nucleon shear viscosity is still smaller than the lepton one in the superfluid NS matter at low temperatures. Accordingly, the shear viscosity cannot stablize canonical NSs against $r$ -mode oscillations even at quite low core temperatures $1 0^{6}$ K.
Comments:
11 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2101.07551 [pdf]
PLB(2020)·14 citations
03
[Submitted on 19 Jan 2021]
Alpha-Cluster formation in heavy alpha-emitters within a multistep model
J. M. Dong🇨🇳 · Q. Zhao🇨🇳 · L. J. Wang🇨🇳 · W. Zuo🇨🇳 · J. Z. Gu🇨🇳
$α$ -decay always has enormous impetuses to the development of physics and chemistry, in particular due to its indispensable role in the research of new elements. Although it has been observed in laboratories for more than a century, it remains a difficult problem to calculate accurately the formation probability $S_{α}$ microscopically. To this end, we establish a new model, i.e., multistep model, and the corresponding formation probability $S_{α}$ values of some typical $α$ -emitters are calculated without adjustable parameters. The experimental half-lives, in particular their irregular behavior around a shell closure, are remarkably well reproduced by half-life laws combined with these $S_{α}$ . In our strategy, the cluster formation is a gradual process in heavy nuclei, different from the situation that cluster pre-exists in light nuclei. The present study may pave the way to a fully understanding of $α$ -decay from the perspective of nuclear structure.
Comments:
7 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2101.07567 [pdf]
PLB(2021)·6 citations
04
[Submitted on 19 Jan 2021]
Nuclear ground states in a consistent implementation of the time-dependent density matrix approach
M. C. Barton · P. D. Stevenson · A. Rios
Background: Time-dependent techniques in nuclear theory often rely on mean-field or Hartree-Fock descriptions. Beyond mean-field dynamical calculations within the time-dependent density matrix (TDDM) theory have often invoked symmetry restrictions and ignored the connection between the mean-field and the induced interaction. Purpose: We study the ground states obtained in a TDDM approach for nuclei from $A = 12$ to $A = 24$ , including examples of even and odd-even nuclei with and without intrinsic deformation. We overcome previous limitations using three-dimensional simulations and employ density-independent Skyrme interactions self-consistently. Methods: The correlated ground states are found starting from the Hartree-Fock solution, by adiabatically including the beyond-mean-field terms in real time. Results: We find that, within this approach, correlations are responsible for $\approx 4 - 5%$ of the total energy. Radii are generally unaffected by the introduction of beyond mean-field correlations. Large nuclear correlation entropies are associated to large correlation energies. By all measures, $^{12}$ C is the most correlated isotope in the mass region considered. Conclusions: Our work is the starting point of a consistent implementation of the TDDM technique for applications into nuclear reactions. Our results indicate that correlation effects in structure are small, but beyond-mean-field dynamical simulations could provide new insight into several issues of interest.
Comments:
14 pages, 7 figures, 8 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2101.07584 [pdf]
PRC(2021)·6 citations
05
[Submitted on 19 Jan 2021]
Second and fourth moments of the charge density and neutron-skin thickness of atomic nuclei
Tomoya Naito · Gianluca Colò · Haozhao Liang · Xavier Roca-Maza
A method is presented to extract the neutron-skin thickness of atomic nuclei from the second and fourth moments of the electric charge distribution. We show that the value of the proton fourth moment must be independently known in order to estimate the neutron skin thickness experimentally. To overcome this problem, we propose the use of a strong linear correlation among the second and fourth moments of the proton distribution as calculated with several energy density functionals of common use. We take special care in estimating the errors associated with the different contributions to the neutron radius and show, for the first time, the analytic expressions for the spin-orbit contribution to the charge fourth moments of neutrons and protons. To reduce the uncertainty on the extraction of the neutron radius, two neighboring even-even isotopes are used. Nevertheless, the error on the fourth moment of the proton distribution, even if determined or assumed with large accuracy, dominates and prevents the present method from being applied for a sound determination of the neutron skin thickness.
Comments:
19 pages, 3 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2101.07680 [pdf]
PRC(2021)·19 citations
06
[Submitted on 19 Jan 2021]
Feasibility of an experimental search for a resonance of a pion and a light nucleus
Hiroyuki Fujioka🇯🇵
A hypothesis is proposed herein, suggesting that a pion-nuclear resonance may be observed in the $α + d \to^{6} Li (3.563) + π^{0}$ reaction. The resonance has a $π N N α$ structure, containing $α N N$ and $π N N$ subsystems. The former corresponds to the $A = 6$ isotriplet ( $^{6} He_{g.s.}$ , $^{6} Li (3.563)$ , $^{6} Be_{g.s.}$ ), whereas the latter is a hypothetical $N N$ -decoupled dibaryon. We propose an experiment to search for this resonance using the $^{7} Li (p, d)$ reaction.
Comments:
7 pages, 2 figures; accepted for publication in PTEP
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2101.07745 [pdf]
PTEP(2021)·0 citations
07
[Submitted on 18 Jan 2021] (cross-list from hep-ph)
Z_c -like spectra from QCD Laplace sum rules at NLO
R.M. Albuquerque (FAT-Univ. Rio de Janeiro, BR)🇧🇷 · S. Narison (LUPM-CNRS Montpellier, FR and iHEPMAD-Univ. Antananarivo, MG)🇫🇷 · D. Rabetiarivony (iHEPMAD-Univ. Antananarivo, MG)🇲🇬
We present a global analysis of the observed Z_c, Z_cs and future Z_css-like spectra using the inverse Laplace transform (LSR) version of QCD spectral sum rules (QSSR) within stability criteria. Integrated compact QCD expressions of the LO spectral functions up to dimension-six condensates are given. Next-to-Leading Order (NLO) factorized perturbative contributions are included. We re-emphasize the importance to include PT radiative corrections (though numerically small) for heavy quark sum rules in order to justify the (ad hoc) definition and value of the heavy quark mass used frequently at LO in the literature. We also demonstrate that, contrary to a naïve qualitative 1/N_c counting, the two-meson scattering contributions to the four-quark spectral functions are numerically negligible confirming the reliability of the LSR predictions. Our results are summarized in Tables III to VI. The Z_c(3900) and Z_cs(3983) spectra are well reproduced by the T_c(3900) and T_cs(3973) tetramoles (superposition of quasi-degenerated molecules and tetraquark states having the same quantum numbers and with almost equal couplings to the currents). The Z_c(4025) or Z_c(4040) state can be fitted with the D*_0D_1 molecule having a mass 4023(130) MeV while the Z_cs bump around 4.1 GeV can be likely due to the (D^*_s0D_1+ D^*_0D_s1) molecules. The Z_c(4430) can be a radial excitation of the Z_c(3900) weakly coupled to the current, while all strongly coupled ones are in the region (5634-6527) MeV. The double strange tetramole state T_css which one may identify with the future Z_css is predicted to be at 4064(46) MeV. It is remarkable to notice the regular mass-spliitings of the tetramoles due to SU(3) breakings M_{T_cs}-M_{T_c}= M_{T_css}-M_{T_cs= (73- 91) MeV.
Comments:
22 pages in two-column format; 24 figures, 6 tables : References corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2101.07281 [pdf]
PRD(2021)·52 citations
08
[Submitted on 19 Jan 2021] (cross-list from cond-mat.quant-gas)
Polaron Problems in Ultracold Atoms: Role of a Fermi Sea across Different Spatial Dimensions and Quantum Fluctuations of a Bose Medium
Hiroyuki Tajima🇯🇵 · Junichi Takahashi🇯🇵 · Simeon I. Mistakidis🇩🇪 · Eiji Nakano🇯🇵 · Kei Iida🇯🇵
The notion of a polaron, originally introduced in the context of electrons in ionic lattices, helps us to understand how a quantum impurity behaves when being immersed in and interacting with a many-body background. We discuss the impact of the impurities on the medium particles by considering feedback effects from polarons that can be realized in ultracold quantum gas experiments. In particular, we exemplify the modifications of the medium in the presence of either Fermi or Bose polarons. Regarding Fermi polarons we present a corresponding many-body diagrammatic approach operating at finite temperatures and discuss how mediated two- and three-body interactions are implemented within this framework. Utilizing this approach, we analyze the behavior of the spectral function of Fermi polarons at finite temperature by varying impurity-medium interactions as well as spatial dimensions from three to one. Interestingly, we reveal that the spectral function of the medium atoms could be a useful quantity for analyzing the transition/crossover from attractive polarons to molecules in three-dimensions. As for the Bose polaron, we showcase the depletion of the background Bose-Einstein condensate in the vicinity of the impurity atom. Such spatial modulations would be important for future investigations regarding the quantification of interpolaron correlations in Bose polaron problems.
Comments:
39 pages, 9 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
arXiv:
2101.07643 [pdf]
Atoms(2021)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE