Nuclear Theory·nucl-th

Monday·July 13, 2020

14 papers—8 primary·6 cross-listed

01
[Submitted on 9 Jul 2020]
Improved quark coalescence model for spin alignment and polarization of hadrons
Xin-Li Sheng🇨🇳 · Qun Wang🇨🇳 · Xin-Nian Wang🇨🇳
We propose an improved quark coalescence model for spin alignment of vector mesons and polarization of baryons by spin density matrix with phase space dependence. The spin density matrix is defined through Wigner functions. Within the model we propose an understanding of spin alignments of vector mesons $ϕ$ and $K^{* 0}$ (including $K ˉ^{* 0}$ ) in the static limit: a large positive deviation of $ρ_{00}$ for $ϕ$ mesons from 1/3 may come from the electric part of the vector $ϕ$ field, while a negative deviation of $ρ_{00}$ for $K^{* 0}$ may come from the electric part of vorticity tensor fields. Such a negative contribution to $ρ_{00}$ for $K^{* 0}$ mesons, in comparison with the same contribution to $ρ_{00}$ for $ϕ$ mesons which is less important, is amplified by a factor of the mass ratio of strange to light quark times the ratio of $⟨ p_{b}^{2} ⟩$ on the wave function of $K^{* 0}$ to $ϕ$ ( $p_{b}$ is the relative momentum of two constituent quarks of $K^{* 0}$ and $ϕ$ ). These results should be tested by a detailed and comprehensive simulation of vorticity tensor fields and vector meson fields in heavy ion collisions.
Comments:
RevTex 4, 20 pages, 3 figures, with minor changes, to appear in PRD
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2007.05106 [pdf]
PRD(2020)·87 citations
02
[Submitted on 10 Jul 2020]
Neutron star equation of state: QMF modeling and applications
A. Li🇨🇳 · Z.-Y. Zhu🇨🇳 · E.-P. Zhou🇩🇪 · J.-M. Dong🇨🇳 · J.-N. Hu🇨🇳 · C.-J. Xia🇨🇳
Because of the development of many-body theories of nuclear matter, the long-standing, open problem of the equation of state (EOS) of dense matter may be understood in the near future through the confrontation of theoretical calculations with laboratory measurements of nuclear properties \& reactions and increasingly accurate observations in astronomy. In this review, we focus on the following six aspects: 1) providing a survey of the quark mean-field (QMF) model, which consistently describes a nucleon and many-body nucleonic system from a quark potential; 2) applying QMF to both nuclear matter and neutron stars; 3) extending QMF formalism to the description of hypernuclei and hyperon matter, as well as hyperon stars; 4) exploring the hadron-quark phase transition and hybrid stars by combining the QMF model with the quark matter model characterized by the sound speed; 5) constraining interquark interactions through both the gravitational wave signals and electromagnetic signals of binary merger event GW170817; and 6) discussing further opportunities to study dense matter EOS from compact objects, such as neutron star cooling and pulsar glitches.
Comments:
101 pages, 20 figures, invited review, to appear in Journal of High Energy Astrophysics
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
2007.05116 [pdf]
JHEAp(2020)·84 citations
03
[Submitted on 10 Jul 2020]
Time-dependent covariant density functional theory in 3D lattice space: benchmark calculation for 16O + 16O reaction
Z. X. Ren · P. W. Zhao · J. Meng
Time-dependent covariant density functional theory with the successful density functional PCPK1 is developed in a three-dimensional coordinate space without any symmetry restrictions, and benchmark calculations for the 16O + 16O reaction are performed systematically. The relativistic kinematics, the conservation laws of the momentum, total energy, and particle number, as well as the time-reversal invariance are examined and confirmed to be satisfied numerically. Two primary applications including the dissipation dynamics and above-barrier fusion cross sections are illustrated. The obtained results are in good agreement with the ones given by the nonrelativistic time-dependent density functional theory and the data available. This demonstrates that the newly developed time-dependent covariant density functional theory could serve as an effective approach for the future studies of nuclear dynamical processes.
Comments:
22 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2007.05126 [pdf]
PRC(2020)·26 citations
04
[Submitted on 10 Jul 2020]
Extended quantum diffusion approach to reactions of astrophysical interests
V.V. Sargsyan · G.G. Adamian · N.V. Antonenko · H. Lenske
The quantum diffusion approach is extended to low energy fusion (capture) reactions of light- and medium-mass nuclei. The dependence of the friction parameter on bombarding energy is taken into account. A simple analytic expression is obtained for the capture probability at extreme sub-barrier energies. The calculated cross-sections are in a good agreement with the experimental data. The fusion excitation functions calculated within the quantum diffusion and WKB approaches are compared and presented in the astrophysical $S$ -factor representation.
Comments:
9 pages, 12 figures. published article
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2007.05232 [pdf]
EPJA(2020)·9 citations
05
[Submitted on 10 Jul 2020]
Compact star deformation and universal relationship for magnetized white dwarfs
Sujan Kumar Roy🇮🇳 · Somnath Mukhopadhyay🇮🇳 · D. N. Basu🇮🇳
Recently super-Chandrasekhar mass limit has been derived theoretically in presence of strong magnetic field to complement experimental observations. In the framework of Newtonian physics, we have studied the equilibrium configurations of such magnetized white dwarfs by using the relativistic Thomas-Fermi equation of state for magnetized white-dwarfs. Hartle formalism, for slowly rotating stars, has been employed to obtain the equations of equilibrium. Various physical quantities of uniformly rotating and non-rotating white dwarfs have been calculated within this formalism. Consequently, the universality relationship between the moment of inertia(I), rotational love number( $λ$ ) and spin induced quadrupole moment(Q), namely the I-Love-Q relationship, has been investigated for such magnetized white dwarfs. The relationship between I, eccentricity and Q i.e. I-eccentricity-Q relationship has also been derived. Further, we have found that, the I-eccentricity-Q relationship is more universal in comparison to I-Love-Q relationship.
Comments:
13 pages including 23 figures and 1 table
Subjects:
Nuclear Theory (nucl-th); General Relativity and Quantum Cosmology (gr-qc)
arXiv:
2007.05328 [pdf]
Eur.Phys.J.Plus(2021)·6 citations
06
[Submitted on 10 Jul 2020]
Impacts of dark matter on the curvature of the neutron star
H. C. Das · Ankit Kumar · Bharat Kumar · S. K. Biswal · S. K. Patra
The effects of dark matter (DM) on the curvatures of the neutron star (NS) are examined by using the stiff and soft relativistic mean-field equation of states. The curvatures of the NSs are calculated with the variation of baryon density. Also, it is found that the radial variation of the different curvatures significantly affected by the presence of DM inside the NS. The effects of DM are less pronounced on the compactness of the maximum NS mass, but still significant. The NS surface curvature is found to be more remarkable for the massive star. The binding energy of the NSs become positive with the increasing DM momentum and makes the system unstable.
Comments:
18 pages, 7 figures, 2 tables, minor changes in Table 1 and 2. Published in JCAP
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
arXiv:
2007.05382 [pdf]
JCAP(2021)·53 citations
07
[Submitted on 10 Jul 2020]
Causality and stability in relativistic viscous non-resistive magneto-fluid dynamics
Rajesh Biswas🇮🇳 · Ashutosh Dash🇮🇳 · Najmul Haque🇮🇳 · Shi Pu🇨🇳 · Victor Roy🇮🇳
We investigate the causality and the stability of the relativistic viscous magneto-hydrodynamics in the framework of the Israel-Stewart (IS) second-order theory, and also within a modified IS theory which incorporates the effect of magnetic fields in the relaxation equations of the viscous stress. We compute the dispersion relation by perturbing the fluid variables around their equilibrium values. In the ideal magnetohydrodynamics limit, the linear dispersion relation yields the well-known propagating modes: the Alfvén and the magneto-sonic modes.In the presence of bulk viscous pressure, the causality bound is found to be independent of the magnitude of the magnetic field. The same bound also remains true, when we take the full non-linear form of the equation using the method of characteristics. In the presence of shear viscous pressure, the causality bound is independent of the magnitude of the magnetic field for the two magneto-sonic modes. The causality bound for the shear-Alfvén modes, however, depends both on the magnitude and the direction of the propagation. For modified IS theory in the presence of shear viscosity, new non-hydrodynamic modes emerge but the asymptotic causality condition is the same as that of IS. In summary, although the magnetic field does influence the wave propagation in the fluid, the study of the stability and asymptotic causality conditions in the fluid rest frame shows that the fluid remains stable and causal given that they obey certain asymptotic causality condition.
Comments:
38 pages, 7 figures, published in JHEP
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2007.05431 [pdf]
JHEP(2020)·44 citations
08
[Submitted on 10 Jul 2020]
Localization of peripheral reactions and sensitivity to the imaginary potential
Imane Moumene · Angela Bonaccorso
The aim of the present study is to make for the first time in the literature a systematic and quantitative assessment of the evaluation of the imaginary part of the optical potential calculated within the folding model and its consequences on the localization of surface reactions. Comparing theoretical and experimental reaction cross sections, for some light projectiles on a $^{9}$ Be target, it has recently been shown that a single-folded s.f. (light-) nucleus- $^{9}$ Be imaginary optical potential is more accurate than a double-folded d.f. optical potential. Within the eikonal formalism for the cross sections and phase shifts, the single-folded potential was obtained using a n- $^{9}$ Be phenomenological optical potential and microscopic projectile densities. This paper is a follow-up in which we systematically study a series of different light and medium-mass projectile induced reactions on $^{9}$ Be. Our results confirm that the s.f. cross sections are larger than the d.f. cross sections and the effect increases with the projectile mass. Furthermore the strong absorption radius parameter extracted from the $S$ matrices calculated with the s.f. has a stable value $r_{s}$ =1.3 - 1.4 fm for all projectile masses in the range of incident energies 40-100AMeV. This indicates that a clear geometrical separation can be made between the region of surface reactions, the region of strong absorption into other channels and the region of weak nuclear interaction. The d.f. results are instead much scattered and the separation between surface reactions and other channels does not seem to be consistent. Excellent agreement with recent experimental results confirms the validity of our approach.
Comments:
9 pages, 4 figures, accepted for publication on Nuclear Physics A
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2007.05506 [pdf]
NPA(2021)·5 citations
09
[Submitted on 10 Jul 2020] (cross-list from hep-ph)
$QQ s ˉ s ˉ$ tetraquarks in the chiral quark model
Gang Yang🇨🇳 · Jialun Ping🇨🇳 · Jorge Segovia🇪🇸
The low-lying $S$ -wave $QQ s ˉ s ˉ$ ( $Q = c, b$ ) tetraquark states with $I J^{P} = 0 0^{+}$ , $0 1^{+}$ and $0 2^{+}$ are systematically investigated in the framework of complex scaling range of chiral quark model. Every structure including meson-meson, diquark-antidiquark and K-type configurations, and all possible color channels in four-body sector are considered by means of a commonly extended variational approach, Gaussian expansion method. Several narrow and wide resonance states are obtained for $cc s ˉ s ˉ$ and $bb s ˉ s ˉ$ tetraquarks with $I J^{P} = 0 0^{+}$ and $0 2^{+}$ . Meanwhile, narrow resonances for $c b s ˉ s ˉ$ tetraquarks are also found in $I J^{P} = 0 0^{+}$ , $0 1^{+}$ and $0 2^{+}$ states. These results confirm the possibility of finding hadronic molecules with masses $\sim 0.6 GeV$ above the noninteracting hadron-hadron thresholds.
Comments:
18 pages, 19 tables and 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2007.05190 [pdf]
PRD(2020)·36 citations
10
[Submitted on 10 Jul 2020] (cross-list from hep-ph)
Charge Distributions of Moving Nucleons
Cédric Lorcé (Ecole Polytechnique, CPHT)🇫🇷
Relativistic charge distributions of targets with arbitrary average momentum are introduced. They provide an interpolation between the usual Breit frame and infinite-momentum frame distributions. We find that Breit frame distributions can be interpreted from a phase-space perspective as internal charge quasi-densities in the rest frame of a localized target, without any relativistic correction. We show also that the apparent discrepancies between Breit frame and infinite-momentum frame distributions simply result from kinematical artifacts associated with spin.
Comments:
5 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2007.05318 [pdf]
PRL(2020)·88 citations
11
[Submitted on 10 Jul 2020] (cross-list from hep-ph)
On the nature of near-threshold bound and virtual states
Inka Matuschek🇩🇪 · Vadim Baru🇩🇪 · Feng-Kun Guo🇨🇳 · Christoph Hanhart🇩🇪
Physical states are characterised uniquely by their pole positions and the corresponding residues. Accordingly, in those parameters also the nature of the states should be encoded. For bound states (poles on the real $s$ -axis below the lowest threshold on the physical sheet) there is an established criterion formulated originally by Weinberg in the 1960s, which allows one to estimate the amount of compact and molecular components in a given state. We demonstrate in this paper that this criterion can be straightforwardly extended to shallow virtual states (poles on the real $s$ -axis below the lowest threshold on the unphysical sheet) which should be classified as molecular. We argue that predominantly non-molecular or compact states exist either as bound states or as resonances (poles on the unphysical sheet off the real energy axis) but not as virtual states. We also discuss the limitations of the mentioned classification scheme.
Comments:
12 pages, 8 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2007.05329 [pdf]
EPJA(2021)·116 citations
12
[Submitted on 10 Jul 2020] (cross-list from hep-lat)
Complex Paths Around The Sign Problem
Andrei Alexandru🇺🇸 · Gokce Basar🇺🇸 · Paulo F. Bedaque🇺🇸 · Neill C. Warrington🇺🇸
The Monte Carlo evaluation of path integrals is one of a few general purpose methods to approach strongly coupled systems. It is used in all branches of Physics, from QCD/nuclear physics to the correlated electron systems. However, many systems of great importance (dense matter inside neutron stars, the repulsive Hubbard model away from half-filling, dynamical and non-equilibrium observables) are not amenable to the Monte Carlo method as it currently stands due to the so-called "sign-problem". We review a new set of ideas recently developed to tackle the sign problem based on the complexification of field space and the Picard-Lefshetz theory accompanying it. The mathematical ideas underpinning this approach, as well as the algorithms so far developed, are described together with non-trivial examples where the method has already been proved successful. Directions of future work, including the burgeoning use of machine learning techniques, are delineated.
Comments:
35 pages, 21 figures
Subjects:
High Energy Physics — Lattice (hep-lat); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2007.05436 [pdf]
RMP(2022)·186 citations
13
[Submitted on 10 Jul 2020] (cross-list from hep-th)
Hydrodynamic gradient expansion in linear response theory
Michal P. Heller🇩🇪 · Alexandre Serantes🇫🇮 · Michał Spaliński🇵🇱 · Viktor Svensson🇩🇪 · Benjamin Withers🇬🇧
A foundational question in relativistic fluid mechanics concerns the properties of the hydrodynamic gradient expansion at large orders. We establish the precise conditions under which this gradient expansion diverges for a broad class of microscopic theories admitting a relativistic hydrodynamic limit, in the linear regime. Our result does not rely on highly symmetric fluid flows utilized by previous studies of heavy-ion collisions and cosmology. The hydrodynamic gradient expansion diverges whenever energy density or velocity fields have support in momentum space exceeding a critical momentum, and converges otherwise. This critical momentum is an intrinsic property of the microscopic theory and is set by branch point singularities of hydrodynamic dispersion relations.
Comments:
10 pages, 2 figures; v2: results unchanged, reorganized and expanded presentation with new figures and new appendix on purely temporal gradient expansion, matches published version
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
arXiv:
2007.05524 [pdf]
PRD(2021)·61 citations
14
[Submitted on 10 Jul 2020] (cross-list from astro-ph.HE)
GW190814: Spin and equation of state of a neutron star companion
Antonios Tsokaros · Milton Ruiz · Stuart L. Shapiro
The recent discovery by LIGO/Virgo of a merging binary having a $\sim 23 M_{⊙}$ black hole and a $\sim 2.6 M_{⊙}$ compact companion has triggered a debate regarding the nature of the secondary, which falls into the so-called mass gap. Here we explore some consequences of the assumption that the secondary was a neutron star (NS). We show with concrete examples of heretofore viable equations of state (EOSs) that rapid uniform rotation may neither be necessary for some EOSs nor sufficient for others to explain the presence of a NS. Absolute upper limits for the maximum mass of a spherical NS derived from GW170817 already suggest that this unknown compact companion might be a slowly or even a nonrotating NS. However several soft NS EOSs favored by GW170817 with maximum spherical masses $≲ 2.1 M_{⊙}$ cannot be invoked to explain this object, even allowing for maximum uniform rotation. By contrast, sufficiently stiff EOSs that yield $2.6 M_{⊙}$ NSs which are slowly rotating or, in some cases, nonrotating, and are compatible with GW170817 and the results of NICER, can account for the black hole companion.
Comments:
7 pages, 2 figures. Matches published version
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2007.05526 [pdf]
ApJ(2020)·97 citations

Affiliations

first authorsco-authorsvia INSPIRE