Nuclear Theory·nucl-th

Wednesday·April 24, 2024

8 papers—4 primary·4 cross-listed

01
Shell-model study of $^{28}$ Si: coexistence of oblate, prolate and superdeformed shapes
Dorian Frycz🇪🇸 · Javier Menéndez🇪🇸 · Arnau Rios🇪🇸 · Benjamin Bally🇫🇷 · Tomás R. Rodríguez🇪🇸 · Antonio M. Romero🇪🇸
We study the shape coexistence in the nucleus $^{28}$ Si with the nuclear shell model using numerical diagonalizations complemented with variational calculations based on the projected generator-coordinate method. The theoretical electric quadrupole moments and transitions as well as the collective wavefunctions indicate that the standard USDB interaction in the $s d$ shell describes well the ground-state oblate rotational band, but misses the experimental prolate band. Guided by the quasi-SU(3) model, we show that the prolate band can be reproduced in the $s d$ shell by reducing the energy of the $0 d_{3/2}$ orbital. Alternatively, in the extended $s d p f$ configuration space a modification of the SDPF-NR interaction that accommodates cross-shell excitations also reproduces the oblate and prolate bands. Finally, we address the possibility of superdeformation in $^{28}$ Si within the $s d p f$ space. Our results indicate that superdeformed structures appear at about $18$ - $20$ ~MeV.
nucl-thnucl-exPRC(2024)·9 citations
02
Parameter dependence of the $β$ -decay properties of neutron-rich Zr isotopes within the interacting boson model
M. Homma · K. Nomura
We investigate parameter dependence of the calculated $β$ -decay properties, as well as low-lying states for the neutron-rich Zr isotopes within the neutron-proton interacting boson model (IBM-2) and interacting boson-fermion-fermion model (IBFFM-2). It is shown that the calculated $lo g_{10} f t$ values for the transitions of the $0_{1}^{+}$ ground states of the parent even-even nuclei $^{96 - 102}$ Zr into the $1_{1}^{+}$ states of the daughter odd-odd nuclei $^{96 - 102}$ Nb consistently exhibit a strong dependence on those parameters associated with the quadrupole-quadrupole boson interaction, and with the residual interaction between an unpaired neutron and an unpaired proton in the IBFFM-2 Hamiltonian for the odd-odd Nb nuclei. By the reduction in magnitude of the quadrupole-quadrupole interaction strength by approximately a factor of 2, the calculated $lo g_{10} f t$ values for the Zr $(0_{1}^{+}) \to$ Nb $(1_{1}^{+})$ transitions increase and agree with the experimental values. This points to a significant improvement over the previous study performed in the same mass region, that consists of the mapping from a relativistic energy density functional calculation onto the IBM-2 Hamiltonian.
nucl-thnucl-exPRC(2024)·5 citations
03
HESS J1731-347 is likely a Quark Star Based on the Density-Dependent vMIT Bag Model
Min Ju🇨🇳 · Pengcheng Chu🇨🇳 · Xuhao Wu🇨🇳 · He Liu🇨🇳
In this study, we extend the MIT bag model by incorporating the vector interaction among quarks and introducing a density-dependent bag pressure.Then we proceed to investigate the thermodynamic properties of strange quark matter (SQM) and pure up-down quark matter (udQM) in quark stars (QSs).Our findings demonstrate that the density dependence of bag pressure $B (n_{b})$ and the vector interaction $G_{V}$ among quarks can significantly stiffen the equation of state (EOS) for both SQM and udQM which allows for the description of massive compact stars such as those observed in GW190814 and PSR J0740+6620 as plausible candidates for QSs.Ultimately, we derived a series of mass-radius relations of QS based on several combinations of ( $B_{a s}$ , $β$ ). Our results support the hypothesis that HESS J1731-347 is a quark star.
nucl-th6 citations
04
Nuclear mass predictions based on convolutional neural network
Yanhua Lu · Tianshuai Shang · Pengxiang Du · Jian Li · Haozhao Liang · Zhongming Niu
A convolutional neural network (CNN) is employed to investigate nuclear mass. By introducing the masses of neighboring nuclei and the paring effects at the input layer of the network, local features of the target nucleus are extracted to predict its mass. Then, through learning the differences between the experimental nuclear masses and the predicted nuclear masses by the WS4 model, a new global-local model (CNN-WS4) is developed, which incorporates both the global nuclear mass model and local features. Due to the incorporation of local features, the CNN-WS4 model achieves high accuracy on the training set. When extrapolating for newly emerged nuclei, the CNN-WS4 also exhibits appreciable stability, thereby demonstrating its robustness.
nucl-thPRC(2025)·20 citations
05
Effective Field Theory for Spontaneously Broken Symmetry
Tomas Brauner🇳🇴
This is a preprint of an open-access book published by Springer Cham. The book gives an up-to-date overview of the physics of spontaneously broken continuous symmetry from the point of view of effective field theory. Upon building up the necessary foundations, the text reviews the classification of Nambu-Goldstone bosons and then focuses on the construction of the effective-field-theoretic description of their dynamics. Both internal and spacetime broken symmetries are covered, including numerous illustrative examples and a few selected applications, worked out in greater detail.
↳ hep-thcond-mat.quant-gashep-phnucl-thLect.Notes Phys.(2024)·21 citations
06
Investigating $Ξ$ resonances from pentaquark perspective
Ye Yan🇨🇳 · Qi Huang🇨🇳 · Xinmei Zhu🇨🇳 · Hongxia Huang🇨🇳 · Jialun Ping🇨🇳
We have investigated the $q ss q ˉ q$ ( $q = u$ or $d$ ) system to find possible pentaquark explanations for the $Ξ$ resonances. The bound state calculation is carried out within the framework of the quark delocalization color screening model. The scattering processes are also studied to examine the possible resonance states. The current results indicate that the $Ξ (1950)$ can be interpreted as $Λ K ˉ^{*}$ state with $J^{P} = 1/ 2^{-}$ . Three states are identified that match the $Ξ (2250)$ , which are $Σ^{*} K ˉ^{*}$ state with $J^{P} = 3/ 2^{-}$ , $Σ^{*} K ˉ^{*}$ state with $J^{P} = 5/ 2^{-}$ , and $Ξ^{*} ρ$ state with $J^{P} = 5/ 2^{-}$ . This may explain the conflicting experimental values for the width of the $Ξ (2250)$ . A new $Ξ$ resonance is predicted, whose mass and width are 2066--2079 MeV and 186--189 MeV, respectively. These results contribute to understanding the nature of the $Ξ$ resonances and to the future search for new $Ξ$ resonances. Moreover, it is meaningful to further investigate the $Ξ$ resonances from an unquenched picture on the basis of pentaquark investigation.
↳ hep-phnucl-thPRD(2024)·8 citations
07
Two-body problem of impurity atoms in dipolar Fermi gas
Eiji Nakano · Takahiko Miyakawa · Hiroyuki Yabu
The polarized dipolar Fermi gas shows exotic properties at low temperatures, characterized by an axially-deformed Fermi surface and anisotropic single-particle energy, due to the long-range and anisotropic nature of dipole-dipole interaction. In cold-atom experiments such a system has been realized, e.g., in degenerate gas of Er and Dy atoms. In the case that non-dipolar impurity atoms are introduced in such system, they undergoes an induced interaction mediated by the density fluctuations of the background dipolar Fermi gas. We derive the induced interaction potential to the single-loop order of fluctuations and show that it becomes indeed an anisotropic Ruderman-Kittel-Kasuya-Yosida-type potential which preserves the axial symmetry around the polarization axis. We then solve the two-body problem of impurity atoms interacting via the anisotropic potential and figure out the dependence of bound state and scattering properties on the parameters of dipolar Fermi gas.
↳ cond-mat.quant-gasnucl-th2 citations
08
Estimating Longitudinal Polarization of $Λ$ and $Λ ˉ$ Hyperons at Relativistic Energies using Hydrodynamic and Transport models
Bhagyarathi Sahoo🇮🇳 · Captain R. Singh🇮🇳 · Raghunath Sahoo🇮🇳
The global and local spin polarization measurements of $Λ$ ( $Λ ˉ$ ) hyperons by STAR and ALICE Collaborations open up an immense interest in investigating the spin polarization dynamics in heavy-ion collisions. Recent studies suggest the transverse component of the vorticity field is responsible for the global spin polarization. In contrast, the longitudinal component of the vorticity field accounts for the local spin polarization. The local (longitudinal) spin polarization of $Λ$ -hyperons arises due to the anisotropic flows in the transverse plane, indicating a quadrupole pattern of the longitudinal vorticity along the beam direction. In this study, we derive a simple solution relating the longitudinal mean spin vector with the second-order anisotropic flow coefficient due to the thermal shear tensor for an ideal uncharged fluid in a longitudinal boost invariant scenario. The present study focuses on the local spin polarization of $Λ$ and $Λ ˉ$ in Au $+$ Au and Pb $+$ Pb collisions at $s_{N N}$ = 200 GeV and 5.02 TeV, respectively. Further, we explore the azimuthal angle, centrality, and transverse momentum ( $p_{T}$ ) dependence study of longitudinal spin polarization using hydrodynamic and transport models. All these models predict a maximum longitudinal spin polarization in mid-central collisions around 30-50 \% centrality at $p_{T} \approx$ 2.0 - 3.0 GeV/c. These findings on longitudinal spin polarization advocate the existence of a thermal medium in non-central heavy-ion collisions.
↳ hep-phhep-exnucl-exnucl-thPhys.Scripta(2025)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE