Nuclear Theory·nucl-th

Friday·September 1, 2023

17 papers—6 primary·11 cross-listed

01
[Submitted on 30 Aug 2023]
Distilling the essential elements of nuclear binding via neural-network quantum states
A. Gnech · B. Fore · A. Lovato
In pursuing the essential elements of nuclear binding, we compute ground-state properties of atomic nuclei with up to $A = 20$ nucleons, using as input a leading order pionless effective field theory Hamiltonian. A variational Monte Carlo method based on a new, highly-expressive, neural-network quantum state ansatz is employed to solve the many-body Schrödinger equation in a systematically improvable fashion. In addition to binding energies and charge radii, we accurately evaluate the magnetic moments of these nuclei, as they reveal the self-emergence of the shell structure, which is not a priori encoded in the neural-network ansatz. To this aim, we introduce a novel computational protocol based on adding an external magnetic field to the nuclear Hamiltonian, which allows the neural network to learn the preferred polarization of the nucleus within the given magnetic field.
Comments:
7 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2308.16266 [pdf]
PRL(2024)·44 citations
02
[Submitted on 30 Aug 2023]
Solid-State $^{229} Th$ Nuclear Laser with Two-Photon Pumping
Haowei Xu · Hao Tang · Guoqing Wang · Changhao Li · Boning Li · Paola Cappellaro · Ju Li
The radiative excitation of the 8.3 eV isomeric state of thorium-229 is an outstanding challenge due to the lack of tunable far-ultraviolet (F-UV) sources. In this work, we propose an efficient two-photon pumping scheme for thorium-229 using the optonuclear quadrupolar effect, which only requires a 300 nm UV-B pumping laser. We further demonstrate that population inversion between the nuclear isomeric and ground states can be achieved at room temperature using a two-step pumping process. The nuclear laser, which has been pursued for decades, may be realized using a Watt-level UV-B pumping laser and ultrawide bandgap thorium compounds (e.g., $Th F_{4}$ , $N a_{2} Th F_{6}$ , or $K_{2} Th F_{6}$ ) as the gain medium.
Comments:
11 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); cond-mat.mtrl-sci (cond-mat.mtrl-sci); physics.optics (physics.optics)
arXiv:
2308.16291 [pdf]
PRA(2023)·9 citations
03
[Submitted on 31 Aug 2023]
Topological transition in a parallel electromagnetic field
Gaoqing Cao🇨🇳
In this work, we attack the problem of "chiral phase instability" ( $χ$ PI) in a quantum chromodynamics (QCD) system under a parallel and constant electromagnetic field. The $χ$ PI refers to that: When $I_{2} \equiv E \cdot B$ is larger than the threshold $I_{2}^{c}$ , no homogeneous solution can be found for $σ$ or $π^{0}$ condensate, and the chiral phase (or angle) $θ$ becomes unstable. Within the two-flavor chiral perturbation theory, we obtain an effective Lagrangian density for $θ (x)$ where the chiral anomalous Wess-Zumino-Witten term is found to play a role of "source" to the "potential field" $θ (x)$ . The Euler-Lagrangian equation is applied to derive the equation of motion for $θ (x)$ , and physical solutions are worked out for several shapes of system. In the case $I_{2} > I_{2}^{c}$ , it is found that the $χ$ PI actually implies an inhomogeneous QCD phase with $θ (x)$ spatially dependent. By its very nature, the homogeneous-inhomogeneous phase transition is of pure topological and second order at $I_{2}^{c}$ . Finally, the work is extended to the three-flavor case, where an inhomogeneous $η$ condensation is also found to be developed for $I_{2} > I_{2}^{c}$ . Correspondingly, there is a second critical point, $I_{2}^{c^{'}} = 24.3 I_{2}^{c}$ , across which the transition is also of topological and second order by its very nature.
Subjects:
Nuclear Theory (nucl-th); cond-mat.mtrl-sci (cond-mat.mtrl-sci); High Energy Physics — Theory (hep-th)
arXiv:
2308.16448 [pdf]
PRD(2024)·3 citations
04
[Submitted on 31 Aug 2023]
Influence of the symmetry energy on the nuclear binding energies and the neutron drip line position
Ante Ravlić · Esra Yüksel · Tamara Nikšić · Nils Paar
A clear connection can be established between properties of nuclear matter and finite-nuclei observables, such as the correlation between the slope of the symmetry energy and dipole polarizability, or between compressibility and the isoscalar monopole giant resonance excitation energy. Establishing a connection between realistic atomic nuclei and an idealized infinite nuclear matter leads to a better understanding of underlying physical mechanisms that govern nuclear dynamics. In this work, we aim to study the dependence of the binding energies and related quantities (e.g. location of drip lines, the total number of bound even-even nuclei) on the symmetry energy $S_{2} (ρ)$ . The properties of finite nuclei are calculated by employing the relativistic Hartree-Bogoliubov (RHB) model, assuming even-even axial and reflection symmetric nuclei. Calculations are performed by employing two families of relativistic energy density functionals (EDFs), based on different effective Lagrangians, constrained to a specific symmetry energy at saturation density $J$ within the interval of $30$ -- $36$ MeV. Nuclear binding energies and related quantities of bound nuclei are calculated between $8 \leq Z \leq 104$ from the two-proton to the two-neutron drip line. As the neutron drip line is approached, the interactions with stiffer $J$ tend to predict more bound nuclei, resulting in a systematic shift of the two-neutron drip line towards more neutron-rich nuclei. Consequentially, a correlation between the number of bound nuclei $N_{n u c l}$ and $S_{2} (ρ)$ is established for a set of functionals constrained using the similar optimization procedures. The direction of the relationship between the number of bound nuclei and symmetry energy highly depends on the density under consideration.
Comments:
9 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2308.16533 [pdf]
PRC(2023)·9 citations
05
[Submitted on 31 Aug 2023]
The nuclear liquid-gas transition in QCD
Kenji Fukushima🇯🇵 · Jan Horak🇩🇪 · Jan M. Pawlowski🇩🇪 · Nicolas Wink🇩🇪 · Carl Philipp Zelle🇩🇪
We estimate the nuclear saturation density and the binding energy in a nuclear liquid from precision data on the coupling of the four-quark scattering vertex in the vector channel, computed within functional QCD. We show that this coupling is directly related to the density-density potential and the latter is used for the estimates. In a first qualitative computation we find a saturation density of 0.2 fm $^{- 3}$ and an upper bound for the binding energy of 21.5 MeV, in agreement with the empirical values of 0.16 fm $^{- 3}$ and 16 MeV, respectively. We also use the scattering vertex for constructing an emergent low-energy effective theory for the liquid gas transition from QCD correlation function, whose coupling parameters can be determined within QCD. As a first consistency check of this construction we estimate the in-medium reduction of the nucleon pole mass.
Comments:
13 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2308.16594 [pdf]
PRD(2024)·12 citations
06
[Submitted on 31 Aug 2023]
Effect of initial-state geometric configurations on the nuclear liquid-gas phase transition
Y. T. Cao · X. G. Deng · Y. G. Ma
Within the framework of an extended quantum molecular dynamics model, we simulated $^{40}$ Ca + $^{16}$ O collisions at beam energies ranging from 60 to 150 MeV/nucleon for $^{16}$ O with different $α$ -cluster configurations. Results imply that different $α$ -cluster configurations lead to different yields of deuteron, triton, $^{3}$ He and $^{4}$ He, but not for proton and neutron. We discuss the effect of geometric fluctuations which are presented by double ratios of light nuclei, namely $O_{p-d-t}$ and $O_{p-d-He}$ . It is found that magnitude hierarchy of geometric fluctuations is chain, kite, square and tetrahedron structure of $^{16}$ O. $O_{p-d-t}$ has maximum value around 80 -- 100 MeV/nucleon which could be related to liquid-gas phase transition, that is consistent with results from the charge distribution of the heaviest fragments in the collisions.
Comments:
10 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2308.16634 [pdf]
PRC(2023)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE

Distilling the essential elements of nuclear binding via neural-network quantum states

Solid-State 229Th Nuclear Laser with Two-Photon Pumping

Topological transition in a parallel electromagnetic field

Influence of the symmetry energy on the nuclear binding energies and the neutron drip line position

The nuclear liquid-gas transition in QCD

Effect of initial-state geometric configurations on the nuclear liquid-gas phase transition

Affiliations

Solid-State $^{229} Th$ Nuclear Laser with Two-Photon Pumping