Nuclear Theory·nucl-th

Tuesday·June 28, 2022

16 papers—9 primary·7 cross-listed

01
Spatial correlation of a particle-hole pair with a repulsive isovector interaction
K. Hagino · H. Sagawa
We study the spatial correlation of a particle-hole pair in the isovector channel in $^{56}$ Co and $^{40}$ K nuclei. To this end, we employ the Hartree-Fock+Tamm-Dancoff approximation with the Skyrme interaction. We find a large concentration of the two-body density at positions where the neutron particle and the proton hole states locate on the opposite side to each other with respect to the core nucleus. This feature originates from a repulsive nature of the isovector residual interaction, which is in stark contrast to the dineutron correlation with an attractive pairing interaction between the valence neutrons discussed e.g., in $^{11}$ Li and $^{6}$ He. A possible experimental implication of the repulsive correlation is also discussed.
nucl-thnucl-exPRC(2022)·1 citation
02
The Hadron-Quark Crossover in Neutron Star within Gaussian Process Regression Method
Kaixuan Huang🇨🇳 · Jinniu Hu🇨🇳 · Ying Zhang🇨🇳 · Hong Shen🇨🇳
The equations of state of the neutron star at the hadron-quark crossover region are interpolated with the Gaussian process regression (GPR) method, which can reduce the randomness of present interpolation schemes. The relativistic mean-field (RMF) model and Nambu-Jona-Lasinio (NJL) model are employed to describe the hadronic phase and quark phase, respectively. In the RMF model, the coupling term between $ω$ and $ρ$ mesons is considered to control the density-dependent behaviors of symmetry energy, i.e. the slope of symmetry energy, $L$ . Furthermore, the vector interaction between quarks is included in the NJL model to obtain the additional repulsive contributions. Their coupling strengths and the crossover windows are discussed in the present framework under the constraints on the neutron star from gravitational wave detections, massive neutron star measurements, mass-radius simultaneous observation of NICER collaboration, and the neutron skin thickness of $^{208}$ Pb from PREX-II. It is found that the slope of symmetry energy, $L$ should be around $50 - 90$ MeV and the crossover window is $(0.3, 0.6) f m^{- 3}$ with these observables. Furthermore, the uncertainties of neutron star masses and radii in the hadron-quark crossover regions are also predicted by the GPR method.
nucl-thApJ(2022)·21 citations
03
Hydrodynamic attractor of noisy plasmas
Zenan Chen🇨🇳 · Derek Teaney🇨🇳 · Li Yan🇨🇳
We provide a generalized formulation of fluctuating hydrodynamics for the far-from-equilibrium noisy medium. As an example, we consider a noisy plasma experiencing Bjorken expansion, for which the leading order evolution is captured by hydrodynamic attractor of classical hydrodynamics, while the quadratic couplings of fluctuations are solved effectively via a generalized version of the hydrodynamic kinetic equation. In the far-from-equilibrium plasma, backreaction of hydrodynamic fluctuations results in renormalization of transport properties, as well as long time tails, of high orders. In particular, corresponding to a renormalized hydrodynamic attractor, evolution in a noisy plasma towards equilibrium becomes non-monotonic.
nucl-thhep-phPRC(2023)·9 citations
04
Nuclear charge radii in Bayesian neural networks revisited
Xiao-Xu Dong · Rong An · Jun-Xu Lu · Li-Sheng Geng
In this work, a refined Bayesian neural network (BNN) based approach with six inputs including the proton number, mass number, and engineered features associated with the pairing effect, shell effect, isospin effect, and ``abnormal" shape staggering effect of $^{181, 183, 185}$ Hg, is proposed to accurately describe nuclear charge radii. The new approach is able to well describe the charge radii of atomic nuclei with $A \geq 40$ and $Z \geq 20$ . The standard root-mean-square (rms) deviation is $0.014$ fm for both the training and validation data. In particular, the predicted charge radii of proton-rich and neutron-rich calcium isotopes are found in good agreement with data. We further demonstrate the reliability of the BNN approach by investigating the variations of the rms deviation with extrapolation distances, mass numbers, and isospin asymmetries.
nucl-thnucl-exPLB(2023)·54 citations
05
Conserving approximations to dilute equilibrium systems. Pair interaction potential
E.E. Kolomeitsev · P.D. Lukianov · D.N. Voskresensky
We study self-consistent approximations such as the $Φ$ -derivable and virial approaches to dilute strongly interacting systems in equilibrium. We consider a system of non-relativistic fermions of one kind interacting via a pair potential Thermodynamical quantities are expressed in terms of various spectral functions. We review the $Φ$ derivable approximation scheme demonstrating the exact conservation of the Noether and the Botermans-Malfliet fermion number densities, and then for $Φ$ described by the tadpole and sandwich diagrams we show the coincidence of these two number densities. As examples of test pair potentials, we consider the Yukawa central nucleon-nucleon potentials within Walecka, CD Bonn, and Reid parameterizations, and the corresponding classical Lennard-Jones potentials. Expressions for the second and third virial coefficients are derived and analyzed for $Φ$ described by the tadpole and sandwich diagrams. Next, we focus on the virial approach to the equation of state. Classical, semiclassical, and purely quantum approaches are studied in detail. Then, different extrapolations of the virial equation of state are considered including the van~der~Waals form and excluded-volume models. We derive the expression for the second virial coefficient using the effective range approximation for the scattering amplitude and compare the result with the purely quantum result using the experimental phase shifts. Attention is focused on the problem of anomalously large value of the nucleon-nucleon scattering length appearing due to the presence of the quasi-bound state in nucleon-nucleon scattering, which can be destroyed in the matter because of the action of the Pauli blocking. We present results for the second virial coefficient subtracting this term. We discuss the validity of such a procedure to describe the equation of state of the nuclear matter in the virial limit.
nucl-thastro-ph.HEnucl-exPhys.Part.Nucl.(2024)·1 citation
06
Potential energy surface and formation of superheavy nuclei with the Skyrme energy-density functional
Cheng Peng · Zhao-Qing Feng
Within the framework of Skyrme energy-density functional theory, the nucleus-nucleus potential is calculated and potential energy surface is obtained with different effective forces for accurately estimating the formation cross sections of superheavy nuclei in massive fusion reactions. The width and height of the potential pocket are influenced by the Skyrme effective forces SkM, SkM $^{*}$ , SkP, SIII, Ska and SLy4, which correspond to the different equation of state for the isospin symmetry nuclear matter. It is found that the nucleus-nucleus potential is associated with the collision orientation and Skyrme parameters. More repulsive nuclear potential is pronounced with increasing the incompressible modulus of nuclear matter. The available data in the fusion-evaporation reaction of $^{48}$ Ca+ $^{238}$ U are nicely reproduced with the SkM $^{*}$ parameter by implementing into the dinuclear system model.
nucl-thCommun.Theor.Phys.(2022)·3 citations
07
Relativistic effects and three-body interactions in atomic nuclei
Y. L. Yang · P. W. Zhao
Based on the leading-order covariant pionless effective field theory, a relativistic nuclear Hamiltonian is derived and solved using the variational Monte Carlo approach for $A \leq 4$ nuclei by representing the nuclear many-body wave functions with a symmetry-based artificial neural network. It is found that the relativistic effects rescue the renormalizability of the theory, and overcome the energy collapse problem for $^{3}$ H and $^{4}$ He without promoting a repulsive three-nucleon interaction to leading order as in nonrelativistic calculations. Nevertheless, to exactly reproduce the experimental ground-state energies, a three-nucleon interaction is needed and its interplay with the relativistic effects plays a crucial role. The strongly repulsive relativistic effects suppress the energy contribution given by the three-nucleon interactions, so a strong strength for the three-nucleon interaction could be required to reproduce the experimental energies. These results shed light on a consistent understanding of relativistic effects and three-body interactions in atomic nuclei.
nucl-thPLB(2022)·38 citations
08
Nuclear properties with semilocal momentum-space regularized chiral interactions beyond N2LO
P. Maris🇺🇸 · R. Roth🇩🇪 · E. Epelbaum🇩🇪 · R.J. Furnstahl🇺🇸 · J. Golak🇵🇱 · K. Hebeler🇩🇪 · T. Hüther🇩🇪 · H. Kamada🇯🇵 · H. Krebs🇩🇪 · H. Le🇩🇪 · Ulf-G. Meißner🇩🇪 · J.A. Melendez🇺🇸 and 6 other authors
We present a comprehensive investigation of few-nucleon systems as well as light and medium-mass nuclei up to $A = 48$ using the current Low Energy Nuclear Physics International Collaboration two-nucleon interactions in combination with the third-order (N $^{2}$ LO) three-nucleon forces. To address the systematic overbinding of nuclei starting from $A \sim 10$ found in our earlier study utilizing the N $^{2}$ LO two- and three-nucleon forces, we take into account higher-order corrections to the two-nucleon potentials up through fifth order in chiral effective field theory. The resulting Hamiltonian can be completely determined using the $A = 3$ binding energies and selected nucleon-deuteron cross sections as input. It is then shown to predict other nucleon-deuteron scattering observables and spectra of light $p$ -shell nuclei, for which a detailed correlated truncation error analysis is performed, in agreement with experimental data. Moreover, the predicted ground state energies of nuclei in the oxygen isotopic chain from $^{14}$ O to $^{26}$ O as well as $^{40}$ Ca and $^{48}$ Ca show a remarkably good agreement with experimental values, given that the Hamiltonian is fixed completely from the $A \leq 3$ data, once the fourth-order (N $^{3}$ LO) corrections to the two-nucleon interactions are taken into account. On the other hand, the charge radii are found to be underpredicted by $\sim 10%$ for the oxygen isotopes and by almost $20%$ for $^{40}$ Ca and $^{48}$ Ca.
nucl-thPRC(2022)·62 citations
09
Emergence of $^{4}$ H $J^{π} = 1^{-}$ resonance in contact theories
Lorenzo Contessi🇫🇷 · Martin Schäfer🇮🇱 · Johannes Kirscher🇮🇳 · Rimantas Lazauskas🇫🇷 · Jaume Carbonel🇫🇷
We obtain the $s$ - and $p$ -wave low-energy scattering parameters for n $^{3}$ H elastic scattering and the position of the $^{4}$ H $J^{π} = 1^{-}$ resonance using the pionless effective field theory at leading order. Results are extracted with three numerical techniques: confining the system in a harmonic oscillator trap, solving the Faddeev-Yakubovsky equations in configuration space, and using an effective two-body cluster approach. The renormalization of the theory for the relevant amplitudes is assessed in a cutoff-regulator range between $1 fm^{- 1}$ and $10 fm^{- 1}$ . Most remarkably, we find a cutoff-stable/RG-invariant resonance in the $^{4}$ H $J^{π} = 1^{-}$ system. This $p$ -wave resonance is a universal consequence of a shallow two-body state and the introduction of a three-body $s$ -wave scale set by the triton binding energy. The stabilization of a resonant state in a few-fermion system through pure contact interactions has a significant consequence for the powercounting of the pionless theory. Specifically, it suggests the appearance of similar resonant states also in larger nuclei, like 16-oxygen, in which the theory's leading order does not predict stable states. Those resonances would provide a starting state to be moved to the correct physical position by the perturbative insertion of sub-leading orders, possibly resolving the discrepancy between data and contact EFT.
nucl-thphysics.atom-phPLB(2023)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE