Nuclear Theory·nucl-th

Tuesday·March 9, 2021

9 papers—5 primary·4 cross-listed

01
[Submitted on 6 Mar 2021]
Deep learning stochastic processes with QCD phase transition
Lijia Jiang🇩🇪 · Lingxiao Wang🇩🇪 · Kai Zhou🇩🇪
It is non-trivial to recognize phase transitions and track dynamics inside a stochastic process because of its intrinsic stochasticity. In this paper, we employ the deep learning method to classify the phase orders and predict the damping coefficient of fluctuating systems under Langevin's description. As a concrete set-up, we demonstrate this paradigm for the scalar condensation in QCD matter near the critical point, in which the order parameter of chiral phase transition can be characterized in a $1 + 1$ -dimensional Langevin equation for $σ$ field. In a supervised learning manner, the Convolutional Neural Networks(CNNs) accurately classify the first-order phase transition and crossover based on $σ$ field configurations with fluctuations. Noise in the stochastic process does not significantly hinder the performance of the well-trained neural network for phase order recognition. For mixed dynamics with diverse dynamical parameters, we further devise and train the machine to predict the damping coefficients $η$ in a broad range. The results show that it is robust to extract the dynamics from the bumpy field configurations.
Comments:
7 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Data Analysis, Statistics and Probability (physics.data-an)
arXiv:
2103.04090 [pdf]
PRD(2021)·34 citations
02
[Submitted on 7 Mar 2021]
The decline rate of the production cross-section of superheavy nuclei with $Z = 114 - 117$ at high excitation energies
J. Hong🇰🇷 · G. G. Adamian🇷🇺 · N. V. Antonenko🇷🇺 · P. Jachimowicz🇵🇱 · M. Kowal🇵🇱
The production cross sections of superheavy nuclei with charge numbers $114 - 117$ are predicted in the $(5 - 9) n$ -evaporation channels of the $^{48}$ Ca-induced complete fusion reactions for future experiments. The estimates of synthesis capabilities are based on a uniform and consistent set of input nuclear data provided by the multidimensional macroscopic-microscopic approach. The contributions of various factors to the final production cross section are discussed. As shown, the specific interplay between survival and fusion probabilities unexpectedly leads to a relatively slow decline of the total cross-sections with increasing excitation energy. This effect is supported by a favorable arrangement of fission barriers protecting the compound nucleus against splitting concerning energetic thresholds for the emission of successive neutrons. In particular, the probabilities of the formation of superheavy nuclei in the $5 n$ -, $6 n$ -, and in some cases even in $7 n$ -evaporation channels are still promising. This may offer a new opportunity for the future synthesis of unknown neutron-deficient superheavy isotopes.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.04454 [pdf]
PRC(2021)·9 citations
03
[Submitted on 8 Mar 2021]
Global study of separable pairing interaction in covariant density functional theory
S. Teeti🇺🇸 · A. V. Afanasjev🇺🇸
A systematic global investigation of pairing properties based on all available experimental data on pairing indicators has been performed for the first time in the framework of covariant density functional theory. It is based on separable pairing interaction of Ref. [1]. The optimization of the scaling factors of this interaction to experimental data clearly reveals its isospin dependence in neutron subsystem. However, the situation is less certain in proton subsystem since similar accuracy of the description of pairing indicators can be achieved both with isospin-dependent and mass-dependent scaling factors. The differences in the functional dependencies of scaling factors lead to the uncertainties in the prediction of proton and neutron pairing properties which are especially pronounced at high isospin and could have a significant impact on some physical observables. For a given part of nuclear chart the scaling factors for spherical nuclei are smaller than those for deformed ones; this feature exists also in non-relativistic density functional theories. Its origin is traced back to particle-vibration coupling in odd- $A$ nuclei which is missing in all existing global studies of pairing. Although the present investigation is based on the NL5(E) covariant energy density functional (CEDF), its general conclusions are expected to be valid also for other CEDFs built at the Hartree level.
Comments:
19 pages, 10 figures, Physical Review C in press
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.04520 [pdf]
PRC(2021)·18 citations
04
[Submitted on 8 Mar 2021]
Bayesian inference on the isospin splitting of nucleon effective mass from giant resonances in $^{208}$ Pb
Zhen Zhang🇨🇳 · Xue-Bin Feng🇨🇳 · Lie-Wen Chen🇨🇳
From a Bayesian analysis of the electric dipole polarizability, the constrained energy of isovector giant dipole resonance, the peak energy of isocalar giant quadrupole resonance and the constrained energy of isocalar giant monopole resonance in $^{208}$ Pb, we extract the isoscalar and isovector effective masses in nuclear matter at saturation density $ρ_{0}$ as $m_{s, 0}^{*} / m = 0.8 7_{- 0.04}^{+ 0.04}$ and $m_{v, 0}^{*} / m = 0.7 8_{- 0.05}^{+ 0.06}$ at $90%$ confidence level. The obtained constraints on $m_{s, 0}^{*}$ and $m_{v, 0}^{*}$ lead to a positive isospin splitting of nucleon effective mass in asymmetric nuclear matter of isospin asymmetry $δ$ at $ρ_{0}$ as $m_{n - p}^{*} / m = (0.2 0_{- 0.14}^{+ 0.15}) δ$ . In addition, the symmetry energy at the subsaturation density $ρ^{*} = 0.05 fm^{- 3}$ is determined to be $E_{sym} (ρ^{*}) = 16.7 \pm 1.3$ MeV at $90%$ confidence level.
Comments:
9 pages, 3 figures, 3 tables, accepted for publication in Chinese Physics C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.04643 [pdf]
CPC(2021)·19 citations
05
[Submitted on 8 Mar 2021]
Derivation of the nonlocal collision term in the relativistic Boltzmann equation for massive spin-1/2 particles from quantum field theory
Nora Weickgenannt🇩🇪 · Enrico Speranza🇩🇪 · Xin-li Sheng🇨🇳 · Qun Wang🇨🇳 · Dirk H. Rischke🇩🇪
We derive the Boltzmann equation and the collision kernel for massive spin-1/2 particles, using the Wigner-function formalism and employing an expansion in powers of $ℏ$ . The phase space is enlarged to include a variable related to the spin degrees of freedom. This allows to reduce the transport equations of the independent components of the Wigner function to one scalar equation. To next-to-leading order in $ℏ$ , we find that the collision kernel contains both local and nonlocal terms. We show that off-shell contributions cancel in the Boltzmann equation. Our framework can be used to study spin-polarization phenomena induced by vorticity as recently observed in heavy-ion collisions and in condensed-matter systems.
Comments:
24 pages
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2103.04896 [pdf]
PRD(2021)·128 citations

Affiliations

first authorsco-authorsvia INSPIRE

Deep learning stochastic processes with QCD phase transition

The decline rate of the production cross-section of superheavy nuclei with Z=114−117 at high excitation energies

Global study of separable pairing interaction in covariant density functional theory

Bayesian inference on the isospin splitting of nucleon effective mass from giant resonances in 208Pb

Derivation of the nonlocal collision term in the relativistic Boltzmann equation for massive spin-1/2 particles from quantum field theory

Affiliations

The decline rate of the production cross-section of superheavy nuclei with $Z = 114 - 117$ at high excitation energies

Bayesian inference on the isospin splitting of nucleon effective mass from giant resonances in $^{208}$ Pb