Nuclear Theory·nucl-th

Friday·March 11, 2022

7 papers—6 primary·1 cross-listed

01
[Submitted on 10 Mar 2022]
Training and Projecting: A Reduced Basis Method Emulator for Many-Body Physics
Edgard Bonilla · Pablo Giuliani · Kyle Godbey · Dean Lee
We present the reduced basis method as a tool for developing emulators for equations with tunable parameters within the context of the nuclear many-body problem. The method uses a basis expansion informed by a set of solutions for a few values of the model parameters and then projects the equations over a well-chosen low-dimensional subspace. We connect some of the results in the eigenvector continuation literature to the formalism of reduced basis methods and show how these methods can be applied to a broad set of problems. As we illustrate, the possible success of the formalism on such problems can be diagnosed beforehand by a principal component analysis. We apply the reduced basis method to the one-dimensional Gross-Pitaevskii equation with a harmonic trapping potential and to nuclear density functional theory for $^{48}$ Ca, achieving speed-ups of more than x150 in both cases when compared to traditional solvers. The outstanding performance of the approach, together with its straightforward implementation, show promise for its application to the emulation of computationally demanding calculations, including uncertainty quantification.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Computational Physics (physics.comp-ph); Data Analysis, Statistics and Probability (physics.data-an); stat.CO (stat.CO)
arXiv:
2203.05284 [pdf]
PRC(2022)·70 citations
02
[Submitted on 10 Mar 2022]
Semi-empirical model to determine pre- and post-neutron fission product yields and neutron multiplicity
Jounghwa Lee · Young-Ouk Lee · Tae-Sun Park · Peter Schillebeeckx · Seung-Woo Hong
Post-neutron emission fission product mass distributions are calculated by using pre-neutron emission fission product yields (FPYs) and neutron multiplicity. A semi-empirical model is used to calculate the pre-neutron FPY, first. Then the neutron multiplicity for each fission fragment mass is used to convert the pre-neutron FPY to the post-neutron FPY. In doing so, assumptions are made for the probability for a pre-emission fission fragment with a mass number $A^{*}$ to decay to a post-emission fragment with a mass number $A$ . The resulting post-neutron FPYs are compared with the data available. The systems where the experimental data of not only the pre- and post-neutron FPY but also neutron multiplicity are available are the thermal neutron-induced fission of $^{233}$ U, $^{235}$ U and $^{239}$ Pu. Thus, we applied the model calculations to these systems and compared the calculation results with those from the GEF and the data from the ENDF and the EXFOR libraries. Both the pre- and post-neutron fission product mass distributions calculated by using the semi-empirical model and the neutron multiplicity reproduce the overall features of the experimental data.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2203.05322 [pdf]
J.Korean Phys.Soc.(2022)·0 citations
03
[Submitted on 10 Mar 2022]
Shape coexistence in Sr isotopes
Esperanza Maya-Barbecho · José Enrique García-Ramos
Sr isotopes are located in the mass region $A \approx 100$ , where a very quick onset of nuclear deformation exists, being other notable examples of this area Yb, Zr, and Nb nuclei. The presence of the proton subshell closure $Z = 40$ allows the existence of particle-hole excitations that produces low-lying intruder bands. Purpose: The goal of this work is the study of the nuclear structure of the even-even $^{92 - 102}$ Sr isotopes through the accurate description of excitation energies, $B (E 2)$ transition rates, nuclear radii and two-neutron separation energies. Method: The interacting boson model with configuration mixing will be the framework to calculate all the observables of the Sr isotopes. Only two types of configurations will be considered, namely, 0particle-0hole and 2particle-2hole excitations. The parameters of the model are determined using a least-squares procedure for the excitation energies and the $B (E 2)$ transition rates. Results: For the whole chain of isotopes, the value of excitation energies, $B (E 2)$ 's, two-neutron separation energies, nuclear radii, and isotope shifts have been obtained, with a good agreement between theory and experiment. Also, a detailed analysis of the wave functions have been performed and, finally, the mean-field energy surfaces and the value of the nuclear deformation, $β$ , have been obtained. Conclusions: The presence of low-lying intruder states in even-even Sr isotopes have been confirmed and its connection with the onset of deformation has been clarified. Lightest Sr isotopes present a spherical structure while the heaviest ones are clearly deformed. The rapid onset of deformation at neutron number $60$ is due to the crossing of the regular and intruder configurations and, moreover, both families of states present an increase of deformation with the neutron number.
Comments:
42 pages, 16 captioned figures. Accepted in PRC
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2203.05324 [pdf]
PRC(2022)·19 citations
04
[Submitted on 10 Mar 2022]
Asymmetric Nuclear Matter and Neutron Star Properties in Relativistic ab initio Theory in the Full Dirac Space
Sibo Wang · Hui Tong · Qiang Zhao · Chencan Wang · Peter Ring · Jie Meng
The long-standing controversy about the isospin dependence of the effective Dirac mass in ab initio calculations of asymmetric nuclear matter is clarified by solving the relativistic Brueckner-Hartree-Fock equations in the full Dirac space. The symmetry energy and its slope parameter at the saturation density are $E_{sym} (ρ_{0}) = 33.1$ MeV and $L = 65.2$ MeV, in agreement with empirical and experimental values. Further applications predict the neutron star radius $R_{1.4 M_{⊙}} \approx 12$ km and the maximum mass of a neutron star $M_{max} \leq 2.4 M_{⊙}$ .
Comments:
6 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2203.05397 [pdf]
PRC(2022)·30 citations
05
[Submitted on 20 Feb 2022]
New constraints on the neutron-star mass and radius relation from terrestrial nuclear experiments
Hajime Sotani · Nobuya Nishimura · Tomoya Naito
The determination of the equation of state (EOS) for nuclear matter has been one of the biggest problems in nuclear astrophysics, because the EOS is essential for determining the properties of neutron stars. To constrain the density-dependence of the nuclear symmetry energy, several nuclear experiments, e.g., reported by the S $π$ RIT and PREX-II collaborations, have recently been performed. However, since their uncertainties are still large, additional constraints such as astronomical observations must be crucial. In addition, it is interesting to see the effect of their reported value on neutron star properties. In this study, focusing on the relatively lower density region, we investigate the allowed area of the neutron-star mass and radius relation by assuming the constraints from S $π$ RIT and PREX-II. Each region predicted by these experiments is still consistent with the allowed area constrained by the various astronomical observations. Our results show that terrestrial nuclear experiments must provide further constraints on the EOS for neutron stars, complementing astronomical observations.
Comments:
10 pages, 2 figures, accepted in PTEP
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
arXiv:
2203.05410 [pdf]
PTEP(2022)·31 citations
06
[Submitted on 10 Mar 2022]
Model reduction methods for nuclear emulators
J. A. Melendez · C. Drischler · R. J. Furnstahl · A. J. Garcia · Xilin Zhang
The field of model order reduction (MOR) is growing in importance due to its ability to extract the key insights from complex simulations while discarding computationally burdensome and superfluous information. We provide an overview of MOR methods for the creation of fast & accurate emulators of memory- and compute-intensive nuclear systems. As an example, we describe how "eigenvector continuation" is a special case of a much more general and well-studied MOR formalism for parameterized systems. We continue with an introduction to the Ritz and Galerkin projection methods that underpin many such emulators, while pointing to the relevant MOR theory and its successful applications along the way. We believe that this will open the door to broader applications in nuclear physics and facilitate communication with practitioners in other fields.
Comments:
13 pages. Added table and minor changes
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Data Analysis, Statistics and Probability (physics.data-an)
arXiv:
2203.05528 [pdf]
J.Phys.G(2022)·64 citations
07
[Submitted on 10 Mar 2022] (cross-list from gr-qc)
Binary neutron star mergers as a probe of quark-hadron crossover equations of state
Atul Kedia🇺🇸 · Hee Il Kim🇰🇷 · In-Saeng Suh🇺🇸 · Grant J. Mathews🇺🇸
It is anticipated that the gravitational radiation detected in future gravitational wave (GW) detectors from binary neutron star (NS) mergers can probe the high-density equation of state (EOS). We perform the first simulations of binary NS mergers which adopt various parametrizations of the quark-hadron crossover (QHC) EOS. These are constructed from combinations of a hadronic EOS ( $n_{b} < 2 n_{0}$ ) and a quark-matter EOS ( $n_{b} > 5 n_{0}$ ), where $n_{b}$ and $n_{0}$ are the baryon number density and the nuclear saturation density, respectively. At the crossover densities ( $2 n_{0} < n_{b} < 5 n_{0}$ ) the QHC EOSs continuously soften, while remaining stiffer than hadronic and first-order phase transition EOSs, achieving the stiffness of strongly correlated quark matter. This enhanced stiffness leads to significantly longer lifetimes of the postmerger NS than that for a pure hadronic EOS. We find a dual nature of these EOSs such that their maximum chirp GW frequencies $f_{ma x}$ fall into the category of a soft EOS while the dominant peak frequencies ( $f_{p e ak}$ ) of the postmerger stage fall in between that of a soft and stiff hadronic EOS. An observation of this kind of dual nature in the characteristic GW frequencies will provide crucial evidence for the existence of strongly interacting quark matter at the crossover densities for QCD.
Comments:
8 pages, 3 figures
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2203.05461 [pdf]
PRD(2022)·40 citations

Affiliations

first authorsco-authorsvia INSPIRE

Training and Projecting: A Reduced Basis Method Emulator for Many-Body Physics

Semi-empirical model to determine pre- and post-neutron fission product yields and neutron multiplicity

Shape coexistence in Sr isotopes

Asymmetric Nuclear Matter and Neutron Star Properties in Relativistic ab initio Theory in the Full Dirac Space

New constraints on the neutron-star mass and radius relation from terrestrial nuclear experiments

Model reduction methods for nuclear emulators

Binary neutron star mergers as a probe of quark-hadron crossover equations of state

Affiliations