Nuclear Theory·nucl-th

Monday·August 27, 2018

8 papers—4 primary·4 cross-listed

01
[Submitted on 23 Aug 2018]
Delineating Effects of Nuclear Symmetry Energy on the Radii and Tidal Polarizabilities of Neutron Stars
Nai-Bo Zhang · Bao-An Li
What can we learn about the density dependence of nuclear symmetry energy $E_{sym} (ρ)$ from precise measurements of the radius ( $R_{1.4}$ ) and/or tidal polarizability ( $Λ_{1.4}$ ) of canonical neutron stars (NSs) with a mass of 1.4 M $_{⊙}$ ? With the $E_{sym} (ρ)$ parameterized using three parameters $L$ , $K_{sym}$ , and $J_{sym}$ which have the asymptotic meaning of being respectively the slope, curvature, and skewness of symmetry energy at saturation density, we found that, while both the $R_{1.4}$ and $Λ_{1.4}$ depend strongly on the slope $L$ , the $K_{sym}$ and $J_{sym}$ parameters characterizing the high-density behavior of $E_{sym} (ρ)$ also play appreciable roles. Thus, there is not a simple relation between the $Λ_{1.4}$ / $R_{1.4}$ and $L$ alone. Precise measurements of just the $Λ_{1.4}$ and $R_{1.4}$ can not completely determine the $E_{sym} (ρ)$ but limit combinations of its parameters. In particular, stringent constraints approximately independent of the $J_{sym}$ on the $L$ - $K_{sym}$ correlations can be obtained. However, infinite combinations of the larger (smaller) $L$ and smaller (larger) $K_{sym}$ can lead to the same $Λ_{1.4}$ and $R_{1.4}$ . Additional observables including those from terrestrial nuclear experiments are thus necessary to break this degeneracy in order to completely determine the density dependence of nuclear symmetry energy $E_{sym} (ρ)$ .
Comments:
Version accepted to the JPG Focus Issue on Hadrons & Gravitational Waves After GW170817. Added refs. [41,42,45,46] and polished several remarks
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc); Nuclear Experiment (nucl-ex)
arXiv:
1808.07955 [pdf]
J.Phys.G(2019)·60 citations
02
[Submitted on 24 Aug 2018]
Adiabatic approach to large-amplitude collective motion with the higher-order collective-coordinate operator
Koichi Sato🇯🇵
We propose a new set of equations to determine the collective Hamiltonian including the second-order collective-coordinate operator on the basis of the adiabatic self-consistent collective-coordinate (ASCC) theory. We illustrate, with the two-level Lipkin model, that the collective operators including the second-order one are self-consistently determined. We compare the results of the calculations with and without the second-order operator and show that, without the second-order operator, the agreement with the exact solution becomes worse as the excitation energy increases, but that, with the second-order operator included, the exact solution is well reproduced even for highly excited states. We also reconsider which equations one should adopt as the basic equations in the case where only the first-order operator is taken into account, and suggest an alternative set of fundamental equations instead of the conventional ASCC equations. Moreover, we briefly discuss the gauge symmetry of the new basic equations we propose in this paper.
Comments:
30 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1808.08077 [pdf]
PTEP(2018)·2 citations
03
[Submitted on 23 Aug 2018]
A nuclear matter calculation with the tensor optimized Fermi sphere method using central interaction
Taiichi Yamada🇯🇵 · Takayuki Myo🇯🇵 · Hisashi Horiuchi🇯🇵 · Kiyomi Ikeda🇯🇵 · Hiroshi Toki🇯🇵
The tensor optimized Fermi sphere (TOFS) method is applied first for the study of the property of nuclear matter using the Argonne V4' $N N$ potential. In the TOFS method, the correlated nuclear matter wave function is taken to be a power-series-type of the correlation function $F$ , where $F$ can induce central, spin-isospin, tensor, etc.~correlations. This expression has been ensured by a cluster expansion theory. In the TOFS calculation, we take into account the contributions from all the many body terms arising from the product of the nuclear-matter Hamiltonian $H$ and $F$ . It is found that the density dependence of the energy per particle in nuclear matter is reasonably reproduced, in comparison with other methods such as the Brueckner-Hartree-Fock (BHF) approach.
Comments:
22 pages, 4 figures. arXiv admin note: text overlap with arXiv:1808.07257
Subjects:
Nuclear Theory (nucl-th); cond-mat.other (cond-mat.other)
arXiv:
1808.08120 [pdf]
PTEP(2019)·10 citations
04
[Submitted on 24 Aug 2018]
Exploring Bayesian parameter estimation for chiral effective field theory using nucleon-nucleon phase shifts
S. Wesolowski🇺🇸 · R. J. Furnstahl🇺🇸 · J. A. Melendez🇺🇸 · D. R. Phillips🇺🇸
We recently developed a Bayesian framework for parameter estimation in general effective field theories. Here we present selected results from using that framework to estimate parameters with a nucleon-nucleon (NN) potential derived using chiral effective field theory ( $χ$ EFT): the semi-local NN potential of Epelbaum, Krebs, and Meißner (EKM). There are many NN scattering data, up to high energies, and with rather small errors, so imposing a penalty for unnatural low-energy constants (LECs) usually has a small effect on the fits. In contrast, we have found that including an estimate of higher orders in $χ$ EFT plays an important role in robust parameter estimation.We present two case studies where our Bayesian machinery illuminates physics issues. The first involves the EKM potential at fourth order in the $χ$ EFT expansion: the two-dimensional posterior probability density function (pdf) for the fourth-order $s$ -wave LECs obtained from the Nijmegen PWA93 phase shifts indicates these parameters in the NN potential are degenerate. We trace this feature of the pdf to the presence of an operator in the fourth-order NN potential that vanishes on-shell. The second case study examines the stability of LEC extractions as more data at higher energies are included in the fit. We show that as long as $χ$ EFT truncation errors are properly accounted for in the parameter estimation, the LEC values extracted using our Bayesian approach are not sensitive to the maximum energy chosen for the fit.Uncorrelated and fully correlated models for the truncation errors are compared, pointing the way to the use of Gaussian processes to more generally model the correlation structure.
Comments:
42 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1808.08211 [pdf]
J.Phys.G(2019)·115 citations

Affiliations

first authorsco-authorsvia INSPIRE

Delineating Effects of Nuclear Symmetry Energy on the Radii and Tidal Polarizabilities of Neutron Stars

Adiabatic approach to large-amplitude collective motion with the higher-order collective-coordinate operator

A nuclear matter calculation with the tensor optimized Fermi sphere method using central interaction

Exploring Bayesian parameter estimation for chiral effective field theory using nucleon-nucleon phase shifts

Affiliations