Nuclear Theory·nucl-th

Tuesday·March 7, 2017

9 papers—6 primary·3 cross-listed

01
Quantum Nuclear Pasta and Nuclear Symmetry Energy
F. J. Fattoyev · C. J. Horowitz · B. Schuetrumpf
Complex and exotic nuclear geometries are expected to appear naturally in dense nuclear matter found in the crust of neutron stars and supernovae environment collectively referred to as nuclear pasta. The pasta geometries depend on the average baryon density, proton fraction and temperature and are critically important in the determination of many transport properties of matter in supernovae and the crust of neutron stars. Using a set of self-consistent microscopic nuclear energy density functionals we present the first results of large scale quantum simulations of pasta phases at baryon densities $0.03 \leq ρ \leq 0.10$ fm $^{- 3}$ , proton fractions $0.05 \leq Y_{p} \leq 0.40$ , and zero temperature. The full quantum simulations, in particular, allow us to thoroughly investigate the role and impact of the nuclear symmetry energy on pasta configurations. We use the Sky3D code that solves the Skyrme Hartree-Fock equations on a three-dimensional Cartesian grid. For the nuclear interaction we use the state of the art UNEDF1 parametrization, which was introduced to study largely deformed nuclei, hence is suitable for studies of the nuclear pasta. Density dependence of the nuclear symmetry energy is simulated by tuning two purely isovector observables that are insensitive to the current available experimental data. We find that a minimum total number of nucleons $A = 2000$ is necessary to prevent the results from containing spurious shell effects and to minimize finite size effects. We find that a variety of nuclear pasta geometries are present in the neutron star crust and the result strongly depends on the nuclear symmetry energy. The impact of the nuclear symmetry energy is less pronounced as the proton fractions increase. Quantum nuclear pasta calculations at $T = 0$ MeV are shown to get easily trapped in meta-stable states, and possible remedies to avoid meta-stable solutions are discussed.
nucl-thastro-ph.SRnucl-exphysics.comp-phPRC(2017)·69 citations
02
A nucleon-pair and boson coexistent description of nuclei
Lianrong Dai · Feng Pan · Jerry P. Draayer
We study a mixture of s-bosons and like-nucleon pairs with the standard pairing interaction outside a inert core. Competition between the nucleon-pairs and s-bosons is investigated in this scenario. The robustness of the BCS-BEC coexistence and crossover phenomena is examined through an analysis of pf-shell nuclei with realistic single-particle energies in which two configurations with Pauli blocking of nucleon-pair orbits due to the formation of the s-bosons is taken into account. When the nucleon-pair orbits are considered to be independent of the s-bosons, the BCS-BEC crossover becomes smooth with the number of the s-bosons noticeably more than that of the nucleonpairs near the half-shell point, a feature that is demonstrated in the pf-shell for several values of the standard pairing interaction strength. As a further test of the robustness of the BCS-BEC coexistence and crossover phenomena in nuclei, results are given for B(E2; 0^{+}_{g}->2^{+}_1) values of even-even 102-130Sn with 100Sn taken as a core and valence neutron pairs confined within the 1d5/2, 0g7/2, 1d3/2, 2s1/2, 1h11/2 orbits in the nucleon-pair orbit and the s-boson independent approximation. The results indicate that the B(E2) values are well reproduced.
nucl-thquant-phCPC(2017)·1 citation
03
A new relativistic viscous hydrodynamics code and its application to the Kelvin-Helmholtz instability in high-energy heavy-ion collisions
Kazuhisa Okamoto🇯🇵 · Chiho Nonaka🇯🇵
We construct a new relativistic viscous hydrodynamics code optimized in the Milne coordinates. We split the conservation equations into an ideal part and a viscous part, using the Strang spitting method. In the code a Riemann solver based on the two-shock approximation is utilized for the ideal part and the Piecewise Exact Solution (PES) method is applied for the viscous part. We check the validity of our numerical calculations by comparing analytical solutions, the viscous Bjorken's flow and the Israel-Stewart theory in Gubser flow regime. Using the code, we discuss possible development of the Kelvin-Helmholtz instability in high-energy heavy-ion collisions.
nucl-thhep-exhep-phEPJC(2017)·21 citations
04
Beyond-mean-field study of the hyperon impurity effect in hypernuclei with shape coexistence
X. Y. Wu🇨🇳 · H. Mei🇨🇳 · J. M. Yao🇨🇳 · Xian-Rong Zhou🇨🇳
[Background] The hyperon impurity effect in nuclei has been extensively studied in different mean-field models. Recently, there is a controversy about whether the $Λ$ hyperon is more tightly bound in the normal deformed (ND) states than that in the superdeformed (SD) states.[Purpose] This article is aimed to provide a beyond-mean-field study of the low-lying states of hypernuclei with shape coexistence and to shed some light on the controversy.[Method] The models of relativistic mean-field and beyond based on a relativistic point-coupling energy functional are adopted to study the low-lying states of both $_{Λ}^{37}$ Ar and $^{36}$ Ar. The wavefunctions of low-lying states are constructed as a superposition of a set of relativistic mean-field states with different values of quadrupole deformation parameter. The projections onto both particle number and angular momentum are considered.[Results] The $Λ$ binding energies in both ND and SD states of $_{Λ}^{37}$ Ar are studied in the case of the $Λ$ hyperon occupying $s, p$ , or $d$ state in the spherical limit, respectively. For comparison, four sets of nucleon-hyperon point-coupling interactions are used respectively. Moreover, the spectra of low-lying states in $^{36}$ Ar and $_{Λ_{s}}^{37}$ Ar are calculated based on the same nuclear energy density functional. The results indicate that the SD states exist in $_{Λ}^{37}$ Ar for all the four effective interactions. Furthermore, the $Λ_{s}$ reduces the quadrupole collectivity of ND states to a greater extent than that of SD states. For $_{Λ}^{37}$ Ar, the beyond-mean-field decreases the $Λ_{s}$ binding energy of the SD state by 0.17 MeV, but it almost has no effect on that of the ND state. [Conclusions] In $_{Λ_{s}}^{37}$ Ar, the $Λ_{p}$ and $Λ_{d}$ binding energies of the SD states ...
nucl-thPRC(2017)·24 citations
05
Electroexcitation of nucleon resonances of the [70,1-] multiplet in a light-front relativistic quark model
Inna Aznauryan🇺🇸 · Volker Burkert🇺🇸
We utilize a light-front relativistic quark model to predict the 3q core contribution to the electroexcitation of nucleon resonances of the [70,1-] multiplet on the proton and neutron at Q2 < 5GeV2. The investigation is stimulated in large degree by expected progress in the studies of the electroexcitation of nucleon resonances in the third resonance region in the CLAS experiment. For the resonances N(1520)3/2-, N(1535)1/2-, and N(1675)5/2-, experimental data on electroexcitation amplitudes on the proton are available in a wide range of Q2. This allowed us to quantify the expected meson-baryon contributions to these amplitudes as a function of Q2.
nucl-thhep-phPRC(2017)·27 citations
06
Are there any narrow $K^{-}$ - nuclear states?
Jaroslava Hrtankova🇨🇿 · Jiri Mares🇨🇿
We performed self-consistent calculations of $K^{-}$ -nuclear quasi-bound states using a single-nucleon $K^{-}$ optical potential derived from chiral meson-baryon coupled-channel interaction models, supplemented by a phenomenological $K^{-}$ multinucleon potential introduced recently to achieve good fits to kaonic atom data [1]. Our calculations show that the effect of $K^{-}$ multinucleon interactions on $K^{-}$ widths in nuclei is decisive. The resulting widths are considerably larger than corresponding binding energies. Moreover, when the density dependence of the $K^{-}$ -multinucleon interactions derived in the fits of kaonic atoms is extended to the nuclear interior, the only two models acceptable after imposing as additional constraint the single-nucleon fraction of $K^{-}$ absorption at rest do not yield any kaonic nuclear bound state in majority of considered nuclei.
nucl-thPLB(2017)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE

Quantum Nuclear Pasta and Nuclear Symmetry Energy

A nucleon-pair and boson coexistent description of nuclei

A new relativistic viscous hydrodynamics code and its application to the Kelvin-Helmholtz instability in high-energy heavy-ion collisions

Beyond-mean-field study of the hyperon impurity effect in hypernuclei with shape coexistence

Electroexcitation of nucleon resonances of the [70,1-] multiplet in a light-front relativistic quark model

Are there any narrow K−- nuclear states?

Affiliations

Are there any narrow $K^{-}$ - nuclear states?