Nuclear Theory·nucl-th

Wednesday·May 20, 2015

8 papers—4 primary·4 cross-listed

01
[Submitted on 18 May 2015]
Spin-polarized neutron matter at different orders of chiral effective field theory
F. Sammarruca · R. Machleidt · N. Kaiser
Spin-polarized neutron matter is studied using chiral two- and three-body forces. We focus, in particular, on predictions of the energy per particle in ferromagnetic neutron matter at different orders of chiral effective field theory and for different choices of the resolution scale. We discuss the convergence pattern of the predictions and their cutoff dependence. We explore to which extent fully polarized neutron matter behaves (nearly) like a free Fermi gas. We also consider the more general case of partial polarization in neutron matter as well as the presence of a small proton fraction. In other words, in our calculations, we vary both spin and isospin asymmetries. Confirming the findings of other microscopic calculations performed with different approaches, we report no evidence for a transition to a polarized phase of neutron matter5
Comments:
21 pages, 5 figures. arXiv admin note: text overlap with arXiv:1104.0437
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1505.04836 [pdf]
PRC(2015)·14 citations
02
[Submitted on 19 May 2015]
Single universal curve for Alpha decay derived from semi-microscopic calculations
M. Ismail · W. M. Seif · A. Y. Ellithi · A. Abdurrahman
The universal curve is one of the simple ways to get preliminary information about the Alpha-decay half-life times of heavy nuclei. We try to find parameterization for the universal curve of Alpha decay based on semi-microscopic calculations, starting from the realistic M3Y-Reid nucleon-nucleon interaction. Within the deformed density-dependent cluster model, the penetration probability and the assault frequency are calculated using the WKB penetration probability. The deformations of daughter nuclei and the ground-state spin and parity of the involved nuclei are considered. We found that it is accurate enough to express the assault frequency, for all studied decays, either as a function of the mass number of the parent nuclei or as a constant average value. The average preformation probability of the Alpha cluster inside four groups of 166 even(Z)-even(N), 117 odd-even, 141 even-odd, and 72 odd-odd Alpha-emitters are obtained, individually. The effect of participating unpaired nucleons in the involved nuclei, as well as the influence of any differences in their ground-state spin and/or parity, appears in the obtained average values of the preformation probability. Based on the calculated WKB penetration probability, we suggested a single universal curve for Alpha decay, with only one parameter. This parameter varies according to the classified four groups. It includes the preformation probability and the average assault frequency, in addition to the pairing contribution.
Comments:
14 pages, 5 Figures, Accepted to be published in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1505.05013 [pdf]
PRC(2015)·18 citations
03
[Submitted on 19 May 2015]
Spurious finite-size instabilities in nuclear energy density functionals: spin channel
A. Pastore🇫🇷 · D. Tarpanov🇵🇱 · D. Davesne🇫🇷 · J. Navarro🇪🇸
It has been recently shown, that some Skyrme functionals can lead to non-converging results in the calculation of some properties of atomic nuclei. A previous study has pointed out a possible link between these convergence problems and the appearance of finite-size instabilities in symmetric nuclear matter (SNM) around saturation density. We show that the finite-size instabilities not only affect the ground state properties of atomic nuclei, but they can also influence the calculations of vibrational excited states in finite nuclei. We perform systematic fully-self consistent Random Phase Approximation (RPA) calculations in spherical doubly-magic nuclei. We employ several Skyrme functionals and vary the isoscalar and isovector coupling constants of the time-odd term $s \cdot Δ s$ . We determine critical values of these coupling constants beyond which the RPA calculations do not converge because RPA the stability matrix becomes non-positive.By comparing the RPA calculations of atomic nuclei with those performed for SNM we establish a correspondence between the critical densities in the infinite system and the critical coupling constants for which the RPA calculations do not converge. We find a quantitative stability criterion to detect finite-size instabilities related to the spin $s \cdot Δ s$ term of a functional. This criterion could be easily implemented into the standard fitting protocols to fix the coupling constants of the Skyrme functional.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1505.05043 [pdf]
PRC(2015)·18 citations
04
[Submitted on 19 May 2015]
Crystalline chiral condensates as a component of compact stars
S. Carignano🇺🇸 · E.J. Ferrer🇺🇸 · V. de la Incera🇺🇸 · L. Paulucci🇧🇷
We investigate the influence of spatially inhomogeneous chiral symmetry-breaking condensates in a magnetic field background on the equation of state for compact stellar objects. After building a hybrid star composed of nuclear and quark matter using the Maxwell construction, we find, by solving the Tolman-Oppenheimer-Volkoff equations for stellar equilibrium, that our equation of state supports stars with masses around 2 $M_{⊙}$ for values of the magnetic field that are in accordance with those inferred from magnetar data. The inclusion of a weak vector interaction term in the quark part allows one to reach 2 solar masses for relatively small central magnetic fields, making this composition a viable possibility for describing the internal degrees of freedom of this class of astrophysical objects.
Comments:
Added new graphs, references and physical discussions. This version to appear at Phys. Rev. D
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1505.05094 [pdf]
PRD(2015)·48 citations
05
[Submitted on 15 May 2015] (cross-list from math-ph)
Clebcsh-Gordan coefficients in the symmric group $S_{n}$
J.D. Vergados (KAIST University and IBS, Daejeon, Republic of Korea and University of S. Carolina, Columbia, SC, USA)🇰🇷
The coefficients of fractional parentage (CFP) or Clebcsh-Gordan coefficients of the outer product of representations of the symmetric group $S_{n}$ are evaluated using an build up algorithm defined in terms of the chain involving the chain $S_{n - 1} \subset S_{n}$ and $S_{n - 2} \subset S_{n}$ chains. Some applications in mathematical physics are considered by combining them with the Clebcsh-Gordan (C-G) coefficients of the inner product of representations of the symmetric group $S_{n}$
Comments:
76 pages, 100 tables. Added references
Subjects:
Mathematical Physics (math-ph); High Energy Physics — Theory (hep-th); math.MP (math.MP); Nuclear Theory (nucl-th)
arXiv:
1505.04200 [pdf]
1 citation
06
[Submitted on 19 May 2015] (cross-list from hep-ph)
From holography towards real-world nuclear matter
Si-wen Li🇨🇳 · Andreas Schmitt🇦🇹 · Qun Wang🇨🇳
Quantum chromodynamics is notoriously difficult to solve at nonzero baryon density, and most models or effective theories of dense quark or nuclear matter are restricted to a particular density regime and/or a particular form of matter. Here we study dense (and mostly cold) matter within the holographic Sakai-Sugimoto model, aiming at a strong-coupling framework in the wide density range between nuclear saturation density and ultra-high quark matter densities. The model contains only three parameters, and we ask whether it fulfills two basic requirements of real-world cold and dense matter, a first-order onset of nuclear matter and a chiral phase transition at high density to quark matter. Such a model would be extremely useful for astrophysical applications because it would provide a single equation of state for all densities relevant in a compact star. Our calculations are based on two approximations for baryonic matter, firstly an instanton gas and secondly a homogeneous ansatz for the non-abelian gauge fields on the flavor branes of the model. While the instanton gas shows chiral restoration at high densities but an unrealistic second-order baryon onset, the homogeneous ansatz behaves exactly the other way around. Our study thus provides all ingredients that are necessary for a more realistic model and allows for systematic improvements of the applied approximations.
Comments:
31 pages, 7 figures, v2: references added, version to appear in Physical Review D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1505.04886 [pdf]
PRD(2015)·71 citations
07
[Submitted on 19 May 2015] (cross-list from hep-ph)
Latest developments in anisotropic hydrodynamics
Leonardo Tinti🇵🇱
We discuss the leading order of anisotropic hydrodynamics expansion. It has already been shown that in the (0+1) and (1+1)-dimensional cases it is consistent with the second order viscous hydrodynamics, and it provides a striking agreement with the exact solutions of the Boltzmann equation. Quite recently, a new set of equations has been proposed for the leading order of anisotropic hydrodynamics, which is consistent with the second order viscous hydrodynamics in the most general (3+1)-dimensional case, and does not require a next-to-leading treatment for describing pressure anisotropies in the transverse plane.
Comments:
Talk presented at Excited QCD 2015,March 8-14, 2015, Tatranska Lomnica, Slovakia. arXiv admin note: substantial text overlap with arXiv:1411.7615
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1505.04960 [pdf]
Acta Phys.Polon.Supp.(2015)·0 citations
08
[Submitted on 19 May 2015] (cross-list from hep-ph)
Viscosities of Gluon Dominated QGP Model within Relativistic Non-Abelian Hydrodynamics
T.P. Djun🇮🇩 · B. Soegijono🇮🇩 · T. Mart🇮🇩 · L.T. Handoko🇮🇩
Based on the first principle calculation, a Lagrangian for the system describing quarks, gluons, and their interactions, is constructed. Ascribed to the existence of dissipative behavior as a consequence of strong interaction within quark-gluon plasma (QGP) matter, auxiliary terms describing viscosities are constituted into the Lagrangian. Through a "kind" of phase transition, gluon field is redefined as a scalar field with four-vector velocity inherently attached. Then, the Lagrangian is elaborated further to produce the energy-momentum tensor of dissipative fluid-like system and the equation of motion (EOM). By imposing the law of energy and momentum conservation, the values of shear and bulk viscosities are analytically calculated. Our result shows that, at the energy level close to hadronization, the bulk viscosity is bigger than shear viscosity. By making use of the conjectured values $η / s \sim 1/4 π$ and $ζ / s \sim 1$ , the ratio of bulk to shear viscosity is found to be $ζ / η > 4 π$ .
Comments:
12 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1505.04994 [pdf]
Int.J.Mod.Phys.A(2015)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE