Nuclear Theory·nucl-th

Thursday·September 21, 2017

5 papers—4 primary·1 cross-listed

01
The anisotropic non-equilibrium hydrodynamic attractor
Michael Strickland🇺🇸 · Jorge Noronha🇧🇷 · Gabriel Denicol🇧🇷
We determine the dynamical attractors associated with anisotropic hydrodynamics (aHydro) and the DNMR equations for a 0+1d conformal system using kinetic theory in the relaxation time approximation. We compare our results to the non-equilibrium attractor obtained from exact solution of the 0+1d conformal Boltzmann equation, Navier-Stokes theory, and second-order Mueller-Israel-Stewart theory. We demonstrate that the aHydro attractor equation resums an infinite number of terms in the inverse Reynolds number. The resulting resummed aHydro attractor possesses a positive longitudinal to transverse pressure ratio and is virtually indistinguishable from the exact attractor. This suggests that kinetic theory involves not only a resummation in gradients (Knudsen number) but also a novel resummation in inverse Reynolds number. We also demonstrate that the DNMR result provides a better approximation to the exact kinetic theory attractor than Mueller-Israel-Stewart theory. Finally, we introduce a new method for obtaining approximate aHydro equations which relies solely on an expansion in inverse Reynolds number, carry out this expansion to third order, and compare these third-order results to the exact kinetic theory solution.
nucl-thhep-phPRD(2018)·180 citations
02
A practical scheme for constructing the minimum weight states of the su(n)-Lipkin model in arbitrary fermion number
Y. Tsue (1) · C. Providencia (2) · J. da Providencia (2) · M. Yamamura (3) ((1) Kochi Univ., Japan, (2) Univ. de Coimbra, Portugal, (3) Kansai Univ., Japan)
With the aim of performing an argument supplement to the previous paper by the present authors, in this paper, a practical scheme for constructing the minimum weight states of the su(n)-Lipkin model in arbitrary fermion number is discussed. The idea comes from the following two points : (i) consideration on the property of one-fermion transfer induced by the su(n)-generators in the Lipkin model and (ii) use of the auxiliary su(2)-algebra presented by the present authors. The form obtained under the points (i) and (ii) is simple.
nucl-thPTEP(2017)·0 citations
03
The role of the elemental nature of A=3 nuclei in neutron-rich nuclei
Anisul Ain. Usmani · Syed Afsar Abbas · Usuf Rahaman · Mohammad Ikram · Farooq Hussain Bhat
The idea of treating the trinucleon systems as elementary entities in the elementary particle model (EPM) as an Effective Field Theory has been a success in explaining the weak charge-changing processes in nuclei. The EPM results are found to be as good as those obtained from nuclear microscopic models using two- and three-body forces. We extend this concept to investigate the validity of the elemental nature of $A = 3$ nuclei through studies of nuclear structure of neutron-rich nuclei. By treating neutron-rich nuclei as primarily made up of tritons as its building blocks, we extract one- and two-triton separation energies of these nuclei. Calculations have been performed here within relativistic mean field (RMF) models with latest interactions. Clear evidence arises of a new shell structure with well-defined predictions of new magic nuclei. These unique predictions have been consolidated by standard one- and two-neutron separation energy calculations. The binding energy per nucleon plots of these nuclei also confirm these predictions. We make unambiguos prediction of six magic nuclei: $_{8}^{24} O_{16}$ , $_{20}^{60} Ca_{40}$ , $_{35}^{105} Br_{70}$ , $_{41}^{123} Nb_{82}$ , $_{63}^{189} Eu_{126}$ and $_{92}^{276} U_{184}$ .
nucl-thIJMPE(2018)·8 citations
04
Electromagnetic Strength Distributions from the Ab Initio No-Core Shell Model
Christina Stumpf · Tobias Wolfgruber · Robert Roth
We present an ab initio approach for the description of collective excitations and transition strength distributions of arbitrary nuclei up into the sd-shell that based on the No-Core Shell Model in combination with the Lanczos strength-function method. Starting from two- and three-nucleon interactions from chiral effective field theory, we investigate the electric monopole, dipole, and quadrupole response of the even oxygen isotopes from 16-O to 24-O. The method describes the full energy range from low-lying excitations to the giant resonance region and beyond in a unified and consistent framework, including a complete description of fragmentation and fine-structure. This opens unique opportunities for understanding dynamic properties of nuclei from first principles and to further constrain nuclear interactions. We demonstrate the computational efficiency and the robust model-space convergence of our approach and compare to established approximate methods, such as the Random Phase Approximation, shedding new light on their deficiencies.
nucl-thnucl-ex12 citations
05
Gluon momentum fraction of the nucleon from lattice QCD
Constantia Alexandrou🇨🇾 · Martha Constantinou🇺🇸 · Kyriakos Hadjiyiannakou🇨🇾 · Karl Jansen🇩🇪 · Haralambos Panagopoulos🇨🇾 · Christian Wiese🇩🇪
We perform a direct calculation of the gluon momentum fraction of the nucleon using maximally twisted mass fermion ensembles with $N_{f} = 2 + 1 + 1$ flavors at a pion mass of about $370 MeV$ and a lattice spacing of $a \approx 0.082 fm$ and with $N_{f} = 2$ flavors at the physical pion mass and a lattice spacing of $a \approx 0.093 fm$ . In the definition of the gluon operator we employ stout smearing to obtain a statistically significant result for the bare matrix elements. In addition, we perform a lattice perturbative calculation including 2 levels of stout smearing to carry out the mixing and the renormalization of the quark and gluon operators. We find, after conversion to the $MS$ scheme at a scale of $2 GeV$ : $⟨ x ⟩_{g}^{R} = 0.284 (23) (23)$ for pion mass of about $370 MeV$ and $⟨ x ⟩_{g}^{R} = 0.283 (23) (15)$ for the physical pion mass.
↳ hep-lathep-exhep-phhep-th+1PRD(2017)·56 citations

Affiliations

first authorsco-authorsvia INSPIRE

The anisotropic non-equilibrium hydrodynamic attractor

A practical scheme for constructing the minimum weight states of the su(n)-Lipkin model in arbitrary fermion number

The role of the elemental nature of A=3 nuclei in neutron-rich nuclei

Electromagnetic Strength Distributions from the Ab Initio No-Core Shell Model

Gluon momentum fraction of the nucleon from lattice QCD

Affiliations