Nuclear Theory·nucl-th

Thu·Sep 21, 2017Thursday·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)·183 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