Nuclear Theory·nucl-th

Monday·January 11, 2016

9 papers—3 primary·6 cross-listed

01
[Submitted on 7 Jan 2016]
Equation of state of a quark-Polyakov loop-meson mixture in the PNJL model at finite temperature
Juan M. Torres-Rincon🇫🇷 · Joerg Aichelin🇫🇷
Recent consensus on the $N_{f} = 2 + 1$ equation of state at vanishing chemical potential from different lattice-QCD groups has spoiled the previous agreement with the outcome from the mean-field Polyakov-Nambu-Jona-Lasinio model. In this letter we review the thermodynamics of the PNJL model introducing two important aspects needed to describe the pressure computed in the lattice QCD. First, we consider the thermodynamics of the model beyond the mean-field approach to include pseudoscalar and scalar mesonic-like fluctuations into the grand-canonical potential. This accounts for the hadronic pressure of the system below the critical temperature. On the other hand we also implement the back reaction of quarks into the Polyakov-loop effective potential bringing a reduction of the pressure above $T_{c}$ from the Stefan-Boltzmann limit. We get a good agreement with lattice-QCD data at low and moderate temperatures, opening the door to a straightforward extension to finite chemical potential.
Comments:
5 pages, 4 figures. This letter has been superseded by arXiv:1704.07858 [nucl-th]. In that manuscript we provide more details of the calculation, and present new results at finite chemical potential
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1601.01706 [pdf]
13 citations
02
[Submitted on 8 Jan 2016]
Low density nuclear matter with quantum molecular dynamics : The role of the symmetry energy
Rana Nandi · Stefan Schramm
We study the effect of isospin-dependent nuclear forces on the pasta phase in the inner crust of neutron stars. To this end we model the crust within the framework of quantum molecular dynamics (QMD). For maximizing the numerical performance, a newly developed code has been implemented on GPU processors. As a first application of the crust studies we investigate the dependence of the particular pasta phases on the isospin dependence of the interaction, including non-linear terms in this sector of the interactions. Our results indicate that in contrast to earlier studies the phase diagram of the pasta phase is not very sensitive to isospin effects. We show that the extraction of the isospin parameters like asymmetry energy and slope from numerical data is affected by higher-order terms in the asymmetry dependence of the energies per particle. Furthermore, a rapid transition from the pasta to a homogeneous phase is observed even for proton-to-neutron ratios typical for a supernova environment.
Comments:
19 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1601.01842 [pdf]
PRC(2016)·32 citations
03
[Submitted on 8 Jan 2016]
Conventional and Unconventional Pairing and Condensates in Dilute Nuclear Matter
John W Clark · Armen Sedrakian · Martin Stein · Xu-Guang Huang · Victor A Khodel · Vasily R Shaginyan · Mikhail V Zverev
This contribution will survey recent progress toward an understanding of diverse pairing phenomena in dilute nuclear matter at small and moderate isospin asymmetry, with results of potential relevance to supernova envelopes and proto-neutron stars. Application of {\it ab initio} many-body techniques has revealed a rich array of temperature-density phase diagrams, indexed by isospin asymmetry, which feature both conventional and unconventional superfluid phases. At low density there exist a homogeneous translationally invariant BCS phase, a homogeneous LOFF phase violating translational invariance, and an inhomogeneous translationally invariant phase-separated BCS phase. The transition from the BCS to the BEC phases is characterized in terms of the evolution, from weak to strong coupling, of the pairing gap, condensate wave function, and quasiparticle occupation numbers and spectra. Additionally, a schematic formal analysis of pairing in neutron matter at low to moderate densities is presented that establishes conditions for the emergence of both conventional and unconventional pairing solutions and encompasses the possibility of dineutron formation.
Comments:
v2: minor changes, 19 pages, 10 figures. Contribution presented by J. W. Clark at XVIII International Conference on Recent Progress in Many-Body Theories, August 16-21, 2015, Niagara Falls, NY USA
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1601.02005 [pdf]
J.Phys.Conf.Ser.(2016)·8 citations
04
[Submitted on 7 Jan 2016] (cross-list from hep-ph)
Spin Polarized versus Chiral Condensate in Quark Matter at Finite Temperature and Density
H. Matsuoka (Kochi Univ., Japan)🇯🇵 · Y. Tsue (Kochi Univ., Japan)🇯🇵 · J. da Providencia (Univ. de Coimbra, Portugal)🇵🇹 · C. Providencia (Univ. de Coimbra, Portugal)🇵🇹 · M. Yamamura (Kansai Univ., Japan)🇯🇵 · H. Bohr (Danish Technical Univ., Denmark)🇩🇰
It is shown that the spin polarized condensate appears in quark matter at high baryon density and low temperature due to the tensor-type four-point interaction in the Nambu-Jona-Lasinio-type model as a low energy effective theory of quantum chromodynamics. It is indicated within this low energy effective model that the chiral symmetry is broken again by the spin polarized condensate as increasing the quark number density, while the chiral symmetry restoration occurs in which the chiral condensate disappears at a certain density.
Comments:
25 pages, 9 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1601.01403 [pdf]
PTEP(2016)·11 citations
05
[Submitted on 7 Jan 2016] (cross-list from astro-ph.HE)
The Role of Nucleon Strangeness in Supernova Explosions
T. J. Hobbs🇺🇸 · Mary Alberg🇺🇸 · Gerald A. Miller🇺🇸
Recent hydrodynamical simulations of supernova (SN) evolution have highlighted the importance of a thorough control over microscopic physics responsible for such internal processes as neutrino heating. In particular, it has been suggested that modifications to the neutrino-nucleon elastic cross section can potentially play a crucial role in producing successful supernova explosions. One possible source of such corrections can be found in a nonzero value for the nucleon's strange helicity content $Δ s$ . In the present analysis, however, we show that theoretical and experimental progress over the past decade has suggested a comparatively small magnitude for $Δ s$ , such that its sole effect is not sufficient to provide the physics leading to supernova explosions.
Comments:
13 pages, 3 figures. Now updated to published version
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1601.01729 [pdf]
PRC(2016)·25 citations
06
[Submitted on 8 Jan 2016] (cross-list from hep-lat)
Nucleon Charges, Form-factors and Neutron EDM
Rajan Gupta🇺🇸 · Tanmoy Bhattacharya🇺🇸 · Vincenzo Cirigliano🇺🇸 · Huey-Wen Lin🇺🇸 · Boram Yoon🇺🇸
We present an update of our analysis of statistical and systematic errors in the calculation of iso-vector scalar, axial and tensor charges of the nucleon. The calculations are done using $N_{f} = 2 + 1 + 1$ flavor HISQ ensembles generated by the MILC Collaboration at three values of the lattice spacing ( $a = 0.12, 0.09,$ and $0.06$ fm) and three values of the quark mass ( $M_{π} \approx 310, 220$ and $130$ MeV); and clover fermions for calculating the correlation functions, i.e., we use a clover-on-HISQ lattice formulation. The all-mode-averaging method allows us to increase the statistics by a factor of eight for the same computational cost leading to a better understanding of and control over excited state contamination. Our current results, after extrapolation to the continuum limit and physical pion mass are $g_{A}^{u - d} = 1.21 (3)$ , $g_{T}^{u - d} = 1.005 (59)$ and $g_{S}^{u - d} = 0.95 (12)$ . Further checks of control over all systematic errors, especially in $g_{A}^{u - d}$ , are still being performed. Using results for the flavor-diagonal charges, $g_{T}^{u}$ , $g_{T}^{d}$ and $g_{T}^{s}$ , we analyze contributions of the quark electric dipole moment to the neutron EDM and the consequences for split SUSY model.
Comments:
Talk at Lattice 2015
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1601.01730 [pdf]
PoS(2016)·3 citations
07
[Submitted on 8 Jan 2016] (cross-list from nucl-ex)
Magnetic dipole excitations of $^{50}$ Cr
H. Pai · T. Beck · J. Beller · R. Beyer · M. Bhike · V. Derya · U. Gayer · J. Isaak · J. Kvasil · B. Loher · V. O. Nesterenko · N. Pietralla and 14 other authors
The low-lying $M 1$ -strength of the open-shell nucleus $^{50}$ Cr has been studied with the method of nuclear resonance fluorescence up to 9.7 MeV, using bremsstrahlung at the superconducting Darmstadt linear electron accelerator S-DALINAC and Compton backscattered photons at the High Intensity $γ$ -ray Source (HI $γ$ S) facility between 6 and 9.7 MeV of the initial photon energy. Fifteen $1^{+}$ states have been observed between 3.6 and 9.7 MeV. Following our analysis, the lowest $1^{+}$ state at 3.6 MeV can be considered as an isovector orbital mode with some spin admixture. The obtained results generally match the estimations and trends typical for the scissors-like mode. Detailed calculations within the Skyrme Quasiparticle Random-Phase-Approximation method and the Large-Scale Shell Model justify our conclusions. The calculated distributions of the orbital current for the lowest $1^{+}$ -state suggest the schematic view of Lipparini and Stringari (isovector rotation-like oscillations inside the rigid surface) rather than the scissors-like picture of Lo Iudice and Palumbo. The spin M1 resonance is shown to be mainly generated by spin-flip transitions between the orbitals of the $f p$ -shell.
Comments:
Accepted in PRC as a regular article
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1601.01905 [pdf]
PRC(2016)·28 citations
08
[Submitted on 8 Jan 2016] (cross-list from astro-ph.SR)
Solar opacity calculations using the super-transition-array method
M. Krief · A. Feigel · D. Gazit (Hebrew U.)
A new opacity model based on the Super-Transition-Array (STA) method for the calculation of monochromatic opacities of local thermodynamic equilibrium plasmas, was developed. The atomic code, named STAR (STA-Revised), is described and used to calculate spectral opacities for a solar model implementing the recent AGSS09 composition. Calculations are carried throughout the solar radiative zone. The relative contributions of different chemical elements and atomic processes to the total Rosseland mean opacity are analyzed in detail. Monochromatic opacities and charge state distributions were compared with the widely used Opacity-Project (OP) code, for several elements near the radiation-convection interface. STAR Rosseland opacities for the solar mixture show a very good agreement with OP and the OPAL opacity code, throughout the radiation zone. Finally, an explicit STA calculation of the full AGSS09 photospheric mixture, including all heavy metals was performed. It was shown that due to their extremely low abundance, and despite being very good photon absorbers, the heavy elements do not affect the Rosseland opacity.
Comments:
Accepted for publication (ApJ). Revised version, please use the numbers in this version
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
1601.01930 [pdf]
ApJ(2016)·23 citations
09
[Submitted on 8 Jan 2016] (cross-list from hep-th)
The light-front vacuum
Wayne Polyzou🇺🇸 · Marc Herrmann🇺🇸
We discuss the relation between the trivial light-front vacuum and the non-trivial Heisenberg vacuum.
Comments:
8 pages; proceedings for light cone 2015
Subjects:
High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1601.01945 [pdf]
Few Body Syst.(2016)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE