Nuclear Theory·nucl-th

Tuesday·May 30, 2017

8 papers—3 primary·5 cross-listed

04
[Submitted on 27 May 2017] (cross-list from hep-ph)
Bulk viscosity of two-flavor quark matter from the Kubo formalism
Arus Harutyunyan (ITP, Frankfurt)🇩🇪 · Armen Sedrakian (FIAS)🇩🇪
We study the bulk viscosity of quark matter in the strong coupling regime within the two-flavor Nambu--Jona-Lasinio model. The dispersive effects that lead to non-zero bulk viscosity arise from quark-meson fluctuations above the Mott transition temperature, where meson decay into two quarks is kinematically allowed. We adopt the Kubo-Zubarev formalism and compute the equilibrium imaginary-time correlation function for pressure in the $O (1/ N_{c})$ power counting scheme. The bulk viscosity of matter is expressed in terms of the Lorentz components of the quark spectral function and includes multi-loop contributions which arise via re-summation of infinite geometrical series of loop diagrams. We show that the multi-loop contributions dominate the single-loop contribution close to the Mott line, whereas at high temperatures the one-loop contribution is dominant. The multi-loop bulk viscosity dominates the shear viscosity close to the Mott temperature by factors 5 to 20, but with increasing temperature the shear viscosity becomes the dominant dissipation mechanism of stresses as the one-loop contribution becomes the main source of bulk viscosity.
Comments:
v2: matches published version, 18 pages, 19 figures, uses RevTeX
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1705.09825 [pdf]
PRD(2017)·13 citations
05
[Submitted on 28 May 2017] (cross-list from astro-ph.HE)
On the stability of strange dwarf hybrid stars
Mark G. Alford · Steven P. Harris · Pratik S. Sachdeva
We investigate the stability of stars with a density discontinuity between a high-density core and a very low density mantle. Previous work on "strange dwarfs" suggested that such a discontinuity could stabilize stars that would have been classified as unstable by the conventional criteria based on extrema in the mass-radius relation. We investigate the stability of such stars by numerically solving the Sturm-Liouville equations for the lowest-energy modes of the star. We find that the conventional criteria are correct, and strange dwarfs are not stable.
Comments:
6 pages, 7 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1705.09880 [pdf]
ApJ(2017)·37 citations
06
[Submitted on 28 May 2017] (cross-list from hep-ph)
Nuclear dependence of $R = \frac{σ _{L}}{σ _{T}}$ and Callan-Gross relation in nuclei
F. Zaidi🇮🇳 · H. Haider🇮🇳 · M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳 · I. Ruiz Simo🇪🇸
The electromagnetic nuclear structure functions $F_{1 A} (x, Q^{2})$ , $F_{2 A} (x, Q^{2})$ and $F_{L A} (x, Q^{2})$ have been calculated using a microscopic model of nucleus to study the nuclear medium effects on the ratio $R_{A} (x, Q^{2}) = \frac{σ _{L A} ( x , Q ^{2} )}{σ _{T A} ( x , Q ^{2} )} = \frac{F _{L A} ( x , Q ^{2} )}{2 x F _{1 A} ( x , Q ^{2} )}$ and the Callan-Gross relation(CGR) in nuclei. The nuclear medium effects due to the Fermi motion, binding energy, nucleon correlations, mesonic contribution and shadowing have been taken into account. The theoretical results for the nuclear dependence of $R_{A} (x, Q^{2})$ and its impact on CGR have been presented and compared with the available experimental data on the various nuclear targets. The predictions have been made for $R_{A} (x, Q^{2})$ in the kinematic region of $x$ and $Q^{2}$ for some nuclei relevant for the future experiments to be performed at the JLab.
Comments:
10 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1705.09903 [pdf]
3 citations
07
[Submitted on 29 May 2017] (cross-list from hep-ph)
Particle production in proton-nucleus collisions beyond leading order
E. Iancu🇫🇷 · A.H. Mueller🇺🇸 · D.N. Triantafyllopoulos🇮🇹
We describe the origin of, and the solution to, the negativity problem which occurs in the perturbative calculation of the cross-section for single-inclusive particle production in proton-nucleus collisions at next-to-leading-order.
Comments:
5 pages, 4 figures. Proceedings for the 26th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2017), February 5-11 2017, Chicago, Illinois, USA
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1705.10128 [pdf]
NPA(2017)·0 citations
08
[Submitted on 29 May 2017] (cross-list from hep-lat)
Landau levels in QCD
F. Bruckmann🇩🇪 · G. Endrodi🇩🇪 · M. Giordano🇭🇺 · S. D. Katz🇭🇺 · T. G. Kovacs🇭🇺 · F. Pittler🇭🇺 · J. Wellnhofer🇩🇪
We present first evidence for the Landau level structure of Dirac eigenmodes in full QCD for nonzero background magnetic fields, based on first principles lattice simulations using staggered quarks. Our approach involves the identification of the lowest Landau level modes in two dimensions, where topological arguments ensure a clear separation of these modes from energetically higher states, and an expansion of the full four-dimensional modes in the basis of these two-dimensional states. We evaluate various fermionic observables including the quark condensate and the spin polarization in this basis to find how much the lowest Landau level contributes to them. The results allow for a deeper insight into the dynamics of quarks and gluons in background magnetic fields and may be directly compared to low-energy models of QCD employing the lowest Landau level approximation.
Comments:
21 pages, 19 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1705.10210 [pdf]
PRD(2017)·61 citations

Affiliations

first authorsco-authorsvia INSPIRE

Bulk viscosity of two-flavor quark matter from the Kubo formalism

On the stability of strange dwarf hybrid stars

Nuclear dependence of R=σT​σL​​ and Callan-Gross relation in nuclei

Particle production in proton-nucleus collisions beyond leading order

Landau levels in QCD

Affiliations

Nuclear dependence of $R = \frac{σ _{L}}{σ _{T}}$ and Callan-Gross relation in nuclei