Nuclear Theory·nucl-th

Thursday·October 20, 2016

10 papers—9 primary·1 cross-listed

01
Surface tension of highly magnetized degenerate quark matter
G. Lugones🇧🇷 · A. G. Grunfeld🇴🇲
We study the surface tension of highly magnetized three flavor quark matter within the formalism of multiple reflection expansion (MRE). Quark matter is described as a mixture of free Fermi gases composed by quarks $u$ , $d$ , $s$ and electrons, in chemical equilibrium under weak interactions. Due to the presence of strong magnetic fields the particles' transverse motion is quantized into Landau levels, and the surface tension has a different value in the parallel and transverse directions with respect to the magnetic field. We calculate the transverse and longitudinal surface tension for different values of the magnetic field and for quark matter drops with different sizes, from a few fm to the bulk limit. For baryon number densities between $2 - 10$ times the nuclear saturation density, the surface tension falls in the range $2 - 20$ MeV /fm $^{2}$ . The largest contribution comes from strange quarks which have a surface tension an order of magnitude larger than the one for $u$ or $d$ quarks and more than two orders of magnitude larger than for electrons. Our results show that the total surface tension is quite insensitive to the size of the drop. We also find that the surface tensions in the transverse and parallel directions are almost unaffected by the magnetic field if $e B$ is below $\sim 5 \times 1 0^{- 3}$ GeV $^{2}$ . Nevertheless, for higher values of $e B$ , there is a significant increase in the parallel surface tension and a significant decrease in the transverse one with respect to the unmagnetized case.
nucl-thastro-ph.HEhep-phPRC(2017)·38 citations
02
Two-photon-exchange effects in the unpolarized $μ p$ scattering within the hadronic model
Hai-Qing Zhou🇨🇳
In this work, the two-photon-exchange (TPE) effects in the unpolarized $μ p$ scattering are discussed within the hadronic model where the intermediate states $N, Δ$ and $σ$ are considered. The contribution from the $N$ intermediate is close to the results given by Ref. \cite{Tomalak2014} at the small $Q$ and there is a sizeable difference when $Q > 0.25$ GeV (where $Q^{2}$ is the four momentum transfer). The contributions from the $Δ$ and the $σ$ intermediate states are much smaller than that from the $N$ intermediate at the small $Q$ . In the kinematic region with $k_{i} \subseteq [0.01, 0.3]$ GeV and $Q \leq 0.4$ GeV (where $k_{i}$ is the three momentum of initial muon at Lab frame), a naive expression for the TPE contributions is given, which can be used directly for other analysis.
nucl-thhep-phnucl-exPRC(2017)·18 citations
03
Gauge covariance of the fermion Schwinger-Dyson equation in QED
Shaoyang Jia🇺🇸 · M.R. Pennington🇺🇸
Any practical application of the Schwinger-Dyson equations to the study of $n$ -point Green's functions of a field theory requires truncations, the best known being finite order perturbation theory. Strong coupling studies require a different approach. In the case of QED, gauge covariance is a powerful constraint. By using a spectral representation for the massive fermion propagator in QED, we are able to show that the constraints imposed by the Landau-Khalatnikov-Fradkin transformations are linear operations on the spectral densities. Here we formally define these group operations and show with a couple of examples how in practice they provide a straightforward way to test the gauge covariance of any viable truncation of the Schwinger-Dyson equation for the fermion 2-point function.
nucl-thhep-phhep-thPLB(2017)·12 citations
04
Pasta phases within the QMC model
Guilherme Grams🇧🇷 · Alexandre M. Santos🇧🇷 · Prafulla K. Panda🇮🇳 · Constança Providência🇵🇹 · Débora P. Menezes🇧🇷
In this work the low density regions of nuclear and neutron star matter are studied. The search for the existence of pasta phases in this region is performed within the context of the quark-meson coupling (QMC) model, which incorporates quark degrees of freedom. Fixed proton fractions are considered, as well as nuclear matter in beta equilibrium at zero temperature. We discuss the recent attempts to better understand the surface energy in the coexistence phases regime and we present results that show the existence of the pasta phases subject to some choices of the surface energy coefficient. We also analyze the influence of the nuclear pasta on some neutron star properties. The equation of state containing the pasta phase will be part of a complete grid for future use in supernova simulations.
nucl-thPRC(2017)·16 citations
05
On the width of N-Delta and Delta-Delta states
J. A. Niskanen🇫🇮
It is seen by a coupled-channel calculation that in the two-baryon N-Delta or Delta-Delta system the width of the state is greatly diminished due to the relative kinetic energy of the two baryons, since the internal energy of the particles, available for pionic decay, is smaller. A similar state dependent effect arises from the centrifugal barrier in N-Delta or Delta-Delta systems with non-zero orbital angular momentum. The double-Delta width can become even smaller than the free width of a single Delta. This has some bearing to the interpretation of the d'(2380) resonance recently discovered at COSY.
nucl-thhep-phnucl-exPRC(2017)·22 citations
06
Production of phi-mesons on nuclear targets in the Quark-Gluon String model
G.H. Arakelyan🇦🇲 · C. Merino🇪🇸 · Yu.M. Shabelski🇷🇺
We consider the experimental data on phi-meson production on nuclear targets, and we find that they present unusually small shadow corrections for the inclusive density in the midrapidity region. We also give a quantitatively consistent description of both the initial energy dependence and the A-dependence of the produced phi-mesons, obtained in the frame of the Quark-Gluon String Model.
nucl-thhep-exhep-phPhys.Atom.Nucl.(2017)·2 citations
07
SU(3) Polyakov linear-sigma model: Conductivity and viscous properties of QCD matter in thermal medium
Abdel Nasser Tawfik🇪🇬 · Abdel Magied Diab (Egyptian Ctr. Theor. Phys., Cairo, WLCAPP, Cairo)🇪🇬 · M. T. Hussein (Cairo U.)🇪🇬
In mean field approximation, the grand canonical potential of SU(3) Polyakov linear- $σ$ model (PLSM) is analysed for chiral phase-transition, $σ_{l}$ and $σ_{s}$ and for deconfinement order-parameters, $ϕ$ and $ϕ^{*}$ of light- and strange-quarks, respectively. Various PLSM parameters are determined from the assumption of global minimization of the real part of the potential. Then, we have calculated the subtracted condensates ( $Δ_{l, s}$ ). All these results are compared with recent lattice QCD simulations. Accordingly, essential PLSM parameters are determined. The modelling of the relaxation time is utilized in estimating the conductivity properties of the QCD matter in thermal medium, namely electric [ $σ_{e l} (T)$ ] and heat [ $κ (T)$ ] conductivities. We found that the PLSM results on the electric conductivity and on the specific heat agree well with the available lattice QCD calculations. Also, we have calculated bulk and shear viscosities normalized to the thermal entropy, $ξ / s$ and $η / s$ , respectively, and compared them with recent lattice QCD. Predictions for $(ξ / s) / (σ_{e l} / T)$ and $(η / s) / (σ_{e l} / T)$ are introduced. We conclude that our results on various transport properties show some essential ingredients, that these properties likely come up with, in studying QCD matter in thermal and dense medium.
nucl-thhep-lathep-phhep-thInt.J.Mod.Phys.A(2016)·33 citations
08
Comparison of the electromagnetic responses of $^{12}$ C obtained from the Green's function Monte Carlo and spectral function approaches
Noemi Rocco🇪🇸 · Alessandro Lovato🇺🇸 · Omar Benhar🇮🇹
The electromagnetic responses of carbon obtained from the Green's function Monte Carlo and spectral function approaches using the same dynamical input are compared in the kinematical region corresponding to momentum transfer in the range 300-570 MeV. The results of our analysis, aimed at pinning down the limits of applicability of the approximations involved in the two schemes, indicate that the factorization ansatz underlying the spectral function formalism provides remarkably accurate results down to momentum transfer as low as 300 MeV. On the other hand, it appears that at 570 MeV relativistic corrections to the electromagnetic current not included in the Monte Carlo calculations may play a significant role in the transverse channel.
nucl-thhep-exPRC(2016)·18 citations
09
Holographic black hole engineering at finite baryon chemical potential
Romulo Rougemont (Sao Paulo U.)🇧🇷
This is a contribution for the Proceedings of the Conference Hot Quarks 2016, held at South Padre Island, Texas, USA, 12-17 September 2016. I briefly review some thermodynamic and baryon transport results obtained from a bottom-up Einstein-Maxwell-Dilaton holographic model engineered to describe the physics of the quark-gluon plasma at finite temperature and baryon density. The results for the equation of state, baryon susceptibilities, and the curvature of the crossover band are in quantitative agreement with the corresponding lattice QCD results with $2 + 1$ flavors and physical quark masses. Baryon diffusion is predicted to be suppressed by increasing the baryon chemical potential.
nucl-thhep-phhep-thJ.Phys.Conf.Ser.(2017)·11 citations
10
Quark Mass Correction to Chiral Separation Effect and Pseudoscalar Condensate
Er-dong Guo🇨🇳 · Shu Lin🇨🇳
We derived an analytic structure of the quark mass correction to chiral separation effect (CSE) in small mass regime. We confirmed this structure by a D3/D7 holographic model study in a finite density, finite magnetic field background. The quark mass correction to CSE can be related to correlators of pseudo-scalar condensate, quark number density and quark condensate in static limit. We found scaling relations of these correlators with spatial momentum in the small momentum regime. They characterize medium responses to electric field, inhomogeneous quark mass and chiral shift. Beyond the small momentum regime, we found existence of normalizable mode, which possibly leads to formation of spiral phase. The normalizable mode exists beyond a critical magnetic field, whose magnitude decreases with quark chemical potential.
↳ hep-thhep-phnucl-thJHEP(2017)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE