Nuclear Theory·nucl-th

Wednesday·March 28, 2018

12 papers—7 primary·5 cross-listed

08
Angular Momentum Sum Rule Violation in QCD Due to Confinement and The Proton Spin Crisis
Gouranga C Nayak🇺🇸
The proton spin crisis remains an unsolved problem in physics. In this paper we find that due to the confinement of partons inside the hadron the angular momentum sum rule in QCD is violated. Hence we find that the non-vanishing angular momentum flux contribution of the partons in QCD should be added to the spin and angular momentum of the partons to solve the proton spin crisis.
↳ hep-phhep-latnucl-th5 citations
09
On the use of running $α_{s}$ in calculations of radiative energy loss of fast partons in a quark-gluon plasma
B.G. Zakharov🇷🇺
The incorporation of running $α_{s}$ for the gluon emission vertex in calculations of radiative parton energy loss in a quark-gluon plasma is discussed. It is argued that the virtuality scale for running $α_{s}$ for induced gluon emission is determined by the square of the transverse momentum of the emitted gluon rather than by the square of the invariant mass of the final two-parton state often used in the literature.
↳ hep-phnucl-thJETP Lett.(2018)·1 citation
10
Entanglement in Reggeized Scattering using AdS/CFT
Yizhuang Liu🇨🇳 · Ismail Zahed🇺🇸
The eikonalized parton-parton scattering amplitude at large $s$ and large impact parameter, is dominated by the exchange of a hyperbolic surface in walled AdS. Its analytical continuation yields a worldsheet instanton that is at the origin of the Reggeization of the amplitude and a thermal-like quantum entropy $S_{T}$ . We explicitly construct the entangled density matrix following from the exchanged surface, and show that its von-Neumann entanglement entropy $S_{E}$ coincides with the thermal-like entropy, i.e. $S_{T} = S_{E}$ . The ratio of the entanglement entropy to the transverse growth of the exchanged surface is similar to the Bekenstein entropy ratio for a black-hole, with a natural definition of saturation and the on-set of chaos in high energy collisions. The largest eigenvalues of the entangled density matrix obey a cascade equation in rapidity, reminiscent of non-linear QCD evolution of wee-dipoles at low-x and weak coupling. We suggest that the largest eigenvalues describe the probability distributions of wee-quanta at low-x and strong coupling that maybe measurable at present and future pp and ep colliders.
↳ hep-phhep-thnucl-thPRD(2019)·35 citations
11
Electrical Resistivity and Hall Effect in Binary Neutron-Star Mergers
Arus Harutyunyan · Antonios Nathanail · Luciano Rezzolla · Armen Sedrakian
We examine the range of rest-mass densities, temperatures and magnetic fields involved in simulations of binary neutron-star mergers and identify the conditions under which the ideal-magnetohydrodynamics approximation breaks down and hence the magnetic-field decay should be accounted for. We use recent calculations of the conductivities of warm correlated plasma in envelopes of compact stars and find that the magnetic-field decay timescales are much larger than the characteristic timescales of the merger process for lengthscales down to a meter. Because these are smaller than the currently available resolution in numerical simulations, the ideal-magnetohydrodynamics approximation is effectively valid for all realistic simulations. At the same time, we find that the Hall effect can be important at low densities and low temperatures, where it can induce a non-dissipative rearrangement of the magnetic field. Finally, we mark the region in temperature and density where the hydrodynamic description breaks down.
↳ astro-ph.HEnucl-thEPJA(2018)·37 citations
12
Are small radii of compact stars ruled out by GW170817/AT2017gfo?
G. F. Burgio🇮🇹 · A. Drago🇮🇹 · G. Pagliara🇮🇹 · H.-J. Schulze🇮🇹 · J.-B. Wei🇮🇹
The detection of GW170817 and its electromagnetic counterparts allows to constrain the equation of state of dense matter in new and complementary ways. Very stiff equations of state are ruled out by the upper limit on the average tidal deformability, $Λ ~ ≲ 800$ , imposed by the detected gravitational wave signal. A lower limit, $Λ ~ ≳ 400$ , can also be extracted by considering the large amount of ejected matter which powers the kilonova AT2017gfo. By using several microscopic nucleonic equations of state, we first confirm the existence of a monotonic relation between $R_{1.5}$ (the radius of the $1.5 M_{⊙}$ configuration) and $Λ ~$ . This translates the limits on $Λ ~$ into limits on the radius: $11.8 km ≲ R_{1.5} ≲ 13.1$ km. We then show that the monotonic relation is violated, if a second branch of compact stars composed of quark matter exists, as in the two-families or the twin-stars scenarios. In particular, it is possible to fulfill the limits on $Λ ~$ while having $R_{1.5}$ significantly smaller than $12$ km. In both those scenarios the event GW170817/AT2017gfo originates from the merger of a hadronic star and a star containing quark matter.
↳ astro-ph.HEhep-phnucl-thApJ(2018)·128 citations

Affiliations

first authorsco-authorsvia INSPIRE

Angular Momentum Sum Rule Violation in QCD Due to Confinement and The Proton Spin Crisis

On the use of running αs​ in calculations of radiative energy loss of fast partons in a quark-gluon plasma

Entanglement in Reggeized Scattering using AdS/CFT

Electrical Resistivity and Hall Effect in Binary Neutron-Star Mergers

Are small radii of compact stars ruled out by GW170817/AT2017gfo?

Affiliations

On the use of running $α_{s}$ in calculations of radiative energy loss of fast partons in a quark-gluon plasma