arXiv subjects

Zheng Xiaoping

Publications and source records attributed to Zheng Xiaoping.

17 recordsLinked to original sources

arXiv2008

"Latent heat" of first-order varying pressure transitions

We consider the energy release associated with first-order transition by Gibbs construction and present such energy release as an accumulation of a series of tiny binding energy differences between over-compressed states and stable ones. Universal formulae for the energy release from one homogeneous phase to the other is given. We find the energy release per converted particle varies with number density. As an example, the deconfinement phase transition at supranuclear densities is discussed in detail. The mean energy release per converted baryon is of order 0.1MeV in RMF theory and MIT bag descriptions for hadronic matter and strange quark matter for a wider parameter region.

hep-ph↗

arXiv2007

Thermal evolution of rotating hybrid stars

As a neutron star spins down, the nuclear matter continuously is converted into quark matter due to the core density increase and then latent heat is released. We have investigated the thermal evolution of neutron stars undergoing such deconfinement phase transition. We have taken into account the conversion in the frame of the general theory of relativity. The released energy has been estimated as a function of change rate of deconfinement baryon number. Numerical solutions to cooling equation are obtained to be very different from the without heating effect. The results show that neutron stars may be heated to higher temperature which is well-matched with pulsar's data despite onset of fast cooling in neutron stars with quark matter core. It is also found that heating effect has magnetic field strength dependence. This feature could be particularly interesting for high temperature of low-field millisecond pulsar at late stage. The high temperature could fit the observed temperature for PSR J0437-4715.

astro-ph↗

arXiv2006

Cooling of strange stars in the color-flavor locked phase with a rotating crust Cooling of strange stars in the color-flavor locked phase with a rotating crust

The presence of the color-flavor locked (CFL) phase strongly suppresses the neutrino emission processes and the quark specific heat. As a result the cooling of the strange stars in the CFL phase is dominated by deconfinement heating and surface emission. The temperature of these stars with strong magnetic field ($B{\geq}10^{10}G$) rise significantly during the first several ten or hundred years, which may be an effective signature of strange stars as implicated by pulsar 0540-69. Furthermore a limit line is predicted, which means compact stars have an upper limit temperature at any moment. We still may search for the candidates for strange stars in the CFL phase along the limit line. The presence of the color-flavor locked (CFL) phase strongly suppresses the neutrino emission processes and the quark specific heat. As a result the cooling of the strange stars in the CFL phase is dominated by deconfinement heating and surface emission. The temperature of these stars with strong magnetic field ($B{\geq}10^{10}G$) rise significantly during the first several ten or hundred years, which may be an effective signature of strange stars as implicated by pulsar 0540-69. Furthermore a limit line is predicted, which means compact stars have an upper limit temperature at any moment. We still may search for the candidates for strange stars in the CFL phase along the limit line.

astro-ph↗

arXiv2005

Effect of strong magnetic field on surface electric field of strange stars

We made a detailed study of the properties of the electron layer near the quark surface of strange stars with strong ($\sim 10^{14}-10^{17}$G) magnetic fields. The electrostatic potential and the electric field at the quark surface were calculated as functions of the magnetic field intensity of bare strange stars. Using an ultrastrong ($B\geq 2.5\times10^{16}$G) magnetic field, we found that the distribution of electrons becomes an exponential function of radial distance, which is quite different in a magnetic field-free case. We also calculated the variation in gap width between the strange core and the normal nuclear crust for strange stars, which is due to magnetic field effect.

astro-ph↗

arXiv2005

Running coupling constant from lattice data and bulk viscosity of strange quark matter

We study the bulk viscosity of strange quark matter (SQM) in a quasiparticle model at finite chemical potential by extrapolating the previous quasiparticle model of finite temperature lattice QCD. The more proper bulk viscosity coefficient can be given in this model where chemical potential $μ$ and coupling constant $\emph{g}$ are interdependent. We also apply our result to determine the critical rotation of strange stars by r-mode instability window. Our model is compatible to the millisecond pulsar data for a wide range of mass and radius of the stars.

hep-ph↗

arXiv2005

Non-leptonic Weak Interaction in Magnetized Quark matter

We investigated the non-leptonic weak interaction in magnetic field. We discussed an improvement of previous method to analytical work out the rate for weak field case.Our result easily goes over to field-free limit.Then we calculated the reaction rate in strong magnetic field where the charged particles are confined to the lowest Landau level. A strong magnetic field strongly suppressed the rate,which will be foreseen to affect viscous dynamics in SQM .We also derived a few approximation formulae under given conditions that can be conveniently applied.

astro-ph↗

arXiv2004

The Neutrino Emissivity of Strange Stars with Ultra Strong Magnetic Field

The effect of a strong magnetic field on the dominant neutrino emissivity in strange stars is investigated. In ultra strong magnetic field, there exists an enhanced neutrino emission because the charged particles are confined to the lowest Landau level. The results show that the neutrino emissivity is proportional to $T^5$ instead of conventional $T^6$, which implies more rapid cooling behavior in magnetars than usual stars

astro-ph↗

arXiv2003

An Astronomical Evidence of Existence of Quark Matter and the Prediction for Submillisecond Pulsars

We derive the bulk viscous time scale of neutron stars with quark matter core, i.e. hybrid stars. The r-mode instability windows of the stars show the theoretical result accords with the rapid rotation pulsar data. The fit gives a strong indication for the existence of quark matter in the interior of neutron stars. Hybrid stars instead of neutron or strange stars may result in submillisecond pulsars if they exist.

astro-ph↗

arXiv2003

Bulk viscosity of strange quark matter in density-dependent quark mass model and dissipation of r-modes in strange stars

We study the bulk viscosity of strange quark matter(SQM) in density dependent quark mass model(DDQM) under the background of self-consistent thermodynamics. The correct formulae, with which the viscosity can be evaluated, are derived. We also find that the viscosity in DDQM can be higher by 2 to 3 orders of magnitude than MIT bag model. We calculate the damping time scales due to viscosity coupled to r-modes. The numerical results show the time scale can't be shorter than $10^{-1}$s.

astro-ph↗

arXiv2003

The Critical Rotation of Strange Stars and Rapidly Rotating Pulsars

We utilize the bulk viscosity of interacting strange quark matter to reevaluate the damping time scale. The presence of medium effect of bulk viscosity leads to a stronger damping of r-modes, which can be over an order of magnitude for realistic parameters. We find that the r-mode instability window is narrowed due to the medium effect, and hence when a pulsar reaches the instability window it will only slow down by gravitational wave emission to a period of 1.78msec instead of 2.5msec given by early estimate. As a theoretical upper rotation limit of pulsars, the period of 1.78msec is very close to the two most rapidly spinning pulsars known, with periods of about 1.6msec.

astro-ph↗

arXiv2002

Bulk viscosity of interacting strange quark matter

The quarks are regarded as quasiparticles, which acquire an effective mass generated by the interaction with the other quarks of the dense system. The bulk viscosity is re-expressed in the case of interacting strange quark matter. We find that the viscosity is a few ~ tens times larger than that of non-interacting quark gas due to the small correction of medium effect to the equation of state. The limiting spins of strange stars will rise so significantly that the pulsars with shorter period may exist.

hep-ph↗

arXiv2002

Kinetic-theory approach to Gluon Self-energy beyond Hard Thermal Loops

We compare the effective dynamics of soft fields, based on temperature field theory, with the mean field dynamics from non-Abelian kinetic theory. We derive the polarization tensor with the leading logarithmic factor $\log({gT\overμ})$ from the effective Boltzmann-Langevin equation given by Litim and Manuel. The tensor is identical with effective one-loop contributions within the hard thermal loop effective theory.

hep-ph↗

arXiv2000

The Nonlinear Permittivity Including Non-Abelian Self-interaction of Plasmons in Quark-Gluon Plasma

By decomposing the distribution functions and color field to regular and fluctuation parts, the solution of the semi-classical kinetic equations of quark-gluon plasma is analyzed. Through expanding the kinetic equations of the fluctuation parts to third order, the nonlinear permittivity including the self-interaction of gauge field is obtained and a rough numerical estimate is given out for the important $\vk =0$ modes of the pure gluon plasma.

hep-ph↗

arXiv1999

An effective relaxation-time approach to collisionless quark-gluon plasma

We present an effective relaxation-time theory to study the collisionless quark-gluon plasma. Applying this method we calculate the damping rate to be of order $g^2T$ and find plasmon scattering is the damping mechanism. The damping for the transverse mode is stronger than the longitudinal one.

hep-ph↗

arXiv1999

Non-Abelian Collective Excitations in Unlinearized Quark-Gluon Plasma Media

We study the effect of unlinearized medium on the collective excitations in quark-gluon plasma. We present two kinds of non-Abelian oscillation solutions which respectively correspond to weakly and strongly nonlinear coupling of field components in color space. We also show that the weakly nonlinear solution is similar to Abelian-like one but has the frequency shift, which is of order $g^2T$, from eigenfrequency.

hep-ph↗

arXiv1997

A Colored Particle Acceleration by Fluctuations in QGP

We discuss the energy variation of a parton passing through a quark-gluon plasma(QGP) taking into account nonlinear polarization effect. We find the parton can be accelerated by fluctuations in QGP, which gives us a new physical insight about the response of QGP to such external the current.

hep-ph↗

arXiv1997

The Asymptotic Method Developed from Weak Turbulent Theory and the Nonlinear Permeability and Damping Rate in QGP

With asymptotic method developed from weak turbulent theory, the kinetic equations for QGP are expanded in fluctuation field potential $A^T_μ$. Considering the second-order and third-order currents, we derive the nonlinear permeability tensor function from Yang-Mills field equation, and find that the third-order current is more important in turbulent theory. The nonlinear permeability formulae for longitudinal color oscillations show that the non-Abelian effects are more important than the Abelian-like effects. To compare with other works, we give the numerical result of the damping rate for the modes with zero wave vector.

hep-th↗