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Defu Hou

Publications and source records attributed to Defu Hou.

At least 91 records · Page 5Linked to original sources
arXiv2011

The Subleading Term of the Strong Coupling Expansion of the Heavy-Quark Potential in a $\mathcal N=4$ Super Yang-Mills Plasma

Applying the AdS/CFT correspondence, the expansion of the heavy-quark potential of the ${\cal N}$ supersymmetric Yang-Mills theory at large $N_c$ is carried out to the sub-leading term in the large 't Hooft coupling at nonzero temperatures. The strong coupling corresponds to the semi-classical expansion of the string-sigma model, the gravity dual of the Wilson loop operator, with the sub-leading term expressed in terms of functional determinants of fluctuations. The contributions of these determinants are evaluated numerically.

hep-ph↗
arXiv2011

Some Field Theoretic Issues Regarding the Chiral Magnetic Effect

In this paper, we shall address some field theoretic issues regarding the chiral magnetic effect. The general structure of the magnetic current consistent with the electromagnetic gauge invariance is obtained and the impact of the infrared divergence is examined. Some subtleties on the relation between the chiral magnetic effect and the axial anomaly are clarified through a careful examination of the infrared limit of the relevant thermal diagrams.

hep-ph↗
arXiv2010

The momentum analyticity of two-point correlators from perturbation theory and AdS/CFT

The momentum plane analyticity of two point function of a relativistic thermal field theory at zero chemical potential is explored. A general principle regarding the location of the singularities is extracted. In the case of the N=4 supersymmetric Yang-Mills theory at large $N_c$, a qualitative change in the nature of the singularity (branch points versus simple poles) from the weak coupling regime to the strong coupling regime is observed with the aid of the AdS/CFT correspondence.

hep-ph↗
arXiv2010

The Subleading Term of the Strong Coupling Expansion of the Heavy-Quark Potential in a $\mathcal N=4$ Super Yang-Mills Vacuum

Applying the AdS/CFT correspondence, the expansion of the heavy-quark potential of the ${\cal N}=4$ supersymmetric Yang-Mills theory at large $N_c$ is carried out to the sub-leading term in the large 't Hooft coupling at zero temperature. The strong coupling corresponds to the semi-classical expansion of the string-sigma model, the gravity dual of the Wilson loop operator, with the sub-leading term expressed in terms of functional determinants of fluctuations. The singularities of these determinants are examined and their contributions are evaluated numerically.

hep-ph↗
arXiv2009

The Single Flavor Color Superconductivity in a Magnetic Field

We investigate the single flavor color superconductivity in a magnetic field. Because of the absence of the electromagnetic Meissner effect, forming a nonspherical CSC phase, polar, A or planar, does not cost energy of excluding magnetic flux. We found that these nonspherical phases do occupy a significant portion of the phase diagram with respect to magnetic field and temperature and may be implemented under the typical quark density and the magnetic field inside a compact star.

hep-ph↗
arXiv2009

On Melting Temperature of Heavy Quarkonium with the AdS/CFT Implied Potential

The quarkonium states in a quark-gluon plasma is examined with the potential implied by AdS/CFT duality. Both the vanila AdS-Schwarzschild metric and the one with an infrared cutoff are considered. The calculated dissociation temperatures for $J/ψ$ and $Υ$ are found to agree with the lattice results within a factor of two.

hep-ph↗
arXiv2008

Higher Angular Momentum Mixing in a Non-spherical Color Superconductor with Time Reversal Invariance Violation

The angular momentum mixing in a non-spherical CSC with nonzero azimuthal quantum number and therefore violating time reversal invariance has been examined. The mixing is bound to occur because of the equal strength of the pairing potential mediated by one-gluon exchange for all partial waves to the leading order QCD running coupling constant and the nonlinearity of the gap equation. The free energy with mixing is lower than that with p-wave pairing only, but still higher than that of the spherical CSL state.

hep-ph↗
arXiv2008

Angular Momentum Mixing in Single Flavor Color Superconductivity with Transverse Pairing

Because of the equal strength of the pairing potential mediated by one-gluon exchange for all partial waves to the leading order QCD running coupling constant and the nonlinearity of the gap equation, the non-spherical pairing in single flavor color superconductivity(CSC) can not be restricted in a single non-s-wave channel and the mixing among different angular momenta will occur. In this paper, we examine the angular momentum mixing in single flavor CSC with transverse pairing, in which the pairing quarks have opposite helicity. We find that the free energy of all non-spherical pairing states are lowered by angular momentum mixing compared with that contain p-wave only. But the amount of the free energy drop is numerically small. Consequently the most stable pairing state that respect the time reversal invariance remains the spherical CSL.

hep-ph↗
arXiv2008

Liquid behavior of hot QGP in the finite temperature field theory

In this paper, we compare the dispersion relations of hard thermal loop and complete one loop. It is shown that in the dynamical screening regime, the completely one-loop calculation presents a prominent threshold frequency, below which no pure imaginary mode survives. This phenomenon is responsible for the oscillatory static in-medium potential and ultimately results in a damping oscillation of the radial distribution function. We consider this typical shape is the footprint of liquid QGP.

hep-ph↗
arXiv2007

Angular Momentum Mixing in a Non-spherical Color Superconductor

We study the angular momentum mixing effects in the color superconductor with non-spherical pairing. We first clarify the concept of the angular momentum mixing with a toy model for non-relativistic and spinless fermions. Then we derive the gap equation for the polar phase of dense QCD by minimizing the CJT free energy. The solution of the gap equation consists of all angular momentum partial waves of odd parity. The corresponding free energy is found to be lower than that reported in the literature with p-wave only.

hep-ph↗
arXiv2007

Heavy Quarkonium States with the Holographic Potential

The quarkonium states in a quark-gluon plasma is examined with the heavy quark potential implied by the holographic principle. Both the vanila AdS-Schwarzschild metric and the one with an infrared cutoff are considered. The dissociation temperature is calculated by solving the Schrö dinger equation of the potential model. In the case of the AdS-Schwarzschild metric with a IR cutoff, the dissociation temperatures for $J/ψ$ and $Υ$ with the U-ansatz of the potential are found to agree with the lattice results within a factor of two.

hep-ph↗
arXiv2007

A Possible Mechanism for the Low Shear Viscosity in the QGP Created by RHIC

We study the Anderson Localization effect on the shear viscosity in a system with random medium by Kubo formula. We show that this effect can reduce the shear viscosity nonperturbatively. Then we discuss its possible implementation in heavy-ion collisions, where the created heavy bound states or other collective modes may play the role of the random scatterer underlying Anderson Localization effect.

hep-ph↗
arXiv2007

Oscillatory behavior of the in-medium interparticle potential in hot gauge system with scalar bound states

We investigate the in-medium interparticle potential of hot gauge system with bound states by employing the QED and scalar QED coupling. At finite temperature an oscillatory behavior of the potential has been found as well as its variation in terms of different free parameters. We expect the competition among the parameters will lead to an appropriate interparticle potential which could be extended to discuss the fluid properties of QGP with scalar bound states.

hep-ph↗
arXiv2006

The imaginary part of the gap function in color superconductivity

We clarify general properties of the energy gap regarding its functional dependence on the energy-momentum dictated by the invariance under a space inversion or a time reversal. Then we derive perturbatively the equation of the imaginary part of the gap function for dense QCD in weak coupling and generalize our results from 2SC case to CFL case. We confirm that the imaginary part is down by $g$ relative to the real part in weak coupling. The numerical results show that, up to the leading order, the imaginary part is no larger than one MeV at extremely large densities and can be as large as several MeV the densities are of physical interest.

nucl-th↗
arXiv2006

Inhomogeneity driven by Higgs instability in gapless superconductor

The fluctuations of the Higgs and pseudo Nambu-Goldstone fields in the 2SC phase with mismatched pairing are described in the nonlinear realization framework of the gauged Nambu--Jona-Lasinio model. In the gapless 2SC phase, not only Nambu-Goldstone currents can be spontaneously generated, but the Higgs field also exhibits instablity. The Nambu-Goldstone currents generation indicates the formation of the single plane wave LOFF state and breaks rotation symmetry, while the Higgs instability favors spatial inhomogeneity and breaks translation invariance. In this paper, we focus on the Higgs instability which has not drawn much attention yet. The Higgs instability cannot be removed without a long range force, thus it persists in the gapless superfluidity and induces phase separation. In the case of g2SC state, the Higgs instability can only be partially removed by the electric Coulomb energy. However, it is not excluded that the Higgs instability might be completely removed in the charge neutral gCFL phase by the color Coulomb energy.

hep-ph↗
arXiv2006

Shear Viscosity and Viscous Entropy Production in Hot QGP at Finite Density

In the framework of irreversible thermodynamics, we studied the transport properties of QGP. Shear viscosity and non-equilibrium entropy density related to viscous process at finite density has been investigated in weakly coupled limit by using kinetic theory. The results show that the chemical potential increases viscosityyet decreases the non-equilibrium entropy density and thus contributes positively to their ratio compared to the pure temperature case. As to the temperature dependence of the ratio, the ratio first decreases rapidly and then increases in the physical region, presenting a minimum value of 0.4 at the temperature around 182MeV.

hep-ph↗
arXiv2006

Higgs instability in gapless superfluidity/superconductivity

In this letter we explore the Higgs instability in the gapless superfluid/superconducting phase. This is in addition to the (chromo)magnetic instability that is related to the fluctuations of the Nambu-Goldstone bosonic fields. While the latter may induce a single-plane-wave LOFF state, the Higgs instability favors spatial inhomogeneity and cannot be removed without a long range force. In the case of the g2SC state the Higgs instability can only be partially removed by the electric Coulomb energy. But this does not exclude the possibility that it can be completely removed in other exotic states such as the gCFL state.

hep-ph↗