Shao-Feng Wu

Analytical study on holographic superconductors in external magnetic field

We investigate the holographic superconductors immersed in an external magnetic field by using the analytical approach. We obtain the spatially dependent condensate solutions in the presence of the magnetism and find analytically that the upper critical magnetic field satisfies the relation given in the Ginzburg-Landau theory. The external magnetic field expels the condensate and makes the condensation harder to form. Extending to the D-dimensional Gauss-Bonnet AdS black holes, we examine the influence given by the Gauss-Bonnet coupling on the condensation. Different from the positive coupling, we find that the negative Gauss-Bonnet coupling enhances the condensation when the external magnetism is not strong enough.

The generalized second law of thermodynamics in generalized gravity theories

We investigate the generalized second law of thermodynamics (GSL) in generalized theories of gravity. We examine the total entropy evolution with time including the horizon entropy, the non-equilibrium entropy production, and the entropy of all matter, field and energy components. We derive a universal condition to protect the generalized second law and study its validity in different gravity theories. In Einstein gravity (even in the phantom-dominated universe with a Schwarzschild black hole), Lovelock gravity and braneworld gravity, we show that the condition to keep the GSL can always be satisfied. In f(R) gravity and scalar?tensor gravity, the condition to protect the GSL can also hold because the temperature should be positive, gravity is always attractive and the effective Newton constant should be an approximate constant satisfying the experimental bounds.

Thermodynamics on the apparent horizon in generalized gravity theories

Abstract We present a general procedure to construct the first law of thermodynamics on the apparent horizon and illustrate its validity by examining it in some extended gravity theories. Applying this procedure, we can describe the thermodynamics on the apparent horizon in Randall–Sundrum braneworld imbedded in a nontrivial bulk. We discuss the mass-like function which was used to link Friedmann equation to the first law of thermodynamics and obtain its special case which gives the generalized Misner–Sharp mass in Lovelock gravity.

Shear viscosity and instability from third order Lovelock gravity

We calculate the ratio of shear viscosity to entropy density for charged black branes in third order Lovelock theory. For chargeless black branes, the result turns out to be consistent with the prediction made by Brustein and Medved [Phys. Rev. D 79, 021901 (2009)]. We find that the third order Lovelock gravity term does not contribute to causality violation unlike the Gauss-Bonnet term. The stability of the black brane again requires the value of the Lovelock coupling constant to be bounded by 1/4 in the infinite dimensionality limit.

Linear growth of entanglement entropy in holographic thermalization captured by horizon interiors and mutual information

A bstractWe study the holographic entanglement entropy in a homogeneous falling shell background, which is dual to the strongly coupled field theory following a global quench. For d=2 conformal field theories, it is known that the entropy has a linear growth regime if the scale of the entangling region is large. In addition, the growth rate approaches a constant when the scale increases. We demonstrate analytically that this behavior is directly related to the part of minimal area surface probing the interior of apparent horizons in the bulk, as well as the mutual information between two disjoint rectangular subsystems in the boundary. Furthermore, we show numerically that all the results are universal for the d=3 conformal field theory, the non-relativistic scale-invariant theory and the dual theory of Gauss-Bonnet gravity.

Gauss-Bonnet correction to Holographic thermalization: two-point functions, circular Wilson loops and entanglement entropy

We study the thermalization of a class of 4-dimensional strongly coupled theories dual to a 5-dimensional AdS-Vaidya spacetime with Gauss-Bonnet curvature corrections. We probe the thermalization using the two-point functions, the expectation values of circular Wilson loops and entanglement entropy. When boundary separation is small, we observe that the thermalization times of these observables have the weak dependence on the Gauss-Bonnet coupling constant

General stationary charged black holes as charged particle accelerators

\alpha

Dynamical horizon entropy and equilibrium thermodynamics of generalized gravity theories

. In addition, the growth rate of entanglement entropy density is nearly volume-independent. We also show that a new kind of swallow-tail behavior may exhibit in the thermalization of the two-point function when

Crossing the phantom divide in brane cosmology with curvature corrections and brane-bulk energy transfer

\alpha

Cosmological equations and Thermodynamics on Apparent Horizon in Thick Braneworld

is negative and