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We reexamined the argument that the quasinormal modes could be a probe of the phase transition of a topological black hole to a hairy configuration by investigating general scalar perturbations. We found further evidence in the quasinormal modes for this phase transition. For the general black hole configurations, we observed that although the quasinormal modes can present us different phases of different configurations, there is no dramatic change in the slope of quasinormal frequencies at the critical point of the phase transition. More detailed studies of quasinormal modes are needed to reveal the subtle behavior of the phase transition., Comment: Revised version, accepted for publication in JHEP

We have studied the wave dynamics and the Hawking radiation for the scalar field as well as the brane-localized gravitational field in the background of the braneworld black hole with tidal charge containing information of the extra dimension. Comparing with the four-dimensional black holes, we have observed the signature of the tidal charge which presents the signals of the extra dimension both in the wave dynamics and the Hawking radiation., Comment: 14 pages, 8 figures, revised version, references added. Accepted for publication in PRD

Based on the observations that there exists an analogy between the Reissner-Nordstr\"om-anti-de Sitter (RN-AdS) black holes and the van der Waals-Maxwell liquid-gas system, in which a correspondence of variables is $(\phi, q) \leftrightarrow (V,P)$, we study the Ruppeiner geometry, defined as Hessian matrix of black hole entropy with respect to the internal energy (not the mass) of black hole and electric potential (angular velocity), for the RN, Kerr and RN-AdS black holes. It is found that the geometry is curved and the scalar curvature goes to negative infinity at the Davies' phase transition point for the RN and Kerr black holes. Our result for the RN-AdS black holes is also in good agreement with the one about phase transition and its critical behavior in the literature., Comment: Revtex, 18 pages including 4 figures

A model is suggested to unify the Einstein GR and Dirac Cosmology. There is one adjusted parameter $b_2$ in our model. After adjusting the parameter $b_2$ in the model by using the supernova data, we have calculated the gravitational constant $\bar G$ and the physical quantities of $a(t)$, $q(t)$ and $\rho_r(t)/ \rho_b(t)$ by using the present day quantities as the initial conditions and found that the equation of state parameter $w_{\theta}$ equals to -0.83, the ratio of the density of the addition creation $\Omega_{\Lambda}=0.8$ and the ratio of the density of the matter including multiplication creation, radiation and normal matter $\Omega_m =0.2$ at present. The results are self-consistent and in good agreement with present knowledge in cosmology. These results suggest that the addition creation and multiplication creation in Dirac cosmology play the role of the dark energy and dark matter., Comment: 13 pages, 8 figures

Employing the Quark Mass Denisity- and temperature- dependent model and the Hartle's method, We have studied the slowly rotating strange star with uniform angular velocity. The mass-radius relation, the moment of inertia and the frame dragging for different frequencies are given. We found that we cannot use the strange star to solve the challenges of Stella and Vietri for the horizontal branch oscillations and the moment of inertia $I_{45}/(M/M_ s)>2.3$. Furthermore, we extended the Hartle's method to study the differential rotating strange star and found that the differential rotation is an effective way to get massive strange star., Comment: Latex file, 13 figures, accepted for publication in Inter. J. Mod. Phys. A

Using the recently obtained holographic cosmic duality, we reached a reasonable quantitative agreement between predictions of the Cosmic Microwave Background Radiation at small l and the WMAP observations, showing the power of the holographic idea. We also got constraints on the dark energy and its behaviour as a function of the redshift upon relating it to the small l CMB spectrum. For a redshift independent dark energy, our constraint is consistent with the supernova results, which again shows the correctness of the cosmic duality prescription. We have also extended our study to the redshift dependence of the dark energy., Comment: accepted for publication in Phys. Lett. B