arXiv subjects
Publications and source records attributed to Ru-Keng Su.
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.
We have studied the uncertainty on the determination of the dark energy equation of state due to a non-vanishing spatial curvature by considering some fundamental observables. We discussed the sensitivity of these observables to the value and redshift history of the equation of state and the spatial curvature and investigated whether these different observables are complementary and can help to reduce the cosmic confusion.
We investigate the question of the suppression of the CMB power spectrum for the lowest multipoles in closed Universes. The intrinsic reason for a lowest cutoff in closed Universes, connected with the discrete spectrum of the wavelength, is shown not to be enough to explain observations. We thus extend the holographic cosmic duality to closed universes by relating the dark energy equation of state and the power spectrum, showing a suppression behavior which describes the low l features extremely well. We also explore the possibility to disclose the nature of the dark energy from the observed small l CMB spectrum by employing the holographic idea.
Based on the observations that there exists an analogy between the Reissner-Nordström-anti-de Sitter (RN-AdS) black holes and the van der Waals-Maxwell liquid-gas system, in which a correspondence of variables is $(ϕ, q) \leftrightarrow (V,P)$, 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.
Using the evolution history of the universe, one can make constraint on the parameter space of dynamic dark energy models. We discuss two different parameterized dark energy models. Our results further restrict the combined constraints obtained from supernova and WMAP observations. From the allowed parameter space, it is found that our universe will experience an eternal acceleration. We also estimate the bound on the physically relevant regions both in the re-inflationary and inflationary phases.
Recently the 1/R gravity has been proposed in order to explain the accelerated expansion of the universe. However, it was argued that the 1/R gravity conflicts with solar system tests. While this statement is true if one views the 1/R gravity as an effective theory, we find that this difficulty might be avoided if one treats the 1/R term as a correction to the scalar curvature term in the high curvature limit $R \gg μ^2$.
An extended quark mass density- and temperature- dependent model which includes the couplings between quarks and the sigma-mesons, omega-mesons is suggested. The MIT bag boundary constrain has been given up and the interactions between quarks and mesons are extended to the whole free space. We show that the present model is successful to describe both the saturation properties and the deconfinement phase transition of nuclear matter. When the effective nucleon masses vanish and the bag radius tends to infinite, the quark deconfinement takes place. The corresponding QGP phase diagram is addressed.
The improved quark mass density- dependent model which includes the coupling between the quarks and a non-linear scalar field is presented. Numerical analysis of solutions of the model is performed over a wide range of parameters. The wave functions of ground state and the lowest one-particle excited states with even and odd parity are given. The root-mean squared radius, the magnetic moment and the ratio between the axial-vector and the vector beta-decay coupling constants of the nucleon are calculated. We found that the present model is successful to describe the properties of nucleon.
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 $ρ_r(t)/ ρ_b(t)$ by using the present day quantities as the initial conditions and found that the equation of state parameter $w_θ$ equals to -0.83, the ratio of the density of the addition creation $Ω_Λ=0.8$ and the ratio of the density of the matter including multiplication creation, radiation and normal matter $Ω_m =0.2$ 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.
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.
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.
Using the holographic principle we constrained the Friedmann equation, modified by brane-cosmology inspired terms which accommodate dark energy contributions in the context of extra dimensions.
We have studied the evolution of the massless scalar field propagating in time-dependent charged Vaidya black hole background. A generalized tortoise coordinate transformation were used to study the evolution of the massless scalar field. It is shown that, for the slowest damped quasinormal modes, the approximate formulae in stationary Reissner-Nordström black hole turn out to be a reasonable prescription, showing that results from quasinormal mode analysis are rather robust.
The liquid-gas phase transition in strange hadronic matter is studied utilizing an extended Furnstahl-Serot-Tang model with nucleons and hyperons. The system is treated as of two components. The phase transition is analyzed by investigating the stability of the system and Gibbs conditions for phase equilibrium. A two-dimensional binodal surface resulted from the two-phase equilibrium, namely the phase boundary, is obtained. For each temperature ranging from T = 8 MeV to T = 12 MeV, a limit pressure on the binodal surface section is found, while a critical point is spotted for the temperature around T = 13 MeV. The Maxwell constructions are also illustrated to give a vivid description of the course of the phase transition. Moreover, the entropy per baryon and heat capacity per baryon as functions of temperature are examined. The entropy is continuous during the phase transition but the heat capacity is discontinuous, indicating that the phase transition is of second order. By these efforts, the L-G phase transition can be concluded to exist in the strange hadronic matter.
We study the possibility to probe the spatial geometry of the Universe by supernova measurement of the cubic correction to the luminosity distance. We illustrate with an accelerating universe model with infinite-volume extra dimensions, for which the 1$σ$ level supernova results indicate that the Universe is closed.
An effective model is used to study the equation of state of warm strange hadronic matter with nucleons, Lambda-hyperons, Xi-hyperons, sigmastar and phi. In the calculation, a newest weak Y-Y interaction deduced from the recent observation of a He double hypernucleus is adopted. Employing this effective model, the results with strong Y-Y interaction and weak Y-Y interaction are compared.
We have studied scalar perturbations as well as fermion perturbations in pure de Sitter space-times. For scalar perturbations we have showed that well-defined quasinormal modes can exist provided that the mass of scalar field $m>\frac{d-1}{2l}$. The quasinormal frequencies of fermion perturbations in three and four dimensional cases have also been presented. We found that different from other dimensional cases, in three dimensional pure de Sitter spacetime there is no quasinormal mode for the s-wave. This interesting difference caused by the spacial dimensions is true for both scalar and fermion perturbations.
By means of the quark mass density-dependent model, a possible explanation for the doubly charged anomalous event with Z/A=0.114 reported by Alpha Magnetic Spectrometer Collaboration is given. It seems a strangelet. The composition, radius and mean lifetime of this strangelet are given.