arXiv subjects

Bin Wang

Publications and source records attributed to Bin Wang.

At least 1,063 records · Page 59Linked to original sources

arXiv2006

Uncertainty on determining the dark energy equation of state due to the spatial curvature

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.

astro-ph↗

arXiv2006

Holographic explanation of wide-angle power correlation suppression in the Cosmic Microwave Background Radiation

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.

hep-th↗

arXiv2006

Constraints on the interacting holographic dark energy model

We examined the interacting holographic dark energy model in a universe with spatial curvature. Using the near-flatness condition and requiring that the universe is experiencing an accelerated expansion, we have constrained the parameter space of the model and found that the model can accommodate a transition of the dark energy from $ω_D>-1$ to $ω_D<-1$.

hep-th↗

arXiv2006

Super-acceleration on the Brane by Energy Flow from the Bulk

We consider a brane cosmological model with energy exchange between brane and bulk. Parameterizing the energy exchange term by the scale factor and Hubble parameter, we are able to exactly solve the modified Friedmann equation on the brane. In this model, the equation of state for the effective dark energy has a transition behavior changing from $w_{de}^{eff}>-1$ to $w_{de}^{eff}<-1$, while the equation of state for the dark energy on the brane has $w>-1$. Fitting data from type Ia supernova, Sloan Digital Sky Survey and Wilkinson Microwave Anisotropy Probe, our universe is predicted now in the state of super-acceleration with $w_{de0}^{eff}=-1.21$.

hep-th↗

arXiv2006

Soliton with a Pion Field in the Global Color Symmetry Model

We calculate the property of the global color symmetry model soliton with the pion field being included explicitly. The calculated results indicate that the pion field provides a strong attraction so that the eigen-energy of a quark and the mass of a soliton reduce drastically, in contrast to those with only the sigma field.

hep-ph↗

arXiv2005

Thermodynamic Geometry and Critical Behavior of Black Holes

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.

gr-qc↗

arXiv2005

Dark Energy: relating the evolution of the universe from the past to the future

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.

astro-ph↗

arXiv2005

Perturbations around black holes

Perturbations around black holes have been an intriguing topic in the last few decades. They are particularly important today, since they relate to the gravitational wave observations which may provide the unique fingerprint of black holes' existence. Besides the astrophysical interest, theoretically perturbations around black holes can be used as testing grounds to examine the proposed AdS/CFT and dS/CFT correspondence.

gr-qc↗

arXiv2005

An alternative explanation of the conflict between 1/R gravity and solar system tests

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 $R \gg μ^2$.

gr-qc↗

arXiv2005

Thermodynamics of an accelerated expanding universe

We investigate the laws of thermodynamics in an accelerating universe driven by dark energy with a time-dependent equation of state. In the case we consider that the physically relevant part of the Universe is that envelopped by the dynamical apparent horizon, we have shown that both the first law and second law of thermodynamics are satisfied. On the other hand, if the boundary of the Universe is considered to be the cosmological event horizon the thermodynamical description based on the definitions of boundary entropy and temperature breaks down. No parameter redefinition can rescue the thermodynamics laws from such a fate, rendering the cosmological event horizon unphysical from the point of view of the laws of thermodynamics.

gr-qc↗

arXiv2005

The Holographic dark energy reexamined

We have reexamined the holographic dark energy model by considering the spatial curvature. We have refined the model parameter and observed that the holographic dark energy model does not behave as phantom model. Comparing the holographic dark energy model to the supernova observation alone, we found that the closed universe is favored. Combining with the Wilkinson Microwave Anisotropy Probe (WMAP) data, we obtained the reasonable value of the spatial curvature of our universe.

hep-th↗

arXiv2005

Dirac Cosmology and the Acceleration of the Contemporary Universe

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.

gr-qc↗

arXiv2005

Transition of the dark energy equation of state in an interacting holographic dark energy model

A model of holographic dark energy with an interaction with matter fields has been investigated. Choosing the future event horizon as an IR cutoff, we have shown that the ratio of energy densities can vary with time. With the interaction between the two different constituents of the universe, we observed the evolution of the universe, from early deceleration to late time acceleration. In addition, we have found that such an interacting dark energy model can accommodate a transition of the dark energy from a normal state where $w_D>-1$ to $w_D<-1$ phantom regimes. Implications of interacting dark energy model for the observation of dark energy transition has been discussed.

hep-th↗

arXiv2005

Slowly rotating proto strange stars in Quark mass density- and temperature- dependent model

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.

gr-qc↗

arXiv2005

Constraints on the Dark Energy from the holographic connection to the small l CMB Suppression

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.

hep-th↗

arXiv2005

Constraints on the dark energy from holography

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.

hep-th↗

arXiv2005

Quasinormal modes in time-dependent black hole background

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.

gr-qc↗

arXiv2004

Probing the curvature of the Universe from supernova measurement

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.

hep-th↗