arXiv subjects

Songbai Chen

Publications and source records attributed to Songbai Chen.

At least 145 records · Page 8Linked to original sources

arXiv2009

Dark energy model with higher derivative of Hubble parameter

In this letter we consider a dark energy model in which the energy density is a function of the Hubble parameter $H$ and its derivative with respect to time $ρ_{de}=3α\ddot{H}H^{-1}+3β\dot{H}+3γH^2$. The behavior of the dark energy and the expansion history of the Universe depend heavily on the parameters of the model $α$, $β$ and $γ$. It is very interesting that the age problem of the well-known three old objects can be alleviated in this models.

gr-qc↗

arXiv2009

Dark energy interacting with dark matter and unparticle

We study dynamical behaviors of the dark energy models interacting with dark matter and unparticle in the standard flat FRW cosmology. We considered four different interacting models and examined the stability of the critical points. We find that there exist late-time scaling attractors corresponding to an accelerating Universe and the alleviation of the coincidence problem depends on the choice of parameters in the models.

gr-qc↗

arXiv2009

Strong field gravitational lensing in the deformed Hǒrava-Lifshitz black hole

Adopting the strong field limit approach, we studied the properties of strong field gravitational lensing in the deformed Hǒrava-Lifshitz black hole and obtained the angular position and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the galaxy described by this metric, we estimated the numerical values of the coefficients and observables for gravitational lensing in the strong field limit. Comparing with the Reissner-Norstr\"{om} black hole, we find that with the increase of parameter $α$, the angular position $θ_{\infty}$ decreases more slowly and $r_m$ more quickly, but angular separation $s$ increases more rapidly. This may offer a way to detect the effects of to distinguish a deformed Hǒrava-Lifshitz black hole from a Reissner-Norstr\"{om} black hole by the astronomical instruments in the future.

gr-qc↗

arXiv2009

Entanglement of coupled massive scalar field in background of dilaton black hole

The entanglement of the coupled massive scalar field in the spacetime of a Garfinkle-Horowitz-Strominger(GHS) dilaton black hole has been investigated. It is found that the entanglement does not depend on the mass of the particle and the coupling between the scalar field and the gravitational field, but it decreases as the dilaton parameter $D$ increases. It is interesting to note that in the limit of $D\to M$, corresponding to the case of an extreme black hole, the state has no longer distillable entanglement for any state parameter $α$, but the mutual information equals to a nonvanishing minimum value, which indicates that the total correlations consist of classical correlations plus bound entanglement in this limit.

gr-qc↗

arXiv2009

Quasinormal modes of charged squashed Kaluza-Klein black holes in the Gödel Universe

We study the quasinormal modes of scalar perturbation in the background of five-dimensional charged Kaluza-Klein black holes with squashed horizons immersed in the Gödel universe. Besides the influence due to the compactness of the extra dimension, we disclose the cosmological rotational effect in the wave dynamics. The wave behavior affected by the Gödel parameter provides an interesting insight into the Gödel universe.

gr-qc↗

arXiv2009

Dynamical evolution of phantom scalar perturbation in the background of Schwarzschild black String spacetime

Using Leaver's continue fraction and time domain method, we study the wave dynamics of phantom scalar perturbation in a Schwarzschild black string spacetime. We find that the quasinormal modes contain the imprint from the wavenumber $k$ of the fifth dimension. The late-time behaviors are dominated by the difference between the wavenumber $k$ and the mass $μ$ of the phantom scalar perturbation. For $k<μ$, the phantom scalar perturbation in the late-time evolution grows with an exponential rate as in the four-dimensional Schwarzschild black hole spacetime. While, for $k=μ$, the late-time behavior has the same form as that of the massless scalar field perturbation in the background of a black hole. Furthermore, for $k>μ$, the late-time evolution of phantom scalar perturbation is dominated by a decaying tail with an oscillation which is consistent with that of the usual massive scalar field. Thus, the Schwarzschild black string is unstable only against the phantom scalar perturbations which satisfy the wavelength $λ>2π/μ$. These information can help us know more about the wave dynamics of phantom scalar perturbation and the properties of black string.

gr-qc↗

arXiv2008

Wave dynamics of phantom scalar perturbation in the background of Schwarzschild black hole

Using Leaver's continue fraction and time domain method, we investigate the wave dynamics of phantom scalar perturbation in the background of Schwarzschild black hole. We find that the presence of the negative kinetic energy terms modifies the standard results in quasinormal spectrums and late-time behaviors of the scalar perturbations. The phantom scalar perturbation in the late-time evolution will grow with an exponential rate.

gr-qc↗

arXiv2008

Dynamics of interacting dark energy model in Einstein and Loop Quantum Cosmology

We investigate the background dynamics when dark energy is coupled to dark matter in the universe described by Einstein cosmology and Loop Quantum Cosmology. We introduce a new general form of dark sector coupling, which presents us a more complicated dynamical phase space. Differences in the phase space in obtaining the accelerated scaling attractor in Einstein cosmology and Loop Quantum Cosmology are disclosed.

gr-qc↗

arXiv2008

Scalar emission in a rotating Gödel black hole

We study the absorption probability and Hawking radiation of the scalar field in the rotating Gödel black hole in minimal five-dimensional gauged supergravity. We find that Gödel parameter $j$ imprints in the greybody factor and Hawking radiation. It plays a different role from the angular momentum of the black hole in the Hawking radiation and super-radiance. These information can help us know more about rotating Gödel black holes in minimal five-dimensional gauged supergravity.

gr-qc↗

arXiv2008

Quasinormal modes and late-time tails in the background of Schwarzschild black hole pierced by a cosmic string: scalar, electromagnetic and gravitational perturbations

We have studied the quasinormal modes and the late-time tail behaviors of scalar, electromagnetic and gravitational perturbations in the Schwarzschild black hole pierced by a cosmic string. Although the metric is locally identical to that of the Schwarzschild black hole so that the presence of the string will not imprint in the motion of test particles, we found that quasinormal modes and the late-time tails can reflect physical signatures of the cosmic string. Compared with the scalar and electromagnetic fields, the gravitational perturbation decays slower, which could be more interesting to disclose the string effect in this background.

gr-qc↗

arXiv2008

Hawking radiation in a $d$-dimensional static spherically-symmetric black Hole surrounded by quintessence

We present a solution of Einstein equations with quintessential matter surrounding a $d$-dimensional black hole, whose asymptotic structures are determined by the state of the quintessential matter. We examine the thermodynamics of this black hole and find that the mass of the black hole depends on the equation of state of the quintessence, while the first law is universal. Investigating the Hawking radiation in this black hole background, we observe that the Hawking radiation dominates on the brane in the low-energy regime. For different asymptotic structures caused by the equation of state of the quintessential matter surrounding the black hole, we learn that the influences by the state parameter of the quintessence on Hawking radiation are different.

gr-qc↗

arXiv2008

Greybody Factors for Rotating Black Holes on Codimension-2 Branes

We study the absorption probability and Hawking radiation of the scalar field in the rotating black holes on codimension-2 branes. We find that finite brane tension modifies the standard results in Hawking radiation if compared with the case when brane tension is completely negligible. We observe that the rotation of the black hole brings richer physics. Nonzero angular momentum triggers the super-radiance which becomes stronger when the angular momentum increases. We also find that rotations along different angles influence the result in absorption probability and Hawking radiation. Compared with the black hole rotating orthogonal to the brane, in the background that black hole spins on the brane, its angular momentum brings less super-radiance effect and the brane tension increases the range of frequency to accommodate super-radiance. These information can help us know more about the rotating codimension-2 black holes.

hep-th↗

arXiv2008

Late-time tail of a coupled scalar field in the background of a black hole with a global monopole

Using the technique of spectral decomposition, we investigated the late-time tails of massless and massive coupled scalar fields in the background of a black hole with a global monopole. We found that due to existence of the coupling between the scalar and gravitational fields, the massless scalar field decay faster at timelike infinity $i_+$, and so does the massive one in the intermediate late time. But the asymptotically late-time tail for the massive scalar field is not affected and its decay rate still is $t^{-5/6}$.

gr-qc↗

arXiv2007

Hawking radiation in a Rotating Kaluza-Klein Black Hole with Squashed Horizons

We explore the signature of the extra dimension in the Hawking radiation in a rotating Kaluza-Klein black hole with squashed horizons. Comparing with the spherical case, we find that the rotating parameter brings richer physics. We obtain the appropriate size of the extra dimension which can enhance the Hawking radiation and may open a window to detect the extra dimensions.

hep-th↗

arXiv2007

Wave dynamics of a six-dimensional black hole localized on a tensional three-brane

We study the quasinormal modes and the late-time tail behavior of scalar perturbation in the background of a black hole localized on a tensional three-brane in a world with two large extra dimensions. We find that finite brane tension modifies the standard results in the wave dynamics for the case of a black hole on a brane with completely negligible tension. We argue that the wave dynamics contains the imprint of the extra dimensions.

hep-th↗

arXiv2007

Influence of Lorentz violation on Dirac quasinormal modes in the Schwarzschild black hole spacetime

Using the third-order WKB approximation and monodromy methods, we investigate the influence of Lorentz violating coefficient $b$ (associated with a special axial-vector $b_μ$ field) on Dirac quasinormal modes in the Schwarzschild black hole spacetime. At fundamental overtone, the real part decreases linearly as the parameter $b$ increases. But the variation of the imaginary part with $b$ becomes more complex. For the larger multiple moment $k$, the magnitude of imaginary part increases with the increase of $b$, which means that presence of Lorentz violation makes Dirac field damps more rapidly. At high overtones, it is found that the real part of high-damped quasinormal frequency does not tend to zero, which is quite a different from the symptotic Dirac quasinormal modes without Lorentz violation.

gr-qc↗

arXiv2005

Asymptotic quasinormal modes of a coupled scalar field in the Gibbons-Maeda dilaton spacetime

Adopting the monodromy technique devised by Motl and Neitzke, we investigate analytically the asymptotic quasinormal frequencies of a coupled scalar field in the Gibbons-Maeda dilaton spacetime. We find that it is described by $ e^{βω}=-[1+2\cos{(\frac{\sqrt{2ξ+1}}{2} π)}]-e^{-β_I ω}[2+2\cos{(\frac{\sqrt{2ξ+1}}{2}π)}]$, which depends on the structure parameters of the background spacetime and on the coupling between the scalar and gravitational fields. As the parameters $ξ$ and $β_I$ tend to zero, the real parts of the asymptotic quasinormal frequencies becomes $T_H\ln{3}$, which is consistent with Hod's conjecture. When $ξ={91/18} $, the formula becomes that of the Reissner-Nordström spacetime.

gr-qc↗

arXiv2005

Quasinormal modes of a black hole surrounded by quintessence

Using the third-order WKB approximation, we evaluate the quasinormal frequencies of massless scalar field perturbation around the black hole which is surrounded by the static and spherically symmetric quintessence. Our result shows that due to the presence of quintessence, the scalar field damps more rapidly. Moreover, we also note that the quintessential state parameter $ε$ (the ratio of pressure $p_q$ to the energy density $ρ_q$) play an important role for the quasinormal frequencies. As the state parameter $ε$ increases the real part increases and the absolute value of the imaginary part decreases. This means that the scalar field decays more slowly in the larger $ε$ quintessence case.

gr-qc↗