arXiv subjects

Wen-Biao Liu

Publications and source records attributed to Wen-Biao Liu.

32 records · Page 2Linked to original sources

arXiv2014

Holographic thermalization with a chemical potential in Gauss-Bonnet gravity

Holographic thermalization is studied in the framework of Einstein-Maxwell-Gauss-Bonnet gravity. We use the two-point correlation function and expectation value of Wilson loop, which are dual to the renormalized geodesic length and minimal area surface in the bulk, to probe the thermalization. The numeric result shows that larger the Gauss-Bonnet coefficient is, shorter the thermalization time is, and larger the charge is, longer the thermalization time is, which implies that the Gauss-Bonnet coefficient can accelerate the thermalization while the charge has an opposite effect. In addition, we obtain the functions with respect to the thermalization time for both the thermalization probes at a fixed charge and Gauss-Bonnet coefficient, and on the basis of these functions, we obtain the thermalization velocity, which shows that the thermalization process is non-monotonic. At the middle and later periods of the thermalization process, we find that there is a phase transition point, which divides the thermalization into an acceleration phase and a deceleration phase. We also study the effect of the charge and Gauss-Bonnet coefficient on the phase transition point.

hep-th↗

arXiv2014

Observational constraint on the interacting dark energy models including the Sandage-Loeb test

Two types of interacting dark energy models are investigated using the type Ia supernova (SNIa), observational $H(z)$ data (OHD), cosmic microwave background (CMB) shift parameter and the secular Sandage-Loeb (SL) test. We find that the inclusion of SL test can obviously provide more stringent constraint on the parameters in both models. For the constant coupling model, the interaction term including the SL test is estimated at $δ=-0.01 \pm 0.01 (1σ) \pm 0.02 (2σ)$, which has been improved to be only a half of original scale on corresponding errors. Comparing with the combination of SNIa and OHD, we find that the inclusion of SL test directly reduces the best-fit of interaction from 0.39 to 0.10, which indicates that the higher-redshift observation including the SL test is necessary to track the evolution of interaction. For the varying coupling model, we reconstruct the interaction $δ(z)$, and find that the interaction is also negative similar as the constant coupling model. However, for high redshift, the interaction generally vanishes at infinity. The constraint result also shows that the $Λ$CDM model still behaves a good fit to the observational data, and the coincidence problem is still quite severe. However, the phantom-like dark energy with $w_X<-1$ is slightly favored over the $Λ$CDM model.

astro-ph.CO↗

arXiv2014

P-V Criticality of Topological Black Holes in Lovelock-Born-Infeld Gravity

To understand the effect of third order Lovelock gravity, $P-V$ criticality of topological AdS black holes in Lovelock-Born-Infeld gravity is investigated. The thermodynamics is further explored with some more extensions and details than the former literature. A detailed analysis of the limit case $β\rightarrow\infty$ is performed for the seven-dimensional black holes. It is shown that for the spherical topology, $P-V$ criticality exists for both the uncharged and charged cases. Our results demonstrate again that the charge is not the indispensable condition of $P-V$ criticality. It may be attributed to the effect of higher derivative terms of curvature because similar phenomenon was also found for Gauss-Bonnet black holes. For $k=0$, there would be no $P-V$ criticality. Interesting findings occur in the case $k=-1$, in which positive solutions of critical points are found for both the uncharged and charged cases. However, the $P-v$ diagram is quite strange. To check whether these findings are physical, we give the analysis on the non-negative definiteness condition of entropy. It is shown that for any nontrivial value of $α$, the entropy is always positive for any specific volume $v$. Since no $P-V$ criticality exists for $k=-1$ in Einstein gravity and Gauss-Bonnet gravity, we can relate our findings with the peculiar property of third order Lovelock gravity. The entropy in third order Lovelock gravity consists of extra terms which is absent in the Gauss-Bonnet black holes, which makes the critical points satisfy the constraint of non-negative definiteness condition of entropy. We also check the Gibbs free energy graph and the "swallow tail" behavior can be observed. Moreover, the effect of nonlinear electrodynamics is also included in our research.

gr-qc↗

arXiv2013

Phase transitions, geometrothermodynamics and critical exponents of black holes with conformal anomaly

We investigate the phase transitions of black holes with conformal anomaly in canonical ensemble from different perspectives. Some interesting and novel phase transition phenomena have been discovered. Firstly, we discuss the behavior of the specific heat and the inverse of the isothermal compressibility. It is shown that there are striking differences in Hawking temperature and phase structure between black holes with conformal anomaly and those without it. In the case with conformal anomaly, there exists local minimum temperature corresponding to the phase transition point. Phase transitions take place not only from an unstable large black hole to a locally stable medium black hole but also from an unstable medium black hole to a locally stable small black hole. Secondly, we probe in details the dependence of phase transitions on the choice of parameters. The results show that black holes with conformal anomaly have much richer phase structure than those without it. There would be two, only one or no phase transition points depending on the parameters we have chosen. The corresponding parameter region are derived both numerically and graphically. Thirdly, geometrothermodynamics are built up to examine the phase structure we have discovered. It is shown that Legendre invariant thermodynamic scalar curvature diverges exactly where the specific heat diverges. Furthermore, critical behaviors are investigated by calculating the relevant critical exponents. It is proved that these critical exponents satisfy the thermodynamic scaling laws, leading to the conclusion that critical exponents and the scaling laws can reserve even when we consider conformal anomaly.

hep-th↗

arXiv2013

Power of the redshift drift on cosmological models and expansion history

We investigate the power of the velocity drift ($Δv$) on cosmological parameters and expansion history with observational Hubble data (OHD), type Ia supernova (SNIa). We estimate the constraints of $Δv$ using the Fisher information matrix based on the model by \citet{pasquini2005codex,whitelock2006scientific}. We find that $Δv$ with 20 years can reduce the uncertainty of $Ω_m$ by more than 42% than available observations. Based on the statistical figures of merit (FoM), we find that in order to match the constraint power of OHD and SNIa, we need 21 and 26 future measurements, respectively. We also quantitatively estimate for the first time the number of years required for the velocity drift to become comparable with current observations on the equation of state $w$. The statistical FoM indicate that we need at least 12 years to cover current observations. Physically, we could monitor 30 quasars for 30 years to obtain the same accuracy of $w$. Considering two parameterized deceleration factor $q(z)$, we find that the available observations give an estimation on current value $-0.9 \lesssim q_0 \lesssim -0.3$. Difference between the two types of $q(z)$ is the precise determination of variation rate $dq/dz$. For the first model with constant $dq/dz$, $Δv$ with only 10 years provides a much better constraint on it, especially when compared with SNIa. However, we need $Δv$ for more years in the variable $dq/dz$ model. We find that $Δv$ with 30 years reduces the uncertainty of transition redshift to approximately three times better than those of OHD and SNIa.

astro-ph.CO↗

arXiv2013

Holographic thermalization in Gauss-Bonnet gravity

In the spirit of AdS/CFT correspondence, we study the thermalization of a dual conformal field theory to Gauss-Bonnet gravity by modeling a thin-shell of dust that interpolates between a pure AdS and a Gauss-Bonnet AdS black brane. The renormalized geodesic length and minimal area surface, which in the dual conformal field theory correspond to two-point correlation function and expectation value of Wilson loop, are investigated respectively as thermalization probes. The result shows that as the Gauss-Bonnet coefficient increases, the thermalization time decreases for both the thermalization probes, which can also be confirmed by studying the motion profile of the geodesic and minimal area surface. In addition, for both the renormalized geodesic length and minimal area surface, there is an overlapped region for a fixed boundary separation, which implies that the Gauss-Bonnet coupling constant has little effect on the thermalization probes there.

hep-th↗

arXiv2012

The accelerated scaling attractor solution of the interacting agegraphic dark energy in Brans-Dicke theory

We investigate the interacting agegraphic dark energy in Brans-Dicke theory and introduce a new series general forms of dark sector coupling. As examples, we select three cases involving a linear interaction form (Model I) and two nonlinear interaction form (Model II and Model III). Our conclusions show that the accelerated scaling attractor solutions do exist in these models. We also find that these interacting agegraphic dark energy modes are consistent with the observational data. The difference in these models is that nonlinear interaction forms give more approached evolution to the standard $Λ$CDM model than the linear one. Our work implies that the nonlinear interaction forms should be payed more attention.

gr-qc↗

arXiv2012

Periodicity and area spectrum of black holes

The recent speculation of Maggiore that the periodicity of a black hole may be the origin of the area quantization law is confirmed. We exclusively utilize the period of motion of an outgoing wave, which is shown to be related to the vibrational frequency of the perturbed black hole, to quantize the horizon areas of a Schwarzschild black hole and a Kerr black hole. It is shown that the equally spaced area spectrum for both cases takes the same form and the spacing is the same as that obtained through the quasinormal mode frequencies. Particularly, for a Kerr black hole, the small angular momentum assumption, which is necessary from the perspective of quasinormal mode, is not employed as the general area spacing is reproduced.

gr-qc↗

arXiv2012

Spectroscopy of a Reissner-Nordström black hole via an action variable

With the help of the Bohr--Sommerfeld quantization rule, the area spectrum of a charged, spherically symmetric spacetime is obtained by studying an adiabatic invariant action variable. The period of the Einstein-Maxwell system, which is related to the surface gravity of a given spacetime, is determined by the Kruskal--like coordinates. It is shown that the area spectrum of the Reissner-Nordström black hole is evenly spaced and the spacing is the same as that of a Schwarzschild black hole, which indicates that the area spectrum of a black hole is independent of its parameters. In contrast to the quasi-normal mode analysis, we do not impose the small charge limit as the general area gap $8π$ is obtained.

gr-qc↗

arXiv2012

Spectroscopy of the rotating BTZ black hole via adiabatic invariance

According to Bohr-Sommerfeld quantization rule, an equally spaced horizon area spectrum of a static, spherically symmetric black hole was obtained under an adiabatic invariant action. This method can be extended to the rotating black holes. As an example, we apply this method to the rotating BTZ black hole and obtain the quantized spectrum of the horizon area. It is shown that the area spectrum of the rotating BTZ black hole is equally spaced and irrelevant to the rotating parameter, which is consistent with the Bekenstein conjecture. Specifically, the derivation do not need the quasinormal frequencies and the small angular momentum limit.

gr-qc↗

arXiv2011

Constraints on $Λ(t)$CDM models as holographic and agegraphic dark energy with the observational Hubble parameter data

The newly released observational $H(z)$ data (OHD) is used to constrain $Λ(t)$CDM models as holographic and agegraphic dark energy. By the use of the length scale and time scale as the IR cut-off including Hubble horizon (HH), future event horizon (FEH), age of the universe (AU), and conformal time (CT), we achieve four different $Λ(t)$CDM models which can describe the present cosmological acceleration respectively. In order to get a comparison between such $Λ(t)$CDM models and standard $Λ$CDM model, we use the information criteria (IC), $Om(z)$ diagnostic, and statefinder diagnostic to measure the deviations. Furthermore, by simulating a larger Hubble parameter data sample in the redshift range of $0.1<z<2.0$, we get the improved constraints and more sufficient comparison. We show that OHD is not only able to play almost the same role in constraining cosmological parameters as SNe Ia does but also provides the effective measurement of the deviation of the DE models from standard $Λ$CDM model. In the holographic and agegraphic scenarios, the results indicate that the FEH is more preferable than HH scenario. However, both two time scenarios show better approximations to $Λ$CDM model than the length scenarios.

astro-ph.CO↗

arXiv2011

Hawking radiation via Landauer transport model

Recently, Nation et al confirmed that fluxes of Hawking radiation energy and entropy from a black hole can be regarded as a one-dimensional (1D) Landauer transport process. Their work can be extended to background spacetimes with gauge potential. The result shows that the energy flux, which is indicated to be equal to the energy-momentum tensor flux, contains not only the contribution of thermal flux but also that of particle flux. We find that the charge can also be regarded as transporting via a 1D quantum channel and the charge flux is equal to the gauge flux.

gr-qc↗

arXiv2011

Hawking radiation from a BTZ black hole viewed as Landauer transport

Viewing Hawking radiation as a 1D single quantum channel Landauer transport process, Nation et al calculated the energy flux and entropy flux from a Schwarzschild black hole without chemical potential. To generalize the method to the case with chemical potential, a rotating charged and non-charged BTZ black hole is investigated. Energy flux and entropy flux obtained are consistent with that from anomaly theory. The maximum energy flux and entropy flux are independent on the statistics of bosons or fermions.

gr-qc↗

arXiv2011

Landauer transport model for Hawking radiation from a Reissner-Nordstrom black hole

The recent work of Nation et al in which Hawking radiation energy and entropy flow from a black hole can be regarded as a one-dimensional (1D) Landauer transport process is extended to the case of a Reissner-Nordstrom (RN) black hole. It is found that the flow of charge current can also be transported via a 1D quantum channel except the current of Hawking radiation. The maximum entropy current, which is shown to be particle statistics independence, is also obtained.

gr-qc↗