119105820
Geometrical diagnostic for purely kinetic k-essence dark energy
Abstract Geometrical diagnostic, involving the statefinder { r , s } and Om ( x ) , is widely used to discriminate different dark energy models. We apply the statefinder { r , s } and Om ( x ) to purely kinetic k-essence dark energy model with Dirac–Born–Infeld-like Lagrangian which can be considered as scalar field realizations of Chaplygin gas. We plot the evolution trajectories of this model in the statefinder parameter-planes and Om ( x ) parameter-plane. We find that the statefinder { r , s } and Om ( x ) fail to distinguish purely kinetic k-essence model from ΛCDM model at 68.3% confidence level for z ≪ 1 .
119237909
Modified clock inequalities and modified black hole lifetime
Based on a generalized uncertainty principle, Salecker-Wigner inequalities are modified. When applied to black holes, they give a modified black hole lifetime: T-MB similar to M-3/m(p)(3)(1 - m(p)(2)/M-2)t(p), and the number of bits required to specify the information content of the black hole as the event horizon area in Planck units N similar to M-2/m(p)(2)(1 - m(p)(2)/M-2).
119289134
Large-scale structure in superfluid Chaplygin gas cosmology
We investigate the growth of the large-scale structure in the superfluid Chaplygin gas (SCG) model. Both linear and nonlinear growth, such as sigma(8) and the skewness S-3, are discussed. We find the growth factor of SCG reduces to the Einstein-de Sitter case at early times while it differs from the cosmological constant model (ACDM) case in the large a limit. We also find there will be more stricture growth on large scales in the SCG scenario than in ACDM and the variations of sigma 8 and S-3 between SCG and ACDM cannot be discriminated.
120945447
Observational Constraints on Purely Kinetic k -Essence Dark Energy Models
We consider constraints on purely kinetic k-essence models from the latest observational data (including 182 gold SNIa data, the shift parameter, and the acoustic scale). We find the best-fit values of the parameters are Ωm = 0.37 ± 0.01 and k0 = 0.064 ± 0.013 at 68.3% confidence level. The phase transition from deceleration to acceleration is found to occur at redshift zq = 0 ~ 0.48−0.52 in 68.3% confidence level limits. By applying model-comparison statistics (F-test, AICc, and BIC), we find that the purely kinetic k-essence scenario is favored over the ?CDM model by the combined data. These results are also confirmed by combined data 307 SNIa + R + la.
120520435
Bound on the Equation of State of Dark Energy from the Generalized Second Law of Thermodynamics
Assuming that the equation of state of dark energy is a constant, we obtain the allowed interval of the equation of state of dark energy: wD≥−1, bounded from the generalized second law of thermodynamics, in a universe enveloped by the apparent horizon and containing a Schwarzschild black hole.
121495245
Theoretical Constraint on Purely Kinetic k -Essence
Purely kinetic k-essence models in which the Lagrangian contains only a kinetic factor and does not depend explicitly on the field itself are considered, and a theoretical constraint is obtained: Fx = F0a−3. Under this theoretical constraint, we discuss a kind of purely k-essence with form F(X) = -(1 + 2Xn)1/2n, which can be considered as the generalized tachyon field, and find that this kind of k-essence is not likely a candidate of dark energy to describe the present accelerated expansion of the Universe. This is contrary to a previous suggestion that k-essence with such a form may be used to describe phantom cosmologies.
12639048
Towards complete phase diagrams of a holographic p-wave superconductor model
A bstractWe study in detail the phase structure of a holographic p-wave superconductor model in a five dimensional Einstein-Maxwell-complex vector field theory with a negative cosmological constant. To construct complete phase diagrams of the model, we consider both the soliton and black hole backgrounds. In both two cases, there exist second order, first order and zeroth order phase transitions, and the so-called “retrograde condensation” also happens. In particular, in the soliton case with the mass of the vector field being beyond a certain critical value, we find a series of phase transitions happen such as “insulator/superconductor/insulator/superconductor”, as the chemical potential continuously increases. We construct complete phase diagrams in terms of temperature and chemical potential and find some new phase boundaries.
119285015
P-V criticality in the extended phase space of Gauss-Bonnet black holes in AdS space
A bstractWe study the P − V criticality and phase transition in the extended phase space of charged Gauss-Bonnet black holes in anti-de Sitter space, where the cosmological constant appears as a dynamical pressure of the system and its conjugate quantity is the thermodynamic volume of the black holes. The black holes can have a Ricci flat (k = 0), spherical (k = 1), or hyperbolic (k = −1) horizon. We find that for the Ricci flat and hyperbolic Gauss-Bonnet black holes, no P − V criticality and phase transition appear, while for the black holes with a spherical horizon, even when the charge of the black hole is absent, the P − V criticality and the small black hole/large black hole phase transition will appear, but it happens only in d = 5 dimensions; when the charge does not vanish, the P − V criticality and the small black hole/large phase transition always appear in d = 5 dimensions; in the case of d ≥ 6, to have the P − V criticality and the small black hole/large black hole phase transition, there exists an upper bound for the parameter $ b=\widetilde{\alpha }{{\left| Q \right|}^{{{-2 \left/ {{\left( {d-3} \right)}} \right.}}}} $, where $ \widetilde{\alpha } $ is the Gauss-Bonnet coefficient and Q is the charge of the black hole. We calculate the critical exponents at the critical point and find that for all cases, they are the same as those in the van der Waals liquid-gas system.
119108999
Holographic model for the paramagnetism/antiferromagnetism phase transition
In this paper we build a holographic model of paramagnetism/antiferromagnetism phase transition, which is realized by introducing two real antisymmetric tensor fields coupling to the background gauge field strength and interacting with each other in a dyonic black brane background. In the case without external magnetic field and in low temperatures, the magnetic moments condense spontaneously in antiparallel manner with the same magnitude and the time reversal symmetry is also broken spontaneously (if boundary spatial dimension is more than 2, spatial rotational symmetry is broken spontaneously as well), which leads to an antiferromagnetic phase. In the case with weak external magnetic field, the magnetic susceptibility density has a peak at the critical temperature and satisfies the Curie-Weiss law in the paramagnetic phase of antiferromagnetism. In the strong external magnetic field case, there is a critical magnetic field $B_c$ in antiferromagnetic phase: when magnetic field reaches $B_c$, the system will return into the paramagnetic phase by a second order phase transition.