Z. G. Huang

Coupled quintessence and phantom based on a dilaton

Based on a dilatonic dark energy model, we consider two cases: a dilaton field with positive kinetic energy (coupled quintessence) and with negative kinetic energy (phantom). In the two cases, we investigate the existence of attractor solutions which correspond to an equation of state parameter ω =− 1 and a cosmic density parameter � σ = 1. We find that the coupled term between matter and dilaton can not affect the existence of attractor solutions. In the Mexican hat potential, the attractor behaviours, the evolution of the state ¨

Statefinder Diagnostic for Dilaton Dark Energy

Statefinder diagnostic is a useful method which can differ one dark energy model from the others. The Statefinder pair {r,s} is algebraically related to the equation of state of dark energy and its first time derivative. We apply in this paper this method to the dilaton dark energy model based on Weyl-Scaled induced gravitational theory. We investigate the effect of the coupling between matter and dilaton when the potential of dilaton field is taken as the Mexican hat form. We find that the evolving trajectory of our model in the r−s diagram is quite different from those of other dark energy models.

Cosmologies with a general non-canonical scalar field

The scalar field models with the Lagrangian L = F(X) − V(), which we call general non-canonical scalar field models, are investigated. We find that a special square potential (with a negative minimum) is needed to drive the linear field solution ( = 0t) in our model, while in the K-essence model (L = −V()F(X)) the potential should be taken as an inverse square one. Hence the cosmological evolutions for these models are totally different. The linear field solutions are found to be highly degenerate, and their cosmological evolutions are equivalent to the model where the sound speed diverges. We also study the stability of the linear field solution and find the condition for stable solutions to exist. The cosmological solution in the presence of matter and radiation is further studied by numerically solving the potential and the cosmological evolution, and the results are shown to be quite different from the case of no matter or radiation. Then we analyze the case with a constant barotropic index γ and show that, unlike in the K-essence model, the detailed form of F(X) depends on the potential V(), and that this constant γ solution is stable for γ0 ≤ 1. When the potential is taken to be a constant, we find the first integral and obtain the corresponding γ, which is similar to that in the K-essence model.

Born–Infeld type phantom model in the ω–ω′ plane

AbstractnIn this paper, we investigate the dynamics of Born–Infeld (B–I) phantom model in the ω–ω′ plane, which is defined by the equation of state parameter for the dark energy and its derivative with respect to N (the logarithm of the scale factor a). We find the scalar field equation of motion in ω–ω′ plane, and show mathematically the property of attractor solutions which correspond to ωφ∼−1, Ωφ=1, which avoid the “Big rip” problem and meets the current observations well.n

Om diagnostic for dilaton dark energy

Om diagnostic can differentiate between different models of dark energy without the accurate current value of matter density. We apply this geometric diagnostic to dilaton dark energy (DDE) model and differentiate DDE model from LCDM. We also investigate the influence of coupled parameter α on the evolutive behavior of Om with respect to redshiftxa0z. According to the numerical result of Om, we get the current value of equation of state ωσ0=−0.952 which fits the WMAP5+BAO+SN very well.

The consistent result of cosmological constant from quantum cosmology and inflation with Born-Infeld scalar field

The Quantum cosmology with Born-Infeld(B-I) type scalar field is considered. In the extreme limits of small cosmological scale factor the wave function of the universe can also be obtained by applying the methods developed by Hartle-Hawking(H-H) and Vilenkin. H-H wave function predicts that most Probable cosmological constant

Parametrization of Born-Infeld type phantom dark energy model

Lambda

Generalized Chaplygin gas model with or without viscosity in the w–w′ plane

equals to

A new type of interaction between generalized Chaplygin gas and dark matter

frac{1}{eta}

The sign-changeable interaction between variable generalized Chaplygin gas and dark matter

(