Probing Ricci dark energy model with perturbations by using WMAP seven-year cosmic microwave background measurements, BAO and Type Ia supernovae

In this paper, we investigate the Ricci dark energy model with perturbations through the joint constraints of current cosmological data sets from dynamical and geometrical perspectives. We use the full cosmic microwave background information from WMAP seven-year data, the baryon acoustic oscillations from the Sloan Digital Sky Survey and the Two Degree Galaxy Redshift Survey, and type Ia supernovae from the Union2 compilation of the Supernova Cosmology Project Collaboration. A global constraint is performed by employing the Markov chain Monte Carlo method. With the best-fitting results, we show the differences of cosmic microwave background power spectra and background evolutions for the cosmological constant model and Ricci dark energy model with perturbations.Comment: 8 pages, 8 figures, 1 tabl

Liquid-gas phase transtion to first order of an argon like fluid modeled by Sutherland potential

In this paper, an argon-like canonical system is studied. We introduce five hypothesis to deal with the total potential of the system. Then the balanced liquid-gas coexistence phenomenon is analyzed. Good equations of state and phase diagram are given. Some of our results is better and more brief than Mayor's Cluster Expansion.Comment: 13 pages, 4 figures, 2 table

An Extension of the Van der Waals Equation of State

We extend the Van der Waals equation of state to a universal form and find that the van der Waals equation of state is a special condition of this form. Then a good form of the equation of state for a balanced liquid-gas coexistence canonical argon-like system is given. The localization of this universal form concludes the paper.Comment: 8 pages, 2 figures, 2 table

The Fourth Gravity Test and Quintessence Matter Field

After the previous work on gravitational frequency shift, light deflection (arXiv:1003.5296) and perihelion advance (arXiv:0812.2332), we calculate carefully the fourth gravity test, i.e. radar echo delay in a central gravity field surrounded by static free quintessence matter, in this paper. Through the Lagrangian method, we find the influence of the quintessence matter on the time delay of null particle is presence by means of an additional integral term. When the quintessence field vanishes, it reduces to the usual Schwarzschild case naturally. Meanwhile, we also use the data of the Viking lander from the Mars and Cassini spacecraft to Saturn to constrain the quintessence field. For the Viking case, the field parameter $\alpha$ is under the order of $10^{-9}$. However, $\alpha$ is under $10^{-18}$ for the Cassini case.Comment: 9 pages, 1 figure, Eur. Phys. J. C in pres

Statefinder Parameters for Tachyon Dark Energy Model

In this paper we study the statefinder parameters for the tachyon dark energy model. There are two kinds of stable attractor solutions in this model. The statefinder diagrams characterize the properties of the tachyon dark energy model. Our results show that the evolving trajectories of the attractor solutions lie in the total region and pass through the LCDM fixed point, which is different from other dark energy model.Comment: 5 pages, 5 figures, accepted by MPL