Constraints on the original Cardassian model and the modified polytropic Cardassian model are examined from the recently derived 42 gamma-ray bursts(GRBs) data calibrated with the method that can avoid the circularity...Constraints on the original Cardassian model and the modified polytropic Cardassian model are examined from the recently derived 42 gamma-ray bursts(GRBs) data calibrated with the method that can avoid the circularity problem.The results show that GRBs can be an optional observation to constrain the Cardassian models.Combining the GRBs data with the newly de-rived size of baryonic acoustic oscillation peak from the Sloan Digital Sky Survey(SDSS),and the position of the first acoustic peak of the Cosmic Microwave Background radiation(CMB) from Wilkinson Microwave Anisotropy Probe(WMAP),we find Ωm0=0.27+0.02-0.02,n=0.06+0.07-0.08(1σ) for the original Cardassian model,and Ωm0=0.27+0.23-0.02,n=-0.09+0.23-1.91,β=0.82+2.10-0.62(1σ) for the modified polytropic Cardassian model.展开更多
In this paper, proceeding from the relation between the Cardassian model and the accelerated expansion of the universe, adopting a parametric method which does not depend on a precise mechanism for gravitational baryo...In this paper, proceeding from the relation between the Cardassian model and the accelerated expansion of the universe, adopting a parametric method which does not depend on a precise mechanism for gravitational baryo/leptogenesis and using the model parameter of CPT-violating interaction, we study the role of the modified Friedmann equation which plays a role in the matter asymmetry of the early epoch and the accelerated expansion of the present universe. Thus the appropriate Cardassian component in the radiatiomdominated era or in the matter-dominated universe can be obtained. The results indicate that early CPT-violation is included in the Cardassian term. In the same way, the present Cardassian term that belongs to a quintessence-like model can drive the universe towards a flat, matter-dominated and accelerating expansion.展开更多
We propose a hyperbolic function form of the Cardassian component in the Cardassian model. Using the repartition of this Cardassian component, we can obtain a non-zero gravitational interaction between the time deriva...We propose a hyperbolic function form of the Cardassian component in the Cardassian model. Using the repartition of this Cardassian component, we can obtain a non-zero gravitational interaction between the time derivative of Ricci scalar curvature and the baryon/lepton number current in the radiation-dominated universe. Furthermore, the other term that acts like a non-zero cosmological constant would give an accelerated expansion of current universe and the features of this model do not violate our desired requirements.展开更多
基金This work is supported by National Science Foundation of China under Grant(10473007)Ph.D Foun-dation Grant of Chinese Education Ministry(20040270006)
文摘Constraints on the original Cardassian model and the modified polytropic Cardassian model are examined from the recently derived 42 gamma-ray bursts(GRBs) data calibrated with the method that can avoid the circularity problem.The results show that GRBs can be an optional observation to constrain the Cardassian models.Combining the GRBs data with the newly de-rived size of baryonic acoustic oscillation peak from the Sloan Digital Sky Survey(SDSS),and the position of the first acoustic peak of the Cosmic Microwave Background radiation(CMB) from Wilkinson Microwave Anisotropy Probe(WMAP),we find Ωm0=0.27+0.02-0.02,n=0.06+0.07-0.08(1σ) for the original Cardassian model,and Ωm0=0.27+0.23-0.02,n=-0.09+0.23-1.91,β=0.82+2.10-0.62(1σ) for the modified polytropic Cardassian model.
文摘In this paper, proceeding from the relation between the Cardassian model and the accelerated expansion of the universe, adopting a parametric method which does not depend on a precise mechanism for gravitational baryo/leptogenesis and using the model parameter of CPT-violating interaction, we study the role of the modified Friedmann equation which plays a role in the matter asymmetry of the early epoch and the accelerated expansion of the present universe. Thus the appropriate Cardassian component in the radiatiomdominated era or in the matter-dominated universe can be obtained. The results indicate that early CPT-violation is included in the Cardassian term. In the same way, the present Cardassian term that belongs to a quintessence-like model can drive the universe towards a flat, matter-dominated and accelerating expansion.
文摘We propose a hyperbolic function form of the Cardassian component in the Cardassian model. Using the repartition of this Cardassian component, we can obtain a non-zero gravitational interaction between the time derivative of Ricci scalar curvature and the baryon/lepton number current in the radiation-dominated universe. Furthermore, the other term that acts like a non-zero cosmological constant would give an accelerated expansion of current universe and the features of this model do not violate our desired requirements.
