Studies On The Limits Of Joint Cosmological Observations With The Hubble Parameter Measurements

The accelerating expansion of the universe was discovered by two observation teams,though the observations of type Ia supernovae.Before long,it was confirmed by various other observations.In order to explain this expanding behavior of the universe,dark energy,a new energy component,has been proposed.It may be the source to produce negative pressure to drive the cosmic acceleration.The current observations reveal that the dark energy contributes about 70%of the total energy in the universe.However,people know little about the nature of the dark energy.Therefore,numerous dark energy models were proposed to investigate dark energy.With the continuous progress of astronomical observation technology,observations have provided a lot of accurate information for studying the accelerated expansion of the universe.From cosmological observations including the type Ⅰa supernovae(SN),baryon acoustic oscillations(BAO),and cosmic microwave background radiation(CMB),we can obtain the cosmic distance,such as the angular diameter distance or the luminosity distance,which are linked to the Hubble expansion rate by a integral operation.There also have an integral between the equation-of-state parameter w(z)and the Hubble parameter H(z).Therefore,it is extremely difficult to constrain the property of dark energy by the cosmic distance.That is to say,it completely ignores the fine structure of the Hubble parameter itself by integrating the Hubble parameter H(z)to obtain the distance scale.Meanwhile some important information is also missing in the integration process.However,for the direct measurement of H(z),there is the fact that between H(z)and w(z)is only one integral.It was a more obvious advantage to limit dark energy model parameters via directly measuring of the Hubble parameter H(z).In order to avoid the inconsistency between the red shift drift data and other observation data,we used the best fitting of the current observation data to simulate the 10 year red shift drift data.In this work,we make an analysis of the constraining power from the direct measurement of Hubble parameter H(z)including the current measurement of H(z)and the future 10-year Sandage-Loeb test observation.Other observational data used in this work include the type Ⅰa supernovae observation,the cosmic microwave background observation,and the baryon acoustic oscillations observation.Four dark energy models are chosen,namely,the ACDM model,wCDM model,αDE model,and GCG model,to make the analysis.The results show that the constraint on the dark energy models can be improved significantly when the current H(z)data and the 10-year SL data are considered.We find that the existing degeneracy between cosmological parameters can be evidently broken through adding the 10-year SL data.Therefore,the accurate data obtained from the direct measurement of Hubble parameters in the future is likely to make a significant contribution to the study of dark energy.