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Indexed by:期刊论文

Date of Publication:2013-10-22

Journal:PHYSICAL REVIEW D

Included Journals:SCIE、Scopus

Volume:88

Issue:8

ISSN No.:1550-7998

Abstract:The growth index gamma L was proposed to investigate the possible deviation from the standard Lambda CDM model and Einstein's gravity theory in a dynamical perspective. Recently, thanks to the measurement of the cosmic growth rate via the redshift-space distortion, one can understand the evolution of the density contrast through f sigma(8)(z), where f(z) = d ln delta/d ln a is the growth rate of matter and sigma(8)(z) is the rms amplitude of the density contrast delta at the comoving 8h(-1) Mpc scale. In this paper, we use the redshift-space distortion data points to study the growth index on the bases of Einstein's gravity theory and a modified gravity theory under the assumption of f = Omega(m)(a)(gamma L). The cosmic background evolution is fixed by the cosmic observations from the type Ia supernovae SNLS3 data, cosmic microwave background radiation data from Planck, and baryon acoustic oscillations. Via the Markov Chain Monte Carlo method, we find the following gamma L values for Einstein's gravity with a cosmological constant (w = const) dark energy and a modified gravity theory in the 1, 2, and 3 sigma regions, respectively: 0.675(-0.0662-0.120-0.155)(+0.0611+0.129+0.178),0.745(-0.0819-0.146-0.190)(+0.0755+0.157+0.205), and 0.555(-0.0167-0.0373-0.0516)(+0.0193+0.0335+0.0436). In Einstein's gravity theory, the values of the growth index gamma L show an almost 2 sigma deviation from the theoretical prediction of 6/11 for the Lambda CDM model. However, in the modified gravity framework, a deviation from Einstein's relativity is not detected in the 1 sigma region. This implies that the currently available cosmic observations do not predict an alternative modified gravity theory beyond the Lambda CDM model under Einstein's gravity, but that the simple assumption of f = Omega(gamma L)(m) should be improved.