Growth factor parametrization in curved space
- College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China) and Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China)
The growth rate of matter perturbation and the expansion rate of the Universe can be used to distinguish modified gravity and dark energy models in explaining cosmic acceleration. We explore here the inclusion of spatial curvature into the growth factor. We expand previous results using the approximation {omega}{sub m}{sup {gamma}} and then suggest a new form, f{sub a}={omega}{sub m}{sup {gamma}}+({gamma}-4/7){omega}{sub k}, as an approximation for the growth factor when the curvature {omega}{sub k} is not negligible, and where the growth index {gamma} is usually model dependent. The expression recovers the standard results for the curved and flat {lambda}CDM and Dvali-Gabadadze-Porrati models. Using the best fit values of {omega}{sub m0} and {omega}{sub k0} to the expansion/distance measurements from Type Ia SNe, baryon acoustic oscillation, WMAP5, and H(z) data, we fit the growth index parameter to current growth factor data and obtain {gamma}{sub {lambda}}({omega}{sub k}{ne}0)=0.65{sub -0.15}{sup +0.17} and {gamma}{sub DGP}({omega}{sub k}{ne}0)=0.53{sub -0.12}{sup +0.14}. For the {lambda}CDM model, the 1-{sigma} observational bounds are found consistent with theoretical value, unlike the case for the Dvali-Gabadadze-Porrati model. We also find that the current data we used is not enough to put significant constraints when the 3 parameters in f{sub a} are fit simultaneously. Importantly, we find that, in the presence of curvature, the analytical expression proposed for f{sub a} provides a better fit to the growth factor than other forms and should be useful for future high precision missions and studies.
- OSTI ID:
- 21316176
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 80, Issue 2; Other Information: DOI: 10.1103/PhysRevD.80.023002; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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