https://doi.org/10.1140/epjc/s10052-019-7191-8
Regular Article - Theoretical Physics
Observational constraints on growth index with cosmography
School of Physics, Beijing Institute of Technology, Beijing, 100081, China
* e-mail: haowei@bit.edu.cn
Received:
20
April
2019
Accepted:
1
August
2019
Published online:
20
August
2019
In the literature, it was proposed that the growth index 
is useful to distinguish the scenarios of dark energy and modified gravity. In the present work, we consider the constraints on the growth index by using the latest observational data. To be model-independent, we use cosmography to describe the cosmic expansion history, and also expand the general 
as a Taylor series with respect to redshift z or y-shift, 
. We find that the present value 
(for most of viable f(R) theories) is inconsistent with the latest observational data at high confidence level (C.L.). On the other hand, 
(for dark energy models in GR) can be consistent with the latest observational data at 
C.L. in five of the nine cases under consideration, but is inconsistent beyond 
C.L. in the other four cases (while it is still consistent within the 
region). Thus, we can say nothing firmly about . We also find that a varying is favored.
© The Author(s), 2019
