https://doi.org/10.1140/epjc/s10052-017-5461-x
Regular Article - Theoretical Physics
The generalized cosmic equation of state: a revised study with cosmological standard rulers
1
School of Physics, Shanxi Datong University, Datong, 037009, China
2
Department of Physics, School of Mathematics and physics, Weinan Normal University, Weinan, 714099, Shanxi, China
3
Department of Astronomy, Beijing Normal University, Beijing, 100875, China
* e-mail: caoshuo@bnu.edu.cn
Received:
20
August
2017
Accepted:
11
December
2017
Published online:
20
December
2017
In this paper, the generalized equation of state (GEoS) for dark energy (
) is investigated with the combined standard ruler data from the observations of intermediate-luminosity radio quasars, galaxy clusters, BAO and CMB. The constraint results show that the best-fit EoS parameters are 
, 
and 
(with a lower limit of 
at 68.3% C.L.), which implies that at early times the dark energy vanishes. In the framework of nine truncated GEoS models with different 
parameters, our findings present very clear evidence disfavoring the case that dark energy always dominates over the other material components in the early universe. Moreover, stringent constraints can be obtained in combination with the latest measurements of Hubble parameter at different redshifts: 
, 
and 
(with a lower limit of 
at 68.3% C.L.). Finally, the results obtained from the transition redshift (
) and Om(z) diagnostic indicate that: (1) The above constraints on the GEoS model agree very well with the transition redshift interval 
within 
error region. (2) At the current observational level, the GEoS model is practically indistinguishable from 
CDM, although a small deviation from CDM cosmology is present in the combined standard ruler data.
© The Author(s), 2017
