Notes on ghost dark energy

Abstract

We study a phenomenological dark energy model which is rooted in the Veneziano ghost of QCD. In this dark energy model, the energy density of dark energy is proportional to Hubble parameter and the proportional coefficient is of the order Λ 3 QCD , where Λ QCD is the mass scale of QCD. The universe has a de Sitter phase at late time and begins to accelerate at redshift around z acc ∼ 0.6. We also fit this model and give the constraints on model parameters, with current observational data including SnIa, BAO, CMB, BBN and Hubble parameter data. We find that the squared sound speed of the dark energy is negative, which may cause an instability. We also study the cosmological evolution of the dark energy with interaction with cold dark matter.

Reconstructing QCD ghost f(R,T) models

“…• ω = −1.13 +0.13 −0.14 , (Planck+WP+SNLS) • ω = −1.084 ± 0.0063, (WMAP+eCMB+BAO+H 0 +SNe) In case of MGDE DE candidate, we set the model parameters following (Cai et al 2012) and show the variation of NEC and EoS parameter in Figure 11. It is found that ω lies in the range −6 × 10 −35 < 1 + ω < −1 representing the phantom era of the universe consistent with the recent observations (Ade et al 2013;Hinshaw et al 2013).…”

“…We have selected two generalized form of GDE models, one suggested by GarciaSalcedo et al (2013) and other model is suggested by Cai et al (2012) named as MGDE. The f (T ) model corresponding to Garcia-Salcedo GDE is introduced in Eq.(18).…”

“…Recently, Cai et al (2012) introduced a modified form of QCD ghost model by involving the term H 2 so that energy density of QCD ghost is given by…”

“…Here, we reconstruct the f (R, T ) = f 1 (R) + f 2 (T ) function corresponding to modified GDE model (Cai et al 2012). Using the model (31), we set expressions for ρ m and ρ GDE (1 + ω GDE ) as given below…”

“…In (Cai et al 2012), authors presented a generalized GDE of the form αH + βH 2 and discussed its dynamical evolution. The energy density of the QCD GDE can be related to the radius of trapping horizon as (Garcia-Salcedo et al 2013) ρ GDE = α(1−ǫ) r T = α(1 − ǫ) H 2 + κ a 2 , here ǫ =˙r T 2Hr T introduces a new time dependent component which is previously ignored.…”