Astronomy and Astrophysics – Astrophysics – General Relativity and Quantum Cosmology
Scientific paper
2009-06-19
Phys.Rev.D80:023503,2009
Astronomy and Astrophysics
Astrophysics
General Relativity and Quantum Cosmology
12 pages, 4 figures, with some corrections
Scientific paper
10.1103/PhysRevD.80.023503
As an extension of $\Lambda$CDM, the decaying vacuum model (DV) describes the dark energy as a varying vacuum whose energy density decays linearly with the Hubble parameter in the late-times, $\rho_\Lambda(t) \propto H(t)$, and produces the matter component. We examine the high-$z$ cosmic age problem in the DV model, and compare it with $\Lambda$CDM and the Yang-Mills condensate (YMC) dark energy model. Without employing a dynamical scalar field for dark energy, these three models share a similar behavior of late-time evolution. It is found that the DV model, like YMC, can accommodate the high-$z$ quasar APM 08279+5255, thus greatly alleviates the high-$z$ cosmic age problem. We also calculate the Statefinder $(r,s)$ and the {\it Om} diagnostics in the model. It is found that the evolutionary trajectories of $r(z)$ and $s(z)$ in the DV model are similar to those in the kinessence model, but are distinguished from those in $\Lambda$CDM and YMC. The ${\it Om}(z)$ in DV has a negative slope and its height depends on the matter fraction, while YMC has a rather flat ${\it Om}(z)$, whose magnitude depends sensitively on the coupling.
Tong Ming-Lei
Zhang Yang
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