Physics – High Energy Physics – High Energy Physics - Theory
Scientific paper
2002-12-27
Phys.Rev.D67:083509,2003; Erratum-idid.D67:109901,2003
Physics
High Energy Physics
High Energy Physics - Theory
Final version accepted in Phys. Rev.D ; some clarifications and references added
Scientific paper
10.1103/PhysRevD.67.083509 10.11
We study the cosmological evolution of a scalar field that couples to the trace $T=T^{a}_a$ of energy momentum tensor of all the fields (including itself). In the case of a shallow exponential potential, the presence of coupling to the trace $T$ in the field equation makes the energy density of the scalar field decrease faster thereby hastening the commencement of radiation domination. This effect gradually diminishes at later epochs allowing the scalar field to dominate the energy density again. We interpret this phase as the current epoch of cosmic acceleration with $\Omega_{\phi}=0.7$. A variant of this model can lead to accelerated expansion at the present epoch followed by a $a(t)\propto t^{2/3}$ behaviour as $t\to \infty$, making the model free from future event horizon. The main features of the model are independent of initial conditions. However, fine tuning of parameters is necessary for viable evolution.
Padmanabhan Thanu
Sami M.
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