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Crossing the Phantom Divide Barrier with Scalar Tensor Theories

L. Perivolaropoulos
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Abstract

There is accumulating observational evidence (based on SnIa data) that the dark energy equation of state parameter $w$ may be evolving with time and crossing the phantom divide barrier $w=-1$ at recent times. The confirmation of these indications by future data would indicate that minimally coupled quintessence can not reproduce the observed expansion rate $H(z)$ for any scalar field potential. Here we explicitly demonstrate that scalar tensor theories of gravity (extended quintessence) can predict crossing of the phantom divide barrier. We reconstruct phenomenologically viable scalar-tensor potentials $F(Φ)$ and $U(Φ)$ that can reproduce a polynomial best fit expansion rate $H(z)$ and the corresponding dark energy equation of state parameter $w(z)$ crossing the $w=-1$ line. The form of the reconstructed scalar tensor potentials is severely constrained but is not uniquely determined. This is due to observational uncertainties in the form of $H(z)$ and also because a single observed function $H(z)$ does not suffice for the reconstruction of the two potential functions $F(Φ)$ and $U(Φ)$.

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L. Perivolaropoulos. 2005-07-14. Crossing the Phantom Divide Barrier with Scalar Tensor Theories. https://doi.org/10.1088/1475-7516%2F2005%2F10%2F001

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