The scalar field potential is found with the two datasets.
Slope of the potential is inflected aftertinflection.Thistime
scale characterizes the time when the Hubble expansion and
˙ Hterms begin to dominate over the dust and curvature
terms. For the WMAP5 dataset, tinflection =5.29 Gyr and
for the WMAP5+BAO+SN dataset,tinflection =5.33 Gyr.
We also consider situation when there is interaction between
dark energy-dark matter in order to see its effects on the potential and equation of state. Constant interaction rate is assumed here withδ=−0.03 from Guo et al. (2007b)corresponding to dark matter decaying into the scalar field. For
interaction case,tinflection =5.48 Gyr (WMAP5 dataset) and
tinflection =5.55 Gyr (WMAP5+BAO+SN dataset). The
interaction affects in lowering the height of scalar potential
and shifting the potential rightwards to later time (see Fig.1
and Table2). In this study, with closed geometry suggested
by WMAP5 data, the field equation of state does not match
the WMAP5 observation (wCDM model), i.e.w≈−1. Effects of interaction is in slightly lowering thewφvalue while
slightly lifting up the weighted effective equation of state
weff at earlier time. We found that the mass potential functionW(φ)of the interaction is approximately in form of exponential decay function.