Physical vs phantom dark energy after DESI: thawing quintessence in a curved background

Recent data from DESI, in combination with other data, provide moderate evidence of dynamical dark energy, $w$ ≠ −1. In the $w$0, $w$a parametrization of $w$, there is a preference for a phantom crossing, $w$ < −1, at redshift $z$ ∼ 0.5. In general relativity, the phantom equation of state is unphysical. Thus it is important to check whether phantom crossing is present in other physically self-consistent models of dark energy that have equivalent evidence to the $w$0, $w$a parametrization. We find that thawing quintessence with nonzero cosmic curvature can fit the recent data as well as $w$0, $w$a in a flat background, based on both parametric and realistic scalar field evolutions. Although the realistic model does not allow $w$ < −1, the parametrizations do allow it. However even if we allow $w$ < −1 the data do not enforce phantom crossing. Thus, the phantom crossing is an artifact of a parametrization that is not based on a physical model.