Scant evidence for thawing quintessence

New constraints on the expansion rate of the Universe seem to favor evolving dark energy in the form of thawing quintessence models, i.e., models for which a canonical, minimally coupled scalar field has, at late times, begun to evolve away from potential energy domination. We scrutinize the evidence for thawing quintessence by exploring what it predicts for the equation of state. We show that, in terms of the usual Chevalier-Polarski-Linder parameters, (w0, wa), thawing quintessence is, in fact, only marginally consistent with a compilation of the current data. Despite this, we embrace the possibility that thawing quintessence is dark energy and find constraints on the microphysics of this scenario. We do so in terms of the effective mass m2 and energy scale V0 of the scalar field potential. We are particularly careful to enforce uninformative, flat priors on these parameters so as to minimize their effect on the final posteriors. While the current data favors a large and negative value of m2, when we compare these models to the standard ΛCDM model we find that there is scant evidence for thawing quintessence. Published by the American Physical Society 2024