Thawing quintessence and transient cosmic acceleration in light of DESI

Recent analysis of the DESI Collaboration challenges the $\mathrm{\ensuremath{\Lambda}}$-cold dark matter ($\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$) model, suggesting evidence for a dynamic dark energy. These results are obtained in the context of generic parametrizations of the dark energy equation of state (EoS), which better fit the data when they exhibit an unphysical phantom behavior in the past. In this paper, we briefly analyze how ambiguous this latter conclusion can be in light of the background degeneracy between EoS parametrizations and minimally coupled quintessence scenarios. We then investigate whether the current observational data can be accommodated with a non-phantom, thawing dark energy EoS, typical of a broad class of quintessence models. We show that the thawing behavior of this EoS performs comparably to the Chevallier-Polarski-Linder parametrization and is statistically competitive with $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ while predicting cosmic acceleration as a transient phenomenon. Such a dynamic behavior aligns with theoretical arguments from string theory and offers a way out of the trans-Planckian problem that challenges the ever-accelerated $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ paradigm.