Understand
Recent results from Type Ia supernovae (SNe Ia) and baryon acoustic oscillations (BAO), in combination with cosmic microwave background (CMB) measurements, have focused renewed attention on dark energy models with a time-varying equation-of-state parameter, $w(z)$.
- In this paper, we describe the simplest, physically motivated models of evolving dark energy that are consistent with the recent data, a broad subclass of the so-called thawing scalar field models that we dub $w_\phi$CDM.
- We provide a quasi-universal, quasi-one-parameter functional fit to the scalar-field $w_\phi(z)$ that captures the behavior of these models more informatively than the standard $w_0w_a$ phenomenological parametrization; their behavior is completely described by the current value of the equation-of-state parameter, $w_0=w(z=0)$.
- Combining current data from BAO (DESI Data Release 2), the CMB (Planck and ACT), large-scale structure (DES Year-3 $3\times2$pt), SNe Ia (DES-SN5YR), and strong lensing (TDCOSMO + SLACS), for $w_\phi$CDM we obtain $w_0=-0.904_{-0.033}^{+0.034}$, 2.9$\sigma$ discrepant from the $\Lambda$ cold dark matter ($\Lambda$CDM) model.