Dark energy after pre-recombination early dark energy in light of DESI DR2 and the latest ACT and SPT data

TL;DR

The paper investigates how pre-recombination Early Dark Energy (EDE) affects inferences about a time-varying dark energy equation of state in the presence of cosmological tensions. Using DESI DR2, ACT DR6, SPT-3G D1, Planck, Pantheon, and SH0ES data within $w_0w_a$CDM+EDE models (axion-like EDE and AdS-EDE), it finds that the evidence for evolving DE is substantially reduced to ≲$2\sigma$, while a quintessence-like component with $w_0+w_a\geq-1$ can still be ~1$\sigma$ consistent. The inclusion of SH0ES strengthens the reported $\Delta\chi^2$ improvements over the non-EDE case, with substantial gains in fit when EDE is included. The results imply that addressing the Hubble tension can alter the inferred nature of dark energy, potentially favoring a canonical evolving scalar field or a cosmological constant, and highlight the need to re-examine DE under the broader context of cosmological tensions. Additionally, the analysis suggests $n_s=1$ may be favored in this framework, with implications for inflationary models.

Abstract

It has been noted that with the pre-recombination early dark energy (EDE) resolution of Hubble tension, the preference of recent datasets for the evolving dark energy (DE) can be suppressed significantly. In this work, we clarify and reconfirm this result with DESI DR2 and the latest ACT DR6 and SPT-3G D1, the tightest small-scale CMB constraints up to date. In the $w_0w_a$CDM model with EDE, a quintessence-like component ($w_0+w_a\geq-1$) can be 1$σ$ consistent with Planck+ACT+SPT+DESI+Pantheon+SH0ES datasets, and $Δχ^2\lesssim -14$ compared with $w_0w_a$CDM model without EDE. This reveals the possibility that when the potential resolutions of Hubble tension are considered, current accelerated expansion can attribute to a canonical evolving scalar field or cosmological constant, and again highlights the importance of re-examining the nature of DE within the broader context of cosmological tensions.

Figures (3)

• Figure 1: 2D contours of the primary parameters at 68% and 95% CL for the $w_0w_a$CDM+axionlike EDE model.
• Figure 2: 2D contours of the primary parameters at 68% and 95% CL for the $w_0w_a$CDM+AdSEDE model.
• Figure 3: 2D contours of the $w_0-w_a$ parameters at 68% and 95% CL for the $w_0w_a$CDM+EDE models. The inclined dashed grey lines depict the phantom-divided bound. It can be seen that with AdS-EDE the quintessence model without the phantom-divided crossing can be still $\sim 1\sigma$ consistent.