Is Dynamical Dark Energy Necessary? DESI BAO and Modified Recombination

Abstract

Recent measurements of baryon acoustic oscillations (BAO) by the Dark Energy Spectroscopic Instrument (DESI) exhibit a mild-to-moderate tension with cosmic microwave background (CMB) and Type Ia supernova (SN) observations when interpreted within the $\Lambda$CDM framework. This discrepancy has been cited as evidence for dynamical dark energy (DDE). Given the profound implications of DDE for fundamental physics, we explore whether the tension can instead be resolved by modifying the physics of recombination. We find that a phenomenological model of modified recombination can effectively reconcile the BAO and CMB datasets and, unlike DDE, also predicts a higher Hubble constant $H_0$, thereby partially alleviating the Hubble tension. A global fit to BAO, CMB, and calibrated SN data favors modified recombination over DDE.

5 pages + appendix, 2 figures, minor revisions in V3, matches the version published in JCAP

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Cited by in corpus (9)

• SPT-3G D1: CMB temperature and polarization power spectra and cosmology from 2019 and 2020 observations of the SPT-3G Main field
• Sound-Horizon-Agnostic Inference of the Hubble Constant and Neutrino Mass from BAO, CMB Lensing, and Galaxy Weak Lensing and Clustering
• Evidence for evolving dark energy from DESI DR2 BAO and Pantheon${}^{+}$, DES-Dovekie, and Union3
• Comparing measures of the Hubble and BAO tensions in $\Lambda$CDM and possible solutions in $f(Q)$ gravity
• Addressing the DESI DR2 Phantom-Crossing Anomaly and Enhanced $H_0$ Tension with Reconstructed Scalar-Tensor Gravity
• Lowering the Horizon on Dark Energy: A Late-Time Response to Early Solutions for the Hubble Tension
• Constraints on the gravitational potential from DESI DR2 BAO and its implications for the local void scenario
• Sound Mode and Scale-Dependent Growth in Two-Fluid Dynamical Dark Energy
• In-depth analysis of the clustering of dark matter particles around primordial black holes. Part III: CMB constraints