Probing early modification of gravity with Planck, ACT and SPT

Abstract

AbstractWe consider a model of early modified gravity (EMG) that was recently proposed as a candidate to resolve the Hubble tension. The model consists of a scalar fieldσwith a nonminimal coupling (NMC) to the Ricci curvature of the formF(σ) = Mpl2+ξσ2and an effective mass induced by a quartic potentialV(σ) = λσ4/4. We present the first analyses of the EMG model in light of the latest ACT DR4 and SPT-3G data in combination with fullPlanckdata, and find a ≳ 2σ preference for a non-zero EMG contribution from a combination of primary CMB data alone, mostly driven by ACT-DR4 data. This is different from popular `Early Dark Energy' models, which are detected only when the high-ℓ information fromPlancktemperature is removed. We find that the NMC plays a key role in controlling the evolution of density perturbations that is favored by the data over the minimally coupled case. Including measurements of supernovae luminosity distance from Pantheon+, baryonic acoustic oscillations and growth factor from BOSS, and CMB lensing ofPlanckleaves the preference unaffected. In the EMG model, the tension with SH0ES is alleviated from ∼ 6σto ∼ 3σ. Further adding SH0ES data raises the detection of the EMG model above 5σ.