Atacama Cosmology Telescope: Constraints on prerecombination early dark energy

J. Colin Hill, Erminia Calabrese, Simone Aiola, Nicholas Battaglia, Boris Bolliet, Steve K. Choi, Mark J. Devlin, Adriaan J. Duivenvoorden, Jo Dunkley, Simone Ferraro, Patricio A. Gallardo, Vera Gluscevic, Matthew Hasselfield, Matt Hilton, Adam D. Hincks, Renée HloŽek, Brian J. Koopman, Arthur Kosowsky, Adrien La Posta, Thibaut LouisMathew S. Madhavacheril, Jeff McMahon, Kavilan Moodley, Sigurd Naess, Umberto Natale, Federico Nati, Laura Newburgh, Michael D. Niemack, Lyman A. Page, Bruce Partridge, Frank J. Qu, Maria Salatino, Alessandro Schillaci, Neelima Sehgal, Blake D. Sherwin, Cristóbal Sifón, David N. Spergel, Suzanne T. Staggs, Emilie R. Storer, Alexander Van Engelen, Eve M. Vavagiakis, Edward J. Wollack, Zhilei Xu

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60 Scopus citations


The early dark energy (EDE) scenario aims to increase the value of the Hubble constant (H0) inferred from cosmic microwave background (CMB) data over that found in the standard cosmological model (ΛCDM), via the introduction of a new form of energy density in the early Universe. The EDE component briefly accelerates cosmic expansion just prior to recombination, which reduces the physical size of the sound horizon imprinted in the CMB. Previous work has found that nonzero EDE is not preferred by Planck CMB power spectrum data alone, which yield a 95% confidence level (C.L.) upper limit fEDE<0.087 on the maximal fractional contribution of the EDE field to the cosmic energy budget. In this paper, we fit the EDE model to CMB data from the Atacama Cosmology Telescope (ACT) data release 4. We find that a combination of ACT, large-scale Planck TT (similar to WMAP), Planck CMB lensing, and BAO data prefers the existence of EDE at >99.7% C.L.: fEDE=0.091-0.036+0.020, with H0=70.9-2.0+1.0 km/s/Mpc (both 68% C.L.). From a model-selection standpoint, we find that EDE is favored over ΛCDM by these data at roughly 3σ significance. In contrast, a joint analysis of the full Planck and ACT data yields no evidence for EDE, as previously found for Planck alone. We show that the preference for EDE in ACT alone is driven by its TE and EE power spectrum data. The tight constraint on EDE from Planck alone is driven by its high-ℓ TT power spectrum data. Understanding whether these differing constraints are physical in nature, due to systematics, or simply a rare statistical fluctuation is of high priority. The best-fit EDE models to ACT and Planck exhibit coherent differences across a wide range of multipoles in TE and EE, indicating that a powerful test of this scenario is anticipated with near-future data from ACT and other ground-based experiments.

Original languageEnglish (US)
Article numbere123536
JournalPhysical Review D
Issue number12
StatePublished - Jun 15 2022

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics


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