Oscillating scalar fields and the Hubble tension: A resolution with novel signatures

By Tristan L. Smith, V. Poulin, M. Amin. Physical Review D, 2019

212 citations recorded by the source corpus.

We present a detailed investigation of a subdominant oscillating scalar field [“early dark energy” (EDE)] in the context of resolving the Hubble tension. Consistent with earlier work, but without relying on fluid approximations, we find that a scalar field frozen due to Hubble friction until log10(zc)∼3.5, reaching ρEDE(zc)/ρtot∼10% and diluting faster than matter afterwards, can bring cosmic microwave background (CMB), baryonic acoustic oscillations, supernovae luminosity distances, and the late-time estimate of the Hubble constant from the SH0ES Collaboration into agreement. A scalar field potential that scales as V(ϕ)∝ϕ2n with 2≲n≲3.4 around the minimum is preferred at the 68% confidence level, and the Planck polarization places additional constraints on the dynamics of perturbations in the scalar field. In particular, the data prefer a potential that flattens at large field displacements. A Markov-chain Monte Carlo analysis of mock data shows that the next-generation CMB observations (i.e., CMB-S4) can unambiguously detect the presence of the EDE at a very high significance. This projected sensitivity to the EDE dynamics is mainly driven by improved measurements of the E-mode polarization. We also explore new observational signatures of EDE scalar field dynamics: (i) We find that depending on the strength of the tensor-to-scalar ratio, the presence of the EDE might imply the existence of isocurvature perturbations in the CMB. (ii) We show that a strikingly rapid, scale-dependent growth of EDE field perturbations can result from parametric resonance driven by the anharmonic oscillating field for n≈2. This instability and ensuing potentially nonlinear, spatially inhomogeneous, dynamics may provide unique signatures of this scenario.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/9611144a01027ff654c9cf91c01dee592eabe816

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Citations in the corpus

The Ups and Downs of Early Dark Energy solutions to the Hubble tension: A review of models, hints and constraints circa 2023 (2023, background): “where $ is the angular frequency of the oscillating background field and is well-approximated by [76, 116, 155]”
Cosmology Intertwined II: The Hubble Constant Tension (2020, unknown): “[96] T.”
Constraining early dark energy with large-scale structure (2020, methodology): “It has been suggested [27, 46] that the null results of searches for EDE in combined data sets that do not include the SH0ES measurement are due to a failure of the Metropolis-Hastings algorithm to explore the EDE parameter space, stemming from parameter degeneracies that emerge in the ΛCDM limit, f”
Early dark energy does not restore cosmological concordance (2020, methodology): “…(Hill et al. (2020)).5 CLASS EDE solves for the evolution of the scalar field perturbations directly using the perturbed Klein–Gordon equation (as in, e.g., Agrawal et al. (2019) and Smith et al. (2020)), avoiding the effective fluid description used in some past works (e.g., Poulin et al. (2019)).”
The Hubble tension in light of the Full-Shape analysis of Large-Scale Structure data (2020, methodology): “6 Two particularly popular models are the so-called Early Dark Energy model (EDE) [62, 63] and the Rock ’n’ Roll (RnR) model [64], that use a scalar field to inject energy in the early universe, raising the inferred value of H0 from CMB and LSS measurements.”