Constraints on Early Dark Energy from Isotropic Cosmic Birefringence

Area of Science:

• Cosmology
• Particle Physics

Background:

• Cosmic Microwave Background (CMB) polarization is sensitive to parity-violating new physics.
• Early Dark Energy (EDE) models with axionlike fields offer solutions to the Hubble tension.
• Photon-axion coupling in EDE models predicts specific CMB polarization patterns.

Purpose of the Study:

• To test the EDE model with a specific potential V(ϕ)∝[1-cos(ϕ/f)]^{3} using Planck CMB polarization data.
• To constrain the photon-axion coupling constant (g) within the EDE framework.
• To explore implications for fundamental physics, including string theory.

Main Methods:

• Fitting the predicted EB power spectrum from the EDE model to Planck polarization data.
• Analyzing the cross-correlation power spectrum of E- and B-mode polarization fields.
• Deriving constraints on the photon-axion coupling constant, independent of instrumental effects and foregrounds.

Main Results:

• The unique EB power spectrum predicted by the EDE model is not favored by the Planck data.
• A first constraint on the photon-axion coupling constant was obtained: g=(0.04±0.16)M_{Pl}^{-1} (68% C.L.).
• The constraint applies to the EDE model that best fits CMB and galaxy clustering data.

Conclusions:

• The tested EDE model is disfavored by current CMB polarization observations.
• The derived limit on the photon-axion coupling constant has significant implications for theoretical physics.
• This research provides valuable insights into early universe physics and potential extensions to the Standard Model.