Resolving the Negative Effective Neutrino Mass Parameter with Cosmic Birefringence

Area of Science:

• Cosmology
• Particle Physics

Background:

• The standard ΛCDM model faces tensions between baryonic acoustic oscillations (DESI) and cosmic microwave background (CMB) observations.
• These tensions suggest lower neutrino mass or higher optical depth (τ), conflicting with existing data.

Purpose of the Study:

• To investigate cosmic birefringence as a resolution to cosmological tensions.
• To explore how axionlike particle-induced birefringence affects cosmological parameters.

Main Methods:

• Analyzing the phase ambiguity of cosmic birefringence angles (β = β₀ + 180n degrees).
• Modeling the effect of birefringence on the reionization bump and CMB polarization spectra.
• Identifying parameter spaces consistent with DESI, CMB, and Planck data.

Main Results:

• Cosmic birefringence with a nonzero integer 'n' suppresses the reionization bump.
• This suppression allows for a higher optical depth (τ) consistent with CMB polarization data.
• A viable parameter space exists where birefringence resolves tensions in low-ℓ polarization spectra and Planck EB correlations.

Conclusions:

• Cosmic birefringence offers a potential solution to current cosmological tensions.
• Axionlike particles inducing birefringence play a significant role in reconciling observational data.
• Further investigation into cosmic birefringence is warranted for a complete cosmological model.