Future constraints on variations of the fine structure constant from combined CMB and weak lensing measurements

TL;DR

This paper forecasts how future CMB and galaxy lensing surveys can improve constraints on variations of the fine structure constant, highlighting potential degeneracies with other cosmological parameters.

Contribution

It demonstrates that lensing data from satellite experiments like Euclid can significantly tighten constraints on , and discusses degeneracies affecting parameter estimation.

Findings

Lensing data could improve  constraints to 8^{-4} accuracy.

Degeneracies with H_0 and n_s can bias parameter estimates if  varies by ~0.5%.

Future surveys can better constrain or detect variations in .

Abstract

We forecast the ability of future CMB and galaxy lensing surveys to constrain variations of the fine structure constant. We found that lensing data, as those expected from satellite experiments as Euclid could improve the constraint from future CMB experiments leading to a \Delta \alpha / \alpha = 8*10^{-4} accuracy. A variation of the fine structure constant \alpha is strongly degenerate with the Hubble constant H_0 and with inflationary parameters as the scalar spectral index n_s. These degeneracies may cause significant biases in the determination of cosmological parameters if a variation in \alpha as large as \sim 0.5 % is present at the epoch of recombination.