Cosmological constraint on light particles

We are now entering the era of precision cosmology. Astrophysical and cosmological tests can be done at high precision to constrain physics beyond standard model. We make inferences on the running of the primordial perturbations spectral index and the effective number of neutrinos in the early universe and show an important statistical degeneracy in their posterior distributions. We calculate the cosmic birefringence spectrum due to a PNGB which may cause early dark energy, showing that the typical acoustic oscillations appear in this spectrum as well.