Green's function of the cosmological thermalization problem – II. Effect of photon injection and constraints

The energy spectrum of the cosmic microwave background (CMB) provides a powerful tool for constraining standard and non-standard physics in the primordial Universe. Previous studies mainly highlight spectral distortions (mu-, y- and r-type) created by episodes of early energy release; however, several processes also lead to copious photon production, which requires a different treatment. Here, we carry out a first detailed study for the...