Rich structure of CMB spectral distortions as a probe of new physics at high redshifts

Energy injected before recombination epoch at redshifts z < 2x 106 can cause deviations from blackbody spectrum in the cosmic microwave background (CMB). All previous work has assumed that the injected energy is deposited as heat in the ionized background baryon-photon plasma giving the characteristic non-relativistic thermal spectral distortions which at redshifts z < 104 are known as the Sunyaev-Zeldovich effect. I revisit this assumption and show that it is incorrect. I evolve the full electromagnetic particle cascade of high energy particles in the expanding universe. I will show that the full spectral distortion spectrum has a non-thermal component which depends on the energy of the injected particles and whether they are electrons, electron-positron pairs or photons. The shape of the spectral distortion carries more information about the energy-injection mechanisms than has been assumed until now.