On a possible nonequilibrium imprint in the cosmic background at low frequencies

Abstract

The cosmic background radiation has been observed to deviate from the Planck law expected from a blackbody at $\sim$ 2.7 K at frequencies below $\sim 3$ GHz. We discuss the abundance of the low-energy photons from the perspective of nonequilibrium statistical mechanics. We propose a mechanism of stochastic frequency-diffusion, the counterpart to stochastic acceleration for charged particles in a turbulent plasma, to modify the standard Kompaneets equation. The resulting violation of the Einstein relation allows to take advantage of low-frequency localization and finally leads to photon cooling. The new equation predicts a frequency distribution in agreement with the absolute temperature measurements of the cosmic background radiation down to about 20 MHz, for which we offer here an updated compilation. In that sense, the so called 'space roar' we observe today is interpreted as a nonequilibrium echo of the early universe, and of nonequilibrium conditions in the primordial plasma more specifically.

14 pages, 3 figures, 1 table. Figure 2 replaced to fix a mistake due to an exchange of files: the printed version is now accompanied by an Erratum

References in corpus (5)

• The contribution of the Unresolved Extragalactic Radio Sources to the Brightness Temperature of the sky
• TRIS II: search for CMB spectral distortions at 0.60, 0.82 and 2.5 GHz
• Effective temperatures of hot Brownian motion
• Cosmic backgrounds due to the formation of the first generation of supermassive black holes
• Avalanche Photon Cooling by Induced Compton Scattering: Higher-Order Kompaneets Equation

Cited by in corpus (6)

• Coexistence of ballistic and Fourier regimes in the $\beta$-FPUT lattice
• Frequency-redshift relation of the Cosmic Microwave Background
• Active velocity processes with suprathermal stationary distributions and long-time tails
• Effects of observer peculiar motion on the isotropic background frequency spectrum: from monopole to higher multipoles
• Resetting photons
• Photon frequency diffusion process