Background of radio photons from primordial black holes

We compute the isotropic radiation background due to the radio emission from gas accretion onto supermassive primordial black holes (PBHs). We find that these PBHs can readily produce radio background explaining not only the magnitude but also the power-law index of the excess radio background observed by the ARCADE2 and LWA1 experiments at frequencies less than similar to 1 GHz. To estimate the radio luminosity of a single accreting black hole we use the empirical relation known as the fundamental plane of black hole activity which connects the luminosity in the radio band to the X-ray band and the mass of black hole. The synchrotron mechanism of relativistic jets and the first-order Fermi acceleration mechanism in shocks support the power-law index observed by ARCADE2/LWA1 experiments.