Decoding infrared imprints of quantum origins of black holes

We analyze the emission spectrum of a (fundamentally quantum) black hole in Kerr-Newman family in a class of quantum gravity theories where the geometry gets quantized and the holographic area entropy relation is obeyed, as prescribed by Bekenstein and Hawking. We demonstrate that, given the above structure of black hole entropy, a macroscopic black hole always has non-continuously separated mass states and therefore they descend down in discrete manner. This discreteness can belong to either of two permissible classes if semiclassical physics and the laws of black hole thermodynamics are to emerge out from the quantum theory at the macroscopic level. We evaluate the step size in both these cases. Such a computation reveals an interesting relation, in each class, between the dynamic and kinematic length scales for all black holes belonging to the Kerr-Newman family, pointing towards a possible universal character across the class, dependent only on black hole mass. This relation is basically made out of low energy parameters associated with a macroscopic black hole, but also reveals the parameters involved in the ultraviolet theory of it. Further, one can compute the maximal number of quanta a macroscopic black hole could emit before turning into a Planck sized remnant or a zero temperature object with extremal character, which in turn can be used to estimate the lifetime a black hole. We also argue the independence of these features from the spacetime dimensions.