Enhanced Correlations in Hawking Radiation from Near-Extremal Collapse

Abstract

We consider the formation of a near-extremal Reissner-Nordstrom black hole by collapse, and show how to compute correlations in the outgoing Hawking radiation due to enhanced gravitational backreaction effects in the near-horizon region. This is done by reducing to the s-wave and employing the Hamiltonian formulation of Einstein-Maxwell theory coupled to a scalar field. Solving the constraints yields an action for the scalar field that incorporates gravitational backreaction effects at the quantum level, governed by an effective coupling g = G/(πr_0^3 T_H) that grows at low temperature, as in recent Schwarzian-based analyses. This action produces corrections to the free field Hawking state which are imprinted on correlation functions of the Hawking radiation measured at null infinity. As part of our analysis, we show that this action evaluated in the AdS_2 region is equivalent, at the level of all tree-level boundary correlators, to the standard JT/Schwarzian description coupled to dressed bilocal operators. We also reproduce some one-loop results. In our approach, metric fluctuations are included quantum mechanically through the reduced scalar action, rather than through a semiclassical expectation value, and our computation of the radiation manifestly reduces to Hawking's original treatment when metric fluctuations are neglected.