Hamiltonian approach to near-extremal black hole evaporation and backreaction

We investigate radiation from near-extremal black holes formed by collapse, focusing on the role of large backreaction effects arising from gravitational fluctuations in the near-horizon region. Such effects have previously been identified from computations based on JT gravity and its Schwarzian description, most notably for the Euclidean partition function. Restricting attention to the s-wave sector, we integrate out gravity by solving the constraint equations in the Hamiltonian formalism, obtaining an effective scalar action with a coupling that grows at low temperature, thus enabling a real-time treatment of quantum backreaction. We then take initial steps toward evaluating the impact of this interaction on correlations of the outgoing radiation, and compare our findings with earlier results.