One loop determinant in the extremal black hole from quasinormal modes
Jyotirmoy Mukherjee
TL;DR
This work computes the one-loop determinant for a scalar field in the near-horizon geometry of extremal RN black holes using the Denef–Hartnoll–Sachdev (DHS) prescription, and verifies that the logarithmic divergence matches the heat-kernel result. It then extends the DHS method to near-extremal Kerr–Newman black holes, showing that at a specific horizon angular velocity $\Omega = 2\pi T$, the finite-temperature determinant reduces to the extremal RN result in AdS$_2\times$S$^2$. For higher-spin fields, the authors identify horizon-regularity constraints that remove certain modes, leading to distinct logarithmic contributions (e.g., the vector case). Overall, the paper demonstrates a universal structure of quantum corrections governed by the near-horizon AdS$_2$ dynamics and establishes a coherent DHS-based framework for scalars, vectors, and potential future extensions to higher spins.
Abstract
In this paper, we evaluate the one-loop partition function of a scalar field in the near-horizon geometry of the extremal Reissner Nordström black hole from an infinite product over quasinormal modes using the Denef-Hartnoll-Sachdev (DHS) formula. We show that the logarithmic divergent term of the one-loop partition function computed using the DHS formula agrees with the heat kernel method. Using the same formula, we also evaluate the one-loop partition function of a scalar field in the near-extremal Kerr-Newman black hole and observe that it reduces to the same in the near-horizon $AdS_2\times S^2$ geometry of the extremal Reissner Nordström black hole when the angular velocity at the horizon is tuned to $2πT_{BH}$ value. We observe that, for higher spin fields, the mode functions are not smooth at the horizon for certain quasinormal frequencies; therefore, we remove them to obtain the one-loop determinant.
