Holography from number theory: Emergent holographic AdS$_2$ space-time from exact BPS black hole microstate counting

Abstract

In this note, starting from the exact counting formulae for 4D BPS black hole degeneracies in the cases of 1/2 BPS $\mathcal{N}=4$ and 1/8 BPS $\mathcal{N}=8$ solutions, expressed as Rademacher expansions for coefficients of modular and Jacobi forms respectively, we explicitly show how the number theoretic data in each Rademacher summand is encoded by a Segal-Bargmann heat kernel calculation in the de Alfaro-Fubini-Furlan (DFF) model of conformal quantum mechanics, thus demonstrating the holographic origin of the BPS Bekenstein-Hawking entropy, and all logarithmic and power law suppressed corrections to it. We then derive the 2D holographically dual bulk space-time for this CQM and show that it is an AdS$_2$ space-time with radial length scale correlated to the energy scale of the DFF model. We further show how the Bekenstein-Hawking entropy emerges from an entanglement entropy computation in this bulk space-time. Hence, for the two classes of 4D BPS black holes under consideration, we have inferred the holographic CQM relevant for microscopic state counting from the exact number-theoretic degeneracy formulae and demonstrated the emergence of the near-horizon AdS$_2$ attractor geometry that is holographically dual to it.