The fundamental constituents of black holes: structure alongside chaos

Objective

Black holes provide an ideal testing ground for any theory of quantum gravity, a unified framework that combines General Relativity and Quantum Mechanics. String Theory, our best candidate for such a theory, has successfully passed many demanding tests in black-hole physics. Yet the exact nature of the fundamental constituents — the microstates — of black holes remains unresolved. Do individual microstates already contain an event horizon, from which nothing can escape, or does the horizon emerge only as a collective, thermodynamic feature? This project aims to resolve these tensions by studying both the individual and collective properties of black-hole microstates. It will proceed along three complementary research routes: (i) determine whether the most generic microstates in string theory are individually smooth geometries that resemble black holes from afar but differ near the horizon; (ii) investigate under what conditions black holes can be composed of highly excited strings or brane bound states; and (iii) apply statistical and quantum-chaos diagnostics to known microstates to identify the ensemble properties they must satisfy. Together, these approaches will provide decisive insights into the microscopic structure of black holes, clarify whether horizons are fundamental or emergent, and advance our broader understanding of quantum gravity.