Degenerate Stars and Gravitational Collapse in AdS/CFT

TL;DR

The paper builds a holographic description of degenerate fermionic matter in AdS, mapping a large-N, zero-temperature Fermi gas in the bulk to degenerate multi-trace boundary operators. It first treats the free (non-interacting) limit to obtain a hydrostatic, Fermi-gas star whose radius and mass match boundary expectations, then introduces gravitational backreaction via a bulk TOV framework and a double-scaling limit in which backreaction remains finite. A Chandrasekhar-type mass limit emerges, signaling instability toward gravitational collapse to a black hole, with a boundary interpretation as a high-density deconfinement transition. The authors also extend the analysis to charged and thermal stars, discuss boundary CFT implications through graviton exchange, and address validity and embedding in string/M-theory contexts. Collectively, the work links bulk macroscopic fermionic stars to boundary operator dynamics, providing a fertile ground for understanding holographic collapse and deconfinement phenomena.

Abstract

We construct composite CFT operators from a large number of fermionic primary fields corresponding to states that are holographically dual to a zero temperature Fermi gas in AdS space. We identify a large N regime in which the fermions behave as free particles. In the hydrodynamic limit the Fermi gas forms a degenerate star with a radius determined by the Fermi level, and a mass and angular momentum that exactly matches the boundary calculations. Next we consider an interacting regime, and calculate the effect of the gravitational back-reaction on the radius and the mass of the star using the Tolman-Oppenheimer-Volkoff equations. Ignoring other interactions, we determine the "Chandrasekhar limit" beyond which the degenerate star (presumably) undergoes gravitational collapse towards a black hole. This is interpreted on the boundary as a high density phase transition from a cold baryonic phase to a hot deconfined phase.

Figures (26)

• Figure 1: Tree level gravitational interaction between two fermions.
• Figure 2: 2-body, 3-body etc. interactions at tree level and higher loop interactions.
• Figure 3: Radial profile of the local chemical potential with (solid line) and without gravitational backreaction (dashed line).
• Figure 4: Fermion number density, with and without backreaction.
• Figure 5: Mass function with and without backreaction. The limiting value as $r/\ell\rightarrow\infty$ is the total mass $M$ of the system.