Études in holography

Thesis

The holographic principle posits that a higher–dimensional system with gravity can be fully described by a lower–dimensional “boundary” theory without gravity. This remarkable relationship has profound implications across physics, influencing fields from quantum gravity and black hole thermodynamics to condensed matter physics and quantum information. This thesis explores two specific problems within this broad domain.

The first part addresses the identification and counting of black hole microstates. Specifically, we study the non-supersymmetric, asymptotically flat 2d black hole through its dual c = 1 matrix quantum mechanics. Our central result is a novel bound state that dominates the partition function in the double-scaling limit, providing an explicit dual description of the black hole microstates.

The second part investigates open effective field theories of fermions interacting with holographic baths. After establishing the case for using holography in studying open effective field theories, we introduce the gravitational Schwinger–Keldysh saddle (grSK saddle). We then analyze Dirac fermions propagating in these backgrounds, demonstrating how this leads to Fermi-Dirac statistics in the boundary theory. Our analysis reveals that the holographic Schwinger-Keldysh boundary conditions naturally select a unique combination of modes consistent with fermionic KMS relations. Through evaluation of the bulk on-shell action using these solutions, we derive an explicit expression for the probe fermion’s influence phase in a gradient expansion. We conclude by extending the holographic Schwinger-Keldysh prescription to charged black branes, enabling the study of systems at both finite temperature and chemical potential.

Authors: Ray, K

• DOI: 10.5287/ora-r5emyqdgd
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: quantum gravity; holography; string theory; matrix models
• Subjects: Quantum field theory; Quantum gravity