Quantum Gravity / String Theory

Quantum Gravity (QG) explores gravitational physics at small length scales where quantum effects become significant. Neither General Relativity (GR) nor Quantum Field Theory (QFT) can accurately describe such physics. Currently, string theory stands as the most promising candidate for a theory of QG. Therefore, it is imperative to delve into string theory and comprehend its physical implications.

Holography

Holographic duality offers a remarkable approach to investigating string theory as a framework for QG. According to holographic duality, a certain string theory on a (d+1)-dimensional Anti-de Sitter (AdS) space accompanied by a (9-d)-dimensional internal manifold becomes equivalent to a d-dimensional Conformal Field Theory (CFT) living on the conformal boundary of the AdS space; thus, holographic duality is also known as the AdS/CFT correspondence. Building upon this duality, we explore the physics of strings propagating around an AdS space by utilizing its dual CFT, which represents one of the most concrete avenues for studying string theory as a theory of QG. In this context, we investigate various intriguing topics such as SuperConformal Field Theories (SCFT), supersymmetric localization, large N expansions, non-perturbative physics, supergravities, black holes/strings, etc.