The Holographic Universe

TL;DR

This paper critically reviews the holographic hypothesis, exploring its origins, implications, and the role of black holes in understanding quantum gravity and dualities across physics fields.

Contribution

It provides a comprehensive analysis of the holographic principle, its theoretical foundations, and discusses its impact and limitations in various physics disciplines.

Findings

Holographic principle links gravity and quantum field theories.

Black holes are central to understanding quantum gravity.

Holography has influenced multiple physics research areas.

Abstract

I give a critical review of the holographic hypothesis, which posits that a universe with gravity can be described by a quantum field theory in fewer dimensions. I first recall how the idea originated from considerations on black hole thermodynamics and the so-called information paradox that arises when Hawking radiation is taken into account. String Quantum Gravity tried to solve the puzzle using the AdS/CFT correspondence, according to which a black hole in a 5-D anti-de Sitter space is like a flat 4-D field of particles and radiation. Although such an interesting holographic property, also called gauge/gravity duality, has never been proved rigorously, it has impulsed a number of research programs in fields as diverse as nuclear physics, condensed matter physics, general relativity and cosmology. I finally discuss the pros and cons of the holographic conjecture, and emphasizes the key role played by black holes for understanding quantum gravity and possible dualities between distant fields of theoretical physics.