Emergence in Holographic Scenarios for Gravity

TL;DR

This paper reviews various holographic approaches in quantum gravity, analyzing their implications for the emergence of gravity and spacetime, and discusses whether these models support the idea of gravity as an emergent phenomenon.

Contribution

It provides a comparative analysis of holographic scenarios, highlighting that only Verlinde's approach straightforwardly supports emergence, while others may do so under different interpretations.

Findings

Verlinde's scheme directly supports emergence of gravity.

AdS/CFT may support emergence under non-standard interpretations.

Holography remains central to understanding quantum gravity.

Abstract

'Holographic' relations between theories have become an important theme in quantum gravity research. These relations entail that a theory without gravity is equivalent to a gravitational theory with an extra spatial dimension. The idea of holography was first proposed in 1993 by Gerard 't Hooft on the basis of his studies of evaporating black holes. Soon afterwards the holographic 'AdS/CFT' duality was introduced, which since has been intensively studied in the string theory community and beyond. Recently, Erik Verlinde has proposed that even Newton's law of gravitation can be related holographically to the `thermodynamics of information' on screens. We discuss these scenarios, with special attention to the status of the holographic relation in them and to the question of whether they make gravity and spacetime emergent. We conclude that only Verlinde's scheme straightfowardly instantiates emergence. However, assuming a non-standard interpretation of AdS/CFT may create room for the emergence of spacetime and gravity there as well.