Holographic Principle
AdS/CFT correspondence
AdS/CFT correspondence is a duality put forward by Juan Maldacena in 1997, which connects quantum gravity with conformal field theory such as Yang-Mills gauge theory. “AdS” means “anti-DeSitter spacetime”, and “CFT” means “conformal field theory”.
There are three main types of the dualities. Here we only discuss the typical one, namely, the case of D3 brane.
In this case, the type IIB superstring theory in 10-D AdS spacetime corresponding to N=4 super Yang-Mills gauge theory (a conformal field theory) on the 4-D boundary of AdS spacetime.
It connects quantum gravity theory (string theory) with gauge theory (SYM), thus the correspondence also named “gauge/gravity duality”, which is one significant discovery during Second Superstring Revolution.
There are three main types of the dualities. Here we only discuss the typical one, namely, the case of D3 brane.
In this case, the type IIB superstring theory in 10-D AdS spacetime corresponding to N=4 super Yang-Mills gauge theory (a conformal field theory) on the 4-D boundary of AdS spacetime.
It connects quantum gravity theory (string theory) with gauge theory (SYM), thus the correspondence also named “gauge/gravity duality”, which is one significant discovery during Second Superstring Revolution.
Fig.3.1 AdS/CFT correspondence and holographic principle
Holographic Principle
There is a famous formula about black hole entropy:
Based on that, we can see the entropy is directly proportional to the area of event horizon. According to Susskind’s idea, everything in 3-D space can be “encoded” completely by the 2-D “pixels” which is Planck scale.
The most important implication of holographic principle is that our 3-D space is only a “hologram” projected from 2-D boundary of universe. In other words, real world is on the boundary of universe, namely, a 2-D space.
The most important implication of holographic principle is that our 3-D space is only a “hologram” projected from 2-D boundary of universe. In other words, real world is on the boundary of universe, namely, a 2-D space.
Fig.3.2 Holographic principle implies the real world is 2-D, everything in 3-D space (including us) is only a “hologram” projected from 2-D world.
These theories stimulated the revolution of the concept of spacetime, and they are also the fields which people studied the most currently.