Holographic Principle

CORE DEFINITION

The holographic principle is a property of string theory and a conjectured quantum gravity, describing that the properties of a space can be encoded on its boundary, such as the light-like boundary of an event horizon. The holographic principle was first proposed by Gerard 't Hooft. Later, Leonard Susskind derived a string theory version of the holographic principle, combining the work of 't Hooft and Charles Thorn. The AdS/CFT correspondence proposed by Juan Maldacena in 1997 is a specific instance of the holographic principle. Raphael Bousso noted that Thorn's 1978 proposal that a low-dimensional description of string theory could naturally give rise to gravity is a result of the holographic principle. The holographic principle suggests that the universe we currently observe is a projection of the real universe. From a more macroscopic perspective, this principle indicates that the entire universe can be viewed as a two-dimensional information structure presented on the cosmological horizon, while the three-dimensional space we observe daily is a macroscopic, low-energy effective description. It is worth noting that the cosmological holographic principle has not yet been mathematically precise. The holographic principle was inspired by black hole thermodynamics, which suggests that the maximum entropy of any region is proportional to the square of its radius, not the cube.