AdS/CFT Correspondence

In physics, the AdS/CFT correspondence (anti de Sitter/conformal field theory correspondence), sometimes called the Maldacena duality, is the conjectured equivalence between a string theory and gravity defined on one space, and a quantum field theory without gravity defined on the conformal boundary of this space, whose dimension is lower by one or more. The name suggests that the first space is the product of anti de Sitter space (AdS) with some closed manifold like sphere, orbifold, or noncommutative space, and that the quantum field theory is a conformal field theory (CFT).

An example is the duality between Type IIB string theory on AdS₅ × S5 space (a product of 5-dimensional AdS space with a 5-dimensional sphere) and a N=4 super Yang-Mills gauge theory (which is a conformal field theory) on the 4-dimensional boundary of AdS₅. It is the most successful realization of the holographic principle, a speculative idea about quantum gravity originally proposed by Gerard 't Hooft and improved and promoted by Leonard Susskind.

The AdS/CFT correspondence was originally proposed by Juan Maldacena in late 1997. Important aspects of the correspondence were given in articles by Steven Gubser, Igor Klebanov and Alexander Markovich Polyakov, and by Edward Witten. The correspondence has also been generalized to many other (non-AdS) backgrounds and their dual (non-conformal) theories. In about five years, Maldacena's article had 3000 citations and became one of the most important conceptual breakthroughs in theoretical physics of the 1990s, providing many new lines of research into both quantum gravity and quantum chromodynamics (QCD).