Free Large N Supersymmetric Yang-Mills Theory as a String Theory
Parviz Haggi-Mani, Bo Sundborg
TL;DR
The authors investigate the conjectured AdS/CFT duality in the zero-tension limit by analyzing the spectrum and correlation structure of free N=4 SYM, treating single- and multi-trace operators as string bits. They show that operator dimensions remain N-independent at $\lambda=0$, while 1/N effects mix states and yield a nontrivial interacting theory with features resembling string interactions, including a CFT realization of crossing symmetry and a duality structure among amplitudes. The work reveals a rich set of marginal/relevant primaries and unexpectedly massless spin-2 candidates, suggesting a complex landscape of backgrounds even in the tensionless regime. Overall, the paper provides indirect but concrete evidence that free gauge theory data can define a consistent, interacting string theory in AdS5×S5, via OPE-driven vertices and duality relations.
Abstract
The strong version of Maldacena's AdS/CFT conjecture implies that the large N expansion of free N=4 super-YM theory describes an interacting string theory in the extreme limit of high spacetime curvature relative to the string length. String states may then be understood as composed of SYM string bits. We investigate part of the low-lying spectrum of the tensionless (zero-coupling) limit and find a large number of states that are not present in the infinite tension (strong-coupling) limit, notably several massless spin two particles. We observe that all conformal dimensions are N-independent in the free SYM theory, implying that masses in the corresponding string theory are unchanged by string interactions. Degenerate string states do however mix in the interacting string theory because of the complicated N-dependence of general CFT two-point functions. Finally we verify the CFT crossing symmetry, which corresponds to the dual properties of string scattering amplitudes. This means that the SYM operator correlation functions define AdS dual models analogous to the Minkowski dual models that gave rise to string theory.
