Multitrace Deformations of Vector and Adjoint Theories and their Holographic Duals

TL;DR

This paper develops methods to analyze multitrace deformations in conformal theories with holographic duals, exploring their instabilities, phase structures, and implications for string theory and UV completions.

Contribution

It introduces general techniques for studying multitrace deformations in holographic conformal theories and examines their effects on stability and phase diagrams.

Findings

Multitrace deformations can induce instabilities in AdS and boundary CFTs.

A phase diagram for large-N marginal deformations shows an IR limit with a single O(N) singlet.

A toy model demonstrates how UV completion can resolve boundary theory instabilities.

Abstract

We present general methods to study the effect of multitrace deformations in conformal theories admitting holographic duals in Anti de Sitter space. In particular, we analyse the case that these deformations introduce an instability both in the bulk AdS space and in the boundary CFT. We also argue that multitrace deformations of the O(N) linear sigma model in three dimensions correspond to nontrivial time-dependent backgrounds in certain theories of infinitely many interacting massless fields on AdS_4, proposed years ago by Fradkin and Vasiliev. We point out that the phase diagram of a truly marginal large-N deformation has an infrared limit in which only an O(N) singlet field survives. We draw from this case lessons on the full string-theoretical interpretation of instabilities of the dual boundary theory and exhibit a toy model that resolves the instability of the O(N) model, generated by a marginal multitrace deformation. The resolution suggests that the instability may not survive in an appropriate UV completion of the CFT.