AdS/CFT, Multitrace Deformations and New Instabilities of Nonlocal String Theories

We study "multitrace" deformations of large $N$ master fields in models with a mass gap. In particular, we determine the conditions for the multitrace couplings to drive tachyonic instabilities. These tachyons represent new local instabilities of the associated nonlocal string theories. In the particular case of Dp-branes at finite temperature, we consider topology-changing phase transitions and the effect of multitrace perturbations on the corresponding phase diagrams.