Notes on relevant, irrelevant, marginal and extremal double trace perturbations

Massimo Porrati, Cedric C.Y. Yu

    Research output: Contribution to journalArticlepeer-review


    Double trace deformations, that is products of two local operators, define perturbations of conformal field theories that can be studied exactly in the large-N limit. Even when the double trace deformation is irrelevant in the infrared, it is believed to flow to an ultraviolet fixed point. In this note we define the Källen-Lehmann representation of the two-point function of a local operator O in a theory perturbed by the square of such operator. We use such representation to discover potential pathologies at intermediate points in the flow that may prevent to reach the UV fixed point. We apply the method to an “extremal” deformation that naively would flow to a UV fixed point where the operator O would saturate the unitarity bound Δ=d2−1. We find that the UV fixed point is not conformal and that the deformed two-point function propagates unphysical modes. We interpret the result as showing that the flow to the UV fixed point does not exist. This resolves a potential puzzle in the holographic interpretation of the deformation.

    Original languageEnglish (US)
    Article number40
    JournalJournal of High Energy Physics
    Issue number11
    StatePublished - Nov 1 2016


    • AdS-CFT Correspondence
    • Conformal Field Theory
    • Renormalization Group

    ASJC Scopus subject areas

    • Nuclear and High Energy Physics


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