Little String Theory from a Double-Scaled Matrix Model

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Following Lin and Maldacena, we find exact supergravity solutions dual to a class of vacua of the plane wave matrix model by solving an electrostatics problem. These are asymptotically near-horizon D0-brane solutions with a throat associated with NS5-brane degrees of freedom. We determine the precise limit required to decouple the asymptotic geometry and leave an infinite throat solution found earlier by Lin and Maldacena, dual to Little String Theory on S⁵. By matching parameters with the gauge theory, we find that this corresponds to a double scaling limit of the plane wave matrix model in which N → ∞ and the 't Hooft coupling λscales as ⁴(N), which we speculate allows all terms in the genus expansion to contribute even at infinite N. Thus, the double-scaled matrix quantum mechanics gives a Lagrangian description of Little String Theory on S⁵, or equivalently a ten-dimensional string theory with linear dilaton background.