Tensionless strings and Galilean Conformal Algebra

Abstract

We discuss an intriguing link between the symmetries of the tensionless limit of closed string theory and the 2-dimensional Galilean Conformal Algebra (2d GCA). 2d GCA has been studied in the context of the non-relativistic limit of AdS/CFT and more recently in flat-space holography as the proposed symmetry algebra of the field theory dual to 3d Minkowski spacetimes. It is best understood as a contraction of two copies of the Virasoro algebra. In this note, we link this to the tensionless limit of bosonic closed string theory showing how it emerges naturally as a contraction of the residual gauge symmetries of the tensile string in the conformal gauge. We also discuss a possible “dual” interpretation in terms of a point-particle like limit. We show that this different contraction, motivated by an exchange of world-sheet space and time co-ordinates, leads to the same symmetry algebra and provide further evidence in support of our claim by looking at the theory on a torus.