Weyl Groups in AdS3/CFT2

The system of D1 and D5 branes with a Kaluza-Klein momentum isre-investigated using the five-dimensional U-duality group E_{6(+6)}(Z). Weshow that the residual U-duality symmetry that keeps this D1-D5-KK systemintact is generically given by a lift of the Weyl group of F_{4(+4)}, embeddedas a finite subgroup in E_{6(+6)}(Z). We also show that the residual U-dualitygroup is enhanced to F_{4(+4)}(Z) when all the three charges coincide. We thenapply the analysis to the AdS(3)/CFT(2) correspondence, and discuss that among28 marginal operators of CFT(2) which couple to massless scalars of AdS(3)gravity at boundary, 16 would behave as exactly marginal operators for genericD1-D5-KK systems. This is shown by analyzing possible three-point couplingsamong 42 Kaluza-Klein scalars with the use of their transformation propertiesunder the residual U-duality group.Comment: 20 pages, 3 figue