SO(2,1) covariant IIB superalgebra

We propose a SO(2, 1) covariant type IIB super-Poincare algebra with centra l extension. Together with SO(2, 1) and SO(9, 1) generators, an SO(2, 1) ve ctor triplet (momenta), a Majorana-spinor doublet (supercharges) and a Rari ta-Schwinger central charge generate a group, G. We consider a coset G/H wh ere H = (SO(2) x Lorentz), and the NS/NS and the R/R two form doublers are obtained. They are associated with their U(1) field strengths and U(1) conn ections can be recognized as the coordinates of the enlarged space. We sugg est that this is the fundamental algebra governing the superstring theories which explains the IIB SL(2, R) duality. (C) 1999 Published by Elsevier Sc ience B.V. All rights reserved.