A note on T-duality of strings in plane-wave backgrounds

We show, by direct computations of bosonic string spectra, the O(d,d;Z) (d=1,2) T-duality in the maximally supersymmetric IIB plane-wave background compactified on S1 and T2. Only half of the ordinary set of zero modes appear in the Hamiltonian. This “half” Narain lattice is proved to be stabilized by the T-duality group.