Oscillator Construction of Spectra of PP-Wave Superalgebras in Eleven   Dimensions
  After reviewing the oscillator realization of the symmetry superalgebra of the BMN matrix model on its maximally supersymmetric plane-wave background and the construction of its zero-mode spectrum, we study a large number of non-maximally supersymmetric pp-wave algebras in eleven dimensions which are obtained by various restrictions from the maximally supersymmetric case (BMN model). We also show how to obtain their zero-mode spectra, which we explicitly construct in some chosen examples. Except for some `exotic' or degenerate special cases, we believe our study covers all possible interesting pp-wave superalgebras of this kind in eleven dimensions. 
S. Fernando, M. Gunaydin and S. Hyun