The Green-Schwarz type formulation of D=11 S-invariant superstring and superparticle actions

The manifestly Poincare-invariant formulations for SO(1, 10) and SO(2, 9) s uperstring actions are proposed. The actions are invariant under a local fe rmionic re-symmetry as well as under a number of global symmetries, which t urn out to be on-shell realization of the known "new supersymmetry" S-algeb ra. Canonical quantization of the theory is performed and the relation of t he quantum state spectrum with that of type IIA Green-Schwarz superstring i s discussed. Besides, a mechanical model is constructed, which is a zero te nsion limit of the D = 11 superstring and which incorporates all essential features of the latter. A corresponding action invariant under off-shell do sed realization of the S-algebra is obtained.