N = 8 supersymmetric mechanics with spin variables from indecomposable multiplets

We define two new indecomposable (not fully reducible) N = 8 , d = 1 off-shell multiplets and consider the corresponding models of N = 8 supersymmetric mechanics with spin variables. Each multiplet is described off shell by a scalar superfield which is a nonlinear deformation of the standard scalar superfield X carrying the d = 1 multiplet ( 1 , 8 , 7 ). Deformed systems involve, as invariant subsets, two different off-shell versions of the irreducible multiplet ( 8 , 8 , 0 ). For both systems we present the manifestly N = 8 supersymmetric superfield constraints, as well as the component off- and on-shell invariant actions, which for one version exactly match those given in . The two models differ off shell, but prove to be equivalent to each other on shell, with the spin variables sitting in the adjoint representation of the maximal R -symmetry group SO ( 8 ) .