Contraction of graded su(2) algebra (Q912193)

The so-called extended Becchi-Rouet-Stora algebra A is the Lie superalgebra obtained from the orthosymplectic Lie superalgebra osp(1,2) by changing the bracket of two odd elements to be zero. The authors point out that A can be obtained from osp(1,2) by an In n -Wigner contraction. They use this fact to construct certain representations of A which have been obtained by \textit{K. Nishijima} [Prog. Theor. Phys. 72, 1214-1224 (1984)] from a different point of view. Using results from deformation theory, they show that osp(1,2) is the only Lie superalgebra that can be contracted to A.