Graded Contractions of

All 2 \Theta 2 --graded contractions preserving space isotropy and the grading induced by the time reversal \Theta and the discrete canonical transformation K exchanging coordinates and momenta are found for the Lie algebra sp(3; ). Some properties and physical aspects of these contractions are discussed, especially in connection with the algebraic formulation of nuclear collective models. 1 Introduction Symmetries can be related by standard morphisms, such as inclusion of one Lie algebra in another. However, since the pioneering work of Wigner and Inonu [1], 40 years ago, a wider class of relations among symmetry algebras has been studied -- Wigner--Inonu contractions of Lie algebras. The recent modifications [2] of Wigner's approach make the vast variety of contractions of Lie algebras more accessible to an exhaustive description: one reduces the scope of study to contractions preserving a fixed grading by a finite Abelian group G. A complete classification of such contractions th..