Abstracto
- The algebraic classification of totally symmetric spinors and of trace-free totally symmetric tensors in three-dimensional spaces is considered. The geometric properties of a family oC geodesics in a space with positive definite metric are expressed in terms oí a one-index spinor that determines a vector field tangent to the geodesics. The usual massless free field equations in Oat space-time are written as evolution equations for spinor fields in three-dimensional space.