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The isomorphism of the conformal algebra on space-time to the orthogonal O(4,2) algebra is exploited to derive in a manifestly covariant way an operator-product expansion on the light cone in terms of irreducible operator representations of the conformal algebra. The expansion provides for a solution of the causality problem for operator expansion on the light cone. Additional properties of the conformally covariant expansion, as well as its relation to the conformally invariant three-point function, are discussed.
Ferrara et al. (Thu,) studied this question.