Answers are grounded in this paper and cite their sources.
Arguments of positivity and conformal invariance in the Gell-Mann-Low limit imply positive anomalies γN [γN=(scaledimension)-2-N] for the operators O_α₁⋯αN (N≡0) which occur in the light-cone expansion of two currents.
No takes yet. Share an insight, caveat, or question.
Ferrara et al. (1974) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: