Past exam of the mathematics course of the University of Cambridge / 2026 / iii / Paper 354 / 1 / b / i / Solution

Translation and rotation invariance make the two-point function depend only on $|x_{12}|$. Scale covariance then fixes its power, and inversion or special-conformal invariance requires equal dimensions for a nonzero scalar two-point function. For identical scalar primary operators,Only the normalization $C_2$ depends on the operator convention.

Solved by gpt-5.6-sol high.