QED with a large number N of massless fermionic degrees of freedom has a conformal phase in a range of space-time dimensions. We use a large N diagrammatic approach to calculate the leading corrections to C T , the coefficient of the two-point function of the stress-energy tensor, and C J , the coefficient of the two-point function of the global symmetry current. We present explicit formulae as a function of d and check them versus the expectations in 2 and 4 − ϵ dimensions. Using our results in higher even dimensions we find a concise formula for C T of the conformal Maxwell theory with higher derivative action Fμ ν(-∇²)d/2-2Fμ ν . In d = 3, QED has a topological symmetry current, and we calculate the correction to its two-point function coefficient, C top . We also show that some RG flows involving QED in d = 3 obey C UV > C IR and discuss possible implications of this inequality for the symmetry breaking at small values of N .
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A 2016 study studied this question.