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 CT , the coefficient of the two-point function of the stress-energy tensor, and CJ , 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 CT of the conformal Maxwell theory with higher derivative action Fμν(−∇2)d2−2Fμν. In d = 3, QED has a topological symmetry current, and we calculate the correction to its two-point function coefficient, CJ top. We also show that some RG flows involving QED in d = 3 obey CT UV > CT IR and discuss possible implications of this inequality for the symmetry breaking at small values of N.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- 1/N Expansion
- Renormalization Group