On Projective Hoops: Loops in Hyperspace

TL;DR

This paper derives Feynman rules in N=2 Projective Superspace to compute loop corrections in Super-Yang-Mills theory, confirming known beta-function results and the finiteness of N=4 SYM.

Contribution

It provides explicit derivations of propagators and Feynman rules in Projective Superspace and calculates loop corrections, offering an alternative proof of N=4 SYM finiteness.

Findings

Only the coupling constant needs renormalization in N=2 SYM.

The 1-loop beta-function matches known results.

N=4 SYM remains finite with no 2-hoops contributions.

Abstract

We (re)derive the propagators and Feynman rules for the massless scalar and vector multiplets in N=2 Projective Superspace ('Projective Hyperspace'). With these, we are able to calculate both the divergent and finite parts of 2, 3 & 4-point functions at 1-loop for N=2 Super-Yang-Mills theory (SYM) explicitly in Projective Hyperspace itself. We find that effectively only the coupling constant needs to be renormalized unlike in the N=1 case where an independent wavefunction renormalization is also required. This feature is similar to that of the background field gauge, even though we are using ordinary Fermi-Feynman gauge. The computation of 1-hoop beta-function is then straightforward and matches with the known result. We also show that it receives no 2-hoops contributions. All these calculations provide an alternative proof of the finiteness of N=4 SYM.