Recent content by Worldsheep

Does anyone know a simple explanation for the following statement: Gauge invariance ⇒ $Πμνϒϒ(0) = ΠμνϒZ(0) = 0$ Where ΠVV' is the V to V' one loop correction, ϒ is the photon field and Z is the Z-boson field. The argument of Π is the incoming momentum q2 = 0