Graviton loop contribution to Higgs potential in gauge-Higgs unification
We study a two-loop finiteness of an effective potential for a Higgs boson that is the fifth component of a gauge field in an $U(1)$ gauge theory coupled to quantum gravity on the five-dimensional space-time $M^4\times S^1$. There are two types of diagrams including quantum gravitational corrections. We find that only one type of diagram contributes to the effective potential for the Higgs boson in fact and its magnitude is finite.