Connected Components of The Space of Surface Group Representations

Let G be a connected, compact, semisimple Lie group. It is known that for a compact closed orientable surface $\mathrm{\Sigma }$ of genus $l>1$, the order of the group $H^2(\mathrm{\Sigma },{\pi }_1(G))$ is equal to the number of connected components of the space $Hom({\pi }_1(\mathrm{\Sigma }),G)\mathrm{/}G$ which can also be identified with the moduli space of gauge equivalence classes of flat G-bundles over $\mathrm{\Sigma }$. We show that the same statement for a closed compact nonorientable surface which is homeomorphic to the connected sum of k copies of the real projective plane, where $k\mathrm{\ne }1,2,4$, can be easily derived from a result in A. Alekseev, A.Malkin and E. Meinrenken’s recent work on Lie group valued moment maps.