I have a homogenushomogeneous Riemannian manifold X with iaometryisometry group Iso. Is Iso a maximal group? By maximal group, I mean that there does not exist otheranother group G, such that:
- Iso is a proper subgroup of G,
- G act transitivlyacts transitively on X by difeomorphismsdiffeomorphisms, and
- G has compact stabilizers G_x,Gx.
I know, that if such a group exists, then there is a G-invariant metric on X. So, in other words, the question is: if I have a Riemannian metric d on X with isometry group Iso, which is homegenushomogeneous, could existscan there exist another Riemannian metric d' on X with isometry group Iso', such that Iso' contains properly the group Iso ?