A new example of compact Riemannian manifold with structure group Spin(7)
In this paper, we give a new variational characterization of certain 4-manifolds. More precisely, let and denote the scalar curvature and Ricci curvature respectively of a Riemannian metric, we prove that if is compact and locally conformally flat and is the critical point of the functional where
We construct a non-homogeneous contact projective structure which is symmetric from the point of view of parabolic geometries.