We describe a new class of holonomy groups on pseudo-Riemannian manifolds.
Namely, we prove the following theorem. Let g be a nondegenerate bilinear form
on a vector space V, and L:V -> V a g-symmetric operator. Then the identity
component of the centraliser of L in SO(g) is a holonomy group for a suitable
Levi-Civita connection.Comment: (revised version
