Holonomy algebras of pseudo-hyper-K\"ahlerian manifolds of index 4

Abstract

The holonomy algebra of a pseudo-hyper-K\"ahlerian manifold of signature $(4,4n+4)$ is a subalgebra of $\sp(1,n+1)$. Possible holonomy algebras of these manifolds are classified. Using this, a new proof of the classification of simply connected pseudo-hyper-K\"ahlerian symmetric spaces of index 4 is obtained.