Bianchi type A hyper-symplectic and hyper-Kähler metrics in 4D
arXiv:1102.1518
Abstract
We present a simple explicit construction of hyper-Kaehler and hyper-symplectic (also known as neutral hyper-Kaehler or hyper-parakaehler) metrics in 4D using the Bianchi type groups of class A. The construction underlies a correspondence between hyper-Kaehler and hyper-symplectic structures in dimension four.
Title changed, exposition and terminology clarified, final vesion to appear Class. Quant. Grav. This paper is an expanded version of sections 7 and 8 of arXiv:0903.1398