Neutral hyperkahler structures on primary Kodaira surfaces
Neutral hyperkahler structures on primary Kodaira surfaces
In the present paper, we study neutral hyperkahler structures on four-dimensional manifolds, which draw attention recentlyin differentialgeometry and especiallyin mathematical physics (cf.Hull [14],Ooguri-Vafa [20]).A neutral hyperkahler structure on a pseudo-Riemannian four-manifold M of metric signature(2,2) consistsofa neutralmetric g and threeendomorphisms (/,'/,'K) on the taneent bundle TM of M such that