5 v 1 5 D ec 1 99 6 Einstein - Weyl structures corresponding to diagonal Kähler Bianchi IX metrics

We analyse in a systematic way the four dimensionnal Einstein-Weyl spaces equipped with a diagonal Kähler Bianchi IX metric. In particular, we show that the subclass of EinsteinWeyl structures with a constant conformal curvature is the one with a conformally flat but not necessarily flat metric ; we exhibit its 3-parameter distance and Weyl one-form. This extends previous analysis of Pedersen et al., limited to the flat, antiself-dual case. We also check that, in agreement with a theorem of Derdzinski, the most general conformally Einstein metric in the family of biaxial Kähler Bianchi IX metrics is an extremal metric of Calabi, conformal to Carter’s metric, thanks to Chave and Valent’s results. PAR/LPTHE/96-52/hep-th/9612xxx November 1996 ∗Laboratoire de Physique Théorique et des Hautes Energies, Unité associée au CNRS URA 280, Université Paris 7, 2 Place Jussieu, 75251 Paris Cedex 05. [email protected]