Sasakian-einstein Structures on 9#(s 2 S 3 )
نویسندگان
چکیده
We show that #9(S 2 S 3) admits an 8-dimensional complex family of inequivalent non-regular Sasakian-Einstein structures. These are the rst known Einstein metrics on this 5-manifold. In particular, the bound b 2 (M)8 which holds for any regular Sasakian-Einstein M does not apply to the non-regular case. We also discuss the failure of the Hitchin-Thorpe inequality in the case of 4-orbifolds and describe the orbifold version.
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