On the Geometry of Sasakian-Einstein 5-Manifolds

Boyer, Charles P.; Galicki, Krzysztof; Nakamaye, Michael

On the Geometry of Sasakian-Einstein 5-Manifolds

Authors

Boyer, Charles P.

Galicki, Krzysztof

Nakamaye, Michael

Description

On simply connected five manifolds Sasakian-Einstein metrics coincide with Riemannian metrics admitting real Killing spinors which are of great interest as models of near horizon geometry for three-brane solutions in superstring theory [KW]. We expand on the recent work of Demailly and Kollár [DK] and Johnson and Kollár [JK1] who give methods for constructing Kähler-Einstein metrics on log del Pezzo surfaces. By [BG1] circle V-bundles over log del Pezzo surfaces with Kähler-Einstein metrics have Sasakian-Einstein metrics on the total space of the bundle. Here these simply connected 5-manifolds arise as links of isolated hypersurface singularities which by the well known work of Smale [Sm] together with [BG3] must be diffeomorphic to $\scriptstyle{S^5#l(S^2\times S^3)}.$ More precisely, using methods from Mori theory in algebraic geometry we prove the existence of 14 inequivalent Sasakian-Einstein structures on $\scriptstyle{S^2\times S^3}$ and infinite families of such structures on $\scriptstyle{#l(S^2\times S^3)}$ with $\scriptstyle{2\leq l\leq7}$. We also discuss the moduli problem for these Sasakian-Einstein structures.
34 pages