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2.2 Semiflat metrics and the Calabi ansatz [0225]

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2.2 Semiflat metrics and the Calabi ansatz

The generalized Calabi ansatz has two familiar special cases:

For m=nm=n, then YY is just a point, and 0<ri≪10<r_{i}\ll 1 amounts to the subset |ξi|≪1|\xi_{i}|\ll 1 inside (ℂ∗)n(\mathbb{C}^{*})^{n}. The NA MA equation is just the real MA equation

det(D2​u)=const.\det(D^{2}u)=\text{const}.

The ansatz then produces a Calabi-Yau metric, known as the semiflat metric, familiar in the SYZ conjecture [15].

For m=1m=1, and LL trivial, then ZZ is the total space of a positive line bundle L1L_{1} over an (n−1)(n-1)-dimensional Calabi-Yau manifold YY. We then take hL1h_{L_{1}} to be the Hermitian metric corresponding to the Calabi-Yau metric in c1​(L1)c_{1}(L_{1}). We can also view hL1h_{L_{1}} as a function on ZZ, equal to rL12r_{L_{1}}^{2}. Up to a normalising constant, the Calabi ansatz is

ωC​a​l=nn+1​d​dc​(−log⁡hL11/2)(n+1)/n.\omega_{Cal}=\frac{n}{n+1}dd^{c}(-\log h_{L_{1}}^{1/2})^{(n+1)/n}.

We compare this to the NA MA equation (4) in this case: uu is a function of a single real variable xx, satisfying

u′′​u′n−1=const.u^{\prime\prime}u^{\prime n-1}=\text{const}.

Up to constant u=x(n+1)/nu=x^{(n+1)/n}. Thus the NA MA equation reproduces the Calabi ansatz.

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