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Channel: Are there examples of Fano manifolds such that Tian's alpha invariant satisfies $\alpha_G(X)=\frac{n}{n+1}$ but without a Kähler-Einstein metric? - MathOverflow
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Answer by Ruadhaí Dervan for Are there examples of Fano manifolds such that...

This question was answered negatively by Kento Fujita today (at least when $G$ is trivial).Theorem (Fujita): If $\alpha(X,-K_X)=\frac{n}{n+1}$, then $X$ is K-stable and hence admits a Kähler-Einstein...

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Answer by Ivan Cheltsov for Are there examples of Fano manifolds such that...

I see. THis is more subtle. There is no known example. I think it will be impossible or very hard to create one.Vanya

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Answer by Ivan Cheltsov for Are there examples of Fano manifolds such that...

No, this is not sharp.General smooth cubic surface with Eckardt point is an example.Then Aut=Z_2, \alpha_G=2/3 and KE metric exists.If you want very non sharp example, use Kollar's paper...

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Are there examples of Fano manifolds such that Tian's alpha invariant...

The alpha invariant $\alpha(X)$ of a Fano manifold $X$ of dimension $n$ is defined as the infimum of log canonical thresholds of (effective) $\mathbb{Q}$-divisors $D\sim_{\mathbb{Q}}-K_X$. Similarly,...

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