Degenerating conic Kähler-Einstein metrics to the normal cone

Abstract: Let $X$ be a Fano manifold of dimension at least $2$ and $D$ be a smooth divisor in a multiple of the anticanonical class, $\frac1\alpha(-K_X)$ with $\alpha>1$. It is well-known that K\"ahler-Einstein metrics on $X$ with conic singularities along $D$ may exist only if the angle $2\pi\beta$ is bigger than some positive limit value $2\pi\beta_$. Under the hypothesis that the automorphisms of $D$ are induced by the automorphisms of the pair $(X,D)$, we prove that for $\beta>\beta_$ close enough to $\beta_$, such K\"ahler-Einstein metrics do exist. We identify the limits at various scales when $\beta\rightarrow\beta_$ and, in particular, we exhibit the appearance of the Tian-Yau metric of $X\setminus D$.