K-stability of cubic threefolds

Abstract

We prove the K-moduli space of cubic threefolds is identical to their GIT moduli. More precisely, the K-(semi,poly)-stability of cubic threefolds coincide to the corresponding GIT stabilities, which could be explicitly calculated. In particular, this implies that all smooth cubic threefolds admit Kähler-Einstein metric as well as provides a precise list of singular KE ones. To achieve this, our main new contribution is an estimate in dimension three of the volumes of kawamata log terminal singularities introduced by Chi Li. This is obtained via a detailed study of the classification of three dimensional canonical and terminal singularities, which was established during the study of the explicit three dimensional minimal model program.

34 pages. Comments are very welcome. v3: minor changes, to appear in Duke Math. J

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• Lagrangian fibrations of hyperkähler fourfolds
• On boundedness of singularities and minimal log discrepancies of Kollár components, II
• Weighted cscK metrics on Kähler varieties
• Stable degeneration of families of klt singularities with constant local volume