Adapted measures and hermitian metrics on the canonical sheaf [02FN]
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Adapted measures and hermitian metrics on the canonical sheaf
Assume is compact with only log terminal singularities, has index and let be a smooth hermitian metric on . Let be a local generator local of . Define to be the volume form on :
Since is independent of , this expression defines an adapted measure with density on .
Now, let be a singular metric on . The Chern-Weil form is then well defined as a quasipositive current. Since has locally +psh potentials is locally bounded above and the above formula defines a measure on such that . In particular
We have , where .
Definition 7.2.
Assume has only log terminal singularities. An adapted measure on is a positive Radon measure locally of the form where is locally given as the sum of a psh and a smooth function on . An adapted measure is , , density if so is .
The definition has the virtue of generalizing the usual equivalence between smooth metrics on the canonical sheaf of a manifold and positive definite volume forms to singular metrics and log terminal spaces. This suggests the following ad hoc:
Definition 7.3.
Let be a -Gorenstein Kähler normal -dimensional complex space with only log terminal singularities. Let be a semi-Kähler current with potential and adapted Monge-Ampère measure. Let be the singular metric on the canonical sheaf such that . We define
where the equality is to be taken in the sense of currents.
The metric will be called a singular Kähler-Einstein metric if for some .