The Calabi conjecture, proved by Yau (1977, 1978), states that if is a compact Kähler manifold
and
is a real closed form of type
representing
, then every cohomology
class containing a Kähler form contains a unique
Kähler metric
whose ricci form is
.
In particular, if the first Chern class of vanishes, then each cohomology
class containing a Kähler form contains a unique
Ricci-flat Kähler metric. This special case
supplies the Ricci-flat Kähler metrics used
in the theory of Calabi-Yau spaces.