We prove a conjecture on the pinching of the bisectional curvature of nonpositively
curved Kähler–Einstein surfaces. We also prove that any compact Kähler–Einstein
surface
is a quotient of the complex two-dimensional unit ball or the complex two-dimensional
plane if
has nonpositive Einstein constant and, at each point, the average holomorphic
sectional curvature is closer to the minimum than to the maximum.
Keywords
Kähler–Einstein metrics, compact complex surfaces,
bisectional curvature, pinching of the curvatures