We first show that a Kähler cone appears as the tangent cone of a complete
expanding gradient Kähler–Ricci soliton with quadratic curvature decay with
derivatives if and only if it has a smooth canonical model (on which the soliton
lives). This allows us to classify two-dimensional complete expanding gradient
Kähler–Ricci solitons with quadratic curvature decay with derivatives. We then
show that any two-dimensional complete shrinking gradient Kähler–Ricci soliton
whose scalar curvature tends to zero at infinity is, up to pullback by an element of
, either the flat Gaussian
shrinking soliton on
or the
–invariant
shrinking gradient Kähler–Ricci soliton of Feldman, Ilmanen and Knopf on the blowup
of
at one point. Finally, we show that up to pullback by an element of
, the
only complete shrinking gradient Kähler–Ricci soliton with bounded Ricci curvature
on
is the flat Gaussian shrinking soliton, and on the total space of
for
is the
–invariant
example of Feldman, Ilmanen and Knopf. In the course of the proof, we establish the
uniqueness of the soliton vector field of a complete shrinking gradient Kähler–Ricci
soliton with bounded Ricci curvature in the Lie algebra of a torus. A key tool used to
achieve this result is the Duistermaat–Heckman theorem from symplectic
geometry. This provides the first step towards understanding the relationship
between complete shrinking gradient Kähler–Ricci solitons and algebraic
geometry.
Keywords
Kähler–Ricci solitons, Kähler–Ricci flow, self-similar
solutions, Duistermaat–Heckman formula