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Ka-Fai Li

Publications and source records attributed to Ka-Fai Li.

5 recordsLinked to original sources

The K"ahler-Ricci flow with Log Canonical Singularities

We establish the existence of the K"ahler-Ricci flow on projective varieties with log canonical singularities. This generalizes some of the existence results of Song-Tian \cite{ST3} in case of projective varieties with klt singularities. We also prove that the normalized K"ahler-Ricci flow will converge to the \ka-Einstein metric with negative Ricci curvature on semi-log canonical models in the sense of currents. Finally we also construct K"ahler-Ricci flow solutions performing divisorial contractions and flips with log canonical singularities.

math.DG

Deformation of Hermitian metrics

In this work, we study the deformation of Hermitian metrics with Chern connection. By adapting the conformal perturbation method of Aubin and Ehrlich to Hermitian setting, we prove that Hermitian metrics with quasi-positive (resp. quasi-negative) second Chern-Ricci curvature can be deformed to one with positive (resp. negative) curvature.

math.DG

Kähler-Ricci flow of cusp singularities on quasi projective varieties

Let $\overline{M}$ be a compact complex manifold with smooth Kähler metric $η$, and let $D$ be a smooth divisor on $\overline{M}$. Let $M=\overline{M}\setminus D$ and let $\hatω$ be a Carlson-Griffiths type metric on $M$. We study complete solutions to Kähler-Ricci flow on $M$ which are comparable to $\hatω$, starting from a smooth initial metric $ω_0=η+i\partial \bar{\partial} ϕ_0$ where $ϕ_0\in C^{\infty}(M)$. When $ω_0\geq c \hatω$ on $M$ for some $c>0$ and $ϕ_0$ has zero Lelong number, we construct a smooth solution $ω(t)$ to Kähler-Ricci flow on $M\times [0, T_{[ω_0 ]})$ where $T_{[ω_0 ]}:= \sup \{ T: [η] +T (c_1(K_{\overline{M}}) + c_1(\mathcal{O}_D))\in \mathcal{K}_M \}$ so that $ω(t)\geq (\frac{1}{n} - \frac{4\hat{K}t}{c} )\hatω$ for all $t\leq \frac{c}{4n\hat{K}}$ where $\hat{K}$ is a non-negative upper bound on the bisectional curvatures of $\hatω$ (see Theorem 1.2). In particular, we do not assume $ω_0$ has bounded curvature. If $ω_0$ has bounded curvature and is asymptotic to $\hatω$ in an appropriate sense, we construct a complete bounded curvature solution on $M\times [0, T_{[ω_0 ]})$ (see Theorem 1.3). These generalize some of the results of Lott-Zhang in [15]. On the other hand if we only assume $ω_0\geq c η$ on $M$ for some $c>0$ and $ϕ_0$ is bounded on $M$, we construct a smooth solution to Kähler-Ricci on $M\times [0, T_{[ω_0 ]})$ which is equivalent to $\hatω$ for all positive times. This includes as a special case when $ω_0$ is smooth on $\overline{M}$ in which case the solution becomes instantaneously complete on $M$ under Kähler-Ricci flow (see Theorem 1.1).

math.DG

Longtime existence of the Kähler-Ricci flow on $\Bbb C ^n$

We produce longtime solutions to the Kähler-Ricci flow for complete Kähler metrics on $\Bbb C ^n$ without assuming the initial metric has bounded curvature, thus extending results in [3]. We prove the existence of a longtime bounded curvature solution emerging from any complete $U(n)$-invariant Kähler metric with non-negative holomorphic bisectional curvature, and that the solution converges as $t\to \infty$ to the standard Euclidean metric after rescaling. We also prove longtime existence results for more general Kähler metrics on $\Bbb C ^n$ which are not necessarily $U(n)$-invariant.

math.DG

Deforming complete Hermitian metrics with unbounded curvature

We produce solutions to the Kähler-Ricci flow emerging from complete initial metrics $g_0$ which are $C^0$ Hermitian limits of Kähler metrics. Of particular interest is when $g_0$ is Kähler with unbounded curvature. We provide such solutions for a wide class of $U(n)$-invariant Kähler metrics $g_0$ on $n$ dimensional complex Euclidean space, many of which having unbounded curvature. As a special case we have the following Corollary: The Kähler-Ricci flow has a smooth short time solution starting from any smooth complete $U(n)$-invariant Käbler metric on $\C^n$ with either non-negative or non-positive holomorphic bisectional curvature, and the solution exists for all time in the case of non-positive curvature.

math.DG