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Kyusik Hong

Publications and source records attributed to Kyusik Hong.

5 recordsLinked to original sources
arXiv2022

K\"ahler-Einstein metrics on smooth Fano toroidal symmetric varieties of type AIII

The wonderful compactification $X_m$ of a symmetric homogeneous space of type AIII$(2,m)$ for each $m \geq 4$ is Fano, and its blowup $Y_m$ along the unique closed orbit is Fano if $m \geq 5$ and Calabi-Yau if $m = 4$. Using a combinatorial criterion for K-polystability of smooth Fano spherical varieties obtained by Delcroix, we prove that $X_m$ admits a K\"ahler-Einstein metric for each $m \geq 4$ and $Y_m$ admits a K\"ahler-Einstein metric if and only if $m = 4, 5$.

math.AG↗
arXiv2014

A remark on the Omori-Yau maximum principle for semi-elliptic operators

We generalize A. Borbély's condition for the conclusion of the Omori-Yau maximum principle for the Laplace operator on a complete Riemannian manifold to a second-order linear semi-elliptic operator $L$ with bounded coefficients and no zeroth order term. Also, we consider a new sufficient condition for the existence of a tamed exhaustion function. As a corollary, we show that the existence of a tamed exhaustion function is more general than the hypotheses in the version of the Omori-Yau maximum principle that was given by A. Ratto, M. Rigoli and A.G. Setti.

math.DG↗
arXiv2013

The symmetry of Spin^c Dirac spectrums on Riemannian product manifolds

It is well-known that the spectrum of a $\text{spin}^{\mathbb{C}}$ Dirac operator on a closed Riemannian $\text{spin}^{\mathbb{C}}$ manifold $M^{2k}$ of dimension $2k$ for $k \in \mathbb{N}$ is symmetric. In this article, we prove that over an odd-dimensional Riemannian product $M_{1}^{2p} \times M_{2}^{2q+1}$ with a product $\text{spin}^{\mathbb{C}}$ structure for $p \geq 1, q \geq 0$, the spectrum of a $\text{spin}^{\mathbb{C}}$ Dirac operator given by a product connection is symmetric if and only if either the $\text{spin}^{\mathbb{C}}$ Dirac spectrum of $M_{2}^{2q+1}$ is symmetric or $(e^{\frac{1}{2}c_{1}(L_{1})} \hat{A}(M_1))[M_{1}]=0$, where $L_1$ is the associated line bundle for the given $\text{spin}^{\mathbb{C}}$ structure of $M_1$.

math.DG↗
arXiv2013

An Omori-Yau maximum principle for semi-elliptic operators and Liouville-type theorems

We generalize the Omori-Yau almost maximum principle of the Laplace-Beltrami operator on a complete Riemannian manifold $M$ to a second-order linear semi-elliptic operator $L$ with bounded coefficients and no zeroth order term. Using this result, we prove some Liouville-type theorems for a real-valued $C^{2}$ function $f$ on $M$ satisfying $L f \geq F(f)+ H(|\nabla f|) $ for real-valued continuous functions $F$ and $H$ on $\Bbb R$ such that $H(0)=0$.

math.DG↗