Searcharxiv⌕ Search

arXiv subjects

Sai-Kee Yeung

Publications and source records attributed to Sai-Kee Yeung.

At least 19 recordsLinked to original sources
arXiv2025

Quasi-projective manifolds uniformized by Carathéodory hyperbolic manifolds and hyperbolicity of their subvarieties

Let $M$ be a Carathéodory hyperbolic complex manifold. We show that $M$ supports a real-analytic bounded strictly plurisubharmonic function. If $M$ is also complete Kähler, we show that $M$ admits the Bergman metric. When $M$ is strongly Carathéodory hyperbolic and is the universal covering of a quasi-projective manifold $X$, the Bergman metric can be estimated in terms of a Poincaré type metric on $X$. It is also proved that any quasi-projective (resp. projective) subvariety of $X$ is of log-general type (resp. general type), a result consistent with a conjecture of Lang.

math.CV↗
arXiv2025

Carathéodory hyperbolicity, volume estimates and level structures over function fields

We give a generalization of the nonexistence of level structures as Nadel, Noguchi, Hwang-To, for quasi-projective manifolds uniformized by strongly Carathéodory hyperbolic complex manifolds. Examples include moduli space of compact Riemann surfaces with a finite number punctures and locally Hermitian symmetric spaces of finite volume. This leads to the nonexistence of a holomorphic map from a Riemann surface of fixed genus into the compactification of such a quasi-projective manifold when the level structure is sufficiently high. To achieve our goal, we have also established some volume estimates for mapping of curves into these manifolds, extending some earlier result of Hwang-To to a more general setting. A version of Schwarz Lemma applicable to manifolds equipped with nonsmooth complex Finsler metric is also given.

math.AG↗
arXiv2022

Limit of Weierstrass Measure on Stable Curves

The goal of the paper is to study the limiting behavior of the Weierstrass measures on a smooth curve of genus $g\geqslant 2$ as the curve approaches a certain nodal stable curve represented by a point in the Deligne-Mumford compactification $\bar{\mathcal M}_g$ of the moduli $\mathcal{M}_g$, including irreducible ones or those of compact type. As a consequence, the Weierstrass measures on a stable rational curve at the boundary of $\mathcal{M}_g$ are completely determined. In the process, the asymptotic behavior of the Bergman measure is also studied.

math.AG↗
arXiv2021

On the syzygies of ample line bundles on fake projective planes

Our goal is to study the syzygies of the projective embeddings defined by ample line bundles on a fake projective plane S. The syzygies are studied in terms of the property $N_p$. For various kinds of ample line bundles, we give explicit lower bounds for their powers above which the property $N_p$ is satisfied.

math.AG↗
arXiv2021

A surface of maximal canonical degree

It has been conjectured that the optimal canonical degree of a minimal surface of general type is 36, from a work in the 70's of Beauville who proved that 36 was an upper bound. The highest canonical degree known for the problem was 16 by Persson in 1978. The purpose of this article is to confirm the conjecture by providing an explicit surface.

math.AG↗
arXiv2021

Open Torelli locus and complex ball quotients

We study the problem of non-existence of totally geodesic complex ball quotients in the open Torelli locus in a moduli space of principally polarized Abelian varieties using analytic techniques.

math.AG↗
arXiv2021

Exceptional collection of objects on some fake projective planes

The purpose of the article is to explain a new method to establish the existence of an exceptional collection of length three for a fake projective plane M with non-trivial automorphism group, related to a conjecture of Galkin-Katzarkov-Mellit-Shinder in 2015. Our method shows that 30 fake projective planes support such a sequence, most of which are new. In particular, this provides many new H-phantom categories.

math.AG↗
arXiv2021

Complex Ball Quotients and New Symplectic 4-manifolds with Nonnegative Signatures

We present the various constructions of new symplectic $4$-manifolds with non-negative signatures using the complex surfaces on the BMY line $c_1^2 = 9χ_h$, the Cartwright-Steger surfaces, the quotients of Hirzebruch's certain line-arrangement surfaces, along with the exotic symplectic $4$-manifolds constructed in \cite{AP2, AS}. In particular, our constructions yield to (i) an irreducible symplectic and infinitely many non-symplectic $4$-manifolds that are homeomorphic but not diffeomorphic to $(2n-1)CP^{2}\#(2n-1)\bar{CP}^{2}$ for each integer $n \geq 9$, (ii) the families of simply connected irreducible nonspin symplectic $4$-manifolds that have the smallest Euler characteristics among the all known simply connected $4$-manifolds with positive signatures and with more than one smooth structure. We also construct a complex surface with positive signature from the Hirzebruch's line-arrangement surfaces, which is a ball quotient.

math.SG↗
arXiv2021

Examples of surfaces with canonical maps of maximal degree

It was shown by A. Beauville that if the canonical map $φ_{|K_M|}$ of a complex smooth projective surface $M$ is generically finite, then ${\rm deg}(φ_{|K_M|})\leq 36$. The first example of a surface with canonical degree 36 was found by the second author. In this article, we show that for any surface which is a degree four Galois étale cover of a fake projective plane $X$ with the largest possible automorphism group ${\rm Aut}(X)=C_7:C_3$ (the unique non-abelian group of order 21), the base locus of the canonical map is finite, and we verify that 35 of these surfaces have maximal canonical degree 36. We also classify all smooth degree four Galois étale covers of fake projective planes, which give possible candidates for surfaces of canonical degree $36$. Finally, we also confirm in this paper the optimal upper bound of the canonical degree of smooth threefolds of general type with sufficiently large geometric genus, related to earlier work of C. Hacon and J.-X. Cai.

math.AG↗
arXiv2019

Fake projective planes

A fake projective plane is a smooth complex surface which is not the complex projective plane but has the same Betti numbers as the complex projective plane. The first example of such a surface was constructed by David Mumford in 1979 using p-adic uniformization. Two more examples were found by Ishida and Kato by related method. Keum has recently given an example which is possibly different from the three known earlier. It is an interesting problem in complex algebraic geometry to determine all fake projective planes. Using the arithmeticity of the fundamental group of fake projective planes, the formula for the covolume of principal arithmetic subgroups given by the first-named auhor, and some number theoretic estimates, we give a classification of fake projective planes in this paper. Twenty eight distinct classes are found. The construction given in the paper appears to be more direct and more natural. It does not use p-adic uniformization.

math.AG↗
arXiv2018

Very ampleness of the bicanonical line bundle on compact complex two ball quotients

The purpose of this note is to show that $2K$ of any smooth compact complex two ball quotient is very ample, except possibly for four pairs of fake projective planes of minimal type, where $K$ is the canonical line bundle. For the four pairs of fake projective planes, sections of $2K_M$ give an embedding of $M$ except possibly for at most two points on $M$.

math.AG↗
arXiv2016

Entire holomorphic curves on a Fermat surface of low degree

The purpose of the paper is to study some problems raised by Hayman and Gundersen about the existence of non-trivial entire and meromorphic solutions for the Fermat type functional equation $f^n+g^n+h^n=1$. Hayman showed that no non-trivial meromorphic solutions and entire solutions exist when $n \ge 9$ and $n \ge 7$ respectively. By considering the entire holomorphic curves on the Fermat surface defined by $X^n+Y^n+Z^n=W^n$ on the complex projective space $\mathbb{P}^3$ and applying the method of jet differentials, we show that no non-trivial meromorphic solutions and entire solutions exist when $n \ge 8$ and $n \ge 6$ respectively. In particular, this completes the investigation of non-trivial entire solutions for all $n$ and respectively, meromorphic solutions for all cases except for $n=7$. Finally, for the generalized Fermat type functional equation $f^n+g^m+h^l=1$, we will also prove the non-existence of non-trivial meromorphic solutions when $1/n+1/m+1/l \le 3/8$, giving the strongest result obtained so far.

math.CV↗
arXiv2015

On the Cartwright-Steger surface

In this article, we study various concrete algebraic and differential geometric properties of the Cartwright-Steger surface. In particular, we determine the genus of a generic fiber of the Albanese fibration, and deduce that the singular fibers are not totally geodesic, answering an open problem about fibrations of a complex ball quotient over a Riemann surface.

math.AG↗