**Affiliated members:**

Jungkai Chen (NTU), Jheng-Jie Chen (NCU), Chen-Yu Chi (NTU), Wu-Yen Chuang (NTU), Shin-Yao Jow (NTHU), Ching-Jui Lai (NCKU), Frank Liou (NCKU), Chih-Chung Liu (NCKU), Jeng-Daw Yu (NTU), Zhu Eugene Xia (NCKU)

**Birational Geometry (Jheng-Jie Chen, Jung-Kai Chen, Ching-Jui Lai)**

The minimal model program (MMP) attempts to find canonical representatives for the birational equivalence class of varieties. The foundation of MMP in characteristic zero is outlined by Reid, Shokurov, Kawamata, Kollar, Mori, and further advanced by Birkar-Cascini-Hacon-McKernan and many others. There are also generalizations of MMP in positive characteristics, by using the Frobenius morphism and the Serre vanishing theorem. Our research program follows and aims to extend these work. For example, a detailed study of three dimensional elementary birational maps in MMP, which is expected to be well understood explicitly, can be generally useful in the study of Sarkisov program, rationality problem and Fano varieties, etc.

**Generalized Hodge Theory and Applications (Jeng-Daw Yu)**

* *We focus on the developments of various generalizations of Hodge theory, in particular, the irregular Hodge theory, motivated by research in mirror symmetry, arithmetic, singularity theory, etc. Conversely, we explore the applications of the generalized Hodge theory to other research areas.

**Linear Systems and Positivity (Shin-Yao Jow)**

* *One way to study the geometry of an algebraic variety is to look at the families of subvarieties it contains. Linear systems are families of codimension-one subvarieties that vary linearly. They have been a useful tool in algebraic geometry since at least the time of the Italian school. In more modern language, a linear system is a linear subspace of sections of a line bundle, and the behavior of the linear system is intimately related to the positivity of the line bundle. There has been ongoing research on this theme: an example of recent development is the theory of Okounkov bodies, which brings in the perspective of convex geometry. Our research program actively follows the recent works on this theme and explores their various implications as well as their generalization to vector bundles of higher ranks.

**Instantons and Quiver Varieties (Chih-Chung Liu) **

Quiver varieties have been used to describe instantons of Kähler-Einstein metrics via the constructions of asymptotically locally Euclidean (ALE) hyperkahler four manifolds. Our research program is active in studying other gauge theoretic equations from these algebraic aspects.

**Analytic Methods in Algebraic Geometry/Complex Geometry (Chen-Yu Chi)**

In recent years analytic methods have played essential roles in studies of algebraic geometry, among which various extension theorems evolving from the work of Ohsawa and Takegoshi have proved powerful in obtaining existence and effective results. It is believed that certain versions of extension theorems will have important applications to the minimal model conjecture/abundance conjecture. Our research project focuses on quantitative and qualitative problems of extension of sections of holomorphic vector bundles equipped with singular hermitian metrics. We are also interested in the local aspect of singular hermitian metrics, such as singularities and approximations of plurisubharmonic functions.

**Topology and Geometry of Moduli spaces (Jia-Ming Frank Liou)**

A moduli space is a geometric space whose points represent isomorphism classes of objects. Such a space arises from classification problems. For example, the moduli space of compact Riemann surfaces is an orbifold whose points are isomorphism classes of compact Riemann surfaces, the Hurwitz space is a complex manifold which classifies meromorphic functions on compact Riemann surfaces, and Grassmannians are complex manifolds which classify subspaces of a given vector space. Our main goal is to use complex analytic tools to study the geometry and topology of moduli spaces.

**Non-Abelian Cohomology and Related Theory (Zhu Eugene Xia)**

The algebraic geometry group is active working on moduli spaces of sheaves, Higgs bundles, character varieties and other related objects over curves and higher dimension varieties.