Center for Complex Geometry

Insong Choe (최인송, Konkuk University)
2023-03-01 - 2024-02-28
Insong Choe (최인송)
Visitor (2023.3.1-2024.2.28) from Konkuk University
Office: B255

Andreas Höring, Projective Manifolds with Pseudoeffective (Co)tangent Bundle, I, II
2023-11-20 15:00 - 17:30 (Asia/Seoul) | B236-1, IBS, Korea, Republic of
Speaker

Andreas Höring
University of Nice

Symmetric holomorphic forms on projective manifolds have been studied from various angles in the last ten years : Brotbek-Darondeau and independently Song-Yan Xie have shown that complete intersections of sufficiently high degree and codimension have an ample cotangent bundle, so many symmetric forms. Vice versa Campana and Paun show that if the cotangent bundle is big, then X is of general type. In this series of lectures I will work under the assumption that the cotangent bundle is pseudoeffective. In general this positivity assumption is too weak to have any useful implications, but we will see that for the (co)tangent bundle it leads to surprisingly many restrictions on the geometry of the manifold. In particular we expect a nonvanishing property that is analogous to the famous nonvanishing conjecture for the canonical bundle. These talks are based on joint papers with Thomas Peternell and Junyan Cao.

Andreas Höring, Projective Manifolds with Pseudoeffective (Co)tangent Bundle, III, IV
2023-11-22 15:00 - 17:30 | B236-1, IBS, Korea, Republic of

Grzegorz Kapustka, Projective Models of Nikulin Orbifolds
2023-12-11 16:00 - 17:00 | B236-1, IBS, Korea, Republic of
Speaker

Grzegorz Kapustka
Jagiellonian University

We describe a locally complete family of projective irreducible holomorphic symplectic orbifolds as double covers of special complete intersections (3, 4) in P6. This is a joint work with C. Camere, A. Garbagnati and M. Kapustka.

Workshop on Classical Algebraic Geometry
2023-12-12 - 2023-12-15 | IBS Science Culture Center, Daejeon, Korea, Republic of
Speakers
Alberto Calabri (University of Ferrara)
Cinzia Casagrande (University of Torino)
Flaminio Flamini (University of Rome Tor Vergata)
Paola Frediani (University of Pavia)
Kangjin Han (DGIST)
Zhi Jiang (SCMS, Fudan University)
Akihiro Kanemitsu (Saitama University)
Grzegorz Kapustka (Jagiellonian University)
Michał Kapustka (IM PAN)
Seonja Kim (Chungwoon University)
Hirokazu Nasu (Tokai University)
Wenbo Niu (University of Arkansas)
Jinhyung Park (KAIST)
Xavier Roulleau (University of Angers)
Francesco Russo (University of Catania)
Eduardo Luis Solá Conde (University of Trento)
Abstracts
PDF file
Schedule
December 12 (Tuesday)

09:30~10:00
Registration

10:00~11:00
Cinzia Casagrande

11:00~11:30
Coffee Break

11:30~12:30
Jinhyung Park

12:30~14:30
Lunch

14:30~15:30
Seonja Kim

15:30~16:00
Coffee Break

16:00~17:00
Eduardo Luis Solá Conde

18:00~20:00
Dinner for Speakers

December 13 (Wednesday)

10:00~11:00
Flaminio Flamini

11:00~11:30
Coffee Break

11:30~12:30
Hirokazu Nasu

12:30~14:30
Lunch

14:30~15:30
Zhi Jiang

15:30~16:00
Coffee Break

16:00~17:00
Akihiro Kanemitsu

December 14 (Thursday)

10:00~11:00
Michał Kapustka

11:00~11:30
Coffee Break

11:30~12:30
Grzegorz Kapustka

12:30~14:30
Lunch

14:30~15:30
Alberto Calabri

15:30~16:00
Coffee Break

16:00~17:00
Francesco Russo

17:30~20:00
Banquet

December 15 (Friday)

10:00~11:00
Xavier Roulleau

11:00~11:30
Coffee Break

11:30~12:30
Wenbo Niu

12:30~14:00
Lunch

14:00~15:00
Kangjin Han

15:00~15:30
Coffee Break

15:30~16:30
Paola Frediani

Organizers
DongSeon Hwang (IBS-CCG)
Jun-Muk Hwang (IBS-CCG)
Yongnam Lee (IBS-CCG/KAIST)
Venue
IBS Science Culture Center
Registration
Please submit Google form by November 10th.
Main Hotel
Lotte City Hotel Daejeon (4-30 Doryong-dong, Yuseong-gu, Daejeon)
More Information
• How to get to IBS-CCG
• From Hotel to IBS

Workshop on Torus Actions in Symplectic and Algebraic Geometry
2024-01-15 - 2024-01-19 | IBS Science Culture Center, Daejeon, Korea, Republic of
Lecture Series
Kiumars Kaveh (University of Pittsburgh)
Hendrik Süß (University of Jena)*
Susan Tolman (University of Illinois at Urbana-Champaign)
Research Talks
Lara Bossinger (UNAM)
Isabelle Charton (University of Haifa)
Oliver Clarke (University of Edinburgh)
Peter Crooks (Utah State University)
Naoki Fujita (Kumamoto University)
Yoosik Kim (Pusan National University)
Donggun Lee (IBS CCG)
Joseph Palmer (University of Illinois at Urbana-Champaign)
Andrea Petracci (Università di Bologna)
Milena Wrobel (University of Oldenburg)
* = online
Abstracts
Website
Schedule

Monday
Tuesday
Wednesday
Thursday
Friday

9:40 – 10:40

Kaveh 2
Kaveh 4
Bossinger
Kim

11:10 – 12:10

Tolman 2
Tolman 3
Clarke
Charton

12:20 – 14:00

Lunch
Lunch
Lunch
Lunch

14:00 -15:00
Kaveh 1
Kaveh 3
Fujita
Petracci
Palmer

15:30 – 16:30
Tolman 1
5-minute talks
Lee
Wrobel
Crooks

17:00 – 18:00
Süß 1
Süß 2
Süß 3
Süß 4

Banquet

Organizers
Yunhyung Cho (Sungkyunkwan University)
Jaehyun Hong (IBS CCG)
Donghoon Jang (Pusan National University)
Eunjeong Lee (Chungbuk National University)
Venue
IBS Science Culture Center
Registration
Please submit Google form by December 17.
Poster
PDF file
More Information
• How to get to IBS-CCG
• Accommodations
• Restaurants

Youngju Kim, Tubular Neighborhoods in Complex Hyperbolic Manifolds
2024-02-07 16:00 - 17:00 | B236-1, IBS, Korea, Republic of
Speaker

Youngju Kim
Konkuk University

The collar lemma says that a closed geodesic in a real hyperbolic 2-manifold has an embedded tubular neighborhood whose width only depends on the length of the geodesic. The width of the collar does not depend on the underlying hyperbolic 2-manifold. On the other hand, a totally geodesic surface with codimension bigger than 1 in a hyperbolic manifold of can be arbitrary closed to itself. Here, we prove that an embedded complex totally geodesic surface in a complex hyperbolic 2-manifold has a tubular neighborhood whose size depends only on its area. This is a joint work with A. Basmajian.

Caucher Birkar, Stable Minimal Models
2024-02-20 17:00 - 18:00 | on-line
Zoom ID: 880 6763 5837
PW: [REDACTED]

Speaker

Caucher Birkar
Tsinghua University

In this talk I will introduce stable minimal models and discuss some related results and if times allows, problems.
(This seminar is a part of School and Workshop on Moduli, K-trivial Varieties, and Related Topics)

School and Workshop on Moduli, K-trivial Varieties, and Related Topics
2024-02-21 - 2024-02-29 | IBS Science Culture Center Daejeon, Korea, Republic of (On Feb 23, the venue will be in B109, IBS)
Speakers for Mini-courses (Feb 21~23)
Harold Blum (University of Utah)
Radu Laza (Stony Brook University)
Colleen Robles (Duke University)
Speakers for Workshop (Feb 21~23, and 26-29)
Kenneth Ascher (UC Irvine)
Philip Engel (Univ. of Bonn)
Laure Flapan (Michigan State University)
Yoon-Joo Kim (Columbia University)
Kyoung-Seog Lee (POSTECH)
Zhiyuan Li (SCMS, Fudan University)
Yuchen Liu (Northwestern University)
Eyal Markman (University of Massachusetts)
Mirko Mauri (École Polytechnique)
Enrica Mazzon (University of Regensburg)
Yuji Odaka (Kyoto University)
Kieran O’Grady (University of Rome, La Sapienza)
Keiji Oguiso (University of Tokyo)
Gianluca Pacienza (University of Lorraine)
Colleen Robles (Duke University)
Justin Sawon (University of North Carolina)
Qizheng Yin (BICMR, Peking University)
Abstracts
• School
• Workshop
Schedule (School and Workshop)
* Additional talk (online) by Caucher Birkar (Tsinghua U.) at 17:00-18:00 in February 20 (Tue)
(Zoom ID and PW can be found here.)
February 21 (Wednesday)

09:30~10:00
Registration

10:00~11:00
Radu Laza, Lect I

11:00~11:30
Coffee Break

11:30~12:30
Colleen Robles, Lect I

12:30~14:30
Lunch

14:30~15:30
Harold Blum, Lect I

15:30~16:00
Coffee Break

16:00~17:00
Keiji Oguiso

17:30~19:30
Dinner (for speakers)

February 22 (Thursday)

10:00~11:00
Radu Laza, Lect II

11:00~11:30
Coffee Break

11:30~12:30
Colleen Robles, Lect II

12:30~14:30
Lunch

14:30~15:30
Harold Blum, Lect II

15:30~16:00
Coffee Break

16:00~17:00
Yuji Odaka

17:30~19:30
Banquet

February 23 (Friday)

10:00~11:00
Radu Laza, Lect III

11:00~11:30
Coffee Break

11:30~12:30
Colleen Robles, Lect III

12:30~14:30
Lunch

14:30~15:30
Harold Blum, Lect III

15:30~16:00
Coffee Break

16:00~17:00
Kyeong-Seog Lee

18:00~20:00
Dinner (for speakers)

February 26 (Monday)

9:30~10:00
Registration

10:00~11:00
Kieran O’Grady

11:00~11:30
Coffee Break

11:30~12:30
Philip Engel

12:30~14:30
Lunch

14:30~15:30
Enrica Mazzon

15:30~16:00
Coffee Break

16:00~17:00
Yoon-Joo Kim

17:30~19:30
Dinner (for speakers)

February 27 (Tuesday)

10:00~11:00
Gianluca Pacienza

11:00~11:30
Coffee Break

11:30~12:30
Laure Flapan

12:30~14:30
Lunch

14:30~15:30
Kenneth Ascher

15:30~16:00
Coffee Break

16:00~17:00
Yuchen Liu

February 28 (Wednesday)

10:00~11:00
Justin Sawon

11:00~11:30
Coffee Break

11:30~12:30
Qizheng Yin

12:30~14:30
Lunch

14:30~15:30
Colleen Robles

15:30~16:00
Coffee Break

16:00~17:00
Mirko Mauri

17:30~19:30
Banquet

February 29 (Thursday)

10:00~11:00
Zhiyuan Li

11:00~11:30
Coffee Break

11:30~12:30
Eyal Markman

12:30~14:30
Lunch

Organizers
Jun-Muk Hwang (IBS-CCG)
Radu Laza (Stony Brook University)
Yongnam Lee (IBS-CCG/KAIST)
Main Hotel
Lotte City Hotel Daejeon (4-30 Doryong-dong, Yuseong-gu, Daejeon)
Venue
IBS Science Culture Center
Registration
Please submit Google form by February 7.
More Information
• How to get to IBS-CCG

Gebhard Martin, Automorphisms of del Pezzo Surfaces I
2024-03-05 11:00 - 12:00 | B236-1, IBS, Korea, Republic of
Speaker

Gebhard Martin
Universität Bonn

Motivated by the classification of finite subgroups of the Cremona group of the plane, I will survey old and new results on automorphism groups of del Pezzo surfaces. In particular, I will report on joint work with Igor Dolgachev on the classification of automorphism groups of smooth del Pezzo surfaces and on joint work with Claudia Stadlmayr on the classification of vector fields on mildly singular del Pezzo surfaces. Special emphasis will be placed on the theory of actions of infinitesimal group schemes and characteristic-free methods in classical algebraic geometry.

Claudia Stadlmayr, Which Rational Double Points Occur on del Pezzo Surfaces?
2024-03-07 15:30 - 16:30 | B236-1, IBS, Korea, Republic of
Speaker

Claudia Stadlmayr
Technische Universität München

Canonical surface singularities, also called rational double points (RDPs), can be classified according to their dual resolution graphs, which are Dynkin diagrams of types A, D, and E. Whereas in characteristic different from 2, 3, and 5, rational double points are “taut”, that is, they are uniquely determined by their dual resolution graph, this is not necessarily the case in small characteristics. To such non-taut RDPs Artin assigned a coindex distinguishing the ones with the same resolution graph in terms of their deformation theory. In 1934, Du Val determined all configurations of rational double points that can appear on complex RDP del Pezzo surfaces. In order to extend Du Val’s work to positive characteristic, one has to determine the Artin coindices to distinguish the non-taut rational double points that occur. In this talk, I will explain how to answer the question “Which rational double points (and configurations of them) occur on del Pezzo surfaces?” for all RDP del Pezzo surfaces in all characteristics. This will be done by first reducing the problem to degree 1 and then exploiting the connection to (Weierstraß models of) rational (quasi-)elliptic surfaces.

Gebhard Martin, Automorphisms of del Pezzo Surfaces II
2024-03-12 16:00 - 17:00 | B236-1, IBS, Korea, Republic of

Gebhard Martin, Automorphisms of del Pezzo Surfaces III
2024-03-14 15:30 - 16:30 | B236-1, IBS, Korea, Republic of

Boris Doubrov, Bifiltered Parabolic Geometries
2024-03-19 16:00 - 17:00 | B266, IBS, Korea, Republic of
Speaker

Boris Doubrov
Belarusian State University, Minsk

We introduce the notion of a bifiltered manifold and generalizing the constructions of the symbol and Tanaka prolongation from nilpotent differential geometry. Next, we consider bifiltered manifolds modeled by bigradings of simple Lie algebras and show how this generalizes known constructions in the parabolic geometries such as existence of a unique normal Cartan connection. Finally, we show how the language of bifiltered manifolds can be used for uniform treatment of correspondence spaces in parabolic geometries, where the covering space is not necessarily regular in the classical sense.

Dennis The, On 4D Split-conformal Structures with G2-symmetric Twistor Distribution
2024-03-21 16:00 - 17:00 | B266, IBS, Korea, Republic of
Speaker

Dennis The
The Artic University of Norway, Tromso

In their 2013 article, An & Nurowski considered two surfaces rolling on each other without twisting or slipping, and defined a twistor distribution (on the space of all real totally null self-dual 2-planes) for the associated 4D split-signature conformal structure. If this split-conformal structure is not anti-self dual, then the twistor distribution is a (2,3,5)-distribution, and An-Nurowski identified interesting rolling examples where it achieves maximal, i.e. G2, symmetry. Relaxing the rolling assumption, a similar construction can be made for any 4D split-conformal structure, and my talk will discuss a broader classification of examples where such exceptional symmetry for the twistor distribution is achieved. (Joint work with Pawel Nurowski & Katja Sagerschnig.)

Yong Hu, Noether Inequality for Irregular Threefolds of General Type
2024-03-26 16:00 - 17:00 | B236-1, IBS, Korea, Republic of
Speaker

Yong Hu
Shanghai Jiao Tong University

Let X be a smooth irregular 3-fold of general type. In this talk, we will prove that the optimal Noether inequality vol(X) ≥ (4/3) pg(X) holds if pg(X) ≥ 16 or if X has a Gorenstein minimal model. Moreover, when X attains the equality and pg(X) ≥ 16, its canonical model will be explicitly described. This is a joint work with Tong Zhang.

Michel Brion, Introduction to Symmetric Spaces
2024-04-09 16:00 - 17:00 | B236-1, IBS, Korea, Republic of
Speaker

Michel Brion
U. Grenoble

This is an introductory lecture on symmetric spaces in algebraic geometry.

Michel Brion, Introduction to Complete Symmetric Varieties
2024-04-11 16:00 - 17:00 | B236-1, IBS, Korea, Republic of
Speaker

Michel Brion
U. Grenoble

This is an introductory lecture on compactifications of symmetric spaces in algebraic geometry.

Workshop on Geometry of Homogeneous Varieties
2024-04-15 - 2024-04-18 | B109, IBS, Korea, Republic of
Speakers
Michel Brion (U. Grenoble)
Jarek Buczynski (IMPAN, Warsaw)
Thibaut Delcroix (U. Montpellier)
Minseong Kwon (KAIST/IBS-CCG)
Qifeng Li (Shandong U.)
Yoshinori Namikawa (RIMS, Kyoto)
Kyeong-Dong Park (Gyeongsang National U.)
Boris Pasquier (U. Poitiers)
Léa Villeneuve (U. Poitiers)
Abstracts
PDF file
Schedule
April 15 (Monday)
10:00-11:00 Brion
11:20-12:20 Brion
12:30-13:20 Lunch
15:00-16:00 Kwon
16:20-17:40 Li
April 16 (Tuesday)
10:00-11:00 Pasquier
11:20-12:20 Pasquier
12:30-13:20 Lunch
15:00-16:00 Park
16:20-17:40 Villeneuve
April 17 (Wednesday)
10:00-11:00 Namikawa
11:20-12:20 Namikawa
12:30-13:20 Lunch
Free Afternoon
April 18 (Thursday)
10:00-11:00 Delcroix
11:20-12:20 Delcroix
12:30-13:20 Lunch
15:00-16:00 Buczynski
16:20-17:20 Buczynski
Organizers
Jaehyun Hong (IBS-CCG)
Jun-Muk Hwang (IBS-CCG)
Main Hotel
Lotte City Hotel Daejeon (4-30 Doryong-dong, Yuseong-gu, Daejeon)
Venue
B109, IBS, Daejeon, Korea
Registration
Please submit Google form by March 31.
More Information
• How to get to IBS-CCG

In-Kyun Kim, Wall-crossing of K-moduli Spaces of Weighted Projective Spaces
2024-04-23 14:00 - 15:00 | B236-1, IBS, Korea, Republic of
Speaker

In-Kyun Kim
KIAS

In algebraic geometry, constructing moduli spaces that parametrize families of algebraic varieties with certain properties is an important problem.
In the case of Fano varieties, the construction of moduli spaces is a challenging problem.
K-stability provides a criterion for selecting nice representatives within the moduli space, which helps create more meaningful and well-behaved moduli spaces.
In this talk, we will study some properties of K-moduli spaces. This is a joint work with Yuchen Liu and Chengxi Wang.

Chuyu Zhou, K-stability of Fano Varieties - Various Viewpoints
2024-04-24 11:00 - 12:00 | B236-1, IBS, Korea, Republic of
Speaker

Chuyu Zhou
Yonsei University

We will present various criterion for K-stability for Fano varieties, including viewpoints from test configurations, valuations, and filtrations.

Chuyu Zhou, Moduli for Fano Varieties with K-stability
2024-04-25 11:00 - 12:00 | B236-1, IBS, Korea, Republic of
Speaker

Chuyu Zhou
Yonsei University

We will present the construction of moduli space of Fano varieties with K-stability, including defining the moduli functor, showing various good properties of the functor, and introducing Alper-Halpern Leistner-Heinloth criterion for the existence of good moduli space.

Chuyu Zhou, Wall Crossing for K-stability
2024-04-26 11:00 - 12:00 | B236-1, IBS, Korea, Republic of
Speaker

Chuyu Zhou
Yonsei University

We will introduce a novel characteristic of K-stability, i.e. wall crossing phenomenon, and present a comparison between K-stability and GIT-stability. Time permitting, we will survey some open problems.

Benjamin Bakker, Hodge Theory and Lagrangian Fibrations
2024-04-29 16:00 - 17:00 | B236-1, IBS, Korea, Republic of
Speaker

Benjamin Bakker
Univ. Illinois Chicago

Compact hyperkahler manifolds X are higher-dimensional generalizations of K3 surfaces; their geometry is tightly constrained by the existence of a holomorphic symplectic form. For example, a result of Matsushita says the only nontrivial fibration structures f:X→B they admit are fibrations by Lagrangian tori. In this talk, I will give an overview of how Hodge theory connects the geometry of B to the variation of these tori in moduli, and how Hodge-theoretic techniques can be used to understand B both locally and globally.

Benjamin Bakker, A Proof of Matsushita's Conjecture
2024-04-30 16:00 - 17:00 | B236-1, IBS, Korea, Republic of
Speaker

Benjamin Bakker
Univ. Illinois Chicago

Matsushita conjectured that for any Lagrangian fibration f:X→B of a compact hyperkahler manifold X, the fibers deform either maximally or trivially in moduli. In this talk I’ll explain how to prove this conjecture via Hodge theory. I will also discuss some other features of the topology of Lagrangian fibrations and a result about the density of torsion points in sections. Time permitting, I will discuss some more recent work with C. Schnell from this perspective reproving a result of J.-M. Hwang that B is projective space if it is smooth.

Shigeyuki Kondo, A Review on Enriques Surfaces: Moduli, Automorphism Groups and Positive Characteristics, I
2024-05-07 16:00 - 17:00 | B236-1, IBS, Korea, Republic of
Speaker

Shigeyuki Kondo
Nagoya University

The Enriques surface was discovered, in 1894 by Federigo Enriques, as a counter-example of a rationality problem.
First I would like to recall the moduli space and the automorphism groups of Enriques surfaces over the complex numbers.
In the later half, I shall mention a recent progress in positive characteristic, especially in characteristic two.

Shigeyuki Kondo, A Review on Enriques Surfaces: Moduli, Automorphism Groups and Positive Characteristics, II
2024-05-08 11:00 - 12:00 | B236-1, IBS, Korea, Republic of

Hsueh-Yung Lin, Motivic Invariants of Birational Automorphisms of Threefolds
2024-05-13 14:30 - 15:30 | B236-1, IBS, Korea, Republic of
Speaker

Hsueh-Yung Lin
National Taiwan University

The motivic invariant c(f) of a birational automorphism f : X – → X measures the difference between the birational types of the exceptional divisors of f and those of the inverse f-1. In general c(f) is nonzero: this is the case when f is some Cremona transformation, which leads to new explanation as to why Cremona groups are not simple. In the other direction, which will be the main focus of the talk, we show that the invariant c(f) always vanishes when X is a complex projective threefold. (joint work in progress with E. Shinder.)

Ching-Jui Lai, Anticanonical Volume of Singular Fano Threefolds
2024-05-13 16:00 - 17:00 | B236-1, IBS, Korea, Republic of
Speaker

Ching-Jui Lai
National Cheung Kung University

The set of canonical Fano threefolds form a bounded family by results of Kawamata, Mori-Miyaoka-Kollar-Tagaki, and in a much more general setting by Birkar. In particular, the anticaonical volume –KX3 is bounded. An optimal lower bound is 1/330 by the work of Chen-Chen. In this talk, we discuss the problem of identifying an optimal upper bound of –KX3.

Workshop on Algebraic Geometry in Busan
2024-05-14 - 2024-05-16 | La Valse Hotel, Busan, Korea, Republic of
Speakers
Lorenzo Barban (IBS-CCG)
Jungkai Chen (National Taiwan University)
Toshiyuki Katsura (University of Tokyo)
Shigeyuki Kondo (Nagoya University)
Ching-Jui Lai (National Cheung Kung University)
Donggun Lee (IBS-CCG)
Hsueh-Yung Lin (National Taiwan University)
Shigeru Mukai (Kyoto University)
Keiji Oguiso (University of Tokyo)
Abstracts
PDF file
Schedule
May 14 (Tuesday)
14:00~14:20 Registration
14:20~15:20 Oguiso
15:40~16:40 Lai
17:00~18:00 Lin
18:30~20:30 Dinner
May 15 (Wednesday)
09:30~10:30 Katsura
11:00~12:00 Kondo
12:00~13:30 Lunch
13:30~17:30 Discussion
18:00~20:00 Banquet
May 16 (Thursday)
09:30~10:30 Chen
11:00~12:00 Barban
12:00~13:30 Lunch
13:30~14:30 Lee
15:00~16:00 Mukai
Organizers
JongHae Keum (KIAS)
Yongnam Lee (IBS-CCG/KAIST)
Venue
La Valse Hotel, Busan
* Due to available hotel rooms and budgets, participation is by invitation only. If you are interested to participate in this workshop, please contact one of the organizers by April 15.
