Seminar on Algebraic and Complex Dynamics

报告人 Speaker: Junyi Xie (Peking University)
组织者 Organizer:Yu-Wei Fan, Hsueh-Yung Lin
时间 Time:Tues.,15:00-17:00,Nov.29, 2022
地点 Venue:Zoom Meeting ID: 897 9522 8294 Passcode: 1.17628

More information about the seminar can be found at:

Upcoming Talk:


Title: Topological entropy for non-archimedean dynamics

Speaker: Junyi Xie (Peking University)

Time: Tues.,15:00-17:00,Nov.29, 2022

Venue: Zoom Meeting ID: 897 9522 8294 Passcode: 1.17628


The talk is based on a joint work with Charles Favre and Tuyen Trung Truong. We prove that the topological entropy of any dominant rational self-map of a projective variety defined over a complete non-Archimedean field is bounded from above by the maximum of its dynamical degrees, thereby extending a theorem of Gromov and Dinh-Sibony from the complex to the non-Archimedean setting. We proceed by proving that any regular self-map which admits a regular extension to a projective model defined over the valuation ring has necessarily zero entropy. To this end we introduce the \epsilon-reduction of a Berkovich analytic space, a notion of independent interest.

Past Talks:


Title: Integral-affine structures and degenerations of K3 surfaces 

Speaker: Philip Engel (University of Georgia)

Time: Tues.,9:00-11:00am,Nov. 22, 2022

Venue: Zoom Meeting ID: 897 9522 8294 Passcode: 1.17628


I will discuss a  correspondence between degenerations of polarized K3 surfaces and integral-affine structures on the 2-sphere containing a weighted balanced graph. Under this correspondence, natural questions emerge about the dynamics of the straight line flow on integral-affine manifolds. We will explore (1) the relationship between closed trajectories and immersed elliptic curves in the K3 surface, and (2) the possibility of a tropical Yau-Zaslow formula for counting immersed trees. 


Title: A comparison of categorical and topological entropies on Weinstein manifolds

Speaker: Hanwool Bae (Seoul National University)

Date and time: Nov. 15, 15:00-17:00

Venue: Zoom Meeting ID: 897 9522 8294 Passcode: 1.17628

Abstract: Every symplectic automorphism on a symplectic manifold induces an auto-equivalence on the (derived) Fukaya category, which gives rise to a categorical dynamical system. In this talk, I will first give a brief review of various Fukaya categories of symplectic manifolds with boundaries. Then, for a given symplectic automorphism, I will discuss how the categorical entropies of auto-equivalences induced by f on different Fukaya categories are compared. Then I will explain that in the case when M is a Weinstein domain and f is an exact symplectic automorphism on M that equals the identity map near the boundary of M, the topological entropy of f is greater than or equal to the categorical entropy of the corresponding auto-equivalence on the wrapped Fukaya category of M. This is based on joint work with D. Choa-W. Jeong-D. Karabas- S. Lee and Sangjin Lee.

Title: Kummer Rigidity for Irreducible Holomorphic Symplectic Manifolds

Speaker: Seung uk Jang (University of Chicago)

Date and time: Nov. 8, 9:00-11:00

Venue: Zoom Meeting ID: 897 9522 8294 Passcode: 1.17628


In the preliminary part, we will go through the notion of irreducible holomorphic symplectic (IHS) manifolds, which is one of the high-dimensional generalizations of K3 surfaces. The action of holomorphic automorphisms on IHS manifolds is well-known, in terms of cohomology actions and characteristic currents (i.e., Green currents) that the automorphism induces. We will briefly go through the known theory, together with an easy, computable example originating from Arnold's Cat map.

The main talk will discuss studying holomorphic automorphisms on IHS manifolds that have the volume-class Green measures. The tools are analogous to those for the K3 surfaces, as seen in recent research by Cantat, Dupont, Filip, and Tosatti.

We will see which part of the arguments for the K3 surface can be generalized easily, and which part faces some difficulties. I will present the current status of overcoming each, and for which assumptions it is known that such automorphisms originate from a toral affine map (i.e., is 'Kummer').


Title: An upper bound for polynomial log-volume growth of automorphisms of zero entropy

Speaker: Fei Hu (University of Oslo)

Date and time: Nov. 1, 9:00-11:00

Venue: Zoom Meeting ID: 897 9522 8294 Passcode: 1.17628


Let f by an automorphism of zero entropy of a smooth projective variety X. The polynomial log-volume growth plov(f) of f is a natural analog of Gromov's log-volume growth of automorphisms (of positive entropy), formally introduced by Cantat and Paris-Romaskevich for slow dynamics in 2020. A surprising fact noticed by Lin, Oguiso, and Zhang in 2021 is that this dynamical invariant plov(f) essentially coincides with the Gelfand–Kirillov dimension of the twisted homogeneous coordinate ring associated with (X, f), introduced by Artin, Tate, and Van den Bergh in the 1990s. It was conjectured by them that plov(f) is bounded above by d^2, where d = dim X.

We prove an upper bound for plov(f) in terms of the dimension d of X and another fundamental invariant k of (X, f) (i.e., the degree growth rate of iterates f^n with respect to an arbitrary ample divisor on X). As a corollary, we prove the above conjecture based on an earlier work of Dinh, Lin, Oguiso, and Zhang. This is joint work with Chen Jiang.


Title: Equidistribution of Hodge loci

Speaker: Salim Tayou (Harvard University)

Date and time: Oct. 25, 9:00-11:00

Venue: Zoom Meeting ID: 897 9522 8294 Passcode: 1.17628

Abstract: Given a polarized variation of Hodge structures, the Hodge locus is a countable union of proper algebraic subvarieties where extra Hodge classes appear. In this talk, I will explain a general equidistribution theorem for these Hodge loci and explain several applications: equidistribution of higher codimension Noether-Lefschetz loci, equidistribution of Hecke translates of a curve in the moduli space of abelian varieties and equidistribution of some families of CM points in Shimura varieties. The results of this talk are joint work with Nicolas Tholozan.


Title: Periodic points for systems of varieties

Speaker: Junho Peter Whang (Seoul National University)

Date and time: Oct. 18, 15:00-17:00

Venue: Zoom Meeting ID: 897 9522 8294 Passcode: 1.17628

Abstract: Given a finite system of regular maps between algebraic varieties, it is natural to seek a procedure that determines whether or not a given (rational) point has finite orbit under repeated application of the maps. In this talk, we establish the existence of such a procedure for some simple system of varieties.


Title: b-divisors and dynamical degrees

Speaker: Charles Favre (École Polytechnique)

Date and time: Oct. 11, 15:00-17:00

Venue: Zoom Meeting ID: 897 9522 8294 Passcode: 1.17628

Abstract: Joint work with Nguyen Bac Dang. We develop an intersection theory for b-divisors and used it to get informations on the degree growth of iterates of rational maps.