Algebraic, Complex, and Arithmetic Dynamics (2024)

Date & Time


Schloss Elmau
In Elmau 2, 82493 Krün Germany

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Registration Closed

Invitation Only

Participation is by invitation only. All participants must register.

Laura DeMarco, Harvard University
Mattias Jonsson, University of Michigan

The Simons Foundation will book and pay for up to six nights at the symposium hotel arriving on Sunday and departing on Saturday. All additional nights are to be paid for directly and will not be reimbursed.

Schloss Elmau
In Elmau 2, 82493 Krün, Germany

Phone: +49 8823 180

Meeting Goals:
Organized by Laura DeMarco (Harvard University) and Mattias Jonsson (University of Michigan), the emphasis of this third and final symposium will be on proof methods: we will explore various proof techniques that have been successfully used in complex, algebraic, and arithmetic dynamics. There will also be a few talks highlighting recent important developments, as we continue to formulate a vision for future developments in these areas. We hope you can join us.

  • Agendaplus--large


    8:30 - 9:30 PMWelcome Dinner @ La Salle


    7:30 - 9:45 AMBreakfast at La Salle
    10:00 - 11:00 AMSerge Cantat | Stable Manifolds and Entire Curves
    11:00-11:30 AMBreak
    11:30 - 12:30 PMRomain Dujardin | Rigidity for Polynomial Automorphisms of C^2
    12:30 - 1:30 PMLunch at La Salle
    1:30 - 4:30 PMDiscussion & Recreation*
    4:30- 5:00 PMTea
    5:00 - 6:00 PMJunyi Xie | Lower Semicontinuity of Dynamical Degrees
    6:00 - 6:15 PMBreak
    6:15 - 7:15 PMYohsuke Matsuzawa | Growth of Local Height Functions Along Orbits
    8:00 - 9:30 PMDinner at Ganesha


    7:30 - 9:45 AMBreakfast at La Salle
    10:00 - 11:00 AMXavier Buff | Differential Calculus in Holomorphic Dynamics
    11:00-11:30 AMBreak
    11:30 - 12:30 PMSarah Koch | Complex Dynamics without Dynamics
    12:30 - 1:30 PMLunch at La Salle
    1:30 - 4:30 PMDiscussion & Recreation*
    4:30- 5:00 PMTea
    5:00 - 6:00 PMThomas Gauthier | Potential-Theoretic Tools for Local Problems in Parameter Spaces of Endomorphisms
    6:00 - 6:15 PMBreak
    6:15 - 7:15 PMJoseph Silverman | Height Counting Functions
    8:00 - 9:30 PMDinner at Fidelio


    7:30 - 9:30 AMBreakfast @ La Salle
    9:45 - 2:00 PMGuided Hike
    2:00 - 3:00 PMLunch @ La Salle
    3:00 - 4:30 PMDiscussion & Recreation*
    4:30 - 5:00 PMTea
    5:00 - 6:00 PMMattias Jonsson | Dynamical Degenerations and Berkovich Spaces
    6:00 - 6:15 PMBreak
    6:15 - 7:15 PMYusheng Luo | Degenerations of Hyperbolic Componen
    8:00 - 9:30 PMDinner at Fidelio


    7:30 - 9:45 AMBreakfast at La Salle
    10:00 - 11:00 AMMyrto Mavraki | Uniform Unlikely Intersections
    11:00-11:30 AMBreak
    11:30 - 12:30 PMXinyi Yuan | Equidistribution Over Finitely Generated Fields
    12:30 - 1:30 PMLunch at La Salle
    1:30 - 4:00 PMDiscussion & Recreation*
    4:00 - 4:30 PMTea
    4:30 - 5:30 PMDiscussion Session
    5:30 - 5:45 PMBreak
    5:45 - 6:45 PMJason Bell | p-Adic Interpolation
    7:00 - 8:00 PMDinner at La Salle
    8:30 - 10:00 PMConcert: Asya Fateyeva & Friends


    7:30 - 9:45 AMBreakfast at La Salle
    10:00 - 11:00 AMValentino Tosatti | Two Applications of Semicontinuity to Complex Dynamics
    11:00-11:30 AMBreak
    11:30 - 12:30 PMCurtis McMullen | Billiards, Heights and Hodge Theory
    12:30 - 1:30 PMLunch at La Salle
    1:30 - 4:30 PMDiscussion & Recreation*
    4:30- 5:00 PMTea
    5:00 - 6:00 PMDiscussion Session
    6:00 - 6:15 PMBreak
    6:15 - 7:15 PMDiscussion Session
    8:00 - 9:30 PMDinner at Summit Pavillion


    SESSIONSPavilion located at the Schloss Elmau Retreat
    MEALSVarious, see agenda
    TEA & DISCUSSIONPavilion located at the Schloss Elmau Retreat
    EXCURSION Meet in Schloss Elmau Lobby
    SATURDAY DEPARTUREMeet in Schloss Elmau Lobby

    *Participants may explore the hotel property and its surrounding areas as well as engage in informal discussion with other participants.

  • Abstractsplus--large

    Jason Bell
    University of Waterloo

    p-Adic Interpolation

    We give an overview of p-adic interpolation methods and highlight some of their applications in arithmetic dynamics.


    Xavier Buff
    Institut Mathématiques de Toulouse

    Differential Calculus in Holomorphic Dynamics

    We will present methods introduced by Adam Epstein to address transversality problems in holomorphic dynamics in complex dimension 1. One associates to each rational map various dynamically relevant vector spaces and linear maps, and then studies the kernel and/or the image of those linear maps. The key ingredient in the proof, which goes back to William Thuston, is the injectivity of the operator id – f_* acting on meromorphic integrable quadratic differentials. All statements are purely algebraic, but we are not aware of an algebraic proof of the key ingredient.


    Serge Cantat

    Stable Manifolds and Entire Curves

    In complex dimension 2, stable manifolds of holomorphic diffeomorphisms are entire curves; that is, they are holomorphically parametrized by the affine complex line. Positive currents, Nevanlinna theory and Hodge theory can then be used to study these curves. In this talk, Serge Cantat will describe some of the results from this circle of ideas.


    Romain Dujardin
    Sorbonne Université

    Rigidity for Polynomial Automorphisms of C^2

    In joint work with Serge Cantat, we establish several new rigidity results for automorphisms with positive entropy, addressing questions such as the smoothness of Julia sets, existence of invariant foliations or characterizations of real-analytic conjugacy classes. Most of these questions are related to properties of stable and unstable eigenvalues of saddle periodic points and the algebraic and geometric constraints they have to satisfy. Another pervasive tool is the existence and properties of the dynamical Green function.


    Thomas Gauthier
    Université Paris-Saclay

    Potential-Theoretic Tools for Local Problems in Parameter Spaces of Endomorphisms

    When studying the global (or local) geography of parameter spaces of endomorphism of projective spaces, one can think of using tools inherited from potential theory, such as closed positive currents. One of the main issues we then encounter is to be able to prove that those objects actually carry useful information. In this talk, Thomas Gauthier will present various situations where we can find this information in a parameter/dynamics similarity phenomenon.


    Mattias Jonsson
    University of Michigan

    Dynamical Degenerations and Berkovich Spaces

    Non-Archimedean analytic spaces in the sense of Berkovich can be used to study degeneration of various types of complex analytic objects. Mattias Jonsson will survey some known results about degenerations in complex dynamics, with an emphasis on the methods used in the proofs.


    Sarah Koch
    University of Michigan

    Complex Dynamics without Dynamics

    Sarah Koch will discuss a variety of dynamical results, many in the realm of PCF rational maps, that arise from exploiting “non-dynamical” ideas and constructions.


    Yusheng Luo
    Cornell University

    Degenerations of Hyperbolic Components

    From a dynamics point of view, a degenerating sequence of conjugacy classes of rational maps in a hyperbolic component usually develops some wide rectangles (arc-degeneration) or annuli (loop-degeneration) in the dynamical plane. In this talk, we will discuss some methods and techniques to prevent these degenerations. Using a hyperbolic component of a Sierpiński carpet Julia set as an example, we will illustrate how renormalization methods can be used to bound the arc-degeneration and how the ideas from the Berkovich spaces can be used to prevent loop-degeneration. Furthermore, we will talk about some limitations, technical challenges and potential generalizations for these methods.


    Yohsuke Matsuzawa
    Osaka Metropolitan University

    Growth of Local Height Functions Along Orbits

    For a dominant self-map f on a projective variety, we explore the problem of whether the ratio (local height of f^n(x))/( ample height of f^n(x)) tends to zero as n approaches infinity. This problem was solved in dimension one by Silverman, with applications to the dynamical Lang-Siegel problem. In higher dimensions, there are two main obstacles: Diophantine approximation (specifically, the upper bound of local height functions) and the growth rate of ample height functions along orbits.

    For the first obstacle, Yohsuke Matsuzawa will introduce how Roth’s theorem and Vojta’s conjecture can be applied. It appears to be very difficult to prove higher dimensional analogue of Silverman’s theorem in full generality without assuming Vojta’s conjecture. However, Matsuzawa will explain that a weaker statement involving Banach density can be proven unconditionally. Regarding the second obstacle, it is well-understood when f is a morphism (on a projective variety). When f is a rational map, the problem becomes much more challenging. Matsuzawa will explain that when f is a cohomologically hyperbolic map, the growth of the ample height is sufficiently well-understood to the extent that we can prove a sufficient condition for our problem. This is an application of recent work by Junyi Xie on recursive inequalities of pull-backs of divisors.


    Myrto Mavraki
    University of Toronto

    Uniform Unlikely Intersections

    Myrto Mavraki will describe techniques used to obtain uniform bounds in families of arithmetic dynamical systems


    Curtis McMullen
    Harvard University

    Billiards, Heights and Hodge Theory

    What are the slopes of periodic billiard trajectories in a regular polygon? We will connect this dynamical question and others to methods lying at the nexus of complex and arithmetic geometry. In particular, we will discuss a new height on P^1(K), determined by a combination of arithmetic and the Hodge norm on the cohomology of an Abelian variety with real multiplication by K. Along the way, we will encounter issues of chaos and decidability, first appearing in polygons with 7 and 12 sides.


    Joseph Silverman
    Brown University

    Height Counting Functions

    Joseph Silverman will start with a 30-year old conjecture that describes the coarse growth of height counting functions on algebraic varieties, show how it leads to a dynamical orbit propagation conjecture, and then use height counting functions to prove a case of the orbit propagation conjecture (joint work with Hector Pasten).


    Valentino Tosatti
    New York University

    Two Applications of Semicontinuity to Complex Dynamics

    Valentino Tosatti will discuss a simple idea involving semicontinuity and how it can be applied in two different contexts to prove interesting results at the intersection of complex dynamics and geometry: to find rigid currents on K3 surfaces (work of Sibony-Verbitsky) and to study the linearization problem for neighborhoods of elliptic curves in complex surfaces with a  topologically trivial normal bundle (ongoing work with Filip).


    Junyi Xie
    BICMR, Peking University

    Lower Semicontinuity of Dynamical Degrees

    For every dominant rational self-map, we find a family of recursive inequalities of some dynamically meaningful cycles. Using these inequalities, we prove that for a family of dominant rational self-maps, the dynamical degrees are lower semi-continuous with respect to the Zariski topology.


    Xinyi Yuan
    Peking University

    Equidistribution Over Finitely Generated Fields

    The equidistribution theorem of Szpiro-Ullmo-Zhang and Yuan assumes that the base field is a number field. In Yuan-Zhang’s work on adelic line bundles, there is a conjecture on equidistribution over finitely generated fields. In this talk, Xinyi Yuan will introduce some recent progress on this conjecture.

  • AVplus--large

    Participants will have access to a projector and screen for computer-based talks and blackboards for those who prefer to give board-based talks.

    High-speed Internet access is available.

  • Participation & Fundingplus--large

    The foundation will arrange and pay for all air and train travel to the Simons Symposium as well as hotel accommodations and reimbursement of local expenses. Business-class or premium economy airfare will be booked for all flights over five hours.

    The Simons Symposium only accommodates full in-person participation. By accepting, you agree to participate fully in the scientific program, arriving on Sunday prior to the welcome dinner and departing on the following Saturday. No accommodations will be made for partial or remote attendance.

    Guests & Children
    It is against Simons Foundation policy for guests, including children, to accompany participants during the meeting week. Guests are welcome to join prior to or at the conclusion of the symposium at their own expense.

  • Travel & Hotelplus--large

    Air & Rail
    The foundation will arrange and pay for round-trip travel from a participant’s home city to the symposium. All travel and hotel arrangements must be booked through the Simons Foundation’s preferred travel agency. Travel arrangements not booked through the preferred agency, including triangle trips and routing/preferred airlines outside budget, must be pre-approved by the Simons Foundation and a reimbursement quote must be obtained through the foundation’s travel agency.

    Travel specifications, including preferred airline, will be accommodated provided that these specifications are reasonable and within budget.

    All costs related to changes made to ticketed travel are to be paid for by the participant and are not reimbursable. Please contact the foundation’s travel agency for further assistance.

    Personal & Rental Cars
    Personal car and rental car trips over 250 miles each way require prior approval from the Simons Foundation via email.

    Regardless of distance, rental cars must be pre-approved by the Simons Foundation.

  • Ground Transportationplus--large

    The Simons Foundation will directly arrange roundtrip ground transportation between the arriving airport and the symposium hotel.

    Expenses for ground transportation outside the above arrangements will be reimbursed for travel days (i.e. traveling to/from the airport) as well as local transportation.

  • Reimbursementplus--large

    Individuals will be reimbursed for meals and local expenses including ground transportation. Expenses should be submitted through the foundation’s online expense reimbursement platform after the meeting’s conclusion.

    Expenses accrued as a result of meetings not directly related to the Simons Foundation-hosted meeting will not be reimbursed by the Simons Foundation and should be paid by other sources.

    Below are key reimbursement takeaways; a full policy will be provided with the final logistics email circulated approximately 2 weeks prior to the meeting’s start.

    The Simons Foundation will coordinate all meals during the symposium weeks. The daily meal limit for all other meals (i.e. those taken on travel days) is $125 and itemized receipts are required for expenses over $24 USD. The foundation DOES NOT provide a meal per diem and only reimburses actual meal expenses.

    • Meals taken on travel days are reimbursable.
    • Meals taken outside those provided by the foundation (breakfast, lunch, breaks and/or dinner) are not reimbursable.
    • If a meal was not provided on a meeting day, dinner for example, that expense is reimbursable.
    • Meals taken on days not associated with Simons Foundation-coordinated events are not reimbursable.
    • Minibar expenses are not reimbursable.
    • Meal expenses for a non-foundation guest are not reimbursable.

    Group meals consisting of fellow meeting participants paid by a single person will be reimbursed up to $65 per person per meal and the amount will count towards each individual’s $125 daily meal limit.

    Ground Transportation
    Expenses for ground transportation will be reimbursed for travel days (i.e. traveling to/from the airport) as well as local transportation. While in NYC, individuals are encouraged to use public transportation and not use taxi, Uber or Lyft services.

  • Contactsplus--large

    Travel & Hotel Assistance

    Ovation Travel Team
    [email protected]

    Meeting Questions & Assistance

    Meghan Fazzi
    Manager, Events & Administration, MPS
    [email protected]
    (212) 524-6080

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