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| 29.10.2025, 14:10 (Wednesday) |
Bernard Derrida (Collège de France, Paris) - MINT
Distinguished Lecture |
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Joint meeting of Geometry and Dynamics Seminar
and Horowitz Seminar "Probability, Ergodic Theory
and Dynamical Systems" |
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| Title: |
The many
faces of the Fisher-KPP equation |
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| Location: |
Schreiber 309
and zoom session |
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| Abstract: |
The
Fisher-KPP equation, introduced in 1937 by the biologist
Fisher
and the mathematicians Kolmogorov, Petrovsky, and
Piscounov, describes
the growth of a stable region into an unstable medium.
It is one of
the classical examples of a traveling wave equation that
exhibits
the phenomenon of velocity selection. For physicists and
biologists,
it appears in many other contexts, ranging from the
theory of
disordered systems to reaction–diffusion problems,
branching Brownian
motion, and models of evolution with selection. It is
also related
to a number of mathematical questions in probability,
PDEs,
stochastic PDEs, and complex analysis. This talk will
review
some classical results as well as recent progress. |
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05.11.2025, 14:10
(Wednesday)
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Cheuk Yu Mak (University of Sheffield)
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Title:
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C^0-rigidity of the Hamiltonian diffeomorphism
group of symplectic rational surfaces |
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| Location: |
Zoom session and screening in Schreiber 309 |
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| Abstract: |
We investigate the problem of the C^0 closure of
Symp_0 in Symp.
Borrowing techniques from the study of mapping class
groups of
symplectic rational surfaces, we show that for most of
the positive
symplectic rational surfaces, Symp_0 is a connected
component of
Symp in the C^0 topology. This is a joint work with
Marcelo
Atallah and Weiwei Wu.
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| 12.11.2025, 14:10 (Wednesday) |
Shmuel Weinberger (UChicago) - Distinguished
Lecture in Pure Mathematics |
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| Title: |
Morse complexity of homology classes |
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| Location: |
Schreiber 309
and zoom session |
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| Abstract: |
In the 1970's Gromov (motivated by ideas of
Thurston) introduced
a pseudonorm on the homology of a space based on the
minimum
number of simplices it takes to represent the
class. This
concept has proved enormously useful in many
investigations.
In this talk, I will discuss the much more elusive
concept
based on minimizing the number of critical points in a
Morse
function for a manifold representative of the homology
class.
In dimension two, these are essentially the same idea,
but
they differ in higher dimensions. I will explain
the little
that we know about this measurement which relates to
some
classical topology (most interestingly open book
decompositions,
and surgery theory), representation theory and elliptic
operators (for the very few nonzero estimates we
know).
(Joint work with Manin and Tshishiku)
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19.11.2025, 14:10 (Wednesday)
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Mark Berezovik (TAU) |
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| Title: |
Billiards and Hofer's Geometry |
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| Location: |
Schreiber 309
and zoom session |
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| Abstract: |
In this talk I will discuss a link between
billiards in convex
planar domains and Hofer’s geometry. For smooth strictly
convex
billiard tables the Hofer distance between the
corresponding
billiard ball maps admits an upper bound in terms of a
simple
geometric distance between the tables. Using this result
one can
embed the billiard ball map of a convex polygon in the
completion,
with respect to Hofer's metric, of the group of smooth
area-preserving
maps of the annulus. This talk is based on joint work
with Konstantin
Kliakhandler, Yaron Ostrover, and Leonid Polterovich. |
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| 26.11.2025, 14:10 (Wednesday) |
Shah Faisal (University of
Strasbourg, Uppsala University) |
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| Title: |
Symplectic embeddings of ellipsoids and extremal
Lagrangian tori |
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| Location: |
Zoom session and screening in Schreiber 309 |
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| Abstract: |
Inspired by Gromov's
pioneering idea in the proof of his non-squeezing
theorem, one can seek sharp numerical obstructions to
symplectic
embeddings by constructing pseudo-holomorphic curves
with carefully
controlled symplectic area. In the case of symplectic
embeddings of
ellipsoids, this approach leads to the problem of
producing
pseudo-holomorphic curves of arbitrarily large degree,
subject to
specific geometric and asymptotic constraints in the
complex
projective spaces. In higher dimensions, constructing
pseudo-holomorphic
curves with the correct symplectic area is often highly
challenging
due to the area constraint. To circumvent this
difficulty, we take a
different perspective: rather than seeking curves of a
prescribed
symplectic area, one observes that the existence of a
symplectic
embedding typically implies the existence of some rigid
pseudo-holomorphic curves. The count of such curves can
be
viewed as an obstruction to the existence of certain
symplectic
embeddings. Using this idea, I will explain a lower
bound for
the embedding capacity of higher-dimensional symplectic
ellipsoids.
This is based on work in progress.
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| 03.12.2025, 14:10 (Wednesday) |
Maksim Stokic (Uppsala University) |
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| Title: |
C^0-contact geometry of surfaces in contact
3-manifolds |
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| Location: |
Schreiber 309
and zoom session |
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| Abstract: |
I will describe how C^0-limits of
contactomorphisms act on surfaces
in contact 3-manifolds. We prove that contact
homeomorphisms preserve
characteristic foliations: both their singular sets and
their
one-dimensional leaves are preserved. This leads to a
rigidity
phenomenon for regular coisotropic surfaces. Conversely,
convex
surfaces admit C^0-flexibility. We construct a contact
homeomorphism
that maps a convex torus to a non-convex one. This is
joint work
with Baptiste Serraile. |
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| 10.12.2025, 14:10 (Wednesday) |
Yoav Zimhony (TAU) |
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| Title: |
TBA |
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| Location: |
Schreiber 309
and zoom session |
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| Abstract: |
TBA |
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| 17.12.2025, 14:10 (Wednesday) |
Bernhard Albach (RWTH Aachen University) |
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| Title: |
Quadratic Growth of Geodesics on the Two-Sphere |
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| Location: |
Zoom session and screening in Schreiber 309 |
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| Abstract: |
Given an arbitrary reversible
Finsler metric on S^2, the question
of how many closed geodesics such a metrics admits has a
long
history. In this talk, we will present a result stating
that the
number of prime closed geodesics grows at least
quadratically
with respect to length. The main tools are an
improvement on
Franks’ theorem about the number of periodic points of
area-preserving annulus maps, together with the theory
of
cylindrical contact homology in the complement of a
link. |
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| 24.12.2025, 14:10 (Wednesday) |
Yael Karshon (TAU) |
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| Title: |
TBA |
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| Location: |
Schreiber 309
and zoom session |
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| Abstract: |
TBA |
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| 31.12.2025, 14:10 (Wednesday) |
Baptiste Serraile
(ETH Zürich) |
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| Title: |
TBA |
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| Location: |
Schreiber 309
and zoom session |
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| Abstract: |
TBA |
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| 07.01.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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| Location: |
TBA |
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| Abstract: |
TBA |
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| 14.01.2026, 14:10 (Wednesday) |
Sergei Tabachnikov (Penn State) |
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| Title: |
A tale of four billiards (with a focus on the
nonconventional ones) |
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| Location: |
Schreiber 309
and zoom session |
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| Abstract: |
A periodic orbit of a Birkhoff billiard is a
polygon of extremal
perimeter inscribed into the billiard table (a plane
oval).
One may replace the word "perimeter" by "area" and/or
the word
"inscribed" by "circumscribed". This provides three
other
billiard-like systems. Two of them, involving area, can
be
generalized to symplectic spaces, with the symplectic
structure
replacing the area form; this gives symplectic inner and
outer
billiards.
I shall discuss properties of the symplectic outer
billiards,
including periodic orbits and the large scale behavior
of its
trajectories. I shall also discuss the large scale
behavior of
the trajectories of the planar outer length billiards.
Finally,
I will relate the inner symplectic billiards with still
another
billiard-like system, the Minkowski billiards, currently
a popular
subject of study in symplectic topology. |
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21.01.2026, 14:10 (Wednesday)
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TBA |
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| Title: |
TBA |
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| Location: |
TBA |
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| Abstract: |
TBA |
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18.03.2026,
14:10 (Wednesday)
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TBA |
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| Title: |
TBA |
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| Location: |
TBA |
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| Abstract: |
TBA |
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| 25.03.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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| Location: |
TBA |
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| Abstract: |
TBA |
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| 15.04.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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| Location: |
TBA |
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| Abstract: |
TBA |
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| 29.04.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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| Location: |
TBA |
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| Abstract: |
TBA |
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| 06.05.2026, 14:10 (Wednesday) |
TBA
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| Title: |
TBA |
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| Location: |
TBA |
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| Abstract: |
TBA |
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| 13.05.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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| Location: |
TBA |
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| Abstract: |
TBA |
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| 20.05.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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| Location: |
TBA |
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| Abstract: |
TBA |
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| 27.05.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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| Location: |
TBA |
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TBA |
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| 03.06.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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| Location: |
TBA |
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TBA |
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| 10.06.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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TBA |
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TBA |
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| 17.06.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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TBA |
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TBA |
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| 24.06.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA |
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TBA |
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TBA |
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| 01.07.2026, 14:10 (Wednesday) |
TBA |
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| Title: |
TBA
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TBA |
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TBA
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