Monday, 18 May
02:15 pm
Bielefeld University V4-106
When is the Ellis semigroup a conjugacy invariant?
Speaker: Johannes Kellendonk
Other
In general, dynamical systems with isomorphic Ellis semigroups are not
conjugate. We present additional conditions on the dynamical systems
under which this is nevertheless the case.
Friday, 22 May
01:00 pm
Bielefeld University D2-136
Homological mirror symmetry via tensor-triangular geometry
Speaker: Kyungmin Rho
Seminar Representation Theory of Algebras
Homological mirror symmetry (HMS) conjectures an equivalence between the Fukaya category of a symplectic manifold and the derived category of coherent sheaves on its mirror scheme. We discuss a tensor-triangular geometric approach and present a necessary and sufficient condition for a Fukaya category to be realized as the perfect derived category of a Noetherian scheme. This also gives a way to build a mirror scheme from purely Fukaya-categorical data and leads to a natural construction of an A∞-functor.
01:00 pm
Bielefeld University D2-136
Homological mirror symmetry via tensor-triangular geometry
Speaker: Kyungmin Rho
Seminar Representation Theory of Algebras
Homological mirror symmetry (HMS) conjectures an equivalence between the Fukaya category of a symplectic manifold and the derived category of coherent sheaves on its mirror scheme. We discuss a tensor-triangular geometric approach and present a necessary and sufficient condition for a Fukaya category to be realized as the perfect derived category of a Noetherian scheme. This also gives a way to build a mirror scheme from purely Fukaya-categorical data and leads to a natural construction of an A∞-functor.
Wednesday, 27 May
02:15 pm
Bielefeld University M4-122/126
Subgroup Zeta Functions of Higher Heisenberg Groups
Speaker: Jianhao Shen
Oberseminar Gruppen und Geometrie
Subgroup zeta functions encode subgroup growth in finitely generated nilpotent groups, but are difficult to compute explicitly, even for one of the simplest families of nonabelian nilpotent groups: the higher Heisenberg groups. I will discuss explicit formulae for these groups, based on recent joint work with C. Voll.
03:45 pm
Bielefeld University M4-122/126
Tba
Speaker: Reza Salarian
Oberseminar Gruppen und Geometrie
Tba
Friday, 29 May
01:00 pm
Bielefeld University D2-136
The classification of integral endotrivial complexes
Speaker: Sam Miller
Seminar Representation Theory of Algebras
Endotrivial complexes are the invertible objects in the derived category of permutation modules for a finite group. Previously, we classified the endotrivials over a field of positive characteristic. In this talk, we will describe how to extend the classification to endotrivials over a commutative Noetherian ring using techniques from representation theory, homotopy theory, and tensor-triangular geometry. This is joint work with J. Omar Gomez.
02:15 pm
Bielefeld University D2-136
Homological aspects of cyclic Nakayama algebras via minimal zero paths
Speaker: Odysseas Giatagantzidis
Seminar Representation Theory of Algebras
This talk revisits key homological aspects of cyclic Nakayama algebras using a new combinatorial framework based on minimal zero paths. As a consequence, we provide a criterion that determines the exact value of their finitistic dimension, which has to be one of two consecutive integers by work of Ringel (2021) building on results of Madsen (2005). Furthermore, we offer novel characterizations for well-studied homological properties, including Iwanaga-Gorensteinness, finite global dimension, and quasi-heredity, recovering prior results in this direction.
02:15 pm
Bielefeld University X-E0-209
De Rham-Betti Structures and Groups for Abelian Varieties
Speaker: Zekun Ji
Algebraic and Arithmetic Geometry
In this talk, we discuss de Rham-Betti structures and groups for abelian varieties over Qbar. This is a framework introduced by Yves André to study the Grothendieck period conjecture, and further developed by Bost-Charles and Kreutz-Shen-Vial etc. I show that the de Rham-Betti group of any abelian variety contains the subgroup of homotheties. And I will explain the techniques involved to explicitly compute the de Rham-Betti groups in several special cases of abelian varieties. The results are based on my PhD thesis.
Thursday, 11 June
03:00 pm
Bielefeld University V2-210/216
Density of rational points near manifolds
Speaker: Damaris Schindler
Mathematisches Kolloquium (TRR 358)
Given a bounded submanifold M in R^n, how many rational points with common bounded denominator are there in a small thickening of M? How does this counting function behave if we let the size of the denominator go to infinity? The study of the density of rational points near manifolds has seen significant progress in the last couple of years. In this talk I will explain why we might be interested in this question, focusing on applications in Diophantine approximation and the (quantitative) arithmetic of projective varieties.
04:45 pm
Bielefeld University X-E0-001
The Mathematical Legacy of Hel Braun
Speaker: Ellen Eischen
Mathematisches Kolloquium (TRR 358)
This colloquium-level talk will survey mathematical contributions of twentieth-century mathematician Hel Braun. If you are wondering "Who's Hel Braun?" this talk is for you. If you already know and instead asked "But why Hel Braun?" it is also for you. Braun's research contributions lie in three areas: classical number theory problems about integers, modular and automorphic forms, and Jordan algebras. I will describe how each of these seemingly distinct topics led Braun naturally to the next, and I will highlight the ongoing impact of some of Braun's work, including in my own research. Along the way, I will briefly mention factors that helped shape her legacy. This talk is intended for a broad audience of mathematicians, and I hope mathematicians from many fields will attend.