Burkhard
Eden
The off-shell one and two-loop box recovered from intersection theory
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12. May
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13. May
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Holger
Dette
Ruhr University Bochum
Multiple change point detection in functional data with applications to biomechanical fatigue data
Abstract.
Injuries to the lower extremity joints are often debilitating, particularly for professional athletes. Understanding the onset of stressful conditions on these joints is therefore important in order to ensure prevention of injuries as well as individualised training for enhanced athletic performance. We study the biomechanical joint angles from the hip, knee and ankle for runners who are experiencing fatigue. The data is cyclic in nature and densely collected by body worn sensors, which makes it ideal to work with in the functional data analysis (FDA) framework. We develop a new method for multiple change point detection for functional data, which improves the state of the art with respect to at least two novel aspects. First, the curves are compared with respect to their maximum absolute deviation, which leads to a better interpretation of local changes in the functional data compared to classical L^2-approaches. Secondly, as slight aberrations are to be often expected in a human movement data, our method will not detect arbitrarily small changes but hunts for relevant changes, where maximum absolute deviation between the curves exceeds a specified threshold, say Δ > 0. We recover multiple changes in a long functional time series of biomechanical knee angle data, which are larger than the desired threshold Δ, allowing us to identify changes purely due to fatigue. In this work, we analyse data from both controlled indoor as well as from an uncontrolled outdoor (marathon) setting.
Quan
Shi
AMSS Chinese Academy of Sciences
Two phase transitions for catalytic branching Markov chains
Abstract.
Consider a continuous-time branching Markov chain $(Z_t,t\ge 0)$ on a locally finite graph $G$ rooted at $\mathbf{o}$. Each particle moves according to an irreducible Markov process $\xi$ and branches at a rate that depends on their location: the branching rate is $\lambda_{rt}\ge 0$ at the root and $\lambda\ge 0$ elsewhere. The offspring distribution is supercritical with mean $m>1$, has no extinction and finite second moment. We characterize the recurrence/transience phase transition for this catalytic branching Markov chain. Furthermore, under suitable assumptions we prove a second phase transition concerning the asymptotic behaviour of the relative empirical density, $(Z_t(G))^{-1} Z_t$, where $Z_t$ is the empirical measure of the particles and $Z_t(G)$ is the total population size. If $(m-1)(\lambda_0-\lambda)> \gamma_{esc}$, where $\gamma_{esc}$ is the escape probability that $\xi$ never returns to the root, then $(Z_t(G))^{-1} Z_t$ converges almost surely to a deterministic probability measure. If $(m-1)(\lambda_0-\lambda)\in (0, \gamma_{esc}]$, then $(Z_t(G))^{-1} Z_t$ converges almost surely to zero. When the graph is the integer lattice $G=\mathbb{Z}^d$ and $\xi$ is the simple random walk, our results confirm several conjectures of Mailler and Schapira [Ann. Appl. Probab. 2026], which studied this model via a different approach. Based on a joint work in progress with Xinxin Chen (Bejing Normal Unversity), Nina Gantert (Technical University of Munich) and Haojie Hou (Beijing Institute of Technology).
Martin
Heida
WIAS
15. May
Fri W19
Laios
Zafeiriou
Aristotle University of Thessaloniki
Eva-Maria
Hekkelman
MPI Bonn
18. May
Mon W20
Chara
Zhu
On pitchfork bifurcations in Phi-4-2
Dhruv
Mubayi
University of Illinois Chicago
Pentagons in triple systems
Abstract.
We consider the question of determining the number of pentagons in a linear triple system and show some connections to number theory, graph theory, theoretical computer science, and geometry. This is joint work with Jozsef Solymosi.
20. May
Wed W20
Eva-Maria
Hekkelman
MPI Bonn
Johannes
Schmidt-Hieber
University of Twente
Julian
Kern
FU Berlin
Riccarda
Rossi
University of Brescia, Italy
Yufei
Zhang
Imperial
Johannes
Rau
Universidad de los Andes
21. May
Thu W20
Egor
Bakaev
Paolo
Pigato
University of Rome
John
Armstrong
King's College London
22. May
Fri W20
Jessica
Fintzen
Universität Bonn
Representing Number Theoretic Symmetries with Linear Algebra
Abstract.
A common theme studied in number theory are congruences between integers modulo prime numbers or modulo powers of prime numbers. A way to encode all those congruences at once is provided by a field that is called the field of p-adic numbers. Out of this field one can build interesting groups, called p-adic groups, which are number theoretic analogues of Lie groups, have a similar rich structure, and which play a central role in the Langlands program, for example. A key question that mathematicians ask is how one can represent these complicated-looking p-adic groups using more common complex matrix groups, in other words, using more traditional linear algebra. In this talk, I will introduce p-adic numbers and p-adic groups and then provide an overview of what we know about the representations of these groups including recent developments. This means I will explain how close we are to answering the key question above. I might also sketch applications to other questions in mathematics.
Johannes
Buchmann
Technische Universität Darmstadt
Numbers, Quantum Computers, and the Question of Responsibility
Abstract.
The lecture traces an arc from the history of a seemingly harmless mathematical problem to highly relevant societal questions. The starting point is the factoring problem. Through early mechanical calculating aids and the first successes of electronic computers, it shows how long and persistently this problem has accompanied mathematics - and why it ultimately became a foundation of modern cryptography. These mathematical ideas are no longer abstract today. They secure the internet, our communications, and our privacy. At the same time, we are witnessing that digital platforms and social networks pose significant risks to the mental health of children and adolescents. This gives rise to a societal responsibility: age limits must be enforceable without resorting to pervasive surveillance or large-scale data collection. The lecture shows that cryptographic methods can solve precisely this problem. Finally, the perspective turns to the future: quantum computers threaten the cryptographic procedures in use today. The lecture explains which attacks are realistic, that post-quantum methods are available as alternatives - and why it is a matter of responsibility to manage this transition in good time.
26. May
Tue W21
Nikolai
Kuchumov
Abo Akademi
27. May
Wed W21
Alexander
Meister
Rostock
Ester
Mariucci
Université de Versailles Saint Quentin, Paris Saclay
David
Dereudre
University of Lille
Tomáš
RoubĂÄŤek
Charles University Prague and Inst. of Thermomechanics, Czech Acad. Sci.
The Stefan problem with a phase transition between visco-elastic fluids and finitely-strained solids
Abstract
28. May
Thu W21
Dana
Wrischnig
Charlotte
Lämbgen
Timm
Oertel
29. May
Fri W21
Angela
Gibney
U Penn
Kovalevskaya Colloquium
01. June
Mon W22
Willem
van Zuijlen
Discrete Anderson Hamiltonians with correlated Gaussian potentials
02. June
Tue W22
Nikolai
Kuchumov
Abo Akademi
Limit shapes and harmonic tricks
Abstract.
The talk will be on the tangent plane method — a novel method for analysis of limit shapes of the dimer model. It will consist of three parts. In the first part, we will briefly introduce the dimer model and the necessary concepts including the associated variational problem. The second part will focus on the underlying geometry using harmonic parametrization. In the third part, we will consider two specific examples of limit shape parametrized by a modular parameter: the Aztec diamond with a hole, and a hexagon with a hexagonal hole. The talk is based on arXiv:2603.21255 (https://arxiv.org/abs/2603.21255).
03. June
Wed W22
Caroline
Hillairet
ENSAE Paris
04. June
Thu W22
Paolo
Villani
Jim
Gatheral
CUNY
Jonathan
Tam
University of Oxford
09. June
Tue W23
Lasse
Merkens
HU Berlin
10. June
Wed W23
Michael
Sørensen
University of Copenhagen
16. June
Tue W24
Bertrand
Eynard
IPhT CEA Saclay
17. June
Wed W24
Anna
Calissano
University College London
John
Armstrong
King’s College
23. June
Tue W25
Anna
Hartkopf
FU Berlin, MIP.labor
24. June
Wed W25
Bertrand
Even
LMO, Orsay
26. June
Fri W25
Emanuel
Milman
Technion
01. July
Wed W26
Stefano
Bonaccorsi
U Trento
Tobias
Rossmann
University of Galway
02. July
Thu W26
Claudia
Schillings
07. July
Tue W27
Alexander
Alexandrov
IBS Pohang
08. July
Wed W27
Gilles
Blanchard
Université Paris Saclay
Romanos
Malikiosis
Aristotle University of Thessaloniki
10. July
Fri W27
Silvia
de Toffoli
IUSS Pavia
14. July
Tue W28
Alexander
Alexandrov
IBS Pohang
Eris
Runa
GSSI L'Aquila, Italy
Sara
Daneri
GSSI L'Aquila, Italy
15. July
Wed W28
Christina
Lienstromberg
Universität Stuttgart
Xiang
Yu
PolyU
16. July
Thu W28
Xiang
Yu
The Hong Kong Polytechnic University
Chiara
Rossato
ETH Zurich
29. July
Wed W30
Bao Quoc
Tang
Universität Graz
17. December
Thu W50
Lars
Kastner
TU Berlin
Drawing algebraic curves in OSCAR