Math Calendar

Thursday, January 16, 2025
16:00-17:00
MI talk Ivan Geffner Fuenmayor
Beyond Nash Equilibrium
Abstract: Nash equilibrium is often heralded as a guiding principle for rational decision-making in strategic interactions. However, it is well-known that Nash equilibrium sometimes fails as a reliable predictor of outcomes. In this talk we will analyze some of its undesirable properties and review some of the models that have been proposed to address its most prominent shortcomings.
Friday, January 17, 2025
15:00-17:00
HFG 707
Friday Fish
Joel Schmitz (Université de Neuchâtel) - Almost Toric Fibrations and Lagrangian Poincaré non-recurrence
Almost Toric Fibrations (ATFs) are a certain type of integrable system and provide a useful tool to study symplectic four-manifolds, allowing for various explicit constructions of Lagrangian torus knots and interesting symplectomorphisms. The latter gives a counterexample to the Lagrangian Poincaré recurrence conjecture. This talk will give a "users manual" to ATFs, outlining the tools used to manipulate them.
Monday, January 20, 2025
10:15-12:00
HFG 707
Log Stacks Seminar
Speakers: Sara Mehidi & Tom Manopulo (Utrecht)
Content: The category of Artin fans, the Artin fan of a logarithmic scheme, Artin fans and functoriality. 
Tuesday, January 21, 2025
11:00-12:00
HFG 707
NT Seminar (Efthymios Sofos)
Title: Ranks of elliptic fibrations
Abstract: In the 1950s, Erdős developed a method to estimate the average of the divisor function over the values of an integer polynomial. Nair and Tenenbaum later extended this to a substantially general class of arithmetic functions.

In 1993 Heath-Brown used character sums to study the average size of the 2-Selmer group in ty^2=x^3-x.

Combining these approaches, we prove that all exponential moments of the rank of P(t)y^2=x^3-x are bounded.

This is joint work with Peter Koymans and Carlo Pagano.
13:15-14:15
BBG 065
AG Seminar (Log Stacks Seminar- Research talks)
Martin Ulirsch (Goethe University Frankfurt am Main) on "How to tropicalize algebraic groups (and why we should care)- Log edition"
Tropical geometry studies a piecewise linear combinatorial shadow of classical algebraic geometry. In many ways, tropical geometry describes the extra information that is added to classical scheme theory in logarithmic geometry in order to study moduli-theoretic problems from a unified perspective. In this talk I will explain what little we currently know about the tropical geometry of algebraic groups. Along the way I will outline how  different avenues of progress towards an answer to this question have already led to numerous advantages within and beyond tropical and logarithmic geometry.

This talk will touch upon joint work with Luca Battistella, Desmond Coles, Andreas Gross, Inder Kaur, Kevin Kühn, Arne Kuhrs, Margarido Melo, Sam Molcho, Annette Werner, Alejandro Vargas, Filippo Viviani, and Dmitry Zakharov.
14:45-15:45
BBG 065
Log Stacks Seminar- Research talks
George Politopoulos (Leiden University/Cergy University) on "(spin)Strata of differentials and (spin)Double ramification cycles"
The strata of k-differentials are spaces parametrizing stable curves with n marking that admit a differential with prescribed zeroes and poles summing to k(2g-2+n). A natural question to ask is whether there exists an explicit formula in the Chow ring of M_{g,n}(bar) for the Chow class of these spaces. When k and all the zeroes and poles are odd numbers, we can define the so-called "spin refinement" of this problem.  In the non-spin case, the theory of Double ramification cycles can help to compute all such classes for the various g and n. In this talk we will recall this story and explain how this works in the spin case. This is a joint work in progress with Adrien Sauvaget and David Holmes.
16:00-17:00
HFG 611
MI talk
Lucas Dahinden - Robustness of Topological Entropy for Geodesic Flows
Topological entropy (=h) is a numerical invariant of maps that measures chaotic behaviour. It is well known, that h is not lower semi-continuous: There are examples where smooth perturbations lead to total collapse of h. However, sometimes a geometric feature prevents this collapse. In this talk we explore some of these features and discuss their consequences: On the 2-torus we investigate contractible closed geodesics, an intersection pattern that we call "ribbon" and on general manifolds we investigate a feature that we call "retractable neck". 
This is joint work with Marcelo Alves, Matthias Meiwes and Louis Merlin.
Seminar webpage https://utrechtgeometrycentre.nl/ugc-seminar/
16:00-17:00
BBG 065
Log Stacks Seminar- Research talks
Qile Chen (Boston College; online talk) on "Campana rational connectedness"
The notion of Campana points were introduced by Campana and Abramovich, which interpolate between rational points and integral points. In this talk, we will focus on the geometric side and introduce Campana rational connectedness --- a version of rational connectedness for varieties with simple normal crossings boundaries. We further prove that over function fields, weak approximations by Campana points at good places hold assuming Campana rational connectedness of fibers, generalizing a theorem of Hassett and Tschinkel. We further verify Campana rational connectedness for many basic examples. Our approach relies on the theory of stable log maps and their moduli. This is a joint work in progress with Brian Lehmann and Sho Tanimoto. 
Wednesday, January 22, 2025
13:30-15:30
HFG 707
Trace Methods and Computations Seminar
Motivic spectral sequence for l via descent from MU - Gijs Heuts

This seminarwill explore important themes in modern homotopy theory, focusing onTopological Hochschild Homology (THH), Topological Cyclic Homology (TC), andtheir applications in algebraic K-theory, with a special emphasis on tracemethods.

Tuesday, January 28, 2025
13:30-14:30
AG Seminar
Martin Lüdtke (University of Groningen)
Wednesday, January 29, 2025
13:30-15:30
HFG 707
Trace Methods and Computations Seminar
TC(F_p) and Redshift phenomenon - Ryan Quinn

This seminarwill explore important themes in modern homotopy theory, focusing onTopological Hochschild Homology (THH), Topological Cyclic Homology (TC), andtheir applications in algebraic K-theory, with a special emphasis on tracemethods.

Tuesday, February 4, 2025
13:30-14:30
Min 009
AG Seminar
16:00-17:00
HFG 611
MI talk
Pieter Belmans - Moduli of vector bundles and quiver representations
Moduli spaces are a geometer's favourite book-keeping device to describe a classification, and they lead to rich geometric objects. We will be concerned with moduli spaces of vector bundles on curves, and quiver representations. These have a very different origin, and a priori look very different. But there exists an extensive dictionary between these types of objects, and the challenge becomes to find the right way to phrase and understand this dictionary. I will survey some aspects of this exciting dictionary.

Seminar webpage https://utrechtgeometrycentre.nl/ugc-seminar/
Wednesday, February 5, 2025
13:30-15:30
HFG 707
Trace Methods and Computations Seminar
THH and Integral p-adic Hodge theory 1

This seminarwill explore important themes in modern homotopy theory, focusing onTopological Hochschild Homology (THH), Topological Cyclic Homology (TC), andtheir applications in algebraic K-theory, with a special emphasis on tracemethods.

Thursday, February 6, 2025
13:15-14:15
HFG611
Janusz Meylahn (UTwente)
Tuesday, February 11, 2025
13:30-14:30
Min 014
AG Seminar
Wednesday, February 12, 2025
13:30-15:30
HFG 707
Trace Methods and Computations Seminar
THH and Integral p-adic Hodge theory 2

This seminarwill explore important themes in modern homotopy theory, focusing onTopological Hochschild Homology (THH), Topological Cyclic Homology (TC), andtheir applications in algebraic K-theory, with a special emphasis on tracemethods.

Tuesday, February 18, 2025
13:30-14:30
Min 014
AG Seminar
16:00-17:00
HFG 611
UGC colloquium
András Vasy (Stanford University) - TBA
TBA

UGC colloquium webpage https://utrechtgeometrycentre.nl/ugc-seminar/
Wednesday, February 19, 2025
13:30-15:30
HFG 707
Trace Methods and Computations Seminar
Prismatic Cohomology of Z and l

This seminarwill explore important themes in modern homotopy theory, focusing onTopological Hochschild Homology (THH), Topological Cyclic Homology (TC), andtheir applications in algebraic K-theory, with a special emphasis on tracemethods.

Thursday, February 20, 2025
13:15-14:15
HFG611
Applied Mathematics Seminar -- Sophia Wiechert (RWTH Aachen)
Tuesday, February 25, 2025
13:30-14:30
DDW 136
AG Seminar
Wednesday, February 26, 2025
13:30-15:30
HFG 707
Trace Methods and Computations Seminar
Syntomic Cohomology of Z and l

This seminarwill explore important themes in modern homotopy theory, focusing onTopological Hochschild Homology (THH), Topological Cyclic Homology (TC), andtheir applications in algebraic K-theory, with a special emphasis on tracemethods.

Thursday, February 27, 2025
13:15-14:15
HFG611
Applied Mathematics Seminar -- Florian Wagener (UvA)
Monday, March 3, 2025
12:00-13:00
Bring Your Own Lunch
Tuesday, March 4, 2025
13:30-14:30
Min 013
AG Seminar
16:00-17:00
HFG 611
MI talk
Mar Curcó-Iranzo - TBA
Wednesday, March 5, 2025
13:30-15:30
HFG 707
Trace Methods and Computations Seminar
Dundas - McCarthy Theorem

This seminarwill explore important themes in modern homotopy theory, focusing onTopological Hochschild Homology (THH), Topological Cyclic Homology (TC), andtheir applications in algebraic K-theory, with a special emphasis on tracemethods.

Monday, March 10, 2025
16:15-17:15
Academy Building
Inaugural address
Daniel Dadush
Tuesday, March 11, 2025
13:30-14:30
HFG 707
AG Seminar
Ekin Ozman (U. of Groningen)
Wednesday, March 12, 2025
13:30-15:30
HFG 707
Trace Methods and Computations Seminar
Redshift for Lubin - Tate Theory

This seminarwill explore important themes in modern homotopy theory, focusing onTopological Hochschild Homology (THH), Topological Cyclic Homology (TC), andtheir applications in algebraic K-theory, with a special emphasis on tracemethods.

Tuesday, March 18, 2025
13:30-14:30
DDW 136
AG Seminar
Lara Vicino (U. of Groningen)
Wednesday, March 19, 2025
13:30-15:30
HFG 707
Trace Methods and Computations Seminar
Land-Tamme and Purity in Localized K-Theory

This seminarwill explore important themes in modern homotopy theory, focusing onTopological Hochschild Homology (THH), Topological Cyclic Homology (TC), andtheir applications in algebraic K-theory, with a special emphasis on tracemethods.

Thursday, March 20, 2025
13:15-14:15
HFG 611
Applied Mathematics Seminar -- Satoshi Fukuda (Bocconi University)
Tuesday, March 25, 2025
13:30-14:30
Min 207
AG Seminar
Wednesday, March 26, 2025
13:30-15:30
HFG 707
Trace Methods and Computations Seminar
Chromatic Localizing Invariants and Descent

This seminarwill explore important themes in modern homotopy theory, focusing onTopological Hochschild Homology (THH), Topological Cyclic Homology (TC), andtheir applications in algebraic K-theory, with a special emphasis on tracemethods.

Tuesday, April 1, 2025
13:30-14:30
Min 014
AG Seminar
Thursday, April 3, 2025
13:15-14:15
Applied mathematics seminar Matteo d'Achille (U Paris Saclay)
Monday, April 7, 2025
12:00-13:00
Bring Your Own Lunch
Tuesday, April 8, 2025
13:30-14:30
Min 014
AG Seminar
Tuesday, April 15, 2025
13:30-14:30
Min 014
AG Seminar
Tuesday, April 22, 2025
10:00-11:00
HFG 707
AG Seminar
Tuesday, April 29, 2025
10:00-11:00
HFG 707
AG Seminar
Tuesday, May 6, 2025
10:00-11:00
HFG 707
AG Seminar
Monday, May 12, 2025
12:00-13:00
Bring Your Own Lunch
Tuesday, May 13, 2025
10:00-11:00
HFG 707
AG Seminar
Tuesday, May 20, 2025
10:00-11:00
HFG 707
AG Seminar
Tuesday, May 27, 2025
10:00-11:00
HFG 707
AG Seminar
Tuesday, June 3, 2025
10:00-11:00
HFG 707
AG Seminar
Tuesday, June 10, 2025
10:00-11:00
HFG 707
AG Seminar
Monday, June 16, 2025
12:00-13:00
Bring Your Own Lunch
Tuesday, June 17, 2025
10:00-11:00
HFG 707
AG Seminar
Tuesday, June 24, 2025
10:00-11:00
HFG 707
AG Seminar