GQT Graduate School and Colloquium 2026

Colloquium abstracts

 

Sara Mehidi (Utrecht): 

Abstract  

 

Xavier Blot (Amsterdam): 

Abstract  

 

Tommy Lundemo (Utrecht): Logarithmic cohomology theories in topology and arithmetic

Abstract: I will survey recent work on how ideas from logarithmic geometry have been applied to tackle problems in homotopy theory and arithmetic geometry. Combining results from both sides, we arrive at an application to (the “deformational” part of) the variational Hodge conjecture. This will touch upon joint projects with Binda, Merici, Park, and Østvær. 

Giulio Ruzza(Lisbon): 

Abstract  

Leonid Ryvkin(Lyon 1): Tepui fibrations and singular vector bundles 

Abstract: 

As a differential-geometric object, a tepui fibration is a type of singular fiber bundle with smooth base space and smooth fibers, however the fiber dimension might jump when moving from one base point to another. Tepui fibrations naturally turn up in differential geometry, when one is quotienting by a smooth family of symmetries, which degenerates at certain points, e.g. in the context of singular foliations. In this talk I will give an introduction to tepui fibrations and show how they provide a natural way to extend the classical Serre-Swan theorem beyond the setting of projective modules.

Based on joint work with Alfonso Garmendia and David Miyamoto.
https://arxiv.org/pdf/2510.20936  

Michael Heins(TU Delft): 

Abstract  

Francesca Pratali (Utrecht): Operads and trees

Operads are combinatorial objects that arose in algebraic topology through the work of May, Boardman, and Vogt to model the up-to-homotopy associative algebra structure of loop spaces. Since then, they have become fundamental tools in many areas of mathematics. In modern homotopy theory, where objects in categories are considered only up to weak equivalence, this notion has evolved into that of ∞-operads.

In this talk, we will introduce the basic notions of operads and algebras over an operad, and explain how they provide a powerful framework for studying the homotopy theory of seemingly different algebraic structures in a unified way. The fun part of the seminar is that we will use the language of trees, namely certain directed connected graphs whose combinatorics makes operad theory more visual and intuitive. This formalism, introduced by Moerdijk and Weiss, also paves the way to the world of ∞-operads—though that will probably be a story for another seminar!