Kristian Seip Norwegian University of Science and Technology – NTNU

17 / 04 / 2024 - 12:15

Location: T1

Títol: Fourier interpolation and the uncertainty principle

Abstract: A new direction of research in analysis, known as Fourier interpolation, has emerged from a celebrated 2019 paper of Radchenko and Viazovska which was an outgrowth of the solution to the sphere packing problem in dimension 8. I will give an overview of this and subsequent developments, with emphasis on a connection with the zeros of the Riemann zeta function. I will comment briefly on Freeman Dyson’s idea to approach the Riemann hypothesis by describing all one-dimensional quasicrystals.

Biography: Kristian Seip (1962) obtained his doctor’s degree at the Norwegian Institute of Technology in 1988, and became a professor in 1994. He was an invited speaker at the International Congress of Mathematicians in Berlin in 1998.
Seip chaired the Norwegian Mathematical Society from 2003 to 2007 and the committee that awards the Abel Prize from 2007 to 2010. He is a member of the Norwegian Academy of Science and Letters and the Royal Norwegian Society of Science. In 2012 he became a fellow of the American Mathematical Society.
His research areas are currently operator related function theory and analytic number theory.

Colloquium to celebrate the 100th anniversary of Albert Einstein’s visit to Catalonia.

20 / 12 / 2023 - 12:15

Contact: Xavier Jarque | Location: T1

On December 20th, 2023, we will have an (extraordinary) colloquium to celebrate the 100th anniversary of Albert Einstein’s visit to Catalonia.

The event will consist of two talks on Einsteien’s work and his historical visit to Barcelona and Catalonia. The talks will be in Catalan.

12.15 – 12.55 Emili Elizalde (CSIC), «Una visió contemporània i actual de les teories de la relativitat i la visita d’Einstein a la Catalunya de 1923»

13.00 – 13.40 Ignasi Mundet (Universitat de Barcelona), «Relativitat general: de l’equació del camp gravitatori a la conjectura de Poincaré i més enllà»

Javier Fresán, Institut de Mathématiques de Jussieu-Paris Rive Gauche. Sorbonne Université

21 / 02 / 2024 - 12:15

Location: T1

Gabor Lugosi (Universitat Pompeu Fabra, Barcelona)

25 / 10 / 2023 - 12:15

Location: T1

Title: Mathematical models of network archaeology

Abstract: Large networks that change dynamically over time are ubiquitous in
various areas such as social networks,
and epidemiology. These networks are often modeled by random dynamics
which, despite being relatively simple,
give a quite accurate macroscopic description of real networks. In
«network archaeology» one studies statistical
problems of inferring the past properties of such growing networks,
given the current state of the network. In this
talk we discuss some simple network models and review recent results
on revealing the past of the networks.

Brief Bio: Gabor Lugosi is an ICREA research professor at the Department of Economics of the
Pompeu Fabra University in Barcelona. His main research interests
include statistical, learning theory, sequential prediction, nonparametric classification
and regression, random graphs, and concentration inequalities.
He has published four research monographs and over 120 papers on these topics.

In 2021, Lugosi delivered the “Breiman lecture» at NeurIPS, the prime conference on Machine Learning,
and was an invited speaker in the newly created Statistics section at the 2022 International Congress of Mathematicians.

He has also been “Medallion Lecturer” and “Blackwell lecturer” in conferences organized by the Institute of Mathematical Statistics.

Alberto Enciso (ICEMAT-CSIC)

22 / 03 / 2023 - 12:00

Contact: http://www.imub.ub.edu/next-colloquium/ | Location: Room T1

Speaker: Alberto Enciso

Affiliation: ICEMAT-CSIC

Title: Water under a bridge: the interplay between analysis and geometry in the study of incompressible fluids

Abstract: It is well known that many high profile problems in the theory of partial differential equations in general, and in fluid mechanics in particular, are of a strongly geometric nature. Our goal is to discuss some problems of this kind. As we will see, their dual character makes them particularly attractive, and their solution frequently involves a rich (and at times surprising) interaction between various areas of mathematics.

Brief Bio: 

Étienne Ghys (École Normale Supérieure de Lyon)

03 / 05 / 2023 - 12:10

Contact: http://www.imub.ub.edu/next-colloquium/ | Location: T1

Speaker: Étienne Ghys

Affiliation: École Normale Supérieure de Lyon

Title: The group of homeomorphisms of the sphere

Abstract: In 1935 Ulam conjectured that the component of the identity in the group of homeomorphisms of the sphere is a simple group (no non-trivial normal subgroup). Today we know that this is indeed the case but since that time many similar problems have been solved. But the question concerning area respecting homeomorphisms has resisted for forty years. To my great surprise, D. Cristofaro-Gardiner, V. Humilière and S. Seyfaddini have shown recently that the corresponding group is not simple. I would like to tell the story of this mathematical adventure, from 1935 to 2023.

Brief Bio: 

Barbara Fantechi. Scuola Internazionale Superiore di Studi Avanzati (SISSA). Enumerative geometry after string theory

23 / 11 / 2022 - 12:10

Contact: http://www.imub.ub.edu/next-colloquium/ | Location: Room T1

Enumerative geometry asks how many solutions a geometric question has: as example, given four generic lines in 3 space, there are exactly two other lines meeting all four.

This led to a Fields medal for a physicist (Edward Witten), and set the ball rolling for a veritable avalanche of new ideas and results that shows no sign of slowing down, three decades later.

Samy Tindel. Purdue University. Waving Marta Goodbye

01 / 06 / 2022 - 12:00

In this talk I will first give a brief overview of some standard stochastic PDE models. Then I will describe some of Marta’s fundamental contributions to the theory of stochastic wave equations. This includes challenging problems such as the definition of noisy wave equations in higher dimensions, as well as further properties of the solution. Those results are based on nontrivial extensions of Itô type integrals and advanced Malliavin calculus tools, for which I intend to give a short and non technical introduction. Eventually I will give an account on more recent pathwise approaches to noisy wave equations, which are still the object of active research.

Michael Röckner. Universität Bielefeld. Taming Uncertainty and Profiting from Randomness

01 / 06 / 2022 - 10:30

Location: Aula Magna

The title of this talk is a short form of the title of a major research project (a socalled Collaborative Research Centre, funded by the German Research Foundation, DFG), currently running at Bielefeld University. It is based on the claim that randomness, which is ubiquitous and cannot be avoided, neither in the natural sciences, nor in the humanities, has in fact two “faces“, one is a kind of a nuisance, which destroys one’s observations or measurements, is hard to quantify and causes uncertainty about the correctness of one’s final conclusions. So, one has to look for means and to develop tools for “taming“ it. On the other hand, in many cases randomness can help to understand observed phenomena which otherwise would remain a mystery, and in addition its mathematical analysis may lead to a deeper understanding of the underlying mechanisms, thus leading to resolving seemingly contradictory conclusions, which with no doubt is a valuable “profit“. In the talk I shall present some examples for the above claim and try to explain what mathematics, in particular stochastic analysis, offers for both “taming uncertainty“ and “profiting from randomness“. One eminent instance for both the latter will be the mathematical approachto understanding dynamical processes under the influence of “noise“, which appear in all sciences. The technical term of this mathematical approach is “stochastic partial differential equations“, but despite this for non-mathematicians maybe a bit “terrifying“ name, I think these can be understood quite well on an intuitive level from a certain view point, as I shall try to explain in the talk.

Ivan Smith. University of Cambridge. Floer homotopy theory.

04 / 05 / 2022 - 12:10

Location: Room T1

Ivan Smith. University of Cambridge.

Homotopy theory studies the algebraic topology of (nice) spaces, and an
important point is that many phenomena become simpler if you work
`stably’ in a certain sense. Floer theory involves counting holomorphic
curves in symplectic manifolds and arises naturally in algebraic geometry
and dynamics; an important point is that one wants to count such
curves, but can traditionally only do so working over the rationals,
because of finite symmetry groups. Recently, ideas from stable
homotopy theory have allowed one to define certain Floer-theoretic
invariants over the integers. I will try and explain some of the
background to both fields, and what makes this new connection
between the two possible.