Mathematical Institute Calendar

Thursday, November 14, 2024

11:00-13:00

Springer Room

Morse spacetimes are Lorentz spacetimes with singularities where time behaves like a Morse function. The intention of the definition is that the spacetimes are "nice" but still allow the topology of "space" to change with time. Borde and Sorkin conjectured that such Morse spacetimes are causally continuous (a.k.a. nice) if and only if neither the index nor the coindex of any critical point is 1. This has been recently confirmed by García-Heveling for the case of small anisotropy and Euclidean background metric. Here, we provide a complementary counterexample: a four dimensional Morse spacetime whose critical point has index 2 and large enough anisotropy is causally discontinuous. Thus, the Borde-Sorkin conjecture does not hold. The proof features a low regularity causal structure and causal bubbling.

Friday, November 15, 2024

15:00-17:00

VU, Maryam

Monday, November 18, 2024

10:15-12:00

HFG 707

14:30-16:00

HFG 707

I'll talk about one particular Grothendieck topos, which is most straighforwardly defined as the topos of sheaves for the countable cover Grothendieck topology on a certain small category. Surprisingly, this topology is both canonical and dense, hence the topos is boolean. Its classical internal logic validates the axiom of dependent choice and also the existence of a translation-invariant measure, extending Lebesgue measure, defined on all subsets of the reals. The measure can be uniquely characterised by exploiting an intrinsic independence relation, closely related to the Day monoidal structure on the topos.

Tuesday, November 19, 2024

11:00-13:00

HFG 7.07B

16:00-17:00

HFG 611

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.

UGC seminar webpage https://utrechtgeometrycentre.nl/ugc-seminar/

UGC seminar webpage https://utrechtgeometrycentre.nl/ugc-seminar/

Wednesday, November 20, 2024

13:30-15:30

HFG 707

Thursday, November 21, 2024

Monday, November 25, 2024

Tuesday, November 26, 2024

11:00-13:00

HFG 7.07B

16:00-17:00

HFG 611

Wednesday, November 27, 2024

13:30-15:30

HFG 707

Thursday, November 28, 2024

16:00-17:00

HFG 611

After giving a gentle and illustrative introduction to classic optimal transport theory we will thoroughly explore the GW transport problem. Subsequently we turn our attention to GW barycenters. Motivated by obtaining a numerically tractable method for their computation, we study the geometry of the induced GW space. Our theoretical results in this context allow us to lift a known fixpoint iteration for the computation of Fréchet means in Riemannian manifolds to the GW setting. The lifted iteration is simple to implement in practice and monotonically improves the quality of the barycenter. We provide numerical evidence of the potential of this method, including multi 3d shape interpolations.

Friday, November 29, 2024

Monday, December 2, 2024

13:00-14:00

HFG 707

Tuesday, December 3, 2024

11:00-13:00

HFG 7.07B

13:30-14:30

Merged with Rational Points Consortium meeting: https://www.rationalpoints.nl/events-2/

Wednesday, December 4, 2024

13:30-15:30

HFG 707

Thursday, December 5, 2024

Monday, December 9, 2024

Tuesday, December 10, 2024

16:00-17:00

HFG 611

Wednesday, December 11, 2024

13:30-15:30

HFG 707

Thursday, December 12, 2024

Tuesday, December 17, 2024

16:00-17:00

HFG 611

Wednesday, December 18, 2024

13:30-15:30

HFG 707

Wednesday, December 25, 2024

13:30-15:30

HFG 707

Wednesday, January 1, 2025

13:30-15:30

HFG 707

Tuesday, January 7, 2025

Wednesday, January 8, 2025

13:30-15:30

HFG 707

Thursday, January 9, 2025

Monday, January 13, 2025

Tuesday, January 14, 2025

Wednesday, January 15, 2025

13:30-15:30

HFG 707

Monday, January 20, 2025

Tuesday, January 21, 2025

Wednesday, January 22, 2025

13:30-15:30

HFG 707

Monday, January 27, 2025

Tuesday, January 28, 2025

Wednesday, January 29, 2025

13:30-15:30

HFG 707

Wednesday, February 5, 2025

13:30-15:30

HFG 707

Thursday, February 6, 2025

Wednesday, February 12, 2025

13:30-15:30

HFG 707

Wednesday, February 19, 2025

13:30-15:30

HFG 707

Thursday, February 20, 2025

Wednesday, February 26, 2025

13:30-15:30

HFG 707

Monday, March 3, 2025

Wednesday, March 5, 2025

13:30-15:30

HFG 707

Monday, March 10, 2025

Wednesday, March 12, 2025

13:30-15:30

HFG 707

Wednesday, March 19, 2025

13:30-15:30

HFG 707

Thursday, March 20, 2025

16:00-17:00

HFG 611

Wednesday, March 26, 2025

13:30-15:30

HFG 707

Monday, April 7, 2025

Monday, May 12, 2025