This week's discoveries: What is the shape of a knot?

A 15-minute lecture inviting the audience to understand knots by curving the space around it.

227 Seminar, Leiden

An exposition of Conway's theorem of rational tangles following Kauffman. The algebra of continued fractions can be mimicked by simple knotting operations on a pair of ropes. Underlying reason: Mapping class group of the 4-punctured sphere is the modular group.

Nationale Wiskunde Dagen 2015 and Nederlands Mathematisch Congres 2014

Lecture on the geometry of rotations, with many hands-on exercises (older English version).

NSA symposium 2013

Lecture: a Random walk through number theory. About probabilistic heuristics in number theory.

Vakantiecursus wiskunde 2013

I gave a series of lectures on G. Perelman's Ricci flow and his solution of the Poincaré conjecture in the context of discrete surfaces.

Dots & Boxes / Kamertjeverhuren

Together with Lisa Steverink and Marie-Beth van Egmond I organised the very first Dutch open Dots and Boxes championship at the University of Amsterdam.

Lecture on quadratic reciprocity

I presented a pretty simple proof of the quadratic reciprocity law at the the Leve de wiskunde 2013 event. Here is the presentation and a short note containing the actual proof (Dutch). The actual lecture can be watched here (mine is the third presentation)

Thesis defence dance performance

To convey the essence of my PhD thesis I gave a short dance demonstration.

Two more less mathematical performances.

Book on the Riemann hypothesis

with Jan van de Craats

English translation under review.

Review in the AMS math reviews.

Website for the book (under construction)

De zeven grootste raadsels van de wiskunde

with Alex van den Brandhof, Barry Koren en Jan van de Craats.

Book website