How to reach me

Niels Bohrweg 1 Room 212
2333CA Leiden kallecccj@math.leidenuniv.nl
The Netherlands +31 71 527 1590

Research interests

My research is in ergodic theory, the area of mathematics concerned with the typical long term behaviour of dynamical systems. I have a special interest in intermittency in random dynamics, dynamics related to number expansions and the fractals that surface naturally in these contexts.

PhD students

Publications

My publications include three textbooks, around twenty peer reviewed scientific articles and a couple of outreach articles. Click on the button below for a full publication list.

Foundation Compositio Mathematica

I am a board member and the secretary of the Foundation Compositio Mathematica, which is the foundation behind the three journals Compositio Mathematica, Algebraic Geometry and Moduli. It has the aim of publishing first class papers in the central areas of mathematical research and supporting mathematics and mathematical research. The foundation supports mathematics via subsidies for mathematical conferences, prizes for mathematical accomplishments and other initiatives. Applications can be done through the foundation's website.

Koninklijk Wiskundig Genootschap

I am a board member and the vice-secretary of the Royal Dutch Mathematical Society, Koninklijk Wiskundig Genootschap, which was founded in 1778 and has the distinction of being the oldest of all present-day national mathematical societies. It serves as the professional organization of individuals, in particularly the Netherlands, whose activities are related to mathematics.

Outreach activities

Teaching activities

In the academic year 2023/2024 I teach the bachelor/master course Ergodic Theory and Fractals together with Olga Lukina, the bachelor course Dynamics and Chaos with Martina Chirilus-Bruckner, and the bachelor course Introduction to Measure Theory with Floske Spieksma.

In the fall of 2023 I am co-teaching the course on Dynamical Systems in the International Mathematics Master in Lahore, Pakistan.

I am a member of the board of examiners for the bachelor and master of mathematics at Leiden University.