Interview with Sylvie Méléard, invited speaker at ICM2022

Link to the virtual ICM 2022 talks

What is your field of research?

I’m trained as a probabilist but have done a lot of work where stochastic processes and partial differential equations meet. For the last 20 years or so, I’ve become more and more interested in developing such tools for modelling and quantifying biological evolutionary phenomena, first theoretically then in increasingly applied projects. What interests me is taking into account the different scales that define the parameters involved in modelling certain biological phenomena and the way in which those scales affect the system’s behaviour. My approach is to describe the unique patterns among individuals via a stochastic process, taking into account interactions among the individuals. This method is particularly well adapted to new measurement techniques in biology (e.g. single-cell microscope, mother machine, microfluidics), that allow us to measure the individual behaviour of bacteria, for example. Biological phenomena are so rich that each new question leads to fascinating mathematical analyses and new theories. This kind of research requires regular contact with biologists and doctors, in order to create the best models for biological questions, but also to guide us to new experiments that can help us to understand our models and to validate them.

What led you to take up mathematics?

That’s ancient history, a decision I made at a very young age, though at 20 years of age, I was still thinking about going into fashion design!

How would you describe your profession?

It’s a passion. My job is to develop mathematics (which contains moments of great excitement when we finally find answers to the questions that have been obsessing us), but also to interact on fundamental questions of biology and medicine, to train young people, to create common projects, and to pass down an enjoyable way of doing maths.

Are there places or moments that were decisive in your career?

My meeting with Régis Ferrière in 2001, when we were jointly supervising Nicolas Champagnat’s thesis, was a turning point in my favourite themes, with the discovery of eco-evolutionary biology and its hypotheses. It was a great joy to see that with the point of view of the particle systems that I had developed in another context, we can build a stochastic approach that can address some of these hypotheses.

My arrival at the CMAP École polytechnique, an applied maths laboratory with many projects and contracts with firms, on highly applied subjects, opened horizons for me, and allowed me to develop my research in an interdisciplinary context. That also gave me a framework in which to establish the chair in mathematical modelling and biodiversity, a scientific network that brings together around 100 mathematician and biologist members.

The encounter with Stéphane Giraudier, oncologist at the Hôpital Saint-Louis, was another new step, pushing me definitively towards increasingly concrete applications, related to developments in leukaemia research.

What do you like about being a mathematician?

The fact that I can do what I love doing. The freedom to choose the subjects that one works on. The exciting moments when one really learns something.

What place does the transmission of ideas about mathematics have in your work?

An important place. People are not really used to associating maths with ecology or biodiversity and it’s important to explain to them how mathematics can intervene in these questions.

What would you say to young people who are thinking about taking up a scientific career?

Go for it. Follow your dreams.

Have you already decided what you are going to say at the ICM?

I will try to demonstrate the richness of multi-scale and individual-centered stochastic systems that arise from certain biological questions.

What does this conference represent for you?

A recognition by the mathematics community of the questions that fascinate me.