*Matematika mugaz bestalde*

Benoît Perthame was born in France on June 23rd, 1959. He studied mathematics at Ecole Normale Superieure and obtained his PhD from University Paris Dauphine in 1982, under the supervision of Pierre-Louis Leions. Currently, he is a professor at Pierre-et-Marie Curie University and at the Laboratoire Jacques-Louis Lions.

Prof. Perthame is an internationally-renowned specialist in partial differential equations and a pioneer in the field of mathematical biology. He has received numerous distinctions including the Blaise Pascal prize, the CNRS Silver Medal and the Inria Prize. He has also been elected a member of Academia Europaea, the French Academy of Sciences and the European Academy of Sciences.

On Wednesday, May 6th, he will be the main speaker at the 8th Math Colloquium organized by the Basque Center for Applied Mathematics – BCAM and the University of the Basque Country. Due to the COVID-19 pandemic the talk will be streamed online and users will be welcome to join using the video conferencing tool Bb Collaborate.

Before his lecture on “Multiphase models of living tissues” we’ve had the chance to interview him and ask him about his scientific career, his research interests and his focus on the application of mathematics to real life problems.

After school, I hesitated between mathematics and physics, but I found mathematics more attractive, mainly because of my teachers and also because it was providing the tools to understand physics.

His approach to mathematics is so clear, insightful and broad that it is difficult not to be influenced when working on PDEs. I can mention two aspects that I try to follow as much as I can. The first one is trying to choose problems coming from application and, the second one, trying to find, at least in a first step, a clear and accessible presentation avoiding technical issues and complicated terminologies.

At the end of the 1990's I realized that there were many teams involved in all areas of physics but very few in problems of biology. That is why I decided to investigate the modeling questions in the various fields of life sciences.

I discovered that the way to think in biology is very different from physics. Models are not well established; the mathematics should tell you about the qualitative behaviours rather than exact numbers and coefficients are not fixed (adaptation of organisms is important).

Behind these questions various theories emerge as pattern formation, waves, uncertainty quantification, instabilities and asymptotic theory because one always learns more from extreme cases than from the normal behaviour.

Evolution (adaptation, variations…) arise everywhere in life sciences. One might consider that it characterizes them compared to physics. So, one cannot think a biology problem without mutations and Darwin view.

My idea was to find these problems coming from life sciences which lead to model written in terms of nonlinear PDEs which are not standard. In each of these fields I could find new challenging mathematical questions. It is clear that many (all) other areas of mathematics have also something to bring to biological modeling.

The present pandemic tells you the answer. At its onset, very few data where available. To advise governments about their decisions, the only arguments where the outcome of mathematical models of epidemic spread.

Now that all these nonlinear PDEs arising from domains of biology have been uncovered, it is time to put forces to understand them and go one step further in biological modeling.

Modeling living tissues is presently a fast-developing problem in many scientific fields (physics, mechanics, biology, medical science). These different points of view have led to many different nonlinear PDEs. I thought it would be interesting to present an area of science where mathematics is progressing in parallel with other sciences.

Many scientists, including many mathematicians, decided to orient their research in the direction of the pandemic. I follow several webinars on the subject. This is the case of control theory, which is important to understand the strategies to release of lock-down.