Franck Sueur has joined the University of Luxembourg since September 2024 as Professor in Partial Differential Equations and Analysis.
Could you introduce yourself?
“After really discovering maths at the Ecole Normale Supérieure (with great teachers such as Emmanuel Grenier, Denis Serre and the fields medalist Cédric Villani !), I did a PhD thesis in the hot city of Marseille, under the (great) supervision of Olivier Guès. Luckily enough, in 2005, I was hired right away as an associate professor in a fantastic math’ lab in Paris: the Jacques-Louis Lions laboratory, after the name of the founder of applied maths in France. I moved to Bordeaux in 2014 as a full professor, where I stayed for ten years, being also a junior member of the Institute Universitaire of France for five short of these long years.”
Could you describe your field of interest ?
“I work on some Partial Differential Equations, PDEs for short. These are mathematical equations describing various phenomena which may be related to physics, biology, finance and to many other applications ! Some of my favourite are the Euler equations and the Navier-Stokes equations, which describe the dynamics of a fluid, in time and space. As a mathematician, on the theoretical side, I consider some quite academical issues regarding the analysis of these systems. I was first dedicated to develop some tools to capture some multi-scale features of the solutions to these equations, what brings me, in the last two decades, to investigate the motion of some small particles carried by a fluid flow. The last decade, I also got quite obsessed with some controllability issues, what amounts to find strategies to modify a flow by the means of an appropriate action.”
Why did you join the University of Luxembourg?
“First of all, the University of Luxembourg provides an excellent research environment, which will hopefully allow me to dedicate more of my time to my fav’ research questions, with the help of a whole group of young enthusiastic PhD students and postdocs. On the top of that I was seduced by the family atmosphere of the math department and actually of the whole friendly administrative staff of the university.”
What are the main mathematical challenges you’re pursuing ?
“One of the great achievement I secretly dream of is to prove a conjecture by Jacques-Louis Lions regarding the possibility to control the Navier-Stokes equations. This is quite challenging, because it is already not fully understood how to use these equations for simply observing the dynamics, with or without any attempt of modifying it. An inspiring mantra to overcome a too reasonable pessimism is attributed to John Von Neumann who was reported to have been heard to say one day that such unstable systems (it seems that he had actually in mind climate models which are more or less based on some variants of the Navier-Stokes equations) are, perhaps, easier to control than to predict.
Recently, in a quite mysterious burst of luck, I found myself with an idea, which turns out to be surprisingly simple and hopefully deep and powerful in the same time. It is more or less about transferring some properties which are known for one operator (that’s a mathematical object which could be for instance a differential operator such as the ones involved in PDEs) to another one, not by achieving a transformation from the former to the latter, but by transferring enough information by the means of some appropriate combinations of equations involving the two of them. At the very moment, I live mostly for that, but it could be that I’ll never think about it at all anymore in less than two years !”