# EPJ E interview – Yves Pomeau. The universality of statistical physics interpretation is ever more obvious

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- Published on 23 June 2016

During the StatPhys Conference on 20th July 2016 in Lyon, France, Yves Pomeau and Daan Frenkel will be awarded the most important prize in the field of Statistical Mechanics: the 2016 Boltzmann Medal. The award recognizes Pomeau’s key contributions to the Statistical Physics of non-equilibrium phenomena in general. And, in particular, for developing our modern understanding of fluid mechanics, instabilities, pattern formation and chaos.

Pomeau, who is an Editor for the European Physical Journal Special Topics, is recognised as an outstanding theorist bridging disciplines from applied mathematics to statistical physics with a profound impact on the neighbouring fields of turbulence and mechanics. In an interview with Sabine Louet, published in EPJ E, Pomeau shares his views and tells how he experienced the rise of Statistical Mechanics in the past few decades. He also touches upon the need to provide funding to people who have the rare ability to discover new things and ideas, and not just those who are good at filling in grant application forms. The full interview is published in the June issue of EPJE.

**The following is an excerpt.**

**Sabine Louet: What has been your first marking exposure to statistical physics?**

Yves Pommeau: It all dates back to the time I was a student in 1962/63, attending the courses from Jacques Yvon at Ecole Normale Supérieure, in Paris. I am rather clumsy by nature. And was always attracted to theory, rather than experiment. I was also very impressed by the first statistical physics conference I attended in the mid-sixties, in Holland, where I heard about the kinetic theory of dense gases, connected to the Boltzmann equations. I have also been influenced by the work of Ilya Prigogine in Brussels. He discovered that dissipation of energy can reverse the principle of minimization of entropy production in situations far beyond equilibrium, which earned him the Chemistry Nobel Prize in 1977.

**SL: What key moments influenced your scientific journey?**

YP: In 1968, during my PhD I was pursuing a demonstration that when a gas it not too diluted, there is a hydrodynamic propagation of correlations outside of equilibrium. I developed this analysis without the help of then nascent molecular dynamics. I proved that such systems exhibit a fundamental divergence in 2D which cannot be eliminated. The timing was interesting, as it was during the French social upheaval of 1968. Revolutionary periods are the best for scientific progress. For instance, during the French revolution, French science had never been better. It does not mean that we have to start wars to progress science! Throughout my scientific career, I changed topic quite often. In the early seventies, I have changed focus and started working on chaos. It requires different tools from the statistical mechanics tools developed by Boltzmann, initially to study gases. The common thread is the ergodic theory. In 1986, when thinking about fluid instabilities in flows, I got an idea that is still investigated further, namely that this transition to turbulence belongs to the class of directed percolation, a good example of how concepts of statistical physics can be applied.

**SL: What characterises statistical physics today?**

YP: Statistical physics has undergone a tremendous expansion since the 1960s. There is, today, an explosion of the domain. And the mode of thinking of statistical physics has been applied to other sectors. The focus has shifted to on system that are time-dependent, such as solids or liquids which are not at equilibrium. What is most interesting nowadays is what happens outside equilibrium. All in all, statistical physics introduces a greater sophistication of the analysis of real word phenomena, such as physics, society, economics. But the field needs to retain a certain consistency throughout its applications.

**Read the full interview: Interview with Yves Pomeau, Boltzmann Medallist 2016. The universality of statistical physics interpretation is ever more obvious. Eur. Phys. J. E (2016) 39: 67**