Yves Pomeau

Yves Pomeau, born in 1942, is a French mathematician and physicist, emeritus research director at the CNRS and corresponding member of the French Academy of sciences.

Career

He was a researcher at the CNRS from 1965 to 2006, ending his career as DR0 in the Physics Department of the Ecole Normale Supérieure (ENS) (Statistical Physics Laboratory) in 2006.

He was a lecturer in physics at the École Polytechnique for two years (1982–1984), then a scientific expert with the Direction générale de l'armement until January 2007.

He was Professor, with tenure, part-time at the Department of Mathematics, University of Arizona, from 1990 to 2008.

He was Visiting Scientist at Schlumberger–Doll Laboratories (Connecticut, USA) from 1983 to 1984.

He was a Visiting Professor at MIT in Applied Mathematics in 1986 and in Physics at UC San Diego in 1993.

He was Ulam Scholar at CNLS, Los Alamos National Lab, in 2007–2008.

He was also one of the founders of the Laboratoire de Physique Statistique, ENS Paris.

He has published nearly 400 scientific articles.

Education

•    École normale supérieure, 1961–1965.
•    Licence (1962).
•    DEA in Plasma Physics, 1964.
•    Aggregation of Physics 1965.
•    State thesis in plasma physics, University of Orsay, 1970.

Research

In his thesis he showed that in a dense fluid the interactions are different from what they are at equilibrium and propagate through hydrodynamic modes, which leads to the divergence of transport coefficients in 2 spatial dimensions.

This aroused his interest in fluid mechanics, and in the transition to turbulence. Together with Paul Manneville they discovered a new mode of transition to turbulence, the transition by temporal intermittency, which was confirmed by numerous experimental observations.

In papers published in 1973 and 1976, Hardy, Pomeau and de Pazzis introduced the first Lattice Boltzmann model, which is called the HPP model after the authors. HPP model is a two-dimensional model of fluid particle interactions. In this model, the lattice is square, and the particles travel independently at a unit speed to the discrete time. The particles can move to any of the four sites whose cells share a common edge. Particles cannot move diagonally.

Generalizing ideas from his thesis, together with Frisch and Hasslacher they found a very simplified microscopic fluid model which allows to simulate very efficiently the complex movements of a real fluid. This has become known as the FHP model after its inventors.

Reflecting on the situation of the transition to turbulence in parallel flows, he showed that turbulence is caused by a contagion mechanism, and not by local instability. The consequence is that this transition belongs to the class of directed percolation phenomena in statistical physics, which has also been amply confirmed by experimental and numerical studies.

From his more recent work we must distinguish those concerning a phenomenon typically out of equilibrium, that of the emission of photons by an atom maintained in an excited state by an intense field that creates Rabi oscillations. The theory of this phenomenon requires a precise consideration of the statistical concepts of quantum mechanics in a theory satisfying the fundamental constraints of such a theory. With Martine Le Berre and Jean Ginibre they showed that the good theory was that of a Kolmogorov equation based on the existence of a small parameter, the ratio of the photon emission rate to the atomic frequency itself.

With his student Basile Audoly and Martine Ben Amar, they developed a theory of large deformations of elastic plates which led them to introduce the concept of "d-cone", that is, a geometrical cone preserving the overall developability of the surface, an idea now taken up by the solid mechanics community.

The theory of superconductivity is based on the idea of the formation of pairs of electrons that become more or less bosons undergoing Bose-Einstein condensation. This pair formation would explain the halving of the flux quantum in a superconducting loop. Together with Len Pismen and Sergio Rica they have shown that, going back to Onsager's idea explaining the quantification of the circulation in fundamental quantum states, it is not necessary to use the notion of electron pairs to understand this halving of the circulation quantum.

Apart from simple situations, capillarity remains an area where fundamental questions remain. He showed that the discrepancies appearing in the hydrodynamics of the moving contact line on a solid surface could only be eliminated by taking into account the evaporation/condensation near this line. Capillary forces are almost always insignificant in solid mechanics. Nevertheless with Serge Mora and collaborators they have shown theoretically and experimentally that soft gel filaments are subject to Rayleigh-Plateau instability, an instability never observed before for a solid.

Prizes and awards

• FPS Paul Langevin Award in 1981.
• FPS Jean Ricard Award in 1985.
• Perronnet–Bettancourt Prize (1993) awarded by the Spanish government for collaborative research between France and Spain.
• Chevalier of the Légion d'Honneur since 1991.
• Elected corresponding member of the French Academy of sciences in 1987 (Mechanical and Computer Sciences).
•   Boltzmann Medal (2016).