Iooss's research deals with functional analysis of the Navier-Stokes equation, nonlinear hydrodynamic stability theory and water waves of different kinds, and general behavior (such as symmetry breaking and normal forms) of bifurcations (branching of solutions) in dynamic systems. In 1971, independently of David H. Sattinger, he treated the Hopf bifurcation in solutions of the Navier-Stokes equation as an infinite dimensional dynamical system. He studied in particular the Couette flow (Taylor-Couette) and discovered there theoretically several waveforms, which were later confirmed experimentally.[2] He collaborated with Alain Chenciner on bifurcation of invariant tori.[4] Iooss, with Pierre Coullet, classified the instabilities of spatially periodic patterns in translation-invariant and mirror-symmetric systems.[2]
Iooss was elected in 1990 a corresponding member of the Académie des sciences. In 1993 he received the Max-Planck-Forschungspreis [de]. He received in 2008 the Prix Ampère and in 1978 the Prix Henri de Partille of the Académie des sciences.
In 1998 he was Invited Speaker with talk Traveling water waves as a paradigm for bifurcations in reversible infinite dimensional dynamical systems at the International Congress of Mathematicians in Berlin.[5]
Selected publications
Articles
1979 A.Chenciner, G.Iooss. Bifurcations de tores invariants. Arch. Rat. Mech. Anal. 69, 2, 109-198. doi:10.1007/bf00281175
1987 C.Elphick, E.Tirapegui, M.Brachet, P.Coullet, G.Iooss. A simple global characterization for normal forms of singular vector fields. Physica 29D, 95-127. doi:10.1016/0167-2789(87)90049-2
1990 P.Coullet, G.Iooss. Instabilities of one-dimensional cellular patterns. Phys. Rev. Lett. 64, 8, 866-869 doi:10.1103/PhysRevLett.64.866
2000 G.Iooss., K.Kirchgässner. Travelling waves in a chain of coupled nonlinear oscillators. Com. Math. Phys. 211, 439-464. doi:10.1007/s002200050821
2003 F.Dias, G.Iooss. Water-waves as a spatial dynamical system. Handbook of Mathematical Fluid Dynamics, chapter 10, 443-499. S.Friedlander, D.Serre, eds., Elsevier.
2005 G.Iooss, P.Plotnikov, J.F.Toland . Standing waves on an infinitely deep perfect fluid under gravity. Arch. Rat. Mech. Anal. 177, 3, 367-478. doi:10.1007/s00205-005-0381-6
2005 G.Iooss, E.Lombardi. Polynomial normal forms with exponentially small remainder for analytical vector fields. J.Diff. Equ. 212, 1-61. doi:10.1016/j.jde.2004.10.015
2019 B.Braaksma, G.Iooss. Existence of bifurcating quasipatterns in steady Bénard-Rayleigh convection. Arch. Rat. Mech. Anal. 231, 3 (2019), 1917-1981. doi:10.1007/s00205-018-1313-6