For seventy years, we have known that Einstein's theory is essentially a theory of propagation of waves for the gravitational field. Confusion enters, however, through the fact that the word wave, in physics, implies sometimes repetition and sometimes not. This confusion is often increased by he use of Fourier transforms, by which a disturbanse which appears to be without repetition is resolved into periodic wave-trains with all frequencies. But, in a general curved space-time, we have nothing corresponding to Fourier transforms. Here, we consider systematically waves corresponding to the propagation of discontinuities of physical quantities describing either fields (essentially electromagnetic fields and gravitational field), or the motion of a fluid, or together, in magnetohydrodynamics, the changes in time of a field and of a fluid. The main equations, for the different studied phenomena, constitute a hyperbolic system and the study of a formal Cauchy problem is possible. We call ordinary waves the case in which the derivative of superior order appearing in the system are discontinuous at the traverse of a hypersurface, the wave front ; we call shock waves the case where the derivatives of an order inferior by one are discontinuous at the traverse of a wave front. XI xii PREFACE From 1950, many well-known scientits (Taub, Synge, Choquet-B ruhat, etc.) have studied the corresponding equations for different physical phenomena : systems associated to the electromagnetic and gravitational fields, to hydrodynamics and to magnetohydrodynamics.

Foreword. Introduction; J.C. Legrand. Relativistic dissipative fluids; A.M. Anile, G. Ali, V. Romano. Mathematical problems related to liquid crystals, superconductors and superfluids; H. Brezis. Microcanonical action and the entropy of a rotating black hole; J.D. Brown, J.W. York, Jr. Probleme de Cauchy sur un conoide caracteristique. Applications a certains systemes non lineaires d'origine physique; F. Cagnac, M. Dossa. Recent progress on the Cauchy problem in general relativity; D. Christodoulou. On some links between mathematical physics and physics in the context of general relativity; T. Damour. Functional integration. A multipurpose tool; C. DeWitt-Morette. Generalized frames of references and intrinsic Cauchy problem in general relativity; G. Ferrarese, C. Cattani. Reducing Einstein's equations to an unconstrained hamiltonian system on the cotangent bundle of Teichmuller space; A.E. Fischer, V. Moncrief. Darboux transformations for a class of integrable systems in n variables; C.H. Gu. Group theoretical treatment of fundamental solutions; N.H. Ibragimov. On the regularity properties of the wave equation; S. Klainerman, M. Machedon. Le probleme de Cauchy lineaire et analytique pour un operateur holomorphe et un second membre ramifie; J. Leray. On Boltzmann equation; P.L. Lions. Star products and quantum groups; C. Moreno, L. Valero. On asymptotic of solutions of a nonlinear elliptic equation in a cylindrical domain; O. Oleinik. Fundamental physics in universal space-time; I. Segal. Interaction of gravitational and electromagnetic waves in general relativity; A.H. Taub. Anti-self dual conformal structures on 4-manifolds; C. Taubes. Chaotic behavior inrelativistic motion; E. Calzetta. Some results on non constant mean curvature solutions of the Einstein constraint equations; J. Isenberg, V. Moncrief. Levi condition for general systems; W. Matsumoto. Conditions invariantes pour un systeme, du type conditions de Levi; J. Vaillant. Black holes in supergravity; P.C. Aichelburg. Low-dimensional behaviour in the rotating driven cavity problem; E.A. Christensen, J.N. Sorensen, M. Brons, P.L. Christiansen. Some geometrical aspects of inhomogeneous elasticity; M. Epstein, G.A. Maugin. Integrating the Kadomtsev-Petviashvili equation in the 1+3 dimensions via the generalised Monge-Ampere equation: an example of conditioned Painleve test; T. Brugarino, A. Greco. Spinning mass endowed with electric charge and magnetic dipole moment; V.S. Manko, N.R. Sibgatullin. Equations de Vlasov en theorie discrete; G. Pichon. Convexity and symmetrization in classical and relativistic balance laws systems; T. Ruggeri.

This volume contains the proceedings of the Colloquium "Analysis, Manifolds and Physics" organized in honour of Yvonne Choquet-Bruhat by her friends, collaborators and former students, on June 3, 4 and 5, 1992 in Paris. Its title accurately reflects the domains to which Yvonne Choquet-Bruhat has made essential contributions. Since the rise of General Relativity, the geometry of Manifolds has become a non-trivial part of space-time physics. At the same time, Functional Analysis has been of enormous importance in Quantum Mechanics, and Quantum Field Theory. Its role becomes decisive when one considers the global behaviour of solutions of differential systems on manifolds. In this sense, General Relativity is an exceptional theory in which the solutions of a highly non-linear system of partial differential equations define by themselves the very manifold on which they are supposed to exist. This is why a solution of Einstein's equations cannot be physically interpreted before its global behaviour is known, taking into account the entire hypothetical underlying manifold. In her youth, Yvonne Choquet-Bruhat contributed in a spectacular way to this domain stretching between physics and mathematics, when she gave the proof of the existence of solutions to Einstein's equations on differential manifolds of a quite general type. The methods she created have been worked out by the French school of mathematics, principally by Jean Leray. Her first proof of the local existence and uniqueness of solutions of Einstein's equations inspired Jean Leray's theory of general hyperbolic systems.

For seventy years, we have known that Einstein's theory is essentially a theory of propagation of waves for the gravitational field. Confusion enters, however, through the fact that the word wave, in physics, implies sometimes repetition and sometimes not. This confusion is often increased by he use of Fourier transforms, by which a disturbanse which appears to be without repetition is resolved into periodic wave-trains with all frequencies. But, in a general curved space-time, we have nothing corresponding to Fourier transforms. Here, we consider systematically waves corresponding to the propagation of discontinuities of physical quantities describing either fields (essentially electromagnetic fields and gravitational field), or the motion of a fluid, or together, in magnetohydrodynamics, the changes in time of a field and of a fluid. The main equations, for the different studied phenomena, constitute a hyperbolic system and the study of a formal Cauchy problem is possible. We call ordinary waves the case in which the derivative of superior order appearing in the system are discontinuous at the traverse of a hypersurface, the wave front ; we call shock waves the case where the derivatives of an order inferior by one are discontinuous at the traverse of a wave front. XI xii PREFACE From 1950, many well-known scientits (Taub, Synge, Choquet-B ruhat, etc.) have studied the corresponding equations for different physical phenomena : systems associated to the electromagnetic and gravitational fields, to hydrodynamics and to magnetohydrodynamics.