REMARKS ON ELLIPTICITY AND REGULARITY FOR NON-INHIBITED SHELLS AND OTHER CONSTRAINED SYSTEMS

We examine ellipticity properties for three examples of constrained sy stems with a Lagrange multiplier. The system of incompressible elastic ity is in the restricted context of the Grubb-Geymonat elliptic system s. The Reissner-Mindlin system of plates is in the Agmon-Douglis-Niren berg context. The system of thin shells which are not geometrically ri gid is elliptic or hyperbolic at elliptic or hyperbolic points of the surface, respectively; moreover, this property is only concerned with equations, without boundary conditions. Some properties of the wave fr onts and propagation of singularities are given.