Geometrical Optics and Related Topics

Blowup of small data solutions for a class of quasilinear wave equations in two dimensions: an outline of the proof.- Concentration effects in critical nonlinear wave equation and scattering theory.- Lower semicontinuity of weighted path length in BV.- Time decay of Lp norms for solutions of the wave equation on exterior domains.- Sobolev embeddings in Weyl-Hörmander calculus.- About the Cauchy problem for a system of conservation laws.- Global existence of the solutions and formation of singularities for a class of hyperbolic systems.- A class of solvable operators.- On the uniqueness of the Cauchy problem under partial analyticity assumptions.- Nonlinear wave diffraction.- Caustics for dissipative semilinear oscillations.- Geometric optics and the bottom of the spectrum.- Hypoellipticity for a class of infinitely degenerate elliptic operators.- Regularity of solutions to characteristic boundary value problem for symmetric systems.