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. Language: English