This book contains papers presented at the "Workshop on Singularities in PDE and the Calculus of Variations" at the CRM in July 2006. The main theme of the meeting was the formation of geometrical singularities in PDE problems with a variational formulation. These equations typically arise in some applications (to physics, engineering, or biology, for example) and their resolution often requires a combination of methods coming from areas such as functional and harmonic analysis, differential geometry and geometric measure theory. Among the PDE problems discussed were: the Cahn-Hilliard model of phase transitions and domain walls; vortices in Ginzburg-Landau type models for superconductivity and superfluidity; the Ohna-Kawasaki model for di-block copolymers; models of image enhancement; and Monge-Ampere functions. The articles give a sampling of problems and methods in this diverse area of mathematics, which touches a large part of modern mathematics and its applications.

This book contains papers presented at the "Workshop on Singularities in PDE and the Calculus of Variations" at the CRM in July 2006. The main theme of the meeting was the formation of geometrical singularities in PDE problems with a variational formulation. These equations typically arise in some applications (to physics, engineering, or biology, for example) and their resolution often requires a combination of methods coming from areas such as functional and harmonic analysis, differential geometry and geometric measure theory. Among the PDE problems discussed were: the Cahn-Hilliard model of phase transitions and domain walls; vortices in Ginzburg-Landau type models for superconductivity and superfluidity; the Ohna-Kawasaki model for di-block copolymers; models of image enhancement; and Monge-Ampere functions. The articles give a sampling of problems and methods in this diverse area of mathematics, which touches a large part of modern mathematics and its applications.

This textbook provides a comprehensive introduction to the classical and modern calculus of variations, serving as a useful reference to advanced undergraduate and graduate students as well as researchers in the field. Starting from ten motivational examples, the book begins with the most important aspects of the classical theory, including the Direct Method, the Euler-Lagrange equation, Lagrange multipliers, Noether’s Theorem and some regularity theory. Based on the efficient Young measure approach, the author then discusses the vectorial theory of integral functionals, including quasiconvexity, polyconvexity, and relaxation. In the second part, more recent material such as rigidity in differential inclusions, microstructure, convex integration, singularities in measures, functionals defined on functions of bounded variation (BV), and Γ-convergence for phase transitions and homogenization are explored. While predominantly designed as a textbook for lecture courses on the calculus of variations, this book can also serve as the basis for a reading seminar or as a companion for self-study. The reader is assumed to be familiar with basic vector analysis, functional analysis, Sobolev spaces, and measure theory, though most of the preliminaries are also recalled in the appendix.

This book is the outcome of a conference held at the Centro De Giorgi of the Scuola Normale of Pisa in September 2012. The aim of the conference was to discuss recent results on nonlinear partial differential equations, and more specifically geometric evolutions and reaction-diffusion equations. Particular attention was paid to self-similar solutions, such as solitons and travelling waves, asymptotic behaviour, formation of singularities and qualitative properties of solutions. These problems arise in many models from Physics, Biology, Image Processing and Applied Mathematics in general, and have attracted a lot of attention in recent years.

This set of lectures, which had its origin in a mini course delivered at the Summer Program of IMPA (Rio de Janeiro), is an introduction to intrinsic scaling, a powerful method in the analysis of degenerate and singular PDEs.In the first part, the theory is presented from scratch for the model case of the degenerate p-Laplace equation. The second part deals with three applications of the theory to relevant models arising from flows in porous media and phase transitions.

From the contents: A. Arosio: Global solvability of second order evolution equations in Banach scales.- H. Beirao da Veiga: On the incompressible limit of the compressible Navier-Stokes equations.- A. Bove: Propagation of singularities for hyperbolic operators with double characteristics.- G. Buttazzo: Relaxation problems in control theory.- R. Finn: The inclination of an H-graph.- P.R. Garabedian: On the mathematical theory of vortex sheets.- N. Garofalo: New estimates of the fundamental solution and Wiener's criterion for parabolic equations with variable coefficients.- M.G. Garroni: Green function and invariant density for an integro-differential operator.- M. Giaquinta: Some remarks on the regularity of minimizers.- E. Giusti: Quadratic functionals with splitting coefficients.- R. Gulliver: Minimal surfaces on finite index in manifolds of positive scalar curvature.- R. Hardt, D. Kinderlehrer, M. Luskin: Remarks about the mathematical theory of liquid crystals.- E. Heinz: On quasi-minimal surfaces.- P. Laurence, E. Stredulinsky: A survey of recent regularity results for second order queer differential equations.- C.-S. Lin, W.-M. Ni: On the diffusion coefficient of a semilinear Neumann problem.- M. Longinetti: Some isoperimetric inequalities for the level curves of capacity and Green's functions on convex plane domains.- P. Marcati: Nonhomogeneous quasilinear hyperbolic systems: initial and boundary value problem.- E. Mascolo: Existence results for non convex problems of the calculus of variations.- U. Mosco: Wiener criteria and variational convergences.- L. Nirenberg: Fully nonlinear second order elliptic equations.- J. Serrin: Positive solutions of a prescribed mean curvature problem.- D. Socolescu: On the convergence at infinity of solutions with finite Dirichlet integral to the exterior Dirichlet problem for the steady plane Navier-Stokes system of equations.- J. Spruck: The elliptic Sinh Gordon equation and the construction of toroidal soap bubbles.

These lecture notes stemming from a course given at the Nankai Institute for Mathematics, Tianjin, in 1986 center on the construction of parametrices for fundamental solutions of hyperbolic differential and pseudodifferential operators. The greater part collects and organizes known material relating to these constructions. The first chapter about constant coefficient operators concludes with the Herglotz-Petrovsky formula with applications to lacunas. The rest is devoted to non-degenerate operators. The main novelty is a simple construction of a global parametrix of a first-order hyperbolic pseudodifferential operator defined on the product of a manifold and the real line. At the end, its simplest singularities are analyzed in detail using the Petrovsky lacuna edition.