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基本説明
Intended for a beginning graduate course on convexity methods for PDEs.
Full Description
How to solve partial differential systems by completing the square. This could well have been the title of this monograph as it grew into a project to develop a s- tematic approach for associating suitable nonnegative energy functionals to a large class of partial differential equations (PDEs) and evolutionary systems. The minima of these functionals are to be the solutions we seek, not because they are critical points (i. e. , from the corresponding Euler-Lagrange equations) but from also - ing zeros of these functionals. The approach can be traced back to Bogomolnyi's trick of "completing squares" in the basic equations of quantum eld theory (e. g. , Yang-Mills, Seiberg-Witten, Ginzburg-Landau, etc. ,), which allows for the deri- tion of the so-called self (or antiself) dual version of these equations. In reality, the "self-dual Lagrangians" we consider here were inspired by a variational - proach proposed - over 30 years ago - by Brezis ' and Ekeland for the heat equation and other gradient ows of convex energies. It is based on Fenchel-Legendre - ality and can be used on any convex functional - not just quadratic ones - making them applicable in a wide range of problems.
In retrospect, we realized that the "- ergy identities" satis ed by Leray's solutions for the Navier-Stokes equations are also another manifestation of the concept of self-duality in the context of evolution equations.
Contents
Convex Analysis on Phase Space.- Legendre-Fenchel Duality on Phase Space.- Self-dual Lagrangians on Phase Space.- Skew-Adjoint Operators and Self-dual Lagrangians.- Self-dual Vector Fields and Their Calculus.- Completely Self-Dual Systems and their Lagrangians.- Variational Principles for Completely Self-dual Functionals.- Semigroups of Contractions Associated to Self-dual Lagrangians.- Iteration of Self-dual Lagrangians and Multiparameter Evolutions.- Direct Sum of Completely Self-dual Functionals.- Semilinear Evolution Equations with Self-dual Boundary Conditions.- Self-Dual Systems and their Antisymmetric Hamiltonians.- The Class of Antisymmetric Hamiltonians.- Variational Principles for Self-dual Functionals and First Applications.- The Role of the Co-Hamiltonian in Self-dual Variational Problems.- Direct Sum of Self-dual Functionals and Hamiltonian Systems.- Superposition of Interacting Self-dual Functionals.- Perturbations of Self-Dual Systems.- Hamiltonian Systems of Partial Differential Equations.- The Self-dual Palais-Smale Condition for Noncoercive Functionals.- Navier-Stokes and other Self-dual Nonlinear Evolutions.
