变分分析 英文

Inthisbookweaimtopresent，inaunifiedframework，abroadspectrumofmathematicaltheorythathasgrowninconnectionwiththestudyofproblemsofoptimization，equilibrium，control，andstabilityoflinearandnonlinearsystems.ThetitleVariationalAnalysisrefiectsthisbreadth.Foralongtime，variationalproblemshavebeenidentifiedmostlywiththe'calculusofvariations'.Inthatvenerablesubject，builtaroundtheminimizationofintegralfunctionals，constraintswererelativelysimpleandmuchofthefocuswasoninfinite-dimensionalfunctionspaces.Amajorthemewastheexplorationofvariationsaroundapoint，withintheboundsimposedbytheconstraints，inordertohelpcharacterizesolutionsandportraythemintermsof'variationalprinciples'.Notionsofperturbation，approximationandevengeneralizeddifferentiabilitywereextensivelyinvestigated，Variationaltheoryprogressedalsotothestudyofso-calledstationarypoints，criticalpoints，andotherindicationsofsingularitythatapointmighthaverelativetoitsneighbors，especiallyinassociationwithexistencetheoremsfordifferentialequations.