Preface
1Preliminaries
1.1Notation
Innerproductofvectors
Supportofafunction
Boundaryofaset
Distancefromapointtoaset
Characteristicfunctionofaset
Multi-indices
Partialderivativeoperators
Functionspaces--continuous,HSldercontinuous,
HSldercontinuousderivatives
1.2MeasuresonRn
Lebesguemeasurablesets
LebesguemeasurabilityofBorelsets
Suslinsets
1.3CoveringTheorems
Hausdorffmaximalprinciple
Generalcoveringtheorem
Vitalicoveringtheorem
Coveringlemma,withn-ballswhoseradiivaryin
Lipschitzianway
Besicovitchcoveringlemma
Besicovitchdifferentiationtheorem
1.4HausdorffMeasure
EquivalenceofHausdorffandLebesguemeasures
Hausdorffdimension
1.5LP-Spaces
Integrationofafunctionviaitsdistribution
function
Young'sinequality
Holder'sandJensen'sinequality
1.6Regularization
LP-spacesandregularization
1.7Distributions
Functionsandmeasures,asdistributions
Positivedistributions
Distributionsdeterminedbytheirlocalbehavior
Convolutionofdistributions
Differentiationofdistributions
1.8LorentzSpaces
Non-increasingrearrangementofafunction
Elementarypropertiesofrearrangedfunctions
Lorentzspaces
O'Neil'sinequality,forrearrangedfunctions
EquivalenceofLP-normand(p,p)-norm
Hardy'sinequality
InclusionrelationsofLorentzspaces
Exercises
HistoricalNotes
2SobolevSpacesandTheirBasicProperties
2.1WeakDerivatives
Sobolevspaces
Absolutecontinuityonlines
LP-normofdifferencequotients
TruncationofSobolevfunctions
CompositionofSobolevfunctions
2.2ChangeofVariablesforSobolevFunctions
Rademacher'stheorem
Bi-Lipschitzianchangeofvariables
2.3ApproximationofSobolevFunctionsbySmooth
Functions
Partitionofunity
SmoothfunctionsaredenseinWk'p
2.4SobolevInequalities
Sobolev'sinequality
2.5TheRellich-KondrachovCompactnessTheorem
Extensiondomains
2.6BesselPotentialsandCapacity
RieszandBesselkernels
Besselpotentials
Besselcapacity
BasicpropertiesofBesselcapacity
CapacitabilityofSuslinsets
Minimaxtheoremandalternateformulationof
Besselcapacity
MetricpropertiesofBesselcapacity
2.7TheBestConstantintheSobolevInequality
Co-areaformula
Sobolev'sinequalityandisoperimetricinequality
2.8AlternateProofsoftheFundamentalInequalities
Hardy-Littlewood-Wienermaximaltheorem
Sobolev'sinequalityforRieszpotentials
2.9LimitingCasesoftheSobolevInequality
Thecasekp=nbyinfiniteseries
Thebestconstantinthecasekp=n
AnL-boundinthelimitingcase
2.10LorentzSpaces,ASlightImprovement
Young'sinequalityinthecontextofLorentzspaces
Sobolev'sinequalityinLorentzspaces
Thelimitingcase
Exercises
HistoricalNotes
3PointwiseBehaviorofSobolevFunctions
3.1LimitsofIntegralAveragesofSobolevFunctions
Limitingvaluesofintegralaveragesexceptfor
capacitynullset
3.2DensitiesofMeasures
3.3LebesguePointsforSobolevFunctions
ExistenceofLebesguepointsexceptforcapacity
nullset
Approximatecontinuity
Finecontinuityeverywhereexceptforcapacitynullset
3.4Lr-DerivativesforSobolevFunctions
ExistenceofTaylorexpansionsLp
3.5PropertiesofLP-Derivatives
ThespacesTk,tk,Tk'p,tk'p
TheimplicationofafunctionbeinginTk,patall
pointsofaclosedset
3.6AnLp-VersionoftheWhitneyExtensionTheorem
ExistenceofaGafunctioncomparabletothe
distancefunctiontoaclosedset
TheWhitneyextensiontheoremforfunctionsin
Tk'pandtk'p
3.7AnObservationonDifferentiation
3.8Rademacher'sTheoremintheLP-Context
AfunctioninTk'peverywhereimpliesitisin
tk'palmosteverywhere
3.9TheImplicationsofPointwiseDifferentiability
ComparisonofLP-derivativesanddistributional
derivatives
IfuEtk'P(x)foreveryx,andifthe
Lp-derivativesareinLp,thenuEWk'p
3.10ALusin-TypeApproximationforSobolevFunctions
IntegralaveragesofSobolevfunctionsareuniformly
closetotheirlimitsonthecomplementofsets
ofsmallcapacity
ExistenceofsmoothfunctionsthatagreewithSobolev
functionsonthecomplementofsetsof
smallcapacity
3.11TheMainApproximation
Existenceofsmoothfunctionsthatagreewith
Sobolevfunctionsonthecomplementofsetsof
smallcapacityandarecloseinnorm
Exercises
HistoricalNotes
4PoincareInequalities--AUnifiedApproach
4.1InequalitiesinaGeneralSetting
AnabstractversionofthePoincar6inequality
4.2ApplicationstoSobolevSpaces
Aninterpolationinequality
4.3TheDualofWm,p()
Therepresentationof(W0m,p())*
4,4SomeMeasuresin(W0m,p())*
Poincareinequalitiesderivedfromtheabstract
versionbyidentifyingLebesgueandHausdorff
measurewithelementsin(Wm,p())*
ThetraceofSobolevfunctionsontheboundaryof
Lipschitzdomains
Poincar6inequalitiesinvolvingthetraceof
aSobolevfunction
4.5Poincar6Inequalities
Inequalitiesinvolvingthecapacityoftheseton
whichafunctionvanishes
4.6AnotherVersionofPoincare'sInequality
Aninequalityinvolvingdependenceontheseton
whichthefunctionvanishes,notmerelyonits
capacity
4.7MoreMeasuresin(Wm,p())*
Sobolev'sinequalityforRieszpotentialsinvolving
measuresotherthanLebesguemeasure
Characterizationofmeasuresin(Wm,p(Rn))*
4.8OtherInequalitiesInvolvingMeasuresin(Wk,p)*
InequalitiesinvolvingtherestrictionofHausdorff
measuretolowerdimensionalmanifolds
4.9TheCasep=1
InequalitiesinvolvingtheL1-normofthegradient
Exercises
HistoricalNotes
5FunctionsofBoundedVariation
5.1Definitions
DefinitionofBVfunctions
Thetotalvariationmeasure‖Du‖
5.2ElementaryPropertiesofBVFunctions
Lowersemicontinuityofthetotalvariationmeasure
Aconditionensuringcontinuityofthetotal
variationmeasure
5.3RegularizationofBVFunctions
RegularizationdocsnotincreasetileBVnorm
ApproximationofBVfunctionsbysmoothfunctions
CompactnessinL1oftheUlfitballinBV
5.4SetsofFinitePerimeter
Definitionofsetsoffiniteperimeter
Tileperimeterofdomainswithsmoothboundaries
Isoperimetricandrelativeisoperimetricinequalityfor
setsoffiniteperimeter
5.5TheGeneralizedExteriorNormal
ApreliminaryversionoftheGauss-Greentheorem
Densityresultsatpointsofthereducedboundary
5.6TangentialPropertiesoftheReducedBoundaryandthe
Measure-TheoreticNormal
Blow-upatapointoftilereducedboundary
Themeasure-theoreticnormal
Thereducedboundaryiscontainedinthe
measure-theoreticboundary
Alowerboundforthedensityof‖DXE‖
Hausdorffmeasurerestrictedtothereducedboundary
isboundedaboveby‖DXE‖
5.7RectifiabilityoftheReducedBoundary
Countably(n-1)-rectifiablesets
Countable(n-1)-rectifiabilityofthe
measure-theoreticboundary
5.8TheGauss-GreenTheorem
TheequivalenceoftherestrictionofHausdorff
measuretothemeasure-theoreticboundary
and‖DXE‖
TheGauss-Greentheoremforsetsoffiniteperimeter
5.9PointwiseBehaviorofBVFunctions
Upperandlowerapproximatelimits
TheBoxinginequality
Thesetofapproximatejumpdiscontinuities
5.10TheTraceofaBVFunction
TheboundedextensionofBVfunctions
TraceofaBVfunctiondefinedintermsofthe
upperandlowerapproximatelimitsofthe
extendedfunction
Theintegrabilityofthetraceoverthe
measure-theoreticboundary
5.11Sobolev-TypeInequalitiesforBVFunctions
Inequalitiesinvolvingelementsin(BV())*
5.12InequalitiesInvolvingCapacity
Characterizationofmeasurein(BV())*
PoincareinequalityforBVfunctions
5.13GeneralizationstotheCasep>1
5.14TraceDefinedinTermsofIntegralAverages
Exercises
HistoricalNotes
Bibliography
ListofSymbols
Index