Cornerstones Series Editors CharlesL.Epstein,UniversityofPennsylvania,Philadelphia StevenG.Krantz,UniversityofWashington,St.Louis Advisory Board AnthonyW.Knapp,StateUniversityofNewYorkatStonyBrook,Emeritus Anthony W. Knapp Basic Real Analysis Along with a companion volume Advanced Real Analysis Birkha¨user Boston • Basel • Berlin AnthonyW.Knapp 81UpperSheepPastureRoad EastSetauket,NY11733-1729 U.S.A. e-mail to: [email protected] http://www.math.sunysb.edu/˜aknapp/books/basic.html CoverdesignbyMaryBurgess. MathematicsSubjectClassicification(2000):28-01,26-01,42-01,54-01,34-01 LibraryofCongressCataloging-in-PublicationData Knapp,AnthonyW. Basicrealanalysis:alongwithacompanionvolumeAdvancedrealanalysis/Anthony W.Knapp p.cm.–(Cornerstones) Includesbibliographicalreferencesandindex. ISBN0-8176-3250-6(alk.paper) 1.Mathematicalanalysis.I.Title.II.Cornerstones(Birkha¨user) QA300.K562005 515–dc22 2005048070 ISBN-100-8176-3250-6 eISBN0-8176-4441-5 Printedonacid-freepaper. ISBN-13978-0-8176-3250-2 AdvancedRealAnalysis ISBN0-8176-4382-6 BasicRealAnalysisandAdvancedRealAnalysis(Set) ISBN0-8176-4407-5 (cid:1)c2005AnthonyW.Knapp All rights reserved. This work may not be translated or copied in whole or in part without the written permissionofthepublisher(Birkha¨userBoston,c/oSpringerScience+BusinessMediaInc.,233Spring Street,NewYork,NY10013,USA)andtheauthor,exceptforbriefexcerptsinconnectionwithreviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation,computersoftware,orbysimilarordissimilarmethodologynowknownorhereafterdeveloped isforbidden. Theuseinthispublicationoftradenames,trademarks,servicemarksandsimilarterms,eveniftheyare notidentifiedassuch,isnottobetakenasanexpressionofopinionastowhetherornottheyaresubjectto proprietaryrights. PrintedintheUnitedStatesofAmerica. (MP) 987654321 SPIN10934074 www.birkhauser.com ToSusan and ToMyReal-AnalysisTeachers: SalomonBochner,WilliamFeller,HillelFurstenberg, Harish-Chandra,SigurdurHelgason,JohnKemeny, JohnLamperti,HazletonMirkil,EdwardNelson, LaurieSnell,EliasStein,RichardWilliamson CONTENTS Preface xi DependenceAmongChapters xiv GuidefortheReader xv ListofFigures xviii Acknowledgments xix StandardNotation xxi I. THEORYOFCALCULUSINONEREALVARIABLE 1 1. ReviewofRealNumbers,Sequences,Continuity 2 2. InterchangeofLimits 13 3. UniformConvergence 15 4. RiemannIntegral 26 5. Complex-ValuedFunctions 41 6. Taylor’sTheoremwithIntegralRemainder 43 7. PowerSeriesandSpecialFunctions 44 8. Summability 53 9. WeierstrassApproximationTheorem 58 10. FourierSeries 61 11. Problems 78 II. METRICSPACES 82 1. DefinitionandExamples 83 2. OpenSetsandClosedSets 91 3. ContinuousFunctions 95 4. SequencesandConvergence 97 5. SubspacesandProducts 102 6. PropertiesofMetricSpaces 105 7. CompactnessandCompleteness 108 8. Connectedness 115 9. BaireCategoryTheorem 117 10. PropertiesofC(S)forCompactMetric S 121 11. Completion 127 12. Problems 130 vii viii Contents III. THEORYOFCALCULUSINSEVERALREALVARIABLES 135 1. OperatorNorm 135 2. NonlinearFunctionsandDifferentiation 139 3. Vector-ValuedPartialDerivativesandRiemannIntegrals 146 4. ExponentialofaMatrix 148 5. PartitionsofUnity 151 6. InverseandImplicitFunctionTheorems 152 7. DefinitionandPropertiesofRiemannIntegral 161 8. RiemannIntegrableFunctions 166 9. Fubini’sTheoremfortheRiemannIntegral 169 10. ChangeofVariablesfortheRiemannIntegral 171 11. Problems 179 IV. THEORYOFORDINARYDIFFERENTIALEQUATIONS ANDSYSTEMS 183 1. QualitativeFeaturesandExamples 183 2. ExistenceandUniqueness 187 3. DependenceonInitialConditionsandParameters 194 4. IntegralCurves 199 5. LinearEquationsandSystems,Wronskian 201 6. HomogeneousEquationswithConstantCoefficients 208 7. HomogeneousSystemswithConstantCoefficients 211 8. SeriesSolutionsintheSecond-OrderLinearCase 218 9. Problems 226 V. LEBESGUEMEASUREANDABSTRACT MEASURETHEORY 231 1. MeasuresandExamples 231 2. MeasurableFunctions 238 3. LebesgueIntegral 241 4. PropertiesoftheIntegral 245 5. ProofoftheExtensionTheorem 253 6. CompletionofaMeasureSpace 262 7. Fubini’sTheoremfortheLebesgueIntegral 265 8. IntegrationofComplex-ValuedandVector-ValuedFunctions 274 9. L1, L2, L∞,andNormedLinearSpaces 279 10. Problems 289 VI. MEASURETHEORYFOREUCLIDEANSPACE 296 1. LebesgueMeasureandOtherBorelMeasures 297 2. Convolution 306 3. BorelMeasuresonOpenSets 314 4. ComparisonofRiemannandLebesgueIntegrals 318 Contents ix VI. MEASURETHEORYFOREUCLIDEANSPACE (Continued) 5. ChangeofVariablesfortheLebesgueIntegral 320 6. Hardy–LittlewoodMaximalTheorem 327 7. FourierSeriesandtheRiesz–FischerTheorem 334 8. StieltjesMeasuresontheLine 339 9. FourierSeriesandtheDirichlet–JordanTheorem 346 10. DistributionFunctions 350 11. Problems 352 VII. DIFFERENTIATIONOFLEBESGUEINTEGRALS ONTHELINE 357 1. DifferentiationofMonotoneFunctions 357 2. AbsoluteContinuity,SingularMeasures,and LebesgueDecomposition 364 3. Problems 370 VIII.FOURIERTRANSFORMINEUCLIDEANSPACE 373 1. ElementaryProperties 373 2. FourierTransformon L1,InversionFormula 377 3. FourierTransformon L2,PlancherelFormula 381 4. SchwartzSpace 384 5. PoissonSummationFormula 389 6. PoissonIntegralFormula 392 7. HilbertTransform 397 8. Problems 404 IX. Lp SPACES 409 1. InequalitiesandCompleteness 409 2. ConvolutionInvolving Lp 417 3. JordanandHahnDecompositions 418 4. Radon–NikodymTheorem 420 5. ContinuousLinearFunctionalson Lp 424 6. MarcinkiewiczInterpolationTheorem 427 7. Problems 436 X. TOPOLOGICALSPACES 441 1. OpenSetsandConstructionsofTopologies 441 2. PropertiesofTopologicalSpaces 447 3. CompactnessandLocalCompactness 451 4. ProductSpacesandtheTychonoffProductTheorem 458 5. SequencesandNets 463 6. QuotientSpaces 471 x Contents X. TOPOLOGICALSPACES (Continued) 7. Urysohn’sLemma 474 8. MetrizationintheSeparableCase 476 9. Ascoli–Arzela` andStone–WeierstrassTheorems 477 10. Problems 480 XI. INTEGRATIONONLOCALLYCOMPACTSPACES 485 1. Setting 485 2. RieszRepresentationTheorem 490 3. RegularBorelMeasures 504 4. DualtoSpaceofFiniteSignedMeasures 509 5. Problems 517 XII. HILBERTANDBANACHSPACES 520 1. DefinitionsandExamples 520 2. GeometryofHilbertSpace 526 3. BoundedLinearOperatorsonHilbertSpaces 535 4. Hahn–BanachTheorem 537 5. UniformBoundednessTheorem 543 6. InteriorMappingPrinciple 545 7. Problems 549 APPENDIX 553 A1. SetsandFunctions 553 A2. MeanValueTheoremandSomeConsequences 559 A3. InverseFunctionTheoreminOneVariable 561 A4. ComplexNumbers 563 A5. ClassicalSchwarzInequality 563 A6. EquivalenceRelations 564 A7. LinearTransformations,Matrices,andDeterminants 565 A8. FactorizationandRootsofPolynomials 568 A9. PartialOrderingsandZorn’sLemma 573 A10.Cardinality 577 HintsforSolutionsofProblems 581 SelectedReferences 637 IndexofNotation 639 Index 643