MEASURE AND INTEGRAL PURE AND APPLIED MATHEMATICS A Program ofMonographs, Textbooks, andLecture Notes EXECUTIVE EDITORS-MoNOGRAPHS, TEXTBOOKS, AND LECTURE NOTES Earl J. Taft Rutgers University New Brunswick, NewJersey Edwin Hewitt University0/Washington Seattle, Washington CHAIRMAN OFTHE EDITORIAL BOARD S. Kobayashi University0/California, Berkeley Berkeley, California EDITORIAL BOARD Masanao Aoki w. S. Massey University0/California, LosAngeles Yale University Glen E. Bredon Irving Reiner Rutgers University UniversityofIllinoisat Urbana-Champaign Sigurdur Helgason PaulJ. Sally, Jr. Massachusetts InstituteofTechnology University0/Chicago G. Leitmann Jane Cronin Scanlon UniversityofCalifornia, Berkeley Rutgers University Marvin Marcus Martin Schechter University0/California, Santa Barbara Yeshiva University Julius L. Shaneson Rutgers University MONOGRAPHS AND TEXTBOOKS IN PURE AND APPLIED MATHEMATICS 1. K. Yano, Integral Formulasin RiemannianGeometry(1970) (outofprint) .2-. S. Kobayashi, HyperbolicManifoldsandHolomorphicMappings (1970) (outofprint) 3. v: S. V/adimirov, EquationsofMathematicalPhysics(A. Jeffrey, editor; A. littlewood,translator)(1970) (outofprint) 4. B. N. Pshenichnyi, NecessaryConditionsforan Extremum(L. Neustadt, translationeditor;K. Makowski, translator)(1971) s. L. Narici, E. Beckenstein,andG. Bachman, FunctionalAnalysisand ValuationTheory(1971) 6. D. S. Passrruzn, InfiniteGroup Rings(1971) 7. L. Dornhoff, Group RepresentationTheory(in two parts). PartA: Ordinary RepresentationTheory. Part B: ModularRepresentationTheory (1971,1972) 8. ~ BoothbyandG:L. Weiss(eds.), SymmetricSpaces: ShortCourses PresentedatWashington University(1972) (outofprint) 9. Y: Matsushima, DifferentiableManifolds(E. T. Kobayashi, translator) (1972) 10. L. E. Ward, Jr., Topology: AnOutline for a FirstCourse(1972) (outofprint} 11. A. Babakhanian, CohomologicalMethodsinGroupTheory (1972) 12. R. Gilmer, Multiplicative IdealTheory(1972) foutofprint) 13. J. Yeh, StochasticProcessesand theWienerIntegral(1973) (outofprint) 14. J. Barros-Nero, Introduction to the TheoryofDistributions(1973)(outofprint) 1S. R. Larsen, Functional Analysis: An Introduction(1973) (outofprint) 16. K. Yano andS. Ishihara, Tangent andCotangentBundles: Differential Geometry(1973) (outofprint) 17. C Procesi, RingswithPolynomialIdentities(1973) 18. R. Hermann, Geometry,Physics,and Systems(1973) (outofprint) 19. N. R. Wallach, HarmonicAnalysisonHomogeneousSpaces(1973) (outofprint) 20. J. Dieudonne, Introduction tothe Theory ofFormal Groups(1973) 21. I. Vaisman, Cohomologyand Differential Forms(1973) 22. B.-Y. Chen, GeometryofSubmanifolds(1973) (outofprint) 23. M Marcus, Finite Dimensional MultilinearAlgebra(in two parts) (1973, 1975) 24. R. Larsen, BanachAlgebras: An Introduction(1973) 25. R. O. KujalaandA. L. Vilterreds.), Value DistributionTheory: Part A; Part B. Deficitand Bezout EstimatesbyWilhelmStoll(1973) 26. K. B. Stolarsky, Algebraic Numbersand Diophantine Approximation(1974) 27. A. R. Magid, The SeparableGaloisTheoryofCommutative Rings(1974) 28. B. R. McDonald, Finite Ringswith Identity(1974) 29. J. Satake, LinearAlgebra(S. Koh, T. Akiba,and S. Ihara, translators) (1975) 30. J. S. Golan, LocalizationofNoncommutative Rings(1975) 31. G. Klambauer, Mathematical Analysis(1975) 32. M. K. Agoston, AlgebraicTopology: AFirstCourse(1976) 33. K. R. Goodearl, RingTheory: Nonsingular Ringsand Modules (1976) 34. L. E. Mansfield, LinearAlgebrawithGeometric Applications(1976) 35. N J. Pullman, MatrixTheory and itsApplications: .Selected Topics(1976) 36. B. R. McDonald, Geometric AlgebraOver Local Rings (1976) 37. C WGroetsch, Generalized InversesofLinearOperators: Representation and Approximation(1977) 38. J. E. KuczkowskiandJ. L. Gersting, Abstract Algebra: AFirst Look (1977) 39. C O. Christenson and W. L. Voxman, AspectsofTopology (1977) 40. M. Nagata, Field Theory (1977) 41. R. L. Long, Algebraic NumberTheory (1977) 42. WF. Pfeffer, Integralsand Measures(1977) 43. R. L. WheedenandA. Zygmund, Measureand Integral: An Introduction to Real Analysis(1977) MEASURE AND INTEGRAL An Introduction to Real Analysis Richard L. Wheeden Antoni Zygmund Department ofMathematics Department ofMathematics Rutgers" the State University University ofChicago ofNew Jersey Chicago" Illinois New Brunswick" New Jersey o ~Y~~F~~;~~oup BocaRaton London NewYork CRCPressisanimprintofthe Taylor&FrancisGroup,aninformabusiness Publishedin 1977by CRCPress Taylor&FrancisGroup 6000BrokenSoundParkwayNW,Suite300 BocaRaton,FL33487-2742 © 1977byTaylor& FrancisGroup,LLC CRCPressisanimprintofTaylor&FrancisGroup NoclaimtooriginalU.S.Governmentworks PrintedintheUnitedStatesofAmericaonacid-freepaper 30 29 28 27 26 25 InternationalStandardBookNumber-l0:0-8247-6499-4(Hardcover) InternationalStandardBookNumber-13:978-0-8247-6499-9(Hardcover) LibraryofCongressCardNumber77-14167 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quotedwithpermission,andsourcesareindicated. Awidevarietyofreferencesarelisted.Reasonableefforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibilityforthevalidityofallmaterialsorfortheconsequencesoftheiruse. No part ofthis book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording,orinanyinformationstorageorretrievalsystem,withoutwrittenpermissionfromthepublishers. TrademarkNotice:Productorcorporatenamesmaybetrademarksorregisteredtrademarks,andareusedonly foridentificationandexplanationwithoutintenttoinfringe. LibraryofCongressCataloging-in-PublicationData Wheeden,RichardL. Measureandintegral. (Monographsandtextbooksinpureandappliedmathematics;43) Includesindex. ISBN0-8247-6499-4 1.Measuretheory. 2. Integrals,Generalized.I.Zygmund,Antoni,jointauthor. II.Title. QA312.W43 515'.42 77-14167 VisittheTaylor& FrancisWebsiteat http://www.taylorandfrancis.com andtheCRC PressWebsiteat http://www.crcpress.com To our families Introduction The modern theory of measure and integration was created, primarily through the work of Lebesgue, at the turn of this century. Although the basic ideas are by now well established, there are ever widening applications whichhavemadethetheoryoneofthecentralpartsofmathematicalanalysis. However, differentapplicationsrequiredifferentemphasis on various aspects ofthe theory. Forexample, certain facts are ofprimary interestfor real and complex analysis, others for functional analysis, and still others for prob ability and statistics. This text is written from the point of view of real variables, and treats the theory primarily as a modern calculus. The book presupposes that the reader has a feeling for rigor and some knowledge of elementary facts from calculus. Some material which is no doubt familiar to many readers has been included; its inclusion seemed desirable in order to make the presentation clearand self-contained. The approach of the book is to develop the theory of measure and integration first in the simple setting of Euclidean space. In this case, there is a rich theory having a close relation to familiar facts from calculus and generalizing those facts. Later on, we introduce a more general treatment based on abstract notions characterized by axioms and with less geometric content. We have chosen this approach purposely, even though it leads to some repetition, since considering a special case first usually helps in de veloping a better understanding of the general situation. Anyway, we all "learn by repetition." The outline ofthe book is as follows. Chapter 1is primarily a collection of various background information, including elementary definitions and results that will be taken for granted later in the book; the reader should already be familiar with most ofthis material. Very few proofs are given in Chapter 1. Actual presentation of the theory begins in Chapter 2, which treats notions associated with functions of bounded variation, such as the Riemann-Stieltjes integral. Strictly speaking, a reading of Chapter 2 could v