HANDBOOKOFALGEBRA VOLUME4 ManagingEditor M.HAZEWINKEL,Amsterdam EditorialBoard M.ARTIN,Cambridge M.NAGATA,Okayama C.PROCESI,Rome R.G.SWAN,Chicago P.M.COHN,London A.DRESS,Bielefeld J.TITS,Paris N.J.A.SLOANE,MurrayHill C.FAITH,NewBrunswick S.I.AD’YAN,Moscow Y.IHARA,Tokyo L.SMALL,SanDiego E.MANES,Amherst I.G.MACDONALD,Oxford M.MARCUS,SantaBarbara L.A.BOKUT’,Novosibirsk HANDBOOK OF ALGEBRA Volume 4 edited by M. HAZEWINKEL CWI,Amsterdam AMSTERDAM•BOSTON•HEIDELBERG•LONDON•NEWYORK•OXFORD PARIS•SANDIEGO•SANFRANCISCO•SINGAPORE•SYDNEY•TOKYO North-HollandisanimprintofElsevier North-HollandisanimprintofElsevier Radarweg29,POBox211,1000AEAmsterdam,TheNetherlands TheBoulevard,LangfordLane,Kidlington,OxfordOX51GB,UK Firstedition2006 Copyright©2006ElsevierB.V.Allrightsreserved Nopartofthispublicationmaybereproduced,storedinaretrievalsystemortransmittedinanyformorbyanymeans electronic,mechanical,photocopying,recordingorotherwisewithoutthepriorwrittenpermissionofthepublisher PermissionsmaybesoughtdirectlyfromElsevier’sScience&TechnologyRightsDepartmentinOxford,UK:phone (+44)(0)1865843830;fax(+44)(0)1865853333;email:[email protected] yourrequestonlinebyvisitingtheElsevierwebsiteathttp://elsevier.com/locate/permissions,andselectingObtaining permissiontouseElseviermaterial Notice Noresponsibilityisassumedbythepublisherforanyinjuryand/ordamagetopersonsorpropertyasamatterof productsliability,negligenceorotherwise,orfromanyuseoroperationofanymethods,products,instructionsor ideascontainedinthematerialherein.Becauseofrapidadvancesinthemedicalsciences,inparticular,independent verificationofdiagnosesanddrugdosagesshouldbemade LibraryofCongressCataloging-in-PublicationData AcatalogrecordforthisbookisavailablefromtheLibraryofCongress BritishLibraryCataloguinginPublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary ISBN-13:978-0-444-52213-9 ISBN-10:0-444-52213-1 ISSN:1570-7954 ForinformationonallNorth-Hollandpublications visitourwebsiteatbooks.elsevier.com PrintedandboundinTheNetherlands 06 07 08 09 10 10 9 8 7 6 5 4 3 2 1 Preface Basicphilosophy Algebra,asweknowittoday(2005),consistsofagreatmanyideas,conceptsandresults. A reasonable estimate of the number of these different “items” would be somewhere be- tween 50000 and 200000. Many of these have been named and many more could (and perhaps should) have a “name”, or other convenient designation. Even a nonspecialist is quitelikelytoencountermostofthese,eithersomewhereinthepublishedliteratureinthe formofanidea,definition,theorem,algorithm,...somewhere,ortohearaboutthem,of- teninsomewhatvagueterms,andtofeeltheneedformoreinformation.Insuchacase,if theconceptrelatestoalgebra,thenoneshouldbeabletofindsomethinginthisHandbook; atleastenoughtojudgewhetheritisworththetroubletotrytofindoutmore.Inaddition totheprimaryinformationthenumerousreferencestoimportantarticles,books,orlecture notesshouldhelpthereaderfindoutmore. As a further tool the index is perhaps more extensive than usual, and is definitely not limitedtodefinitions,(famous)namedtheoremsandthelike. ForthepurposesofthisHandbook,“algebra”ismoreorlessdefinedastheunionofthe followingareasoftheMathematicsSubjectClassificationScheme: –20 (Grouptheory) –19 (K-theory; this will be treated at an intermediate level; a separate Handbook of K-theorywhichgoesintofarmoredetailthanthesectionplannedforthisHandbook ofAlgebraisunderconsideration) –18 (Categorytheoryandhomologicalalgebra;includingsomeoftheusesofcategoryin computerscience,oftenclassifiedsomewhereinsection68) –17 (Nonassociativeringsandalgebras;especiallyLiealgebras) –16 (Associativeringsandalgebras) –15 (Linearandmultilinearalgebra,Matrixtheory) –13 (Commutativeringsandalgebras;herethereisafinelinetotreadbetweencommu- tative algebras and algebraic geometry; algebraic geometry is definitely not a topic thatwillbedealtwithinthisHandbook;therewill,hopefully,onedaybeaseparate Handbookonthattopic) –12 (Fieldtheoryandpolynomials) –11 Thepartofthatalsousedtobeclassifiedunder12(Algebraicnumbertheory) –08 (Generalalgebraicsystems) –06 (Certainparts;butnottopicsspecifictoBooleanalgebrasasthereisaseparatethree- volumeHandbookofBooleanAlgebras) v vi Preface Planning Originally (1992), we expected to cover the whole field in a systematic way. Volume 1 wouldbedevotedtowhatisnowcalledSection1(seebelow),Volume2toSection2,and so on.A quitedetailedandcomprehensiveplanwasmadeintermsof topicsthatneeded to be covered and authors to be invited. That turned out to be an inefficient approach. Differentauthorshavedifferentprioritiesandtowaitforthelastcontributiontoavolume, asplannedoriginally,wouldhaveresultedinlongdelays.Insteadthereisnowadynamic evolvingplan.Thisalsopermitstotakenewdevelopmentsintoaccount. Chaptersarestillbyinvitationonlyaccordingtothethencurrentversionoftheplan,but the various chapters are published as they arrive, allowingfor faster publication.Thus in this Volume4 of the Handbookof Algebra the reader will find contributionsfrom 5 sec- tions. As the plan is dynamic suggestions from users, both as to topics that could or should becovered,andauthors,aremostwelcomeandwillbegivenseriousconsiderationbythe boardandeditor. Thelistofsectionslooksasfollows: Section1: Linearalgebra.Fields.Algebraicnumbertheory Section2: Categorytheory.Homologicalandhomotopicalalgebra.Methodsfromlogic (algebraicmodeltheory) Section3: Commutativeandassociativeringsandalgebras Section4: Otheralgebraicstructures.Nonassociativeringsandalgebras.Commutative andassociativeringsandalgebraswithextrastructure Section5: Groupsandsemigroups Section6: Representationsandinvarianttheory Section7: Machinecomputation.Algorithms.Tables Section8: Appliedalgebra Section9: Historyofalgebra For the detailed plan (2005 version), the reader is referred to the Outline of the Series followingthispreface. Theindividualchapters Itisnottheintentionthatthehandbookasawholecanalsobeasubstituteundergraduate orevengraduate,textbook.Indeed,thetreatmentsofthevarioustopicswillbemuchtoo dense and professional for that. Basically, the level should be graduate and up, and such materialascanbefoundinP.M.Cohn’sthreevolumetextbook‘Algebra’(Wiley)should, asarule,beassumedknown.ThemostimportantfunctionofthearticlesinthisHandbook istoprovideprofessionalmathematiciansworkinginadifferentareawithasufficiencyof informationonthetopicinquestionifandwhenitisneeded. Each of the chapters combines some of the features of both a graduate level textbook andaresearch-levelsurvey.Notalloftheingredientsmentionedbelowwillbeappropriate ineachcase,butauthorshavebeenaskedtoincludethefollowing: Preface vii – Introduction(includingmotivationandhistoricalremarks) – Outlineofthechapter – Basicconcepts,definitions,andresults.(Thesemaybeaccompaniedbyproofsor(usu- allybetter)ideas/sketchesoftheproofswhenspacepermits) – Commentsontherelevanceoftheresults,relationstootherresults,andapplications – Reviewoftherelevantliterature;possiblycompletewiththeopinionsoftheauthoron recentdevelopmentsandfuturedirections – Extensivebibliography(severalhundreditemswillnotbeexceptional) Thepresent Volume1appearedin1995(copyright1996),Volume2in2000,Volume3in2003.Vol- ume5isplannedfor2006.Thereafter,weaimatonevolumeeverytwoyears(orbetter). Thefuture Ofcourse,ideally,acomprehensiveseriesofbookslikethisshouldbeinteractiveandhave a hypertext structure to make finding material and navigation through it immediate and intuitive.Itshouldalsoincorporatethevariousalgorithmsinimplementedformaswellas permitacertainamountofdialoguewiththereader.Plansforsuchaninteractive,hypertext, CDROM(DVD)-basedversioncertainlyexistbuttherealizationisstillanontrivialnumber ofyearsinthefuture. Kvoseliai,July2005 MichielHazewinkel KaumnenntmandieDingebeimrichtigenNamen soverlierensieihrengefährlichenZauber (Youhavebuttoknowanobjectbyitspropername forittoloseitsdangerousmagic) EliasCanetti This page intentionally left blank Outline of the Series (asofJuly2005) PhilosophyandprinciplesoftheHandbookofAlgebra ComparedtotheoutlineinVolume1thisversiondiffersinseveralaspects. First, there is a major shift in emphasis away from completeness as far as the more elementarymaterialisconcernedandtowardsmoreemphasisonrecentdevelopmentsand activeareas.Second,theplanisnowmoredynamicinthatthereisnolongerafixedlistof topicstobecovered,determinedlonginadvance.Insteadthereisamoreflexiblenonrigid listthatcananddoeschangeinresponsetonewdevelopmentsandavailabilityofauthors. The new policy, starting with Volume 2, is to work with a dynamic list of topics that should be covered, to arrange these in sections and larger groups according to the major divisionsintowhichalgebrafalls,andtopublishcollectionsofcontributions(i.e.chapters) astheybecomeavailablefromtheinvitedauthors. Thecodingbelowisbystyleandisasfollows. – Author(s)inbold,followedbychaptertitle:articles(chapters)thathavebeenreceived andarepublishedorarebeingpublishedinthisvolume. – Chaptertitleinitalic:chaptersthatarebeingwritten. – Chaptertitleinplaintext:topicsthatshouldbecoveredbutforwhichnoauthorhasyet beendefinitelycontracted. ChaptersthatareincludedinVolumes1–4havea(x;yypp.)afterthem,where‘x’isthe volumenumberand‘yy’isthenumberofpages. Compared to the plan that appeared in Volume 1 the section on “Representation and invariant theory” has been thoroughly revised. The changes of this current version com- paredtotheoneinVolume2(2000)andVolume3(2003)arerelativelyminor:mostlythe additionofquiteafewtopics. Editorialset-up Managingeditor:M.Hazewinkel. Editorial board: M. Artin, M. Nagata, C. Procesi, O. Tausky-Todd,† R.G. Swan, P.M.Cohn,A.Dress,J.Tits,N.J.A.Sloane,C.Faith,S.I.Ad’yan,Y.Ihara,L.Small, E.Manes,I.G.Macdonald,M.Marcus,L.A.Bokut’,Eliezer(LouisHalle)Rowen, JohnS.Wilson,VlastimilDlab.Notethatthreeeditorshavebeenaddedstartingwith Volume5. Plannedpublishingschedule(asofJuly2005) 1996:Volume1(published) 2001:Volume2(published) 2003:Volume3(published) ix