Methods of Quantization

Thisvolumecontainsthewrittenversionsofinvitedlecturespresentedat the“39. InternationaleUniversit ̈atswochenfur ̈ Kern-undTeilchenphysik”in Schladming, Austria, which took place from February 26th to March 4th, 2000. The title of the school was “Methods of Quantization”. This is, of course,averybroad?eld,soonlysomeofthenewandinterestingdevel- mentscouldbecoveredwithinthescopeoftheschool. About75yearsagoSchr ̈odingerpresentedhisfamouswaveequationand Heisenbergcameupwithhisalgebraicapproachtothequantum-theoretical treatmentofatoms. Aimingmainlyatanappropriatedescriptionofatomic systems, these original developments did not take into consideration E- stein’stheoryofspecialrelativity. WiththeworkofDirac,Heisenberg,and Pauliitsoonbecameobviousthatauni?edtreatmentofrelativisticandqu- tume?ectsisachievedbymeansoflocalquantum?eldtheory,i. e. anintrinsic many-particletheory. Mostofourpresentunderstandingoftheelementary buildingblocksofmatterandtheforcesbetweenthemisbasedonthequ- tizedversionof?eldtheorieswhicharelocallysymmetricundergaugetra- formations. Nowadays,theprevailingtoolsforquantum-?eldtheoreticalc- culationsarecovariantperturbationtheoryandfunctional-integralmethods. Beingnotmanifestlycovariant,theHamiltonianapproachtoquantum-?eld theorieslagssomewhatbehind,althoughitresemblesverymuchthefamiliar nonrelativisticquantummechanicsofpointparticles. Aparticularlyintere- ingHamiltonianformulationofquantum-?eldtheoriesisobtainedbyqu- tizingthe?eldsonhypersurfacesoftheMinkowsispacewhicharetangential tothelightcone. The“timeevolution”ofthesystemisthenconsideredin + “light-conetime”x =t+z/c. Theappealingfeaturesof“light-conequ- tization”,whicharethereasonsfortherenewedinterestinthisformulation ofquantum?eldtheories,werehighlightedinthelecturesofBernardBakker andThomasHeinzl. Oneoftheopenproblemsoflight-conequantizationis theissueofspontaneoussymmetrybreaking. Thiscanbetracedbacktozero modeswhich,ingeneral,aresubjecttocomplicatedconstraintequations. A generalformalismforthequantizationofphysicalsystemswithconstraints waspresentedbyJohnKlauder. Theperturbativede?nitionofquantum?eld theoriesisingenerala?ictedbysingularitieswhichareovercomebyare- larizationandrenormalizationprocedure. Structuralaspectsoftherenormal- VI Preface izationprobleminthecaseofgaugeinvariant?eldtheorieswerediscussed inthelectureofKlausSibold. Areviewofthemathematicsunderlyingthe functional-integralquantizationwasgivenbyLudwigStreit. Apartfromthetopicsincludedinthisvolumetherewerealsolectures ontheKaluza–Kleinprogramforsupergravity(P. vanNieuwenhuizen),on dynamicalr-matricesandquantization(A. Alekseev),andonthequantum Liouvillemodelasaninstructiveexampleofquantumintegrablemodels(L. Faddeev). Inaddition,theschoolwascomplementedbymanyexcellents- inars. Thelistofseminarspeakersandthetopicsaddressedbythemcanbe foundattheendofthisvolume. Theinterestedreaderisrequestedtocontact thespeakersdirectlyfordetailedinformationorpertinentmaterial. Finally,wewouldliketoexpressourgratitudetothelecturersforalltheir e?ortsandtothemainsponsorsoftheschool,theAustrianMinistryofE- cation,Science,andCultureandtheGovernmentofStyria,forprovidingg- eroussupport. Wealsoappreciatethevaluableorganizationalandtechnical assistanceofthetownofSchladming,theSteyr-Daimler-PuchFahrzeugte- nik, Ricoh Austria, Styria Online, and the Hornig company. Furthermore, wethankoursecretaries,S. FuchsandE. Monschein,anumberofgra- atestudentsfromourinstitute,and,lastbutnotleast,ourcolleaguesfrom theorganizingcommitteefortheirassistanceinpreparingandrunningthe school. Graz, HeimoLatal March2001 WolfgangSchweiger Contents FormsofRelativisticDynamics BernardL. G. Bakker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 ThePoincar ́eGroup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 FormsofRelativisticDynamics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. 1 ComparisonofInstantForm,FrontForm,andPointForm. . . 6 4 Light-FrontDynamics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4. 1 RelativeMomentum,InvariantMass. . . . . . . . . . . . . . . . . . . . . . 9 4. 2 TheBoxDiagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5 Poincar ́eGeneratorsinFieldTheory. . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5. 1 FermionsInteractingwithaScalarField. . . . . . . . . . . . . . . . . . . 20 5. 2 InstantForm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5. 3 FrontForm(LF). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5. 4 InteractingandNon-interactingGeneratorsonanInstant andontheLightFront. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 6 Light-FrontPerturbationTheory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 6. 1 ConnectionofCovariantAmplitudes toLight-FrontAmplitudes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6. 2 Regularization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 6. 3 MinusRegularization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 7 TriangleDiagraminYukawaTheory. . . . . . . . . . . . . . . . . . . . . . . . . . . 27 7. 1 CovariantCalculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7. 2 ConstructionoftheCurrentinLFD. . . . . . . . . . . . . . . . . . . . . . . 30 7. 3 NumericalResults. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3 8 FourVariationsonaThemein? Theory. . . . . . . . . . . . . . . . . . . . . . 37 8. 1 CovariantCalculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 8. 2 Instant-FormCalculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 8. 3 CalculationinLight-FrontCoordinates. . . . . . . . . . . . . . . . . . . . 47 8. 4 Front-FormCalculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 9 DimensionalRegularization:BasicFormulae. . . . . . . . . . . . . . . . . . . . 51 10 Four-DimensionalIntegration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 11 SomeUsefulIntegrals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 VIII Contents Light-ConeQuantization:FoundationsandApplications ThomasHeinzl. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .