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《an introduction to quantum field theory - peskin and schroeder》由會員上傳分享，免費(fèi)在線閱讀，更多相關(guān)內(nèi)容在學(xué)術(shù)論文-天天文庫。
1、PartIFeynmanDiagramsandQuantumElectrodynamicsChapter1Invitation:PairProduction+;ineeAnnihilationThemainpurposeofPartIofthisbookistodevelopthebasiccalculationalmethodofquantum eldtheory,theformalismofFeynmandiagrams.WewillthenapplythisformalismtocomputationsinQuantumElectrodynamics,thequantumtheor
2、yofelectronsandphotons.QuantumElectrodynamics(QED)isperhapsthebestfundamentalphys-icaltheorywehave.Thetheoryisformulatedasasetofsimpleequations(Maxwell'sequationsandtheDiracequation)whoseformisessentiallydeter-minedbyrelativisticinvariance.Thequantum-mechanicalsolutionsoftheseequationsgivedetaile
3、dpredictionsofelectromagneticphenomenafrommacro-scopicdistancesdowntoregionsseveralhundredtimessmallerthanthepro-ton.Feynmandiagramsprovideforthiseleganttheoryanequallyelegantpro-cedureforcalculation:Imagineaprocessthatcanbecarriedoutbyelectronsandphotons,drawadiagram,andthenusethediagramtowritet
4、hemathe-maticalformofthequantum-mechanicalamplitudeforthatprocesstooccur.Inthis rstpartofthebookwewilldevelopboththetheoryofQEDandthemethodofFeynmandiagramsfromthebasicprinciplesofquantummechanicsandrelativity.Eventually,wewillarriveatapointwherewecancalculateobservablequantitiesthatareofgreatint
5、erestinthestudyofele-mentaryparticles.Buttoreachourgoalofderivingthissimplecalculationalmethod,wemust rst,unfortunately,makeaseriousdetourintoformalism.Thethreechaptersthatfollowthisonearealmostcompletelyformal,andthereadermightwonder,inthecourseofthisdevelopment,wherewearego-ing.Wewouldliketopar
6、tiallyanswerthatquestioninadvancebydiscussingthephysicsofanespeciallysimpleQEDprocess
7、onesucientlysimplethatmanyofitsfeaturesfollowdirectlyfromphysicalintuition.Ofcourse,thisintuitive,bottom-upapproachwilcontainmanygaps.InChapter5wewillreturntothisprocesswiththefullpoweroftheFeynmandiagramformal
8、ism.Workingfromthetopdown,wewillthenseeallofthesedicultiessweptaway.3+;4Chapter1Invitation:PairProductionineeAnnihilation+;+;Figure1.1.Theannihilationreactionee!,showninthecenter-of-massframe.TheSimplestSituationSin
