資源描述：
《Feynman-Diagram》由會(huì)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(kù)。
1、Feynmandiagram1FeynmandiagramFeynmandiagramsareapictorialrepresentationschemeforthemathematicalexpressionsgoverningthebehaviorofsubatomicparticles.Thecalculationofprobabilityamplitudesintheoreticalparticlephysicsrequirestheuseofsomeratherlargeandcomplicatedintegralsoveralargenumberofvariables.The
2、seintegralsdo,however,havearegularstructure,andmayberepresentedgraphicallyasFeynmandiagrams.AFeynmandiagramallowsforasimplevisualizationofwhatwouldotherwisebearatherarcaneandabstractformula.InthisFeynmandiagram,anelectronandapositronannihilate,producingavirtualphotonthatbecomesaquark-antiquarkpai
3、r.Thenoneradiatesagluon.Moreprecisely,aFeynmandiagramisagraphicalrepresentationofaperturbativecontributiontothetransitionamplitudeorcorrelationfunctionofaquantummechanicalorstatisticalfieldtheory.WithinthecanonicalformulationofquantumfieldtheoryaFeynmandiagramrepresentsatermintheWick'sexpansionof
4、theperturbativeS-matrix.Alternatively,thepathintegralformulationofquantumfieldtheoryrepresentsthetransitionamplitudeasaweightedsumofallpossiblehistoriesofthesystemfromtheinitialtothefinalstate,intermsofeitherparticlesorfields.AFeynmandiagramisthenacontributionofaparticularclassofparticlepaths,whi
5、chjoinandsplitasdescribedbythediagram.ThetransitionamplitudeisthengivenasthematrixelementoftheS-matrixbetweentheinitialandthefinalstatesofthequantumsystem.FeynmandiagramsweredevelopedbyRichardFeynman,andarenamedafterhim.Therearemanyapplications,primarilyinquantumfieldtheory,butalsoinotherfields,e
6、.g.,insolid-statetheory.MotivationandhistoryWhencalculatingscatteringcrosssectionsinparticlephysics,theinteractionbetweenparticlescanbedescribedbystartingfromafreefieldwhichdescribestheincomingandoutgoingparticles,andincludinganinteractionHamiltoniantodescribehowtheparticlesdeflectoneanother.Thea
7、mplitudeforscatteringisthesumofeachpossibleinteractionhistoryoverallpossibleInthisdiagram,akaon,madeofanupandanti-strangequark,decaysbothweaklyintermediateparticlestates.Thenumberofandstronglyintothreepions,withinterme
