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1、GRAVITY,GAUGETHEORIESANDGEOMETRICALGEBRAAnthonyLasenby,ChrisDoranandStephenGullMRAO,CavendishLaboratory,MadingleyRoad,CambridgeCB30HE,UK.AbstractAnewgaugetheoryofgravityispresented.Thetheoryisconstructedina
atbackgroundspacetimeandemploysgauge eldstoensure
2、thatallrelationsbetweenphysicalquantitiesareindependentofthepositionandorientationofthematter elds.Inthismannerallpropertiesofthebackgroundspacetimeareremovedfromphysics,andwhatremainsareasetof`intrinsic'relationsbetweenphysical elds.Forawiderangeofphenome
3、na,includingallpresentexperimentaltests,thetheoryreproducesthepredictionsofgeneralrelativity.Di erencesdoemerge,however,throughthe rst-ordernatureoftheequationsandtheglobalpropertiesofthegauge elds,andthroughtherelationshipwithquantumtheory.Thepropertiesof
4、thegravitationalgauge eldsarederivedfrombothclassicalandquantumviewpoints.Fieldequationsarethenderivedfromanactionprinciple,andconsistencywiththeminimalcouplingprocedureselectsanactionwhichisuniqueuptothepossibleinclusionofacosmologicalconstant.Thisinturns
5、inglesoutauniqueformofspin-torsioninteraction.Anewmethodforsolvingthe eldequationsisoutlinedandappliedtothecaseofatime-dependent,spherically-symmetricperfect
uid.AgaugeisfoundwhichreducesthephysicstoasetofessentiallyNewtonianequations.Theseequationsarethen
6、appliedtothestudyofcosmology,andtotheformationandpropertiesofblackholes.Insistenceon ndingglobalsolutions,togetherwiththe rst-ordernatureoftheequations,leadstoanewunderstandingoftheroleplayedbytimereversal.Thisaltersthephysicalpictureofthepropertiesofahori
7、zonaroundablackhole.Theexistenceofglobalsolutionsenablesonetodiscussthepropertiesof eldlinesinsidethehorizonduetoapointchargeheldoutsideit.TheDiracequationisstudiedinablackholebackgroundandprovidesaquick(thoughultimatelyunsound)derivationoftheHawkingtem-pe
8、rature.Someapplicationstocosmologyarealsodiscussed,andastudyoftheDiracequationinacosmologicalbackgroundrevealsthattheonlymodelsconsistentwithhomogeneityarespatially
at.Itisemphasisedthroughoutthatthedescripti
