lecture01 what you need to know about string theory

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1、MITOpenCourseWarehttp://ocw.mit.edu8.821StringTheoryFall2008ForinformationaboutcitingthesematerialsorourTermsofUse,visit:http://ocw.mit.edu/terms.8.821Lecture01:WhatyouneedtoknowaboutstringtheoryLecturer:McGreevyScribe:McGreevySinceIlearnedthatwewouldge

2、ttohavethisclass,I’vebeentornbetweena)startingoverwithstringperturbationtheoryandb)continuingwhereweleftoff.Optiona)isfavoredbysomepeoplewhodidn’ttakelastyear’sclass,andbymewhenI’mfeelinglikeIshoulddomoreresearch.Butbecauseofasneakyandperhapssurprisingfa

3、ctofnatureandthehistoryofsciencethereisawaytodooptionb)whichdoesn’tleaveoutthepeoplewhomissedlastyear’sclass(andisonlynotintheinterestofthelazyversionofme).Thefactisthis.Itisactuallyrarethatthestructureofworldsheetperturbationtheoryisdirectlyusedinresea

4、rchinthesubjectthatiscalledstringtheory.Andfurther,oneofthemostimportantdevelopmentsinthissubject,whichisusuallycalled,synecdochically,theAdS/CFTcorrespondence,canbediscussedwithoutactuallyusingthismachinery.Themostwell-developedresultsinvolveonlyclassi

5、calgravityandquantumfieldtheory.Sohere’smycrazyplan:wewillstudytheAdS/CFTcorrespondenceanditsapplicationsandgeneralizations,withoutrelyingonstringperturbationtheory.Whyshouldwedothis?Youmayhaveheardthatstringtheorypromisestoputanendonceandforalltothatpes

6、kybusinessofphysicalscience.Maybesomethinglikeitunifiesparticlephysicsandgravityandcooksyourbreakfast.Frankly,inthiscapacity,itisatbestanideamachineatthemoment.ButthisAdS/CFTcorrespondence,wherebythestringtheoryunderdiscussionlivesnotinthespaceinwhichour

7、quantumfieldsarelocal,butinanauxiliarycurvedextra-dimensionalspace(likeasouped-upfouriertransformspace),iswherestringtheorycomestheclosesttophysics.Thereason:itoffersotherwise-unavailableinsightintostrongly-coupledfieldtheories(examplesofwhich:QCDintheinfr

8、ared,high-temperaturesuperconductors,coldatomsatunitarity),andintoquantumgravity(questionsaboutwhichincludetheblack-holeinformationparadoxandtheresolutionofsingularities),andbecausethroughthiscorrespondence,gaugetheoriesprovideab