Dark Matter and Dark Energy[暗物质和暗能量](-30).ppt

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1、DarkMatterandDarkEnergyHitoshiMurayama290ESeptember5,2001IntroductionWecan’tseeneitherDarkMatternorDarkEnergyThenwhydowetalkaboutit?Thistalk:BriefreviewofstandardcosmologyBig-BangNucleosynthesisObservationalevidenceforDarkMatterObservationalevidenceforDarkEnergyPa

2、rticle-physicsimplicationsBriefreviewofstandardcosmologyTheIsotropicUniverseTheCosmologicalPrincipleUniversehighlyisotropicCMBRanisotropyO(10–5)Unlessweoccupythe“centeroftheUniverse,”itmustalsobehomogenousIsotropyandHomogeneitymaximallysymmetricspaceFlatEuclide

3、anspaceR3Closedthree-sphereS3=SO(4)/SO(3)Openthree-hyperbolaSO(3,1)/SO(3)FriedmanEquationEquationthatgovernsexpansionoftheUniversek=–1(closed),k=1(open),k=0(flat)energydensityrFirstlawofthermodynamics:ForflatUniverse:Matter-dominatedUniverseRadiation-dominatedUniv

4、erseVacuum-dominatedUniverseStructureFormationJeansinstabilityofself-gravitatingsystemcausesstructuretoformNeedsinitialseeddensityfluctuationDensityfluctuationgrowslittleinradiation-orvacuum-dominatedUniverseDensityfluctuationgrowslinearlyinmatter-dominatedUnivers

5、eIfonlymatter=baryons,hadonlytimefor103growthfrom10–5:notenoughtimebynow!Big-BangNucleosynthesisThermo-NuclearFusioninEarlyUniverseBesttestedtheoryofEarlyUniverseBaryon-to-photonratiohnB/ngonlyparameterNeutrondecay-anti-decayequilibriumendswhenT~1MeV,theydecayun

6、tiltheyarecapturedindeuteriumDeuteriumeventuallyform3He,4He,7Li,etcMostofneutronsendupin4HeAstronomicalobservationsmaysufferfromfurtherchemicalprocessinginstarsData“Crisis”thepastfewyearsThuan-Izotovreevaluationof4HeabundanceSangaliaDabundanceprobablyfalseNowconco

7、rdanceWBh2=0.0170.004(Thuan,Izotov)CMB+LSSnowconsistentWB=0.02–0.037(Tegmark,Zaldarriaga.Hamilton)ObservationalevidenceforDarkMatterTheoreticalArgumentsforDarkMatterSpiralgalaxiesmadeofbulge+disk:unstableasaself-gravitatingsystemneeda(near)sphericalhaloWithonl

8、ybaryonsasmatter,structurestartsformingtoolate:wewon’texistMatter-radiationequalitytoolateBaryondensityfluctuationdoesn’tgrowuntildecouplingNeedelectric