引力波探测历史现状未来

引⼒力波探测历史现状未来加州理⼯工学院陈雁北1905:狭义相对论2爱因斯坦电磁波（⽆无线电、光）理论适⽤用于所有“惯性参照系”30万公⾥里／秒⻋车上看到的光速还是30万公⾥里／秒！！20万公⾥里／秒时空⼏几何从原点出发的光线构成光锥从原点出发只能到达光锥内部光锥外的事件，在不同观测者看来，可能发⽣生在原点之前或者之后空间时间光锥光锥未来可到达的范围1秒2秒30万公⾥里60万公⾥里－30万公⾥里－60万公⾥里⽜牛顿的万有引⼒力和狭义相对论有⽭矛盾！引⼒力是⼀一个很特殊的相互作⽤用：等效原理3GalileoGalilei(1564-1642)各种物体在引⼒力场中⾃自由下落的加速度⼀一样！伽⾥里略爱因斯坦：引⼒力可以由弯曲的时空⼏几何来实现！对电磁⼒力完全不适⽤用！！！1915:⼴广义相对论4不同材质的物体都沿“测地线”运动！有质量的物体会让时空弯曲能量和动量的分布时空的⼏几何结构dxdt=[L(x)]Pad´e[dE(x)/dx]Pad´e(12)dE/dxL#Taylordx=dt)x↵(1&x&x2&...)=t(13)x=t1/↵(1&t1/↵&t2/↵&...)(14)h(f)=f7/6eif5/3(1&f2/3&...)(15)r↵r↵¯hµ⌫+2Rµ↵⌫¯h↵=0.(16)h+ih⇥=1R+1Xl=2+lXm=lHl,m(t)2Ylm(✓,')(17):orbitalphase(s)!GM|sr|+DP(18)DP=1014m(19)Gµ⌫=8⇡Tµ⌫(20)2爱因斯坦⽅方程⿊黑洞:时空弯曲的“极端”情况5视界视界⿊黑洞的视界：只能进⼊入，没法逃出时间空间⿊黑洞内部视界视界内：光锥全部不能逃出视界外附近：光锥⼤大部分落⼊入⿊黑洞时间停⽌止时间停⽌止时间变慢：到⿊黑洞附近的旅⾏行者，回到地球后时钟⽐比地球慢！6⿊黑洞的“嵌⼊入图”视界外部的时空：空间弯曲，时间变慢科幻电影中⿊黑洞的外观7Fig.3.3.ThestarsinGargantua’sgalaxy,asseenaroundGargantua’sshadow.Gargantuabendsthelightrayscomingfromeachstar,therebydistortingenormouslytheappearanceofitsgalaxy:“gravitationallylensing”thegalaxy.[FromasimulationforthisbookbytheDoubleNegativevisual-effectsteam.]Einstein’srelativisticlawspredict,unequivocally,allthepropertiesofblackholesfromtheirsurfacesoutward,includingtheirgravitationallensing.7Astronomershavefirmobservationalevidencethatblackholesexistinouruniverse,includinggiganticblackholeslikeGargantua.Astronomershaveseengravitationallensingbyotherobjects(forexample,Figure24.3),thoughnotyetbyblackholes,andtheobservedlensingisinpreciseaccordwiththepredictionsofEinstein’srelativisticlaws.Thisisenoughforme.Gargantua’sgravitationallensing,assimulatedbyPaulFranklin’sDoubleNegativeteamusingrelativityequationsIgavetothem,istrue.Thisiswhatitreallywouldlooklike.Bycontrast,theblightthatendangershumanlifeonEarthinInterstellar(Figure3.4andChapter11)isaneducatedguessinonesense,andaspeculationinanother.Letmeexplain.Throughoutrecordedhistory,thecropsthathumansgrowhavebeenplaguedbyoccasionalblights(rapidlyspreadingdiseasescausedbymicrobes).Thebiologythatunderliestheseblightsisbasedonchemistry,whichinturnisbasedonthequantumlaws.Scientistsdonotyetknowhowtodeduce,fromthequantumlaws,alloftherelevantchemistry(buttheycandeducemuchofit);andtheydonotyetknowhowtodeducefromchemistryalloftherelevantbiology.Nevertheless,科幻电影⾥里⾯面的物理是真的吗？6000光年外的天鹅座X-18天鹅座天鹅座X-19倍太阳质量的⿊黑洞！⽓气体落到⿊黑洞时被加热到10亿度以上，发出X-射线银河系中⼼心的超⼤大质量⿊黑洞26000光年外，4百万倍太阳质量！9引⼒力波：时空的涟漪10爱因斯坦发现，弱引⼒力下，他的⽅方程描述了引⼒力波时空⼏几何的振荡以光速传播引⼒力波引起距离的变化11半波⻓长以内，相距越远的物体，引⼒力波引起的距离变化就越⼤大！波⻓长引⼒力波对物质的作⽤用12L振幅为h的引力波引⼒力波的振幅，是物体距离变化的⽐比例：ΔL〜～Lh⾃自由下落物体⾃自由下落物体+偏振:h+×偏振:h×引⼒力波是横波：只导致和传播⽅方向垂直的平⾯面上的运动引⼒力波是很难产⽣生的！13产⽣生引⼒力波需要⼤大量物质或者能量加速运动历史上最⼤大的氢弹（5千万顿当量）爆炸附近1⽶米处物体间距离变化的⽐比例h~10-27ΔL〜～Lh60年代：共振法•20世纪60年代，JosephWeber进⾏行了⼀一系列的实验，并宣布探测到引⼒力波14•Weber的实验结果⽆无法重复。•天体物理中难以预测到Weber实验能够探测到的强度。•但是Weber开创了引⼒力波探测这个领域。共振频率上引⼒力波的效果被放⼤大！70年代：引⼒力波存在的证据151974年,Hulse和Taylor发现脉冲双星PSR1913+16双星轨道能量的衰减与引⼒力波辐射带⾛走的能量相符双中子星和双黑洞的并合成为引力波探测的主要目标70年代：激光⼲干涉探测引⼒力波•Michelson干涉仪：⽤用光相位的干涉来测量位移(R.Weiss,R.Forward).16LLLhLh•臂⻓长可以放⼤大引⼒力波信号。•光学⽅方法有利于对距离变化的灵敏测量。激光17激光⼲干涉探测引⼒力波谐振腔：进⼀一步提⾼高测距灵敏度90年代：LIGO计划•1992年NSF开始资助，世界上第⼀一个⼤大规模引⼒力波探测项⺫⽬目。•由Caltech和MIT共同建造。18(LaserInterferometerGravitational-waveObservatory)19LIGOHanfordObservatoryL=4km20LIGOLivingstonObservatoryL=4km光在⾼高真空中传播21悬挂系统：隔离地⾯面震动22⼲干涉仪的具体灵敏度分析233.1QuantumnoiseQuantumnoiseencompassestheeffectsofstatisticalfluctuationsindetectedphotonarrivalrate(shotnoise)andradiationpressureduetophotonnumberfluctuations.QuantumnoiseiscalculatedusingtheformulationofBuonannoandChen[14].Weassume75ppmround-triplossineacharmcavity,and10-3lossinthepowerrecyclingcavity,whichleadsto5.2kWofpoweratthebeamsplitterand750kWofpowerineacharmcavity.Adetectionefficiencyof90%isassumed;thisaccountsforfinitetransmissionthroughtheoutputFaradayisolatorandoutputmodecleaner,aswellasphotodetectorquantumefficiency.3.2TestmassthermalnoiseCoatingBrowniannoiseisthedominantofthevarioustestmassthermalnoiseterms.Itarisesfrommechanicaldissipationinthecoatings,andiscalculatedaccordingtoreference[15].Thecoatingdesignandmaterialparametersaredescribedinsection4.3.Coatingthermo-opticnoisearisesfromthermaldissipationinthecoatings,producingnoiseviathethermoelasticandthermorefractivecoefficientsofthecoatingmaterials.Thetwoeffectsarecalculatedcoherently,accordingtoreference[16].MechanicallossintheFigure2Principalnoisetermsforthenominal(highpower,broadband)modeofoperationofAdvancedLIGO.shotnoiseradiationpressurenoisecoatingthermalnoisesuspensionthermalnoiseNewtonianGravityNoiseseismicnoiseLIGO灵敏度的进步24210100100010-2410-2310-2210-21Frequency(Hz)StrainNoise(1/Hz)FIG.1.Theleftplotshowsthestrainsensitivityduringthefirstobservationrun(O1)oftheAdvancedLIGOdetectorsandduringthelastsciencerun(S6)oftheinitialLIGOdetectors.TheO1strainnoisecurveisshownforH1(darkred)andL1(lightred);thetwodetectorshavesimilarperformance.TheAdvancedLIGOdesignsensitivityaswellasapossiblefutureupgrade[11]areshowntohighlightthediscoverypotentialinthecomingyears.Therightplotshowsthesingledetectorsig