二十一世纪第二个十年的宇宙学

1、二十一世纪第二个十年的宇宙学1The origin of “cosmic acceleration”: void? backreaction? modified gravity? dark energy? or simply Lambda?张鹏杰中国科学院上海天文台二十一世纪第二个十年的宇宙学2The standard cosmologySix parameters describe (almost) everything (cosmological observations). 二十一世纪第二个十年的宇宙学3宇宙学探针宇宙学探针膨胀历史和几何膨胀历史和几何 一型超新星一型超新星 重子声波振荡

2、重子声波振荡 强引力透镜强引力透镜 星系团星系团SZ+X-ray 、 年龄（球状星团、星系）年龄（球状星团、星系） 、 标准警报、脉泽测距、标准警报、脉泽测距、real time cosmology、大尺度结构大尺度结构 弱引力透镜弱引力透镜 红移畸变红移畸变 ISW效应效应 星系团计数星系团计数 星系成团性星系成团性 星系和星系团速度星系和星系团速度 热热SZ和运动学和运动学SZ效应效应 、宇宙初始条件：微波背景辐射、中微子背景、引力波背景、星系动力学星系动力学 （kpc-Mpc尺度）、尺度）、二十一世纪第二个十年的宇宙学4Initial condition of the universeP

3、hysical principlesThe observableuniverseCopernican principle implies thatthe observable universeis a fair sample of THE universe?Uncertainties in modern cosmology?Nonlinearity in GR,Nonlinearity in matter fluidGastrophysics?Gaussian, adiabatic, nearly scale invariant primordial fluctuationsGR+SM+Col

4、d dark matter+Cosmological constantDynamical dark energyPMG? B-mode?Standard Cosmology321二十一世纪第二个十年的宇宙学5 Unexpected dimming of type Ia supernovae was first detected in 1998 Riess et al. 2005Riess et al. 1998Perlmutter et al. 1999二十一世纪第二个十年的宇宙学6What causes the Supernova dimming? Violations of the Cop

5、ernican Principle: What if we live at or near the center of a gigantic void?Cosmic acceleration The cosmological constant or dynamical dark energy Alternatives: GR backreaction(?) Modified gravityAstrophysics: Intrinsic evolution (?); Dust extinction. Compton dimming. Not sufficient.321二十一世纪第二个十年的宇宙

6、学7Low density region（void)(1) LTB: cosmic acceleration without dark energyLemaitre-Tolman-Bondi model:The universe has a centerWe live at or near the centerMatter distribution is isotropic with respect to and only to the center (us)In this radially nhomogeneous universe, supernovae can appear dimmer

7、 than in a FRW universe, without cosmic acceleration.Gravitationalpotentialdistancebackground universe(higher density)compensating shell二十一世纪第二个十年的宇宙学8哥白尼原理的宇宙学检验 宇宙微波背景黑体谱检验 排除了许多void模型 星系团运动学SZ效应检验 排除了许多void模型 背景运动学SZ效应功率谱检验 排除了void模型，证实了哥白尼原理 除非微调，破坏掉宇宙极早期的均匀性和物质-辐射的强耦合M(r), E(r),t_b(r)r二十一世纪第二个十

8、年的宇宙学9Testing the Copernican principle with free electrons as messengerGoodman 1995; Caldwell & Stebbins, 2008; Garcia-Bellideo & Haughbolle 2008; ZPJ & Stebbins, 2010eCompton scatteringsallow us to sit atdistant universe andjudge whether CP holdsconsequence 1:CMB spectrum willbe non-bla

9、ckbodyT3T2T1二十一世纪第二个十年的宇宙学102008Void sizevoid densityrules out manyvoid modelscapable of replacing darkenergy, but not allof them. Furthermore, ICSinduces non-blackbody too.二十一世纪第二个十年的宇宙学11Galaxy clusters (a bunch of electrons) as moving mirrorsDust (matter) frameViolation of the Copernican principl

10、e Violation of CP causes relative motion between CMB and the matter comoving frame Causes a large cluster kSZ effectpredictionobservationsCMB frameIn a homogeneous universe, no motion between the twoGoodman 1995rules out manyvoid modelscapable of replacing darkenergy, but not allof them 二十一世纪第二个十年的宇

11、宙学12The kSZ power spectrum measurement rules out void modelsCopernican principle is confirmedCosmic acceleration is REAL! Background universeCompensating shellvoidThe Hubble bubble modelat l=3000, a few arcminute13 uk2 (SPT)-8 uk2(ACT)-6.5 uk2(SPT)ZPJ & Stebbins 2010二十一世纪第二个十年的宇宙学13So, cosmic ac

12、celeration is REAL!But what causes it? Mirage of GR backreaction? Infrared corrections to GR? Cosmological constant/dark energy?二十一世纪第二个十年的宇宙学14(2) GR backreaction on the background expansion()uvuvabTGg()FRWuvuvabTGg2221()()2FRWFRWuvuvuvuvababuvabababababGGTGghGghhggLeffuvTExact equationUsual approx

13、imationBackreactionA century old topic, still highly controversial!二十一世纪第二个十年的宇宙学15(3) Modified gravity and the cosmic accelerationf(R)DGP该领域研究在过去十年出现了长足进展 New/old models: f(T), cascading gravity, Galileo gravity, Einstein-Ather, etc. Refer to the review article by Jain & Khoury, 2010 N-body cod

14、es/simulations! (e.g. Oyaizu 08; Fabian et al. 08-11; Chan & Scoccimarro 09; Zhao et al. 01) Fundamental features/impacts: Gravity is environmental depenent Screening mechanisms required Violation of the Birkhoff theorem Violation of equivalence principle (apparent or real)二十一世纪第二个十年的宇宙学16广义相对论的

15、宇宙学检验广义相对论的宇宙学检验宇宙膨胀历史+宇宙大尺度结构+太阳系检验太阳系检验 具体模型的检验 参数拟合 Smoking gunsSN Ia, BAO,CMBJain & Khoury 2010二十一世纪第二个十年的宇宙学17Song et al. 2006DGP is disfavored comparing to LCDMZhu & Alcaniz 2004Testing specific models: expansion and DGP二十一世纪第二个十年的宇宙学18CMB and DGPFang et al. 2008二十一世纪第二个十年的宇宙学19Redshif

16、t distortion and DGPGuzzo et al. 2008Blake et al. 2010f=dlnD/dlna二十一世纪第二个十年的宇宙学20参数化引力的宇宙学数据拟合Daniel et al. 2010Gong-Bo Zhao et al. 2010一般一般2个参量，分别描述物质个参量，分别描述物质弯曲时空的总能力和弯曲时间弯曲时空的总能力和弯曲时间、空间的相对能力、空间的相对能力二十一世纪第二个十年的宇宙学21The first E_G measurement: confirmed GR at 10-40 Mpc/h scalesReyes et al. 20102ga

17、laxy-lensing()galaxy-velocityGEZPJ et al. 2007BigBOSS can improveby a factor of 10检验宇宙学尺度上的检验宇宙学尺度上的广义泊松方程广义泊松方程二十一世纪第二个十年的宇宙学22The origin of “cosmic acceleration”: Void? Backreaction? Modified gravity? Dynamical dark energy? or simply Lambda?X?X?二十一世纪第二个十年的宇宙学23lensingSNe IaBAOcluster abundancepecu

18、liar velocityCMBIn O(10) years, hopefully we are able to put everything together to reconstruct the elephant.the dark universe二十一世纪第二个十年的宇宙学24Systematics, Systematics, Systematicsstatistical errorTheoryThe dark degeneracies!Unbiased parametrizationsCalculationNonlinearity and gastrophysicsN-body and hydro simulationsMeasurementSN Ia: evolu