confronting physics with the cosmos

科大交叉学科理论研究中心，2008

Confronting physics with the cosmos

张鹏杰中科院上海天文台


报告概要天文学的历史巨变

– 困惑– 机遇

当物理遇到宇宙– 宇宙初条件

• 宇宙学原理？– 物理规律

• Testing general relativity in the cosmos– 时空维度– 场方程


Dark energy is bad

for astronomy

Dark energy can begood

for astronomy

ArXiv:0704.2291 ArXiv:0708.1199


天文学的转变

已知物理规律传统天文

天体物理

未知物理规律暗物质暗能量

修正引力sterile neutrino

、、、

当代天体物理的重要方向

梦想把世界还原成几个原理，几个常数，几个方程

把宇宙当成动物园和植物园，越丰富越美好

价值观的激烈冲突


Laboratories in the cosmos

z ~ 1000 z ~ 30 z ~ 6 z ~ 0z ~ 1000 z ~ 30 z ~ 6 z ~ 0z ~ 1000 z ~ 30 z ~ 6 z ~ 0


In observational astronomy, nothing is impossible(1) CMB （ 1978 and 2006 Nobel prizes)(2) Weak lensing. Measure images of million galaxies billions of light years away at 1% accuracy

Wittman et al. 2000 Fu et al. 2007

A factor of ~100improvement

LSSTEuclidSKA

SNAP

~2015-2020


They make dark energy "luminous"

Cluster abundace Type Ia supernovae Weak gravitational lensing Peculiar velocity (bulk flow) Baryon acoustic oscillation

CMB

mid-90s 1998- 2000- 2001- 2005-

2000 ： Boomerang 、 Maxima和宇宙平坦性

2002 ： DASI 和 CMB 偏振 2003 ： WMAP 和精确宇宙学 2003 ： ISW 效应 2007 ： CMB lensing


二十一世纪的十一个问题

暗物质暗能量宇宙起源

中微子引力性质

额外维度

甚高能标物理


暗物质暗能量大尺度上的引力性质

小尺度上的引力性质

高密度区强子物理

精细结构常数的演化洛仑兹不变性的检验中微子质量和 species

甚高能高密实验室普朗克能标物理暴涨场引力波


报告概要天文学的历史转变






宇宙初始条件伽利略时代：物理学的里程碑

– 意识到初始条件和物理规律的区别– 通过物理实验设定初始条件– 物理规律才可能从变化多端的物理现象中分离出来！

同样的革命正在天文领域发生！– 天文学：无法设定宇宙初始条件– 但是当代天文学能够直接观测宇宙的初始条件！感谢

保存在时间里的宇宙化石！– 宇宙原初扰动是高斯、绝热、接近标度不变的吗？

对标度不变的偏离• 非高斯性（？）• 非绝热性（？）

– 宇宙学原理？


宇宙学原理我们在宇宙中的位置

– 哥白尼原理：宇宙没有中心• 宇宙学原理：宇宙不仅仅没有中心（均匀的），而且是各向同

性的。这个宇宙由 FRW 模型描述

我们能够检验这个基本原理或者基本假设吗？– CMB– The kinetic Sunyaev Zel'dovich effect– Other probes

这个基本原理的破坏会导致什么？– Dark energy as an illusion


各向同性的宇宙CMB 观测表明，宇宙在统计上是各向同性的。有争议！但是，严格来说， CMB 只证明，

对我们来说，宇宙是各向同性的！


The LTB universe

Lemaitre-Tolman-Bondi model– The universe is onion-like– Mass distribution is isotro

pic with respect to the center

– But varies along the radial direction

– We live near the center– Isotropic with respect to us

(and only to us)


LTB: "cosmic accelaration" without dark energy

低密度区（ void)

在这个非均匀的宇宙中，超新星会变得比均匀宇宙（ FRW ）中暗

如果我们假设宇宙是均匀各向同性的（宇宙学原理），就会误以为宇宙在加速膨胀，误以为暗能量存在或者广义相对论需要修改

既然我们只能从地球观测宇宙，我们如何区分 LTB 模型和 FRW 模型？


2008 ， PRLarxiv:0711.3459

电离宇宙是一面镜子能够反射其他区域的CMB 光子到达我们，从而告诉我们对哥白尼原理的偏离

对黑体谱的偏离


Moving mirrors: the kinetic Sunyaev Zel'dovich effect

物质随动参考系

Violation of the Copernican principle

对哥白尼原理的违背造成微波背景参考系和物质随动参考系的相对运动

运动的散射镜产生the kinetic Sunyaev Zel'dovich 效应

prediction

observations

微波背景参考系

在均匀宇宙中，两个参考系重合，没有相对运动


报告概要天文学的历史转变






General relativity and GR testsfrom ~10^-5 m to ~10^13 m

General principle of relativity

Equivalence principle

Field equation

Confirmed at 10^(-13)

Gen

eral covarian

ceT

enso

r analysis

perihelion shiftlight deflectiontime dilation/frequency shiftorbital decay (gravitational wave)time delaygeodetic effect?frame dragging effect

(e.g. 5

2 2 1 2 2

1 10

2 2(1 ) (1 )

GM GMds dt dr r d

r r

－＝

：


额外维度（ 1 ）：引力波

• Independent methods to measure the distances.– D(EM): from EM waves

(SN, BAO, maser, etc) – D(GW): from gravitationa

l waves (GW)

• If gravity is GR in 4D, then D(GW)=D(EM)

• Otherwise, interesting things can happen– Example: if GW can leak

into the 5th dimension, as in 5D braneworld DGP,

– D(GW)>D(EM)

Deffayet & Menou, 2007

D(EM)

D(GW)


额外维度：星系团密度轮廓

Qin, Pen & Silk 2005


对场方程的检验宇宙学检验和太阳系检验的本质区别

• 相对论

– 时空弯曲项 = 物质、能量项

宇宙学检验：未知！！暗物质、暗能量、

有质量的中微子

太阳系试验：可测

可测


18

2visible

uv uv uv uvR g R g GT CDMuvT

( )uvf g

DEuvT

The standard cosmology is based upon GR and is consistent with observations

Modified gravityminimally coupled to matter

Dynamical DE

Modified gravity non-minimally coupled to matter/energy

Dark matter/dark energy? Modified gravity?


lensing

SNe Ia

BAOcluster abundance

peculiar velocity

CMBWe are able to put everything together to reconstruct the elephant!

the dark universe


Probes of the expansion (zeroth order)• Type Ia supernovae (standard candles) • Baryon acoustic oscillation in LSS and CMB (standard ruler)

• Fundamental plane, Faber-Jackson & Tully-Fisher of galaxies• Age (globular clusters, galaxy age-z..)• Gravitational lensing time delay• SZ-X ray cluster fluxes• Cluster gas fraction• Gamma ray bursts• Alcock-Paczynski (AP) test• Water maser• ....• Standard sirens (GWs from black hole binaries)• Sandage-Loeb test• .....


Probes of the large scale structure (first order)They may not probe what we think that they probe!!

• gravitational potentials– Gravitational lensing– Galaxy/cluster peculiar velocities– The integrated Sachs-Wolfe effect

• density– galaxy clustering– cluster abundance

• fluid velocity– The kinetic Sunyaev Zel'dovich effect?

－.

v ( )

d

dt

g gb

(1 )p v

Refer to Jain & ZPJ, 2007arXiv:0709.2375for details

??


Consistency check of GR at cosmological scales

02

33/32

200

22

2

aH

H

aaH

dadH

da

d

da

d

The expansion rateThe rate of

structure growthConsistency relation

observables


Consistency check of GR: Real data!!

Wang et al. 2007 arXiv:0705.0165

Consistent with GR

Expansion

structure growth


自洽关系后面的物理

02

33/32

200

22

2

aH

H

aaH

dadH

da

d

da

d

2 ( ) 8 G

= / 1

18

2visible

uv uv uv uvR g R g GT CDMuvT


~

1

~

~ ~

( ) gravity:

DGP gravity: 1

TeVeS: ( ,other fields)

R

Geff f

eff

eff eff uv

f R G

G

G G g

/ 1 2DE: ( ) 12 (1 )

DGP: = (z) 1

k G w

2 ( ) 8 G

=effG

)10(1 5 O

ZPJ et al. 2007; Amendola et al. 20074Caldwell et al. 2007; Bertschinger& Zukin. 2008

Also Uzan 2006Hu & Sawicki 2007


2 412( , ) ( 2 ) ( )s

g g gv vP k u P u P u P F ku

引力透镜•cosmic shear•用我们 2005年提出的宇宙放大效应分析方法•CMB/21cm lensing

本动速度：利用红移畸变


4 个引力模型 : GR ，f(R) ， DGP ， TeVeS

第四阶段宇宙学项目能够在 1% 的精度上在宇宙学尺度上检验泊松方程！


ZPJ et al. to be submitted to PRL

•eta quantifies how a mass concentration distorts space with respect to time

SKA forecast

DGP

TeVeS

dark energy with anisotropic stress

测量时空的相对扰动：

结合这两种检验方法，在十年到二十年之内，我们或者能够在 1% 的精度上检验广义相对论，或者能够在 1% 的精度上否定广义相对论。我们提出的检验方法依赖的假设非常少，所以这个 1% 是一个保守估计。总之，二十年以内，一定有令人振奋的事情发生。


总结天文学正在成为探索基础物理规律的精密实验室

宇宙是一个巨大的交叉学科中心！


Sign of violation: the cosmic axis of evil

宇宙存在一个特殊取向？邪恶轴心！


Modifications in particle physics

Modifications in general relativity

Theories beyond the GR (with non-zero cc)+DM LCDM cosmology

Dark matterWIMPAxionetc

MG replacing DMMOND (TeVeS)etc

Unified DM/DEDM/DE interaction

Unified MG

Dark energyQuintessencePhantomQuintometc

MG replacing DEDGPf(R)etc

Cosmological consequences

Expansion Well understood Partly understood

Linear perturbation Almost well understood Partly understood

Nonlinear evolution(simulations and/orsemi-analytical cal.)

Almost well understood for smooth DEClustered DE: preliminary

Preliminary


Testing the (generalized) Poisson Equation

)d 2s＝（－）W( ,

2 ( ) 8 G

=

Gravitational lensing

v H

f

fH

/

from peculiar velocity

?

Galaxy redshifts to recover redshift information (2D ->3D)


A discriminating probe of gravity

•No dependence on galaxy bias

•No dependence on the shape and amplitude of the matter power spectrum, in the linear regime

•Scale independent in LCDM and QCDM, whose amplitude is completely fixed by the expansion rate

•Contains smoking guns of modifications in gravity and particle physics•Changes in the amplitude•Violation of the scale independence

22

( ) ( ) 1gG

g

PE

P

Poisson equation!

Linear density growth rate

galaxy-galaxy lensing

redshift distortion

f

confronting physics with the cosmos

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