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Confirmation of the Copernican principle at Gpc radial scale and above. 张鹏杰 Zhang, Pengjie 中科院上海天文台 Shanghai Astronomical Observatory. ZPJ and Stebbins, 2010. The standard cosmology. Initial condition: inflation Laws: General relativity+SM Ingredients:

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Confirmation of the copernican principle at gpc radial scale and above

Confirmation of the Copernican principleat Gpc radial scale and above

张鹏杰 Zhang, Pengjie

中科院上海天文台

Shanghai Astronomical Observatory

ZPJ and Stebbins, 2010

9th Sino-German workshop, Hangzhou, 2011


The standard cosmology
The standard cosmology

  • Initial condition: inflation

  • Laws: General relativity+SM

  • Ingredients:

  • Baryons, photons, etc.(SM particles)

  • Cold non-baryonic dark matter

  • Non-zero cosmological constant

9th Sino-German workshop, Hangzhou, 2011


Foundation of modern cosmology
Foundation of modern cosmology

  • Cosmological Principle

    • Is our universe (statistically) homogeneous and isotropic?

      • CMB: The universe is (statistically) isotropic with respect to us.

      • Copernican principle: No special regions in the universe

        • The universe must be statistically homogeneous.

  • General relativity

    • Is GR valid at cosmological scales?

      • Gravity with infrared modification?

    • Is the standard simplification in treating GR cosmology valid?

      • Backreaction, metric-observable relations, etc.

?

9th Sino-German workshop, Hangzhou, 2011


Non copernican universe consistent with cmb galaxy distribution the ltb universe
Non-Copernican universe consistent with CMB/galaxy distribution: the LTB universe

  • Lemaitre-Tolman-Bondi model

    • The universe is onion-like

    • Mass distribution is isotropic 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)

9th Sino-German workshop, Hangzhou, 2011


Dark energy mirage of gigantic void
Dark energy: mirage of gigantic void? distribution:

In this inhomogeneous universe, type Ia supernovae can appear dimmer than in a FRW universe.

No cosmic acceleration,

No dark energy

No modified gravity

compensating shell

Low density

region

(~Gpc void)

background universe

(higher density)

Gravitational

potential

distance

9th Sino-German workshop, Hangzhou, 2011


Testing the copernican principle
Testing the Copernican principle distribution:

M(r), E(r),t_b(r)

r

  • Type Ia supernovae, BAO, etc.

    • Suffers from a severe degeneracy problem

  • Galaxy distribution test

    • Uncertainties in galaxy evolution

  • New tests free of the above degeneracy

    • CMB non-blackbody test (Goodman 1995, Caldwell & Stebbins, 2008)

    • Cluster kinetic Sunyaev Zel'dovich (kSZ) effect test (Goodman 1995, Garcia-Bellido & Haugbolle 2008)

    • Diffuse kSZ background test (ZPJ 2010; ZPJ & Stebbins, 2010)

9th Sino-German workshop, Hangzhou, 2011


The key to test the copernican principle space travel to billion light years away to do observation
The key to test the Copernican principle: distribution: Space travel to billion light years away to do observation

8 Gyr

4 Gyr

the light cone effect

2 Gyr

1 Gyr

9th Sino-German workshop, Hangzhou, 2011


Free electrons as mirrors goodman 1995 caldwell stebbins 2008
Free electrons as mirrors distribution: Goodman 1995; Caldwell & Stebbins, 2008

Compton scatterings

allow us to sit at

distant universe and

judge whether CP holds

consequence 1:

CMB spectrum will

be non-blackbody

T1

e

T2

T3

9th Sino-German workshop, Hangzhou, 2011


2008, PRL, arxiv:0711.3459 distribution:

rules out many

void models

capable of

replacing dark

energy, but not all

of them.

Furthermore, ICS

induces

non-blackbody too.

void density

Void size

9th Sino-German workshop, Hangzhou, 2011


Galaxy clusters a bunch of electrons as moving mirrors
Galaxy clusters (a bunch of electrons) as moving mirrors distribution:

CMB frame

Dust (matter) frame

Violation of the

Copernican principle

prediction

  • Violation of CP causes relative motion between CMB and the matter comoving frame

  • Causes a large cluster kSZ effect

In a homogeneous universe, no motion between the two

rules out many

void models

capable of

replacing dark

energy, but not all

of them

observations

Goodman 1995

9th Sino-German workshop, Hangzhou, 2011


A more sensitive test the anisotropic kinetic sunyaev zel dovich effect
A more sensitive test: the anisotropic kinetic Sunyaev Zel'dovich effect

`

CMB

Anisotropic due to

inhomogeneous

electron

distribution

All free electrons

contribute

Up to the z~10

reionization

ZPJ 2010

matter frame

e

X

9th Sino-German workshop, Hangzhou, 2011


Void model predicts much larger ksz than allowed by observations
Void model predicts much larger kSZ than allowed by observations

13 uK^2(SPT)->8 uK^2 (ACT)->6.5 uK^2 (SPT)

Allowed by

kSZ observations

Consistent

with SN data

l=3000

a few arcminute

ZPJ & Stebbins 2010

9th Sino-German workshop, Hangzhou, 2011


Testing the copernican principle1
Testing the Copernican Principle observations

  • CMB and galaxy distribution are isotropic→ the metric is LTB

  • SN Ia→ Giant (~Gpc) void must exist in the center, if we do not resort to dark energy, modified gravity or GR backreaction.

  • The kSZ test rules out these void models.

    • Violations of the Copernican principle cause motions between CMB and matter frame

      • Typical velocity: 10,000 km/s

    • Such motion is modulated by electron density inhomogeneity and hence induces a first order anisotropic kSZ effect

    • The induce KSZ power spectrum is much larger than the existing ACT/SPT upper limit

    • Adiabatic void models are ruled out.

  • The Copernican principle at Gpc scales and above is confirmed.

  • Copernican principle+SN Ia: cosmic acceleration indeed exists!

9th Sino-German workshop, Hangzhou, 2011


When shall we resort to occam s razor
When shall we resort to Occam's razor? observations

9th Sino-German workshop, Hangzhou, 2011


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