How much we don’t know abou t the universe

The Ninth Texas-Mexico Conference on Astrophysics April 16, 2005

Eiichiro Komatsu

(University of Texas at Austin)

Cosmic Microwave Background, Large -scale Structure, and the Inflatio nary Universe

WMAP CIP

SDSS

Exciting, but Embarrassing Situation

Recent, very successful determinations of the cosmological parameters have re vealed that we don’t understand most of

How much we don’t know abou t the universe

~10^-34 sec Inflation Dark Energy I

<30,000 yrs Radiation Era Radiation

<8 billion yrs Matter Era Dark Matter

<now Dark Energy Era Dark Energy II

Log(Time)

Four Big Questions in Cosmo logy

The nature of dark matter

 What are they? How many of them?

The nature of dark energy

 What is it?

The origin of baryons

 How was the matter-antimatter symmetry broken?

The physics of inflation

 Did it happen at all?

 If so, how did it happen?

Why Inflation?

Inflation saves the Big Bang Model

• The isotropy of the cosmic background radiation (T/T ~ 10^-5 ).

• The flatness of the universe (_ =1).

• The origin of cosmic structure.

By exponentially expanding a small region, Inflation na turally solves several problems not addressed by the Bi g Bang model:

Inside Horizon Exit Horizon

Enter Horizon Fluctuations conserved

outside the Horizon

Direct probe of physics of Inflation!!

“Observe” Inflation

Observables

Inflation generates primordial fluctuations in spa cetime.

Fluctuations inherited in radiation

 Cosmic Microwave Background

 Temperature Anisotropy

 Polarization Anisotropy

Fluctuations inherited in matter

 Matter Distribution (Gravitaional Lensing)

 Galaxy Distribution (Redshift Surveys)

Fluctuations in spacetime itself

 Primordial Gravitational Waves

Horizon size at the decoupling ~ 2 degrees

Inside Horizon V()

V()

galac

tic size COBE

Different wavelengths

measure different locations of V()

Need to cover a wide range of .





Andrei Linde

The number of papers whose title contai ns “inflation” (as of today): 119

 New Inflation (1981, cited 1405 times)

 Chaotic Inflation (1983, cited 852 times ）

 Hybrid Inflation (1994, cited 424 times ）

Dr. Inflationary Universe Dr. Inflationary Universe

But, which model is right?

Approaching the Inflationar y Paradigm

0^th order test: did inflation happen?

1. Is the observable universe flat?

2. Are fluctuations Gaussian?

3. Are fluctuations nearly scale independent?

4. Are fluctuations adiabatic?

1^st order test: which model is right?

1. Deviation from Gaussianity?

2. Deviation from scale independence?

3. Deviation from adiabaticity?

WMAP, 2003

•WMAP’s beam is ~10 times a s small as the horizon size at th e surface of last scatter.

180 deg/l .

Bennett et al. (2003)

Sound wave on the sky: WMAP temperature power spectrum

THEORY FITS!!

400 800

200 40 100

10 Multipole moment l~

Geometry, h, Age

Baryon density Dark

matt er

densi ty

Amplitude of temperature fluctuations at a given scale, l

Small scales Large scales

(1) Testing flatness: Method

FLAT (zero curv.) Negative curv.

Sound horizon

θ

220

~ or deg

1

~ l

θ

θ

(1) Flatness

In a flat universe, _m_



(No Prior on H₀)

(No Prior on H₀)



(_m=1 disfavored)

Spergel, Verde, Peiris, Komatsu et al. (2003)

(2) Testing Gaussianity

Testing clustering properties: 3-point function

Testing Gaussianity: What d oes it mean?

WMAP data are consistent with Gaussianity

 What does it mean?

“How Gaussian are the data?” needs to be quantified

 A model-dependent question

WMAP results ： -58<f_NL<134 (95%)

 The second term < 2×10^-5 times the first

 C.f. simple inflationary models predict 10-100 times smaller v alues! (Bartolo, Komatsu, Matarrese, Riotto, 2004)

( )

( )

( )

Φ

Komatsu et al. (2003)

Testing Scale Invariance

Different wave- numbers probe different parts of potential.

Since a scale field is slowly

rolling, we need to cover many

decades in wave- number to obtain a meaningful

Observables  Potential

parameters describing the shape of V()

 : slope (V’/V)²

 : curvature V’’/V

 : jerk (V’/V)(V’’’/V)

⎪⎩

⎪⎨

⎧

 −

 −



 −



24 2

16 2

ln /

2 6

1 16

ε εη

ξ η ε

ε

k d

dn n r

s s

Amplitude of gravitational waves Scale invariance: n=1, dn/dlnk=0

V()



(3) Testing scale invariance

λφ4

λφ4

λφ4





Consistent with a scale

invariant spectrum dn/dlnk<0? No evidence for the gravitational

waves （ but

Peiris, Komatsu et al. (2003)

The best fit model?

λφ4

λφ4

λφ4





V()



V() V() V()

  

Recent Updates

WMAP+SDSS QSO

 ~3000 QSO spectra

Complexities due to non- linearity and gas dynamics

Seljak et al. (2004)

Physics of CMB Pol.

Temperature quadrupole at the surface of last scatter generates polarization.

electron isotropic

anisotropic

no net polarization

net polarization

Temperature-Polarization Corre lation

Radial (tangential) pattern around cold (hot) spots.

Polarization as a Test of t he Standard Model

Polarization is generated from temperature fluc tuations, which are already measured very prec isely.

Since we know temperature, we can make pre dictions for “what we should see in the polarizat ion”.

Do we see it or not?

 FUNDAMENTAL TEST OF THE STANDARD MODFUNDAMENTAL TEST OF THE STANDARD MOD EL!!EL!!

WMAP Polarization Confirms It!

Adiabatic Prediction from the Adiabatic Prediction from the Temperature Data

Temperature Data What is this?

What is this?

The Universe Reionized

CMB emitted at z~1089.

15% of CMB was re-scattered in a reionized universe.

The estimated reionization redshift ~20, or 200 million year s after the Big-Bang.

z=1089,  ～ 1

z ～ 20,

=0.17 First-star

formation

z=0 IONIZED

REIONIZED NEUTRAL

Primordial Gravity Waves

Gravity waves create quadrupolar temp erature anisotropy --> Polarization

E-mode and B-mode

Polarization is a rank-2 tensor field.

One can decompose it into a gradient- like “E-mode” and a curl-like “B-mode”.

E-mode B-mode

B-mode is a “Smoking-Gun”

of Gravity Waves

Sachs-Wolfe effect and hydrodynamical effects mentioned before DO NOT PRO DUCE ANY B-MODE BUT ONLY E-MO DE.

Detection of the B-mode is a strong evid ence for the primordial gravity waves fro m Inflation.

But, direct detection of GW (if possible a

Did Inflation Happen?

Flatness: _tot = 1

Gaussianity: ƒNL ~ 1-10 Scale invariance: ns ~ 1

Adiabaticity: T/T = (1/3)*

( )

( )

( )

Φ

3 −1

∝

ΦΦ k^n k

Sufficient Circumstantial Evidence

Flatness: _tot = 1.02 ± 0.02 Gaussianity: -58 < ƒNL < 134

Scale invariance: ns = 0.99 ± 0.04 Adiabaticity: T/T = (1/3)*

( )

( )

( )

Φ

3 −1

∝

ΦΦ k^n k

Summary

Single field inflation models are consistent with the WMAP data

 20 years from the first predictions of inflation

 Still standard paradigm

However, we can’t answer the question, “what is a true model?”, yet.

 The next frontier I: improved determination of nThe next frontier I _s

 Go to small scales!!

 The next frontier II: Gravitational wavesThe next frontier II

 WMAP 2-year will provide the first direct estimate of B-mode

 Would WMAP 8 years detect it?

 Polarization-dedicated satellite experiments?

Cosmic Inflation Probe

NASA ORIGINS future space mission candidate PI: Gary Melnick (CfA)

 Co-Is at Texas include Dan Jaffe, Karl Gebhardt, Volker Bromm, EK Main stream method: measure correlation of galaxies to 1%

Redshift 4<z<6: Wider coverage in k space because of less non-linearity A factor 10 improvement (or more if combined with CMB) on tilt and running

CIP CIP alone