1

Latest Measurements in Cosmology and their

Implications

Λ. Περιβολαρόπουλος

Φυσικό Τμήμα

Παν/μιο Κρήτης

και

Ινστιτούτο Πυρηνικής Φυσικής

Κέντρο Ερευνών ‘Δημόκριτος’

http://leandros.physics.uch.gr

WWW Site of Talk: http://leandros.physics.uch.gr/CosmoStatus99/index.html

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Contents

1. Big Bang: The Basic Framework

2. Open Questions, Free Parameters, Goals of Modern Cosmology

3. Observations:• Microwave Background• Supernova’s : Accelerated Expansion• Large Scale Velocity Flows• Lensing of QSO’s• Large Scale Structure• Hubble Constant: The Age Crisis• SuperKamiokande: Hot Dark Matter?• X-Rays from Intracluster Gas

4. Is ΛCDM the final theory?

5. Summary - Bibliography

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Big Bang: The Basic Framework

Big Bang

Isotropy+

Homogeneity

GeneralRelativity

Perfect Fluidwp

HubbleExpansion

CMB

Nucleosynthesis

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Open Questions

1. Quantity and Quality of Matter(Ωi, wi, where pi = wi pi )

2. Origin of Density Fluctuations• Physical Mechanism

• Power Spectrum

•Statistics

) ,( )()(2

nSkSkkP n

2?

2

)(

exP

3. Expansion Rate - Age of the Universe

4. Gravitational Waves

Tng kTk )( ,

2

MpckmhH sec/ 1000

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Goals of Cosmology

1. Measure Cosmological Parameters

2. Derive Minimal Theories that produce these values.

Inflation Defects

x

δρ/ρ

x

Scale Invariant - GaussianRandom Phase Waves Superposed

Scale Invariant - Non GaussianSeeds Superposed

δρ/ρ

ikxi

kk eex k

||)(

2

2

2

)/(

)/(

eP

seediixxx

)()(

2

2

2

)/(

)/(

eP

Example: Density Fluctuations

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Matter in the Universe

Most of the Matter is Dark and most of theDark Matter is Non-Baryonic.

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Observations I:Microwave Background

8

Angular Power Spectrum

0

4

/200200

) 24(

1

peakl

MpcST

nCOBE

Smaller Scales

10

9

CMB Statistics

Non-Gaussianity in the COBE Data

3|| lma : The Angular Bispectrum is 0 for Gausian Fluctuations

Ferreira et. Al. 1998Perivolaropoulos, Simatos 1998

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Observations II:Cosmic Acceleration

3.0 7.0

3.03

44.04.0

1

20

zqzH

RR

SNIa:

(Perlmutter et. al. 1997)

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Results from 40 Supernovae

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Observations III:Large Scale Velocity Flows

3.0

POTENT Method: Assumption: Peculiar Velocities are generated by gravity

Result: Gravitational Potential, Ωm

Dekel 1999:

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Observations IV:Frequency of QSO Lensing

65.0

Frequency of multiply lensed quasars is higher in accelerating Universe.

Kochanek 1996

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Observations V:Large Scale Structure + COBE

1 1 HDMCDM

(Kolb 1998)

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Viable CDM Models

ΛCDM can tolerate the largest values of theHubble Constant

(Dodelson et. al. 1996)

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Observations VI:The Age Crisis

10

10

3

21

)55.0( 113

21

Ht

hGyrHt

BB

BB

Ages of oldest stars: GyrstBB 12

Age of the Universe as a function of Parameters

3.0or 10 GyrstBB

GyrstGyrst BBBB 13 and 10

13GyrstBB

Dodelson et. al.1996

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Not Dark Matter (Neutrinos)

SuperKamiokande:

starsv

vv

eV

m

eVh

m

eVmeVmm

02.04090

1.010

2

2222

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Minimum Neutrino mass detectable from Large Scale Structure Power Spectrum Measurements

(Hu et. al. 1998)

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Observations VIIX-Rays from Baryons

1. X-Ray Flux fixes the mas in baryons2. X-Ray Temperature fixes the total mass

(virial theorem).

3.0

thesis)(Nucleosyn )04.001.0(

)1.004.0(

2

2/3

h

hfBM

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Converging Puzzle?

ΛCDM: 1. Density Fluctuations are Gaussian - Scale Invariant.2. ΩΛ=0.7, ΩCDM=0.25, ΩΒ=0.05, Ων=0.02, n=1

Advantages Disadvantages

1. Consistent with Ωtot=1CMB - Inflation

2. Consistent with SN Ia

3. Less power on smallscales than sCDM(teq occurs later)

4. Settles the Age Crisis

5. Consistent with Baryonic x-RaysVelocity Flows

6. Consistent with QSOlensing: ΩΛ<0.66

0)R( 00 q

GyrsHtBB 113

2 10

3.0m

1. Fine Tuning: 48107.0 eVvac

Dominated Vacuum be willUniverse

.3

R

const

m

We live at Special Time

2.

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Upcoming Probes

1. Sloan Digital Sky Survey (density power spectrum)

2. Anglo - Australian Two Degree Field250.000 redshifts on 20 patches

Sky theof 25%

Redshifts and Positions Galactic 102 8

1, 2 will give Density Power Spectrum up to COBE scales (50)

3. MAP (NASA)

4. PLANCK (ESA)

2001.in scheduled 500max l

2004.in scheduled 2000max l

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Summary

1. The ΛCDM model with ΩΛ=0.7, ΩCDM=0.25, ΩΒ=0.05, Ων=0.02, n=1is currently the most consistent model withcosmological observations.

2. It’s main disadvantage is fine tuning but it opens new window for exotic theoretical physics.

3. New observational probes will probably offer conclusive evidence for the right cosmological model in the next 5 years.

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References

1. CONSTRAINTS ON THE COSMOLOGICAL CONSTANT FROM FLOWS AND SUPERNOVAE. By Idit Zehavi, Avishai Dekel. e-Print Archive: astro-ph/9904221

2. WHY COSMOLOGISTS BELIEVE THE UNIVERSE IS ACCELERATING.By Michael S. Turner. e-Print Archive: astro-ph/9904049

3. PARTICLE PHYSICS IN THE EARLY UNIVERSE.

By Edward W. Kolb. e-Print Archive: hep-ph/9810362

4. COLD DARK MATTER MODELS.By Scott Dodelson, Evalyn I. Gates, Michael S. Turner Science 274:69-75,1996, astro-ph/9603081

5. IS THERE A COSMOLOGICAL CONSTANT?

By Christopher S. Kochanek, astro-ph/9510077

6. WEIGHING NEUTRINOS WITH GALAXY SURVEYS.By Wayne Hu, Daniel J. Eisenstein, Max Tegmark.

Phys.Rev.Lett.80:5255-5258,1998, astro-ph/9712057