1. 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

2. 2 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

3. 3 Big Bang: The Basic Framework Big Bang Isotropy + Homogeneity General Relativity Perfect Fluid Hubble Expansion CMB Nucleosynthesis

4. 4 Open Questions 1. Quantity and Quality of Matter (Ω i, w i, where p i = w i p i ) 2. Origin of Density Fluctuations Physical Mechanism Power Spectrum Statistics 3. Expansion Rate - Age of the Universe 4. Gravitational Waves

5. 5 Goals of Cosmology 1. Measure Cosmological Parameters 2. Derive Minimal Theories that produce these values. Inflation Defects x δρ/ρ x Scale Invariant - Gaussian Random Phase Waves Superposed Scale Invariant - Non Gaussian Seeds Superposed δρ/ρ Example: Density Fluctuations

6. 6 Matter in the Universe Most of the Matter is Dark and most of the Dark Matter is Non-Baryonic.

7. 7 Observations I: Microwave Background

8. 8 Angular Power Spectrum COBE Smaller Scales

9. 9 CMB Statistics Non-Gaussianity in the COBE Data : The Angular Bispectrum is 0 for Gausian Fluctuations Ferreira et. Al. 1998 Perivolaropoulos, Simatos 1998

10. 10 Observations II: Cosmic Acceleration SNIa: (Perlmutter et. al. 1997)

11. 11 Results from 40 Supernovae

12. 12 Observations III: Large Scale Velocity Flows POTENT Method: Assumption: Peculiar Velocities are generated by gravity Result: Gravitational Potential, Ω m Dekel 1999:

13. 13 Observations IV: Frequency of QSO Lensing Frequency of multiply lensed quasars is higher in accelerating Universe. Kochanek 1996

14. 14 Observations V: Large Scale Structure + COBE (Kolb 1998)

15. 15 Viable CDM Models ΛCDM can tolerate the largest values of the Hubble Constant (Dodelson et. al. 1996)

16. 16 Observations VI: The Age Crisis Ages of oldest stars: Age of the Universe as a function of Parameters Dodelson et. al. 1996

17. 17 Not Dark Matter (Neutrinos) SuperKamiokande: Minimum Neutrino mass detectable from Large Scale Structure Power Spectrum Measurements (Hu et. al. 1998)

18. 18 Observations VII X-Rays from Baryons 1. X-Ray Flux fixes the mas in baryons 2. X-Ray Temperature fixes the total mass (virial theorem).

19. 19 Converging Puzzle? ΛCDM: 1. Density Fluctuations are Gaussian - Scale Invariant. 2. Ω Λ =0.7, Ω CDM =0.25, Ω Β =0.05, Ω ν =0.02, n=1 AdvantagesDisadvantages 1. Consistent with Ω tot =1 CMB - Inflation 2. Consistent with SN Ia 3. Less power on small scales than sCDM (t eq occurs later) 4. Settles the Age Crisis 5. Consistent with Baryonic x-Rays Velocity Flows 6. Consistent with QSO lensing: Ω Λ <0.66 1. Fine Tuning: We live at Special Time 2.

20. 20 Upcoming Probes 1. Sloan Digital Sky Survey (density power spectrum) 2. Anglo - Australian Two Degree Field 250.000 redshifts on 2 0 patches 1, 2 will give Density Power Spectrum up to COBE scales (5 0 ) 3. MAP (NASA) 4. PLANCK (ESA)

21. 21 Summary 1. The ΛCDM model with Ω Λ =0.7, Ω CDM =0.25, Ω Β =0.05, Ω ν =0.02, n=1 is currently the most consistent model with cosmological 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.

22. 22 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