L. Perivolaropoulos http://leandros.physics.uoi.gr Department of Physics University of Ioannina

1. Cosmological Parameters From Type Ia Supernovae L. Perivolaropouloshttp://leandros.physics.uoi.gr Department of Physics University of Ioannina

2. Structure of Talk I. Observations II. Analysis of Data III. Cosmological Parameters IV. The Future

3. Obs Dist. Ind. Expansion History from Luminosity Distance Absolute luminocity L: Total Power Radiated Apparent luminocity l: Luminocity Distance: Physical Distance in Static Universe Expanding Universe: comoving distance

4. Expansion History from Luminosity Distance Expanding Universe: 1 Light Geodesics 2 1 2 Know L Measure l(z) Distance Modulus:

5. Observational Teams Supernova Cosmology Project (SCP) S. Perlmutter et. al. (Berkeley) High-z Supernova Search Team (HZT) B. Schmidt et. al. (Mt. Stromlo Obs.) Higher-z Supernova Search Team (HZT) A. Riess et. al. (Space Telescope Sci. Inst.) Supernova Acceleration Probe (SNAP) S. Perlmutter et. al. (Berkeley) Future Space Satellite ESSENCE C. Stubbs et. al. (Harvard) Canada-France-Hawaii Legacy Survey

6. Hubble Diagram Accelerating Universe: (rate of expansion) was smaller in the past. Thus H-1(t) was larger in the past. Standard Candles SNeIa Luminus Objects of a given redshift appear to be further away (dimmer) in an Accelerating Universe

7. Distance Indicators (Standard Candles) Expand. Phot. Meth./SnII Best Choicefor Cosmology Planetary Nebulae Surf. Brightness Fluct. Tully Fisher Brightest Cluster Gal. Glob. Cluster Lum. Fun. Sunyaev-Zeldovich Gravitational Lensing

8. SnIa Physics White Dwarf Accretion from Companion Cross Chandrasekhar Limit Ignite Carbon Fusion Explode

9. Why SnIa 1. Exceedingly Luminus 2. Small Dispersion of peak amplitude 3. Good understanding of Explosion Mechanism 4. Small Cosmic Evolution Expected Degeneracy pressure always fails at same mass. 5. Local Tests for Calibration Problem: Predict a SnIa Explosion 1-2 SnIa per galaxy per millenium

10. Search Strategy 1. Observe a number of empty sky wide fields (~10000 gal) 2. Observe same patch after three weeks. 3. Subtract Images to identify 12-14 SnIa 4. Schedule Follow-up Photometry and Spectroscopy HST

11. SnIa Spectral Evolution

12. SnIa Luminosity Corrections I SnIa follow similar light curves (similar luminosities) Q: How can we distiguish the small luminosity differences? closeby SnIa A: Streched lightcurves - brighter SnIa Contracted lightcurves - fainter SnIa Verify Strech Factor-Brightness Correlation: Contract while reducing peak luminosity Stretch while increasing peak luminosity

13. SnIa Luminosity Corrections II SnIa spectra appear shifted due to Hubble expansion Apply proper filters to compare time evolution of the same part of the spectrum Apply K-Correction. Also, a time interval dt at redshift z corresponds to a time interval dt (1+z) at present time. Correct light curve timescale for cosmological time dilation

14. Observed Hubble Diagram Accelerating Decelerating ? Gold Dataset (157 SNeIa): Riess et. al. 2004

15. Observed Hubble Diagram Gold Dataset (157 SNeIa): Riess et. al. 2004

16. Possible Systematic Errors Q: What (other than distance) could be making high-z SnIa dimmer? No! Dust absorbs blue light more than red light. Distant SnIa have similar spectra as nearby SnIa. Could it be Dust? No! The diming does not continue to amplify at z>0.5 Could it be Grey Dust? No! The time evolution of SnIa spectrum is identical for close and for distant SnIa. Could it be Evolution of SnIa?

17. Observed Hubble Diagram Gold Dataset (157 SNeIa): Riess et. al. 2004 dust produced from vacuum with time

18. SnIa Projects SN Factory Carnegie SN Project ESSENCE CFHT Legacy Survey Higher-z SN Search (GOODS) SNAP

19. Expansion History of the Universe Expected: Decelerated Expansion due to Gravity Observed: Accelerated Expansion Q: What causes the Acceleration?

20. Negative Pressure Acceleration from Dynamics of scale factor a(t): Friedman eqn General Relativity Homogeneity-Isotropy Equation of State: Necessary condition for acceleration: Dark Energy Antigravity

21. Evolution Dark Energy Energy Conservation: Friedman Equation Best Fit ? (from large scale structure observations)

22. Cosmological Parameters from SnIa H(z) Most Powerful Probe

23. the cosmological constant w=-1 Gmn = k Tmn • Einstein (1915) G.R.: • Einstein (1917) G.R. + Static Universe + Matter only: Gmn- L gmn = k Tmn Cosmic Repulsion Cosmological Constant Then came: Hubble's Discovery (1929) • The biggest blunder of my life Einstein :

24. Since I introduced this term, I had always a bad conscience.... I am unable to believe that such an ugly thing is actually realized in nature A. Einstein 1947 letter to Lemaitre

25. Fitting the Cosmological Constant Friedman Equation Observations Theory -Observations Theory- Compare:

26. History of SnIa Results 1. Measurements of the Cosmological Parameters Omega and Lambda from the First 7 Supernovae at z >= 0.35S. Perlmutter et al., Astrophys.J. 483 (1997) 565 2. Observational Evidence from Supernovae for anAccelerating Universe and a Cosmological ConstantS. Perlmutter et al., Nature 391 (1998) 51 3. Discovery of Supernova Explosion at Half the Age of the Universe A.G. Riess et al., Astron.J. 116 (1998) 1009-1038

27. Evolution of SnIa Results 4. Cosmological results from high-z supernovaeTonry et al. The Astrophysical Journal, 594:1-24, 2003 September 1 5. New Constraints on ΩM, ΩΛ, and w from an Independent Set of 11 High-Redshift Supernovae Observed with the Hubble Space TelescopeR.A. Knop et al., The Astrophysical Journal, Volume 598, Issue 1, pp. 102-137 11 new SnIa observed from HST 6. Type Ia Supernova Discoveries at z > 1 From the Hubble SpaceTelescope: Evidence for Past Deceleration and Constraints on Dark Energy Evolution A. Riess et al. The Astrophysical 607:665-687,2004 16 new SnIa observed from HST7 of them with z>1.25 Decelerating Expansion starts at z=0.46

28. SnIa: Most Sensitive Probe of D.E.

29. Quality of Fit Ruled out ! Q: Can we get better fits?

30. Strategy

31. Testing H(z) Parametrizations Example: Dark Energy Evolution

32. Testing H(z) Parametrizations Dark Energy Metamorphosis

33. Other H(z) Parametrizations Almost 2σ better than ΛCDM Crossing Phantom Divide w=-1

34. Criticism on Metamorphosis Statistical Fluctuations can produce data that indicate metamorphosis even within LCDM

35. Criticism on Metamorphosis Statistical Fluctuations even within 68% can produce data that indicate metamorphosis even within LCDM

36. Criticism on Metamorphosis Statistical Fluctuations even within 68% can produce data that indicate metamorphosis even within LCDM

37. Status of Debate LCDM is the simplest model consistent with current data Dark Energy Metamorphosis is Less Apealing Theoretically But Is more probable than LCDM on the basis of current data < 1σ Q: How much more probable? < 2σ > 1σ

38. Basic Questions What theory produces the features of best parametrizations? What is the Fate of the Universe? (extrapolating w(z) to z<0 (w(z)<-1))

39. Dark Energy Models • Quintessence: tracking scalar fields (Ratra & Peebles, Wetterich 1988, Coble et al. 1997, Ferreira & Joyce 1998, Liddle & Scherrer 1999, Steinhardt et al. 1999, Perrotta & Baccigalupi 1999, Brax & Martin 2000, Masiero et al. 2001, Doran et al. 2001, Corasaniti & Copeland 2003,Perivolaropoulos 2005,Tsujikawa 2005) • Extended Quintessence: non-minimal coupling to Gravity (Chiba, Uzan 1999, Perrotta et al. 2000, Baccigalupi et al. 2000, Faraoni 2000, Bartolo & Pietroni 2000, Esposito-Farese & Polarski 2001, Perrotta & Baccigalupi 2002, Perivolaropoulos 2005,Tsujikawa 2005) • Coupled Quintessence: coupling with dark matter (Carroll 1998, Amendola 2000, Matarrese et al. 2003) • k-essence: modified kinetic scalar field energy (Aramendariz-Picon et al. 2001, Caldwell 2002, Malquarti et al. 2003) • Quantum Fluctuations of Scalar Field: (Onemli and Woodard 2004) • Spacetime microstructure: self-adjusting spacetime capable to absorb vacuum energy (Padmanabhan, 2002) • Matter-Energy Transition: dark matter undergoes a phase transition to dark energy at low redshifts (Basset et al. 2003) • Brane worlds: brane tension (Shani & Sthanov 2002, Sami & Dadhich 2004, Brown, Maartens Papantonopoulos, & Zamarias 2005); cyclic-ekpyrotic cosmic vacuum (Steinhardt &Tutok 2001) • Exotic particle physics: photons oscillating in something else at cosmological distances (Csaki et al. 2002) • Chaplygin gas: dark matter and energy described by a single gas having variable equation of state (Den et al. 2003, Carturan & Finelli 2003) • Scale-dependent Gravity: Gravity weaker on large scales (Dvali et al. 2003)

40. Scalar Fields No w=-1 crossing Homogeneous Minimally Coupled Scalar: +: Quintessence -: Phantom Equation of State: To cross the w=-1 line the kinetic energy term must change sign (impossible for single phantom or quintessence field)

41. Example Linear Potential V(Φ) = s Φ Scalar Field: No crossing of w=-1 line (poor fits) Crossing the w=-1 line (better fits e.g. scalar tensor theories) L.P., astro-ph/0504582 Best Scalar Fit:

42. w<-1 Big Rip Bound Systems in Expanding Background: Radial Geodesics: S. Nesseris, L. P., Phys.Rev.D70:123529,2004 Repulsion Increases with time for w<-1 Big Rip Repulsion Explodes at t*~w/(w+1)

43. w=-1.5 Bound System Dissociation

44. Dissociation Bound System w=-1.2 S. Nesseris, L. Perivolaropoulos, Phys.Rev.D70:123529,2004

45. The Future • 2m Telescope • ~1 billion pixels, 144 CCDs • 350-1700 nm wavelength coverage • Finds and follows 2500 SnIa each year, out to z = 1.7 • Place good limits on both w and its time evolution

46. SUMMARY • Dark Energy with Negative Pressure can explain SnIa cosmological data indicating accelerating expansion of the Universe. • The existence of a cosmological constant is consistent with SnIa data but other evolving forms of dark energy crossing the w=-1 line provide better fits to the data. • New observational projects are underway and are expected to lead to significant progress in the understanding of the properties of dark energy.

47. We measure shadows, and we search among ghostly errors ofmeasurement for landmarks that are scarcely more substantial. The search will continue. E. Hubble in The Realm of the Nebulae,