Cosmological structure formation and dark energy

1. Cosmological structure formation and dark energy Carlo Baccigalupi Heidelberg, May 31, 2005

2. L Cosmological Constant Problem G=8 T f

3. L Cosmological Constant Problem Geometry G+ g=8 T +Vg f Quantum Vacuum

4. L Cosmological Constant Problem : ? |-V|/M4Planck10-123 f 4 V: ? M Planck

5. ?? L for Physics Two ? Why so small with respect to any particle physics scale ? Why comparable to the cosmological matter density today f

6. outline • Quintessence scheme • Cosmological expansion rate • Cosmological perturbations • Cosmic microwave background • Gravitational lensing • Non-linear structure formation • Quintessence, dark matter and gravity • Conclusion

7. Quintessence scheme

8. The Quintessence: a minimal generalization of  • setting up a phenomenology of the impact of vacuum energy in cosmology • Predicting observable signatures if the acceleration is not due to a constant into the Einstein equations

9. Quintessence tracking solutions • Classical trajectories for the Quintessence field converging to the present energy density from a large set of initial conditions • The field may (Wetterich 1988) or may not (Ratra-Peebles 1998) scale as the dominant component • Dark energy abundance today still severely tuned

10. Where are we now? L Present constraints from CMB and LSS on the redshift average of the equation of state: -1.1 ‹w›z -0.9 Quest to be continued, the study of the dark energy is one of the core topics of the Beyond Einstein (NASA) and Cosmic Vision (ESA) programs for the next decades… f

11. Cosmological expansion

12. Cosmological expansion rate • For a fixed value today, H-1 is larger if w > -1 in the past • The comoving distance at a given redshift gets contracted • The redshift dependence of w is washed out by two redshift integrals

13. Cosmological expansion rate • For a fixed value today, H-1 is larger if w > -1 in the past • The comoving distance at a given redshift gets contracted • The redshift dependence of w is washed out by two redshift integrals

14. Cosmological perturbations

15. Effects on cosmological perturbations • Modified geometry affects the growth of linear perturbations • The dark energy possesses fluctuations which are dragged on large scales by the background evolution (Brax & Martin 2000)

16. Effects on cosmological perturbations • Modified geometry affects the growth of linear perturbations • The dark energy possesses fluctuations which are dragged on large scales by the background evolution (Brax & Martin 2000)

17. Effects from modified geometry • For w greater than -1, the cosmological friction gets enhanced for a fixed H0 • This affects the linear density perturbations growth and the dynamics of the gravitational potentials on all scales in linear regime

18. Effects from quintessence perturbations • A minimally coupled quintessence field is light, mf»(d2V/df2)1/2» H-1 • Fluctuations live on horizon and super-horizon scales • Excess power visible on small wavenumbers in the density power spectrum (Ma et al. 1999)

19. Cosmic microwave background

20. Projection

21. Integrated sachs-wolfe

22. Effects at decoupling • If the dark energy tracks the dominant component at a few percent level, the physics at decoupling is affected at a measurable level (early quintessence, see Caldwell et al. 2005 and references therein) • The equivalence epoch is shifted • The dark energy sound speed enters into the acoustic oscillations

23. Constraining dark energy with primary CMB anisotropies • Main effect from the shift of acoustic peaks due to the variation of distances • The constraining power is limited by the projection degeneracy

24. Constraining dark energy with primary CMB anisotropies • Assume flatness, fix H, gravitational waves in single field inflation • Fit with B98, COBE, MAXIMA, DASI, get some preference for a dynamical dark energy (Baccigalupi et al. 2002) • Mind degeneracies • Is WMAP Wtot=1.02§ 0.02 a similar indication? • Probably not…

25. Gravitational lensing

26. Weak lensing in dark energy cosmology • Probing intermediate redshifts only • Collecting effects from modified geometry and perturbations • Details in Acquaviva et al. 2004

27. Breaking the projection degeneracy Dark energy records in lensed CMB, Acquaviva and Baccigalupi, 2005, in preparation

28. Breaking the projection degeneracy Dark energy records in lensed CMB, Acquaviva and Baccigalupi, 2005, in preparation

29. CMB three-point correlation function from lensing

30. CMB bispectrum l1 l3 l2

31. CMB bispectrum

32. Lensing chronology Giovi et al. 2003, PhD thesis

33. CMB three-point statistics and dark energy Giovi et al. 2003, 2005, PhD thesis

34. CMB three-point statistics and dark energy Giovi et al. 2003, 2005, PhD thesis

35. Non-linear structure formation

36. Galaxy clusters

37. Matthias Bartelmann Massimo Meneghetti Klaus Dolag Carlo Baccigalupi Viviana Acquaviva Francesca Perrotta Lauro Moscardini

38. Matthias Bartelmann Massimo Meneghetti Klaus Dolag Carlo Baccigalupi Viviana Acquaviva Francesca Perrotta Lauro Moscardini Heidelberg

39. Matthias Bartelmann Massimo Meneghetti Klaus Dolag Carlo Baccigalupi Viviana Acquaviva Francesca Perrotta Lauro Moscardini MPA, Garching

40. Matthias Bartelmann Massimo Meneghetti Klaus Dolag Carlo Baccigalupi Viviana Acquaviva Francesca Perrotta Lauro Moscardini SISSA, Trieste

41. Matthias Bartelmann Massimo Meneghetti Klaus Dolag Carlo Baccigalupi Viviana Acquaviva Francesca Perrotta Lauro Moscardini Bologna

42. Dark energy records in galaxy cluster concentrations Dolag et al. 2004

43. Strong lensing arc statistics • Numerical ray tracing machines integrate null geodesics across structures out of N-body codes • Internal parameters of structures may be constrained through the lensing pattern Meneghetti et al. 2004

44. Strong lensing arc statistics • A w > -1 dynamics in the dark energy makes the linear growth rate of perturbations behaving in the middle between an open and a LCDM universe • The number of giant arcs is a cosmological probe, which favours an open universe (Bartelmann 1999) Meneghetti et al. 2004

45. Quintessence, dark matter and gravity

46. Coupled quintessence • Coupling with baryons severely constrained by standard model physics • Dark matter coupling realized with exchange in the energy density (Amendola 2000), variable masses for dark matter particles (Matarrese et al. 2003)

47. Extended quintessence • Relating gravity and dark energy through an explicit coupling with the Ricci scalar • Severely constrained on solar system scales • Cosmological bounds improving with incoming data

48. Why weird cosmologies for the dark energy? • Is it a new component or the signature of a modification in known physics? • Coincidence unsolved • The couplings with dark matter or gravity may induce new attractor mechanism driving the dark energy density to the present abundance from a large set of initial conditions (Bartolo and Pietroni 2000, Tocchini-Valentini and Amendola 2000, Matarrese et al. 2004)

49. Weird dark energy dynamics

50. Weird dark energy dynamics