1. Michael Doran Institute for Theoretical Physics Universität Heidelberg Time Evolution of Dark Energy (if any …)

2. Dark energy (a.k.a. quintessence)

3. (Semi-) Known Dark Energy Properties D.E. does not cluster on scales within horizon, because canonical: D.E. not coupled or very weakly coupled to matter Cosmological constant fits all observations Descriptions in terms of modified Einstein action and scalar fields possible and related

4. Extracting information on

5. Effects of dark energy I -- Geometry Additional component changes expansion history and horizons. Geometrical tests include: –Acoustic scale of the CMB –Baryon acoustic oscillations at low redshifts –Luminosity distance at low redshift from SNe Ia –Luminosity distance up to from  -ray bursts (?) –Angular diameter distance using shape of

6. Effects of dark energy II -- Couplings If D.E. coupled to baryons: –mediates additional fifth force (hence very restricted) –might be linked to running coupling constants If D.E. coupled to cold dark matter: acts like self-interaction for dark matter, i.e. enhances clustering. Caution exchange.

7. Effects of dark energy III -- Structure growth & CMB Not coupled: Suppresses growth of linear matter perturbations because additional non-clustering component is present. Consequences?

8. Consequences! Gravitational potential decays during matter domination if D.E. present ISW effect in CMB The longer a mode is inside the horizon, the more it gets suppressed if D.E. present. However, all modes inside horizon at matter-radiation equality are equally suppressed. Up to running spectral index – then equal suppression. Rough rule of thumb: 10% dark energy during structure formation 50% less

9. Linear Power Spectrum  CDM Early Dark Energy

10. Counterintuitive: More structure at higher redshifts Conditions for collapse roughly the same as in -CDM Yet, even after collapse of some halo starts, linear theory fluctuations grow less compared to -CDM So linear overdensity corresponding to collapsed object is lower than in -CDM Same non-linear structure with lower

11. .. more non-linear structure at higher redshift Mass Function rel. toLCDM 1 10 10 13 10 14 10 15 Halo Mass [h -1 M sun ] z=1 z=0

12. Early Dark Energy influences the CMB... R.R. Caldwell et. al. (2003)

13. Dark Energy influences structure growth... Linear fluctuations grow less with dark energy. CMB normalized, early dark energy predicts more non-linear structure at higher redshifts compared to standard cosmological constant. M. Bartelmann, M.D., C. Wetterich (2005) Mass Function rel. to LCDM Halo mass

14. .. more non-linear structure at higher redshift Mass Function rel. toLCDM 1 10 10 13 10 14 10 15 Halo Mass [h -1 M sun ] z=1 z=0