1. Dark Energy vs. Dark Matter Towards a unification… Centre de Recherche Astronomique de Lyon Alexandre ARBEY March 5, 2006

2. The Dark Side of the Universe Galactic Scale Striking problems arrive from the Galaxy Rotation Curves. Clusters Scale At this scale, the existence of a great amount of non-visible matter can be deduced from cluster gas and weak lensing observations. 90 % of the effective matter is invisible ! Same conclusions ! Cosmological Studies Different studies enable to know the proportions of baryonic and non-baryonic matters in the global energy of the cosmic fluids. 30 % of the total Energy in the Universe is Matter. 15 % of this Matter is baryonic. 70 % of the total Energy in the Universe is unknown ! 2

3. Usual Description of the Universe Components: Radiation: photons, neutrinos Baryonic matter Dark Matter: WIMPS, axions… Dark Energy: cosmological constant, quintessence… Other: inflaton, vacuum energy… SCP 3

4. Dark Matter vs. Dark Energy Tradition WIMPS models seem OK Cosmological Constant could be OK WIMPS have never been detected Some other problems remain with WIMPS Nature of Dark Energy Observations tend to show: Why 2 components? Problems and Questions Non-usual models 4

5. Dark Fluid ? One unique fluid to replace Dark Matter and Dark Energy Today: Matter behaviour at local scales. Repulsing behaviour at cosmological scales. Early Universe: Matter behaviour at all scales. Constraints AdvantagesOne unique Dark Fluid instead of two. Can lead to a High Energy Physics Theory. 5

6. 6 Towards a unification ? Supernovae of Type Ia Structure formation Big-Bang Nucleosynthesis Equation of state: Low redshift: A. Arbey, astro-ph/0506732 or

7. Scalar Fields… Appear in: Particle Physics: Spin 0 particles, Higgs field High Energy Physics: Unification Theories Cosmology: Quintessence, Inflation Difficulty: Never observed… 7

8. Scalar Fields as Dark Energy Quintessence radiation matter Inverse Power Law “SUGRA” Inverse Power Law “SUGRA” 8

9. Scalar Fields as Dark Matter Internal rotation: (Complex scalar field) 9 A. Arbey et al., astro-ph/0105564, astro-ph/0112324, astro-ph/ 0301533.

10. 10 Homogeneous vs. Inhomogeneous Attractive inside structures with Repulsive in empty space Repulsive on cosmological scales  seems possible to unify both visions !

11. Scalar Field as Dark Fluid ? Local scalesCosmological scales Complex scalar field Superposition of potentials 11

12. Promissing potential ? Local scales (galaxies) Cosmological scales 12 Local scales (clusters)

13. Some results… 13

14. Conclusions 14 Unifying Dark Fluids can be compatible with observations Many constraints on the models: - constraints on the matter behaviour - constraints on the dark energy behaviour - inhomogeneous modelization: local vs. global Examples of possible Dark Fluids: - Scalar fields with specific potentials - Chaplygin Gas, … ?  More tests needed