Particle Interpretation of Dark Matter and Energy

Particle Interpretation of Dark Matter and Energy Hans Peter Nilles Physikalisches Institut Universität Bonn representing aspects of the projects A1, C2 and C4 Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.1/12

Cosmology and Particle Physics Early universe cosmology is very sensitive to particle physics phenomena: Inflation Big Bang Nucleosynthesis Energy density Ω. Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.2/12

Cosmology and Particle Physics Early universe cosmology is very sensitive to particle physics phenomena: Inflation Big Bang Nucleosynthesis Energy density Ω. Often, particle physics models are ruled out because they give a density Ω that is much too large, but sometimes it is just of the right order of magnitude. Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.2/12

Physics beyond the Standard Model Hints come from cosmological observations baryon asymmetry Ω B 0.05 dark matter Ω DM 0.23 dark energy Ω DE 0.72 Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.3/12

Physics beyond the Standard Model Hints come from cosmological observations baryon asymmetry Ω B 0.05 dark matter Ω DM 0.23 dark energy Ω DE 0.72 but we know only a few parameters. It just might be the tip of an iceberg. We have to understand details of particle physics phenomena before we can analyze many cosmological questions. Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.3/12

Dark energy is a question of the ground state of the system. a stable ground state (vacuum) provides us with a cosmological constant Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.4/12

Dark energy is a question of the ground state of the system. a stable ground state (vacuum) provides us with a cosmological constant a false (sliding) vacuum might provide a situation of scalar quintessence pseudoscalar quintessence We need detailed obervations to distinguish between these options: this is an important aspect analysed in the projects of section B Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.4/12

Dark Matter seems to be closer to a direct particle physics description. This makes us confident that we can find a solution to this problem. Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.5/12

Dark Matter seems to be closer to a direct particle physics description. This makes us confident that we can find a solution to this problem. But we seem to have (too) many solutions WIMPs (Susy neutralino, lightest KK-particle), or even weaker coupled particles (axion, gravitino, axino), some of them well motivated from particle physics, like supersymmetry a solution to the strong CP-problem Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.5/12

Scalar Quintessence (A1) implies the existence of a very light scalar particle (cosmon). This might lead to modification of Newtons law variation of fundamental constants Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.6/12

Scalar Quintessence (A1) implies the existence of a very light scalar particle (cosmon). This might lead to modification of Newtons law variation of fundamental constants this gives us a few possibilities to check this picture. We need more information than just the density ρ, e.g. w = p/ρ and even time dependence of w Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.6/12

Scalar quintessence (II) There still remains the problem of the cosmological constant : Why is ρ so small? Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.7/12

Scalar quintessence (II) There still remains the problem of the cosmological constant : Why is ρ so small? New theoretical ideas come from extra dimensions and string theory moduli fields in string theory self tuning of the cosmological constant Project A1 tries to tackle these questions by the construction of explicit solutions as a guiding principle. Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.7/12

Pseudoscalar quintessence (C4) Axions are well motivated by particle physics and string theory strong CP-problem (dynamical Θ angle), antisymmetric tensor fields in string theory, linear multiplet in supersymmetry. Axions couple only through derivatives: field strength H µνρ µ B νρ with H µνρ ɛ µνρσ σ Θ, no problems with modifications of Newtons law, variation of α. Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.8/12

Dark matter studies in C2 We need a detailed understanding of dark matter phenomena to learn about the properties of dark energy. Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.9/12

Dark matter studies in C2 We need a detailed understanding of dark matter phenomena to learn about the properties of dark energy. It is important to study abundance of dark matter, distribution of dark matter. Dark Matter can be used as a tool to learn about the contribution of dark enery in the early universe. This seems to be especially promising if dark matter comes in form of WIMPs. Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.9/12

A unified picture (C4) Is there a relation between the various contributions? Does it make sense to study the origin of the various contributions to Ω seperately? Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.10/12

A unified picture (C4) Is there a relation between the various contributions? Does it make sense to study the origin of the various contributions to Ω seperately? Clues to attack these questions might come from a careful examination of the apparent mass scales: for dark energy we have 10 3 ev from vacuum energy and, 10 32 ev from cosmon mass. for dark matter we might consider 10 3 GeV in the case of a WIMP or 10 11 GeV in the case of an axion. Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.10/12

The axion system (C4) Axions could be the origin of both dark matter and dark energy. Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.11/12

The axion system (C4) Axions could be the origin of both dark matter and dark energy. The possibility of a multiple see-saw mechanism: axion decay constant f A 10 11 GeV for dark matter induces weak scale (µ-term) through f A /M Planck dark energy is given by M DE = M 2 weak /M Planck quintaxion mass turns out to be M 2 DE /M Planck 10 19 GeV : 10 11 GeV : 10 3 GeV : 10 3 ev : 10 32 ev Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.11/12

Outlook We have just seen the tip of the iceberg: various Ω i determined but the origin is not understood. There are many theoretical ideas to be tested, but me need more detailed observations to guide us. Some fundamental questions have to be addressed: size of the cosmological constant, coincidence of abundance of various Ω i, a unified description of matter content of universe. Hopefully, something unexpected will show up! Particle Interpretation of DM and DE, Heidelberg Jan. 2006 p.12/12