C3 Dark Energy - Dark Matter Interaction
Many theoretical ideas for explaining the physical origin of Dark Energy involve effective field theories like quintessence, non-linear extensions of general relativity (e.g. f(R)-gravity), or higher-dimensional gravity theories like DGP gravity. Generically, spatial inhomogeneities of Dark Energy and/or a coupling between Dark Energy and Dark Matter are expected in such scenarios, but little is known so far about the impact of these effects on non-linear structure formation.
It seems well possible that some of these theories alleviate small-scale challenges that have arisen in the standard LCDM model, or produce non-linear structures that can be readily excluded with existing observations. In particular, the effect on structure formation of the coupling between Dark Energy and neutrinos in recently proposed growing neutrino quintessence needs to be investigated.
This project aims to identify interesting candidate theories for which an extrapolation of structure formation in the non-linear regime seems promising. We develop the necessary numerical methods to allow accurate structure formation simulations in these coupled Dark Energy cosmologies, and compare their results to standard LCDM and to observations. This promises to provide interesting constraints on the viability of these physical scenarios, and will identify their specific observational signatures.
Role within the Transregional Collaborative Research Centre
This project plays an important role in the Transregio as it links the communities concerned with theoretical research into coupled quintessence and alternative theories of gravity with the community studying structure formation through observations and computer simulations. Notably, the work of this project can potentially provide strong constraints on theoretical coupled quintessence scenarios. In fact, even whole classes of models may be ruled out if they produce non-linear outcomes that are strongly inconsistent with data.
The investigation of structure formation in growing neutrino quintessence will be performed in close collaboration with project C6
(The why now problem of Dark Energy).
The project will also provide novel insights into the phenomenology of interacting Dark Energy - Dark Matter cosmologies in the realm of non-linear galaxy formation physics, guiding the search for Dark Energy signatures in the observational tests carried out by the projects B5
(Weak lensing and constraints on the Dark Energy equation-of-state), B6
(Gravitational lensing and X-ray emission by non-linear structures), and B7
(Probing Dark Matter and Dark Energy with observations of the evolution and spatial distribution of galaxy clusters).