GalaxyDance · Dance of galaxies: testing General Relativity and alternatives using galaxy velocity fields

Dance of galaxies: testing General Relativity and alternatives using galaxy velocity fields

Cosmology has recently become one of the most important and successful branches of physical sciences. This status was sanctioned by three Nobel Prizes in physics awarded in the recent years for studies in this field (including this year prize for Jim Peebles). The standard cosmological model - LCDM (Lambda Cold Dark Matter) - is very successful in explaining the emergence of large-scale structures and the evolution of the Universe as a whole. Nonetheless, currently it is troubled by several fundamental puzzles regarding the physical nature of our Universe. One of the most pressing issues is to find and understand the physical origin of the observed late-time cosmic acceleration. One of the most fundamental problems of contemporary physics is to explain the physical mechanism behind the observed acceleration of the Universal expansion. The LCDM model employs General Relativity (GR) as the underlying theory of gravity, assumed to be valid on all scales. When interpreted within GR, the universal acceleration is caused by a cosmological constant of a very small value. However, this is very difficult to reconcile with particle physics which predicts it to be some 50 orders of magnitude larger than measured. This mismatch has motivated vivid research activity on the cosmological constant problem. On the theoretical side we have in particular seen the emergence of a plethora of modified gravity (MG) theories, which attribute the observed acceleration to a breakdown of GR on cosmological scales. On the observational side, many new ambitious astronomical surveys are being deployed to both test GR and Dark Energy and to study the cosmic acceleration in exquisite details; a prime example is the flagship European space mission Euclid to be launched already in 2021. Testing GR and verifying its validity on large scales is one of the main goals of the 21st-century extragalactic astronomy. However, so far Einstein’s theory of gravity has only been rigorously probed on astrophysical scales, i.e. in the Solar System or for compact objects like black holes and neutron stars. At present, by using Einstein's theory to describe the whole observable Universe we make an extrapolation of 15 orders of magnitude. “GalaxyDance” takes at heart the urgent need to design possible tests of Dark Energy and Dark Matter models. To envisage such tests a new state-of-the-art computer simulations of standard and alternative cosmological models are used. Such “virtual universes” created with a help of supercomputers are then a subject of a high-level analysis that indicate which properties of the observed Universe can be used to test different models and to shed the light on the dark side of the Cosmos.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз