Structure Formation
Our current model of the Universe assumes that after the Big Bang, the Universe is expanding and that its contents (several forms of matter & energy) are distributed roughly homogeneously and isotropically. About 60.000 years into the expansion, gravitational forces started to dominate the dynamic evolution of matter and the Universe as a whole.
The imprint of the fluctuations on the radiation field as seen by the Planck satellite (the Planck Collaboration 2013)
We often assume that most mass in the Universe is made up of Dark Matter, which does not interact with normal matter. For reasons still unclear, the otherwise homogeneous Dark Matter distribution was fluctuating slighty after the Big Bang, which started a runaway process that collapsed nearly all matter into sheets, filaments and roughly spherical objects called haloes.
The collapse started with the smallest fluctuations and then worked is way to larger and larger objects. This process is called hierarchical structure formation and can be simulated pretty accurately.
In our project, cosmological structure formation is the first problem we have to solve accurately. The main issue here is computing chaotic motions in galaxy clusters accurately. They form the basis mechanism amplifying magnetic fields and accelerating particles.
Slice through the observed galaxy distribution around our Milkyway from the 2dFGRS survey data (Colless and colleagues).