# Frank Steiner's Group

Ulm University | and | Observatoire de Lyon Centre de Recherche Astrophysique de Lyon Ecole Normale Supérieure de Lyon, Université Lyon 1, CNRS 9, avenue Charles André F-69230 Saint-Genis Laval France |

# Infos

# Cosmic Microwave Background (CMB) Radiation

The cosmic microwave background (CMB) radiation is the earliest electromagnetic radiation after the Big Bang which can be observed e.g. by the NASA-satellite WMAP and the ESA-satellite Planck. The tiny anisotropies in the CMB radiation are believed to be generated by quantum fluctuations in the early Universe and represent the seeds for the large scale structure formation that is the cause for the formation of galaxy clusters and galaxies. An introduction into the complex physics can be found here.

Our focus is on cosmic topology. It addresses the question whether a non-trivial topological structure of the Universe is betrayed by cosmological observations. The best chances for such a detection are provided by anisotropies found in the CMB radiation. A non-trivial topology of the Universe can lead to a finite volume which in turn implies a suppression of anisotropies on the largest scales. Such a suppression is indeed observed in the CMB radiation.

In the case of a spatially flat Universe the simplest non-trivial example is that of a 3-torus which can be interpreted as a 3-dimensional box where three pairs of opposing sides of the box are identified. In this way a flat space of finite volume without a boundary is constructed. Below a CMB simulation for such a 3-torus topology is shown.

A cosmic microwave background simulation is shown for a 3-torus topology using more than 5.5 million eigenfunctions. The anisotropies of the CMB are encoded as colours whereby red means hotter than the average temperature and blue cooler temperatures. The average temperature is approximately 2.7 Kelvin.