Fredagskollokvium: Torsten Bringmann: Identifying the particle nature of dark matter: from the distribution of matter at small scales to cosmic ray observations
Torstein Bringmann, Department of Physics, UiO.
The leading candidate for the observed cosmological dark matter (DM) is a new type of
weakly interacting massive particle (WIMP) which is thermally produced in the early
universe. Its decoupling from the thermal bath, however, does not only set the observed
DM relic density today but also imprints a small-scale cutoff in the spectrum of primordial
density fluctuations, corresponding to the least massive protohalos that can form. A dark
force between the WIMPs could further modify the matter distribution at small scales.
The clustering of (dark) matter thus potentially provides valuable information about the
WIMP particle nature, fully complementary to more traditional ways of searching for DM.
The second part of the talk will focus on one of those more traditional methods, intrinsically
connected to the way DM clusters: indirect searches aim at identifying a possible
contribution from DM self-annihilation or decay to the observed flux in cosmic rays. Special
emphasis is put on the basic principles and current status of observations in gamma rays,
the 'golden channel' of this technique, but I will also comment about what the apparently
anomalous high-energy rise in the cosmic ray positron fraction can tell us about the nature