by Maxim Khlopov on Sat 18 Apr 2015 20:07
Dear Anastasia,
Thank you for your question.
People look for a single form of dark matter (DM) for simplicity. However, we have different physical motivations for different DM candidates, what appeals to a multicomponent dark matter scenarios.
Different DM fractions may be comparable by their contribution into the total DM density, or there may be some dominant form of dark matter accompanied by (several?) sub-dominant components.
These components can be homogeneously mixed, or separated in space.
The separation in space may be due to domain structures of various kind, or (in the simplest case) due to the difference in DM particle properties - the simplest example is a mixture of Hot and Cold dark matter, the ratio of the corresponding fractions changes from large to small scales.
With the best regards
M.Yu.Khlopov
[i]Хлопов Максим Юрьевич
Maxim Khlopov[/i]