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Abstract: Cosmological observations have revealed the existence of a dark mattersector, which is commonly assumed to be made up of one particle species only.However, this sector might be more complicated than we currently believe: theremight be more than one dark matter species for example two components of colddark matter or a mixture of hot and cold dark matter and there may be newinteractions between these particles. In this paper we study the possibility ofmultiple dark matter species and interactions mediated by a dark energy field.We study both the background and the perturbation evolution in these scenarios.We find that the background evolution of a system of multiple dark matterparticles with constant couplings mimics a single fluid with a time-varyingcoupling parameter. However, this is no longer true on the perturbative level.We study the case of attractive and repulsive forces as well as a mixture ofcold and hot dark matter particles.



Author: A. W. Brookfield, C. van de Bruck, L. M. H. Hall

Source: https://arxiv.org/







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