The generation of dark matter in late decays of quasistable massive particles has been proposed as a viable framework to address the excess of power found in numerical N-body simulations for cold dark matter cosmologies. We identify a convenient set of variables to illustrate which requirements need to be satisfied in any generic particle-physics model to address the small-scale problems and to fulfill other astrophysical constraints. As a result of this model-independent analysis, we point out that meeting these requirements in a completely natural way is inherently difficult. In particular, we reexamine the role of gravitinos and Kaluza-Klein gravitons in this context and find them disfavored as a solution to the small-scale problems in case they are dark matter candidates generated in the decay of thermally produced weakly interacting massive particles. We propose right-handed sneutrinos and right-handed Kaluza-Klein neutrinos as alternatives. We find that they are viable dark matter candidates, but that they can contribute to a solution of the small-scale problems only in case the associated Dirac neutrino mass term appears as a subdominant contribution in the neutrino mass matrix.
|ジャーナル||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|出版ステータス||Published - 2008 3 12|
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