http://arxiv.org/abs/2007.12181
We present a phase-space analysis of the qualitative dynamics cosmologies where dark matter exchanges energy with the vacuum component. We find fixed points corresponding to power-law solutions where the different components remain a constant fraction of the total energy density and given an existence condition for any fixed points with non-vanishing energy transfer. For some interaction models we find novel fixed points in the presence of a third non-interacting fluid with constant equation of state, such as radiation, where the interacting vacuum+matter tracks the evolution of the third fluid, analogous to tracker solutions previously found for self-interacting scalar fields. We illustrate the phase-plane behaviour, determining the equation of state and stability of the fixed points in the case of a simple linear interaction model, for interacting vacuum and dark matter, including the presence of non-interacting radiation. We give approximate solutions for the equation of state in matter- or vacuum-dominated solutions in the case of small interaction parameters.
C. Kaeonikhom, P. Rangdee, H. Assadullahi, et. al.
Mon, 27 Jul 20
-552/60
Comments: 20 pages, 8 figures
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