Qualitative dynamics of interacting vacuum cosmologies. (arXiv:2007.12181v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kaeonikhom_C/0/1/0/all/0/1">Chakkrit Kaeonikhom</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Rangdee_P/0/1/0/all/0/1">Phongsaphat Rangdee</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Assadullahi_H/0/1/0/all/0/1">Hooshyar Assadullahi</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Gumjudpai_B/0/1/0/all/0/1">Burin Gumjudpai</a> (3 and 4), <a href="http://arxiv.org/find/astro-ph/1/au:+Schewtschenko_J/0/1/0/all/0/1">Jascha A. Schewtschenko</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Wands_D/0/1/0/all/0/1">David Wands</a> (1) ((1) Institute of Cosmology and Gravitation, University of Portsmouth, United Kingdom, (2) Department of Physics, School of Science, University of Phayao, Thailand, (3) The Institute for Fundamental Study "The Tah Poe Academia Institute", Naresuan University, Thailand, (4) Thailand Center of Excellence in Physics, Ministry of Higher Education, Science, Research and Innovation, Bangkok, Thailand)
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.
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.
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