TY - JOUR

T1 - Qualitative dynamics of interacting vacuum cosmologies

AU - Kaeonikhom, Chakkrit

AU - Rangdee, Phongsaphat

AU - Assadullahi, Hooshyar

AU - Gumjudpai, Burin

AU - Schewtschenko, Jascha A.

AU - Wands, David

N1 - 20 pages, 8 figures; version accepted for publication

PY - 2020/12/7

Y1 - 2020/12/7

N2 - 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 nonvanishing energy transfer. For some interaction models we find novel fixed points in the presence of a third noninteracting 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 behavior, 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 noninteracting radiation. We give approximate solutions for the equation of state in matter- or vacuum-dominated solutions in the case of small interaction parameters.

AB - 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 nonvanishing energy transfer. For some interaction models we find novel fixed points in the presence of a third noninteracting 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 behavior, 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 noninteracting radiation. We give approximate solutions for the equation of state in matter- or vacuum-dominated solutions in the case of small interaction parameters.

KW - cosmology

KW - dark energy

KW - RCUK

KW - STFC

KW - ST/S000550/1

UR - https://arxiv.org/abs/2007.12181

U2 - 10.1103/PhysRevD.102.123519

DO - 10.1103/PhysRevD.102.123519

M3 - Article

VL - 102

JO - Physical Review D

JF - Physical Review D

SN - 1550-7998

IS - 12

M1 - 123519

ER -