The Dynamics of a TwoFluid Bianchi Type I Universe
Abstract
We use a dynamical systems approach based on the method of orthonormal frames to study the dynamics of a twofluid, nontilted Bianchi Type I cosmological model. In our model, one of the fluids is a fluid with bulk viscosity, while the other fluid assumes the role of a cosmological constant and represents nonnegative vacuum energy. We begin by completing a detailed fixedpoints analysis of the system which gives information about the local sinks, sources and saddles. We then proceeded to analyze the global features of the dynamical system by using topological methods by finding the $\alpha$ and $\omega$limit sets. The fixed points found are a flat FLRW universe, an Einsteinde Sitter universe, a de Sitter universe, a mixed FLRW universe with both vacuum and nonvacuum energy, and a Kasner universe. We then find conditions for which each equilibrium point was a saddle, sink, or source, and attempt to describe the global and past asymptotic behaviour of the model with respect to each fixed point. The flat FLRW universe solution we found with both vacuum and nonvacuum energy is clearly of primary importance with respect to modelling the presentday universe. In particular, we show that this equilibrium point is a local sink and a saddle of the dynamical system, so there are orbits that approach this equilibrium point in the future. Therefore, there exists a time period for which our cosmological model will isotropize and be compatible with presentday observations of a high degree of isotropy of the cosmic microwave background in addition to the existence of both vacuum and nonvacuum energy.
 Publication:

arXiv eprints
 Pub Date:
 February 2014
 arXiv:
 arXiv:1402.1967
 Bibcode:
 2014arXiv1402.1967S
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Mathematical Physics;
 Mathematics  Classical Analysis and ODEs;
 Mathematics  Dynamical Systems