2014/02/28 by Dmitry Shogin, Sigbjørn Hervik
Physics and Astronomy · #Anomalous diffusion #Black Holes and Theoretical Physics #Classical mechanics #Cosmology and Gravitation Theories #Diffusion #Einstein #Einstein field equations #Mathematical physics #Physics #Quantum mechanics #Relativity and Gravitational Theory #Scalar (mathematics) #Scalar field #astro-ph.CO #gr-qc
paper · pdf · doi:10.1088/0264-9381/32/5/055008
published as Class. Quant. Grav. 32 (2015) 055008 · 26 pages, 8 figures
arxiv created 2014/12/06 · openalex publication_date 2015/02/03 · arxiv updated 2015/02/05 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We investigate the three types of class B Bianchi cosmologies filled with a tilted perfect fluid undergoing velocity diffusion in a scalar field background. We consider the two most important cases: dust and radiation. A complete numerical integration of the Einstein field equations coupled with the diffusion equations is done to demonstrate how the presence of diffusion can affect the dynamics of cosmological evolution, where the most attention is paid to changes to the late-time behaviour. We show that aside from quantitative effects, diffusion can result in significant qualitative differences. For example, the Universe may recollapse if diffusion is sufficiently strong, or evolve towards the de Sitter state otherwise. In constrast to the diffusionless case, radiation isotropizes in the presence of diffusion, and the tilt decreases exponentially at later times: V ∼ e − 0.25 τ ; also, we determine the decay rates of energy density, which become slower when the diffusion term is non-zero.