Tilted two-fluid Bianchi type I models

In this paper we investigate expanding Bianchi type I models with two tilted fluids with the same linear equation of state, characterized by the equation of state parameter w. Individually the fluids have non-zero energy fluxes w.r.t. the symmetry surfaces, but these cancel each other because of the Codazzi constraint. We prove that when w = 0 the model isotropizes to the future. Using numerical simulations and a linear analysis we also find the asymptotic states of models with w > 0. We find that future isotropization occurs if and only if w ≤ 1 3 . The results are compared to similar models investigated previously where the two fluids have different equation of state parameters. PACS numbers: 04.20.-q, 04.20.Dw, 04.20.Ha, 98.80.-k, 98.80.Bp, 98.80.Jk ∗Electronic address: [email protected]