Late-time behaviour of the tilted Bianchi type VI−1/9 models

We study tilted perfect fluid cosmological models with a constant-equation-of-state parameter in spatially homogeneous models of Bianchi type VI−1/9 using dynamical systems methods and numerical simulations. We study models with and without vorticity, with an emphasis on their future asymptotic evolution. We show that for models with vorticity there exists, in a small region of parameter space, a closed curve acting as the attractor.