Friedmann-like universes with weak torsion: a dynamical system approach
  We consider Friedmann-like universes with torsion and take a step towards
studying their stability. In so doing, we apply dynamical-system techniques to
an autonomous system of differential equations, which monitors the evolution of
these models via the associated density parameters. Assuming relatively weak
torsion, we identify the system's equilibrium points. These are found to
represent homogeneous and isotropic spacetimes with nonzero torsion that
undergo accelerated expansion. We then examine the linear stability of the
aforementioned fixed points. Our results indicate that Friedmann-like
cosmologies with weak torsion are generally stable attractors, either
asymptotically or in the Lyapunov sense. In addition, depending on the equation
of state of the matter, the equilibrium states can also act as intermediate
saddle points, marking a transition from a torsional to a torsion-free
universe.
