  Dense suspensions of self-propelled rod-like particles exhibit a fascinating
variety of non-equilibrium phenomena. By means of computer simulations of a
minimal model for rigid self-propelled colloidal rods with variable shape we
explore the generic diagram of emerging states over a large range of rod
densities and aspect ratios. The dynamics is studied using a simple numerical
scheme for the overdamped noiseless frictional dynamics of a many-body system
in which steric forces are dominant over hydrodynamic ones. The different
emergent states are identified by various characteristic correlation functions
and suitable order parameter fields. At low density and aspect ratio, a
disordered phase with no coherent motion precedes a highly-cooperative swarming
state at large aspect ratio. Conversely, at high densities weakly anisometric
particles show a distinct jamming transition whereas slender particles form
dynamic laning patterns. In between there is a large window corresponding to
strongly vortical, turbulent flow. The different dynamical states should be
verifiable in systems of swimming bacteria and artificial rod-like
micro-swimmers.
