  We use Langevin dynamics simulations to study dynamical behaviour of a dense
planar layer of active semi-flexible filaments. Using the strength of active
force and the thermal persistence length as parameters, we map a detailed phase
diagram and identify several non-equilibrium phases in this system. In addition
to a slowly flowing melt phase, we observe that for sufficiently high activity,
collective flow accompanied by signatures of local polar and nematic order
appears in the system. This state is also characterised by strong density
fluctuations. Furthermore, we identify an activity-driven cross-over from this
state of coherently flowing bundles of filaments to a phase with no global
flow, formed by individual filaments coiled into rotating spirals. This
suggests a mechanism where the system responds to activity by changing the
shape of active agents, an effect with no analogue in systems of active
particles without internal degrees of freedom.
