  We investigate an array of identical phase oscillators non-locally coupled
without time delay, and find that chimera state with two coherent clusters
exists which is only reported in delay-coupled systems previously. Moreover, we
find that the chimera state is not stationary for any finite number of
oscillators. The existence of the two-cluster chimera state and its
time-dependent behaviors for finite number of oscillators are confirmed by the
theoretical analysis based on the self-consistency treatment and the
Ott-Antonsen ansatz.
