Multistability in coupled oscillator systems with time delay

We analyze the dynamic behavior of coupled oscillators with time-delayed interaction under a pinning force. With intermediate delay times the system shows multistability of synchronized and desynchronized states. In the synchronized states there are multiple states with different collective frequencies showing hysteresis as the pinning force increases and decreases. In the desynchronized states the oscillators are distributed almost uniformly. The multistability presents a possible mechanism of the perception of ambiguous or reversible figures.