Pitchfork bifurcation and vibrational resonance in a neutral delayed system

The pitchfork bifurcation and vibrational resonance phenomenon are analytically and numerically investigated in the neutral delayed system. The results show that the neutral delayed time induces the pitchfork bifurcation transiting between supercritical and subcritical cases while the neutral delayed strength may induce supercritical pitchfork bifurcation. The neutral delayed time can also induce the periodic or quasi-periodic vibrational resonance. This period simultaneously contains the period of the low-frequency harmonic excitation and period of the high-frequency harmonic excitation. The results extend the investigations of the pitchfork bifurcation and vibrational resonance.