Effect of trapping perturbation on the collective dynamics of self-propelled particles

Collective dynamics of self-propelled particles (SPPs) with inherent perturbation in the system is modelled, incorporating a trapping perturbation in the Vicsek model (VM). Under this perturbation, the particles get trapped for a while with a position-dependent trapping probability as they pass through the trapping region and pick up a random velocity direction on release. The effect of the perturbation on the VM is studied, varying the scalar noise eta and the perturbation strength alpha. The system's response is obtained at two different velocities upsilon(0) = 0.5, and upsilon(0) = 1.0 for several systems of sizes L with a specific density rho(0). The formation of the travelling band and discontinuous order-disorder transition in the VM is known to occur above a crossover system size L* (rho(0), upsilon(0)). The perturbation in the VM can destroy the travelling band up to a specific system size beyond L* (rho(0), upsilon(0)). Consequently, the value of the crossover size has increased to a higher value L*(alpha)(rho(0), upsilon(0)). Below L*(alpha), the transition is continuous with the same critical exponents of the VM, and above L*(alpha), the transition is discontinuous. It seems that the VM, even in the presence of inherent perturbation, will always exhibit a discontinuous transition in the asymptotic limit. Copyright (C) 2021 EPLA