Active Brownian Particles

Parameters

Self-propulsion v₀ 2.0

Rotational diff. D_r 0.5

Translational diff. D_t 0.1

Particles N 80

Exclusion radius 8

Observables

Polar order ⟨cos θ⟩—

Mean cluster size—

MSD slope (est)—

Péclet number Pe—

Active Brownian Particles (ABPs) self-propel at speed v₀ along orientation θ, which diffuses with rate D_r. Persistence length ℓ = v₀/D_r. At high Pe = v₀/(D_r·σ) and density, ABPs undergo Motility-Induced Phase Separation (MIPS): a gas-liquid transition with NO attractive forces — pure non-equilibrium effect. Watch clusters nucleate and grow!