Topological vs Metric Flocking

Topological flocking (Ballerini et al. 2008, starlings): each bird aligns with its k nearest neighbors regardless of distance — creating scale-free cohesion robust to density changes and predator attacks. Metric flocking (Vicsek model): align with all birds within radius r — cohesion fails when flock density drops. "Predator Attack" disperses a fraction of the flock; observe how quickly each mode recovers order. Order parameter φ = |⟨ê⟩| measures alignment.