Many-Body Theory for Multi-Agent Complex Systems

Multi-agent complex systems comprising populations of decision-making particles, have wide application across the biological, informational and social sciences. We uncover a formal analogy between these systems' time-averaged dynamics and conventional many-body theory in Physics. Their behavior is dominated by the formation of 'Crowd-Anticrowd' quasiparticles. For the specific example of the Minority Game, our formalism yields analytic expressions which are in excellent agreement with numerical simulations.