The nature of self-organized criticality (SOC) is pin-pointed with a simple mechanical model: a pinball machine. Its phase space is fully parameterized by two integer variables, one describing the state of an on-going game, the other describing the state of the machine. This is the simplest possible SOC system, having only two degrees of freedom and no spatial correlations, yet is not solvable by analytical means. (C) 2004 Elsevier B.V. All rights reserved.
Physica A: Statistical Mechanics and Its Applications, 2004, Vol 340, Issue 4, p. 552-558