Gate accounting: flux and divergence

Learning goal: Boundary flux should match the population-change account. An uncounted exit contributes a sink and makes the incomplete accounts disagree.

North gate East gate South gate West gate

Divergence heatmap Hidden exit Hidden-exit rate k Uncounted train doors

Gate account: Actual change: Discrepancy: 　

Red: source / net outward field flux; blue: sink / net inward field flux. A separate removal term is shown as a blue sink.