From phase transitions to food market crises
The Ising model describes a lattice of interacting elements — here, 16 countries arranged on a 4×4 grid whose trade policies (open vs. closed) influence their neighbors. The lattice uses periodic boundary conditions: the top row connects to the bottom, the left column connects to the right, forming a torus. This means every country has exactly four neighbors and there are no edge effects — every node sits in an equivalent position, just as in the global trade network where no major trader sits at a periphery.
When local interactions accumulate past a critical threshold, the whole system can collectively and suddenly flip from one ordered configuration to another: a phase transition. This is the same mathematical intuition behind the CHSH and quantum decision-making work. Food markets and human mobility systems exhibit analogous transitions from stability to crisis. Standard rational-actor models assume independent agents and smooth dynamics — they miss the precursor signatures of these transitions. Quantum probability frameworks can detect them, because they allow for superposition, tunneling, and interference effects that characterize real decision-making under stress. The 29× difference in Bell violation ratios between crisis and non-crisis periods is precisely such a signature.
Classical Ising Model
16 countries on a 4×4 torus, each with a definite trade policy — open (−1) or closed (+1). Periodic boundary conditions eliminate edge effects: every country has exactly four neighbors. Adjust coupling J (do countries prefer to coordinate or compete?) and external field h (institutional bias toward protectionism or liberalization). Watch energy minimize and policy clusters form.
Quantum Ising Model
The same 4×4 torus extended with quantum superposition and tunneling. Countries exist in mixed policy states simultaneously — neither fully open nor fully closed. Neighbor coupling J and tunneling rate Δ compete: strong J locks in ordered clusters, strong Δ keeps countries in superposition. Hit Measure to collapse all superpositions to definite states — the quantum analog of a crisis resolution, when uncertainty suddenly resolves into a new order.
Connection to food systems
Trade policy cascades, food market crises, and evacuation decisions are all systems where many interacting agents collectively and suddenly transition from stable to crisis behavior. The 2D lattice with periodic boundaries captures the closed, interdependent structure of the global food network. The quantum extension models the interference effects that arise when decisions are not independent — which is exactly what crises produce.
Classical & Quantum Ising — Interactive Visualization
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