[D] Boltzmann machine "evolution equation"

While reading about Boltzmann machine I keep seeing expressions like "let the system reach the termal equilibrium state". I understand how this works in real physical systems, but what does it mean in the context of the ML model? Let's assume we set visible neurons to be in some particular state. What exactly is supposed to happen next? What is the rule according to which the hidden neurons will update? I'm talking about concrete instructions like take this neuron value, …

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