Equation 14 · The Arrow of Time and the Engine of Evolution
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the w exactly equals. Read the equation part by part below; each part has a contextual explanation and a link to its mathematical background.
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Capital delta attached to a quantity marks a difference between two values of that quantity; the article’s sign convention determines the order.
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What the article says around this equation
[ 6 ] . Where W exactly equals F , the ratio is one and the forward distribution crosses the reflected reverse distribution; away from that point, the ratio grows exponentially in how far W departs from F , which is the precise, quantitative sense in which a trajectory doing much more work than the equilibrium minimum is exponentially more typical of the forward process than of its reverse. This is the arrow of time rendered as an odds ratio rather than an inequality: not “entropy increases,” but “this particular trajectory is times more likely to have been produced running forward than running backward.”
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