In Statistical Mechanics, the key step in the derivation of the Canonical Ensemble is that the probability of S being in the m-th state, P_m , is proportional to the corresponding number of microstates available to the reservoir when S is in the m-th state. That is(adsbygoogle = window.adsbygoogle || []).push({});

[itex]P_m=c\Omega(E_0-E_m)[/itex],

where E_0 is the total energy.

Where does this rule come from? It seems to be inserted ad hoc in my textbook, and even in Wikipedia.

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# Canonical ensemble derivation

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