A Ensemble Theory of Fluctuations

Let us calculate K6N2 y using the grand canonical ensemble. In the grand ensemble the probability of finding N particles in the volume V is 

This latter result can be written as = c mNQn- The derivative of this with 

The density p is only a function of intensive variables so that the derivative of p with respect to p, P, T is the same whether N or V is held constant. This gives 

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