Maximizing Gibbs Entropy in Canonical Ensemble

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The discussion focuses on maximizing Gibbs entropy in a canonical ensemble using Lagrange multipliers. The user is seeking clarification on the derivatives of two specific summations: Ʃln(P(i)) and ƩE(i). It is emphasized that when deriving with respect to multiple quantities P(i), only one term will survive in the derivative process. The example provided illustrates how to handle derivatives for functions of multiple variables. The thread aims to clarify these mathematical concepts for better understanding and application.
Sekonda
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Hey,

Here is the problem:

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The method by which we solve is by Langrange Multipliers, and so I believe I found the derivative of f with respects to P(i) but I have two quantities I'm sure what they equal:

Summations over i=1 to N : Ʃln(P(i)) and ƩE(i)

Thanks for any help,
S
 
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Sekonda said:
The method by which we solve is by Langrange Multipliers, and so I believe I found the derivative of f with respects to P(i) but I have two quantities I'm sure what they equal:

Summations over i=1 to N : Ʃln(P(i)) and ƩE(i)

Thanks for any help,
S

Remember you have N different quantities Pi that you are derivating with respect to. So for example if you have f(x,y) = x ln x + y ln y, then ∂f/∂x = ln x + 1 and likewise for y. There are no mixed terms, and even with a function of N variables, only one term survives the derivative.
 

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