Monday, May 9, 2016

statistical mechanics - What is the relationship between Maxwell–Boltzmann statistics and the grand canonical ensemble?


In the grand canonical ensemble one derives the expectation value ˆnr± for fermions and bosons of sort r:


ˆnr±  1exp[(εrμ)/kBT]1.


For (εrμ)/kBT0, we find


ˆnr±  1exp[(εrμ)/kBT] exp[(εrμ)/kBT].


The same motivation seems to be found in this Wikipedia article. However, on the same page, right at the beginning, that intuitive statement is made:



In statistical mechanics, Maxwell–Boltzmann statistics describes the average distribution of non-interacting material particles over various energy states in thermal equilibrium, and is applicable when the temperature is high enough or the particle density is low enough to render quantum effects negligible.




Now from my derivation above, it seems that "temperature is high enough" does the opposite of helping (εrμ)/kBT0 to be fulfilled. What is going on?




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