Fluctuations

• How complete is the mean as a statistic of ensemble behavior?

  • Are there many members of the ensemble that have properties that deviate substantially from the mean?
  • Look at the standard deviation s
  • This relates to the heat capacity
  • Relative to mean is the important measure

• Fluctuations vanish in thermodynamic limit N??

• Similar measures apply in other ensembles

  • volume fluctuations in NPT; molecule-number fluctuations in mVT

• Click here for an applet illustrating fluctuations

p(E)

E

sE

<E>

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