Thermal Physics: Evaluating Limits at Zero Temperature

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SUMMARY

The discussion focuses on evaluating the heat capacity at constant volume, \(C_v\), as temperature \(T\) approaches zero using the expression \(C_v = 2\left( {\frac{{\hbar \omega }}{T}} \right)^2 \frac{{\exp \left( {\frac{{\hbar \omega }}{T}} \right)}}{{\left( {\exp \left( {\frac{{\hbar \omega }}{T}} \right) - 1} \right)^2 }}\). Participants suggest changing variables to a dimensionless form, \(x = \frac{\hbar \omega}{T}\), and evaluating the limit as \(x\) approaches infinity. They confirm that using L'Hôpital's rule is a valid approach, although it may require multiple applications.

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Niles
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Homework Statement


Hi all.

Please take a look at this expression, where T is our variable (it represents temperature):

[tex] C_v = 2\left( {\frac{{\hbar \omega }}{T}} \right)^2 \frac{{\exp \left( {\frac{{\hbar \omega }}{T}} \right)}}{{\left( {\exp \left( {\frac{{\hbar \omega }}{T}} \right) - 1} \right)^2 }}.[/tex]

I have to evaluate this for [itex]T \rightarrow 0[/itex]. I would use L'Hopital, but isn't there an easier way? Because when I differentiate the nominator (the top), then I will end up with an expression like the original nominator, which won't help me.

Thanks in advance.


Niles.
 
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Thermal physics correct?

I had some sort of this question, it goes like this:
change variables, to dimensionless i.e x=hbar*w/T
so you now evaluate:
[tex]lim_{x\leftarrow \infty} 2x^2(\frac{e^x}{(e^x-1)^2})[/tex]
Other than L'hopital twice there isn't any other approach.
 
Yeah, thermal physics :smile:

Thanks!
 

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