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We suspect

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times

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then it's

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dot. Okay, now if you look at this, yeah, we can of course recognize at least one

quantity that we knew before, namely the derivative of Psi with respect to

Epsilon, that's something we can see up there, that defines the stresses, no? And

then apparently also the stresses depend on temperature, so this would be the

change of the stresses with temperature. So essentially this term is nothing else

but the change of stress with temperature. How does, how do the stresses

depend on the temperature? Okay, and then what we do is that we abbreviate this

term here, let's say the curvature of the free energy with respect to the

temperature and with the negative sign here, we abbreviate that as a constant

that you might have heard of, we will call that the heat capacity and then for

convenience we normalize that by the absolute temperature, we can always

divide by absolute temperature because that's never zero, no? And then you see if

I define this thing here as Cv divided by theta, it shows up here being

multiplied by theta, so we only stay with Cv that I shall call the heat capacity

in a minute times the change of temperature, no? Okay, we will discuss it