- #1
Hiero
- 322
- 68
In this video (the link should take you 23 minutes in, where) Professor Susskind writes a theorem. (He says E and S are functions of T and V.) I am just wondering if what he writes is an abuse of notation? And if so, how would you write it?
(Susskind gives his own proof from 26:30 to 36:00 if you want to see his way.)
I am tempted to prove it from the chain rule, like this:
Let E(V, T) = F(V, S(V, T))
(How can we be sure there is such an F(V, S)?)
Then partially differentiating both sides with respect to V (using the chain rule on the right side) yields:
∂E(V, T)/∂V = ∂F(V, S)/∂V + ∂F(V, S)/∂S • ∂S(V, T)/∂V
Then the final step is to subtract the last term to the other side.
The arguments of each function makes clear what is held fixed.
Both E and F represent energy, but we cannot put F = E because they are different functions.
Is this a valid way to articulate/prove it? Is Susskind’s notation valid? Any clarification is appreciated.
(Susskind gives his own proof from 26:30 to 36:00 if you want to see his way.)
I am tempted to prove it from the chain rule, like this:
Let E(V, T) = F(V, S(V, T))
(How can we be sure there is such an F(V, S)?)
Then partially differentiating both sides with respect to V (using the chain rule on the right side) yields:
∂E(V, T)/∂V = ∂F(V, S)/∂V + ∂F(V, S)/∂S • ∂S(V, T)/∂V
Then the final step is to subtract the last term to the other side.
The arguments of each function makes clear what is held fixed.
Both E and F represent energy, but we cannot put F = E because they are different functions.
Is this a valid way to articulate/prove it? Is Susskind’s notation valid? Any clarification is appreciated.