So I have been thinking about the photon gas, and I have read several papers talking about how a Carnot cycle could be created for it. This is fantastic, and it is something I am quite comfortable with. All of the papers present the P-V diagram as the "golden" Carnot cycle for the photon gas, and say that the construction of a T-S diagram would be "trivial", but do not present what the cycle would actually look like, and I have searched/read for quite some time, but have not been able to come up with definitively what it should look like. Would it differ from the one presented for the ideal gas? Such as http://en.wikipedia.org/wiki/Carnot_cycle#The_temperature-entropy_diagram I apologize if this is something trivial to you, but it bothers me since P does not depend on V, and that P and T are not independent in the photon gas. It seems like such a diagram would be more convoluted than the one presented for an ideal gas.