Example 11.9: Difference between entropies Boxes A and B are separated by a common partition with a tiny hole. With an explosive device A is filled with photons which then gradually escape through the hole into B. Sketch roughly the behaviour of the difference of coarse grained and fine grained entropies of B as a function of the fraction of photons escaped from A.

[Hint: B starts in a pure state and also ends in a pure state, see [73], p.76].