I've just looked and I have no idea either. If anyone wants to help there's a copy of the book here.
EDIT: The numbers in that copy are off by 1 from the book. "18.10" = "18-9" and so on.
Yeah, so to add some redundancy for y'all, here's the text surrounding the equations I'm having trouble with.
The 18.10 to 18.11 jump I'm having trouble with is the one in this part of the text:
But suppose that, for a given E_b, (18.8) holds independently of what E_a might be; call this 'strong irrelevance'. Then we have (what I'm calling 18.10) But if this is to hold for all (A_p|E_a), the integrands must be the same: (what I'm calling 18.11, and can't derive) .
And equation 18.15, which I can't justify, is in this part of the text:
...But then, by defini
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.