I just wanted to say that this is a really fantastic explanation of the current state of the art, particularly the way you state the high-level motivation for u

I just wanted to say that this is a really fantastic explanation of the current state of the art, particularly the way you state the high-level motivation for ultra high energy colliders. Of course, without a few orders of magnitude gain in acceleration gradient, the necessary collider size is impractically large, so these sorts of questions may not be investigated for a while.