[zachf]

If anyone is looking to learn some actual physics instead of media crit, it would be worthwhile to sit down with the wikipedia pages for the AdS/CFT correspondence and the black hole information paradox. There’s a lot of things you can learn about the nature of quantum gravity. Some of it is built on assumptions about nature, of course, which leads a lot of people to assume that the enterprise is built on a house of cards, but even this is worth really digging in to. You may find that in fact there are only a few assumptions about reality that need to be made, and that removing any one of them is harder than you might think.

And AdS/CFT is genuinely fascinating. It’s a type of theoretical construct that’s quite unique in the history of physics. So it’s very hard to talk about it in English sometimes! That’s partly what happened in this Quanta article. AdS/CFT asserts an equality between two very different systems (here, the quantum system is identified with the wormhole) in an extremely complex and nonlinear way. Does this mean that the quantum system is a wormhole? It’s a harder question than it appears on the surface.

[zmgsabst]

Is it that hard to talk about?

A tangle in the interior of a cylinder loses information when viewed on the boundary because you lose a dimension (ie, the shadow cast by string around a light bulb as you see it on the lamp shade). You then have to allocate probabilities to pseudoknot resolutions (ie, guesses about crossings). So you end up with something that looks like continuous geometry on the inside and quantized statistics about interactions on the boundary.

Entanglement looks like taking two filaments in a plasma globe and moving one in a circle around the other. Their ribbons are now tangled. (As a 2+1-D analog.)

[zachf]

Respectfully, your metaphor doesn’t bear any similarity to the way AdS/CFT works. In AdS/CFT there are dual quantum systems with no information loss. A bit more precisely, the correspondence relates the partition functions of quantum gravity in AdS with the partition functions of conformal fields. This implies the existence of a map between the two, which in this case happens to be extremely complex and nonlocal.

Another way of saying it is that the two descriptions are different representations of the same object. There is no projection or information lost in switching between descriptions.

[zmgsabst]

Yes — that non-locality on the surface is because the braiding structure is non-local when projected.

You are correct and I misspoke:

You don’t lose the information, it becomes non-local on the surface — and so if you’re building a model of the interior from a local sampling of the surface, you get a statistical model built on pseudoknots (again, like a shadow from a lamp).

[zachf]

I think it proves my point that AdS/CFT is hard to talk about :) I’ve still got mixed feelings about the lamp/shadow analogy but thanks for the clarification.

[zmgsabst]

Sure — just one last thought:

The thread-lamp model isn’t arbitrary; ultimately, we’re looking for some kind of tangle model that rescues geons. So we’re going to need something that looks like continuous tangles on the inside and Feynman diagrams on the outside.