Holistic Yarn Theory

Bee asks: "when you write: but we missed on the deep guiding principle which tells us how to select the true theory (such as it is) and where the exact theory came from and leads to. Do you have anything specific in mind? "

Uh, yeah, sure...

er, well, I did, but the boxes of this 'ere blog were too narrow to fit it...

(I should note that one of Backreaction's recent blog entries is on an apparently non-existent topic
Bother that.

I don't know, honestly, obviously I have some ideas, but if they were even half-baked I'd write them up for GRF or something. So, here is the half-assed bloggy version:

There are big holes in our conceptualization of what is going on, and I suspect that if we were to click on maybe two underlying principles we would have a much better picture of how it all fit together.
Or, I could be completely wrong. But that is ok, so is almost everyone else.

I suspect holography is an important clue - that it is even plausible that our universe is holographic is very interesting, and slightly surprising (to some of use at least). If we understood why, and how general that property is, it might move us along. It would be interesting to know if there are consistent universes that are definitely no holographic, I am aware of arguments that some classes of classical universes could not be holographic, but not sure if the argument is robust.
Oh, and it would be useful to know if the universe is actually holographic, but that is a different level of difficutly.

I suspect another clue is somewhere back in the Copenhagen interpretation, and is probably staring at us in the face in the Aspect experiments, and quantum computing, but I do not know what it is and don't know that I would recognise it if someone told me.

So... one root question is whether the universe is actually discretized - is geometry quantum? Or, not quite equivalently, is the ensemble of all possible universe a finite, or countably infinite number of states. It would be very interesting if the set of universes were actually a finite number of discrete states. Philosophically bothersome, but interesting. Tegmark likes to play on this angle.

Another root question is whether inflation is eternal and we're in a small frozen out patch.
It is also a bothersome question, for the opposite but same reasons. Enough to drive people to anthropic reasoning.

Next issue is whether the topology of the universe, to the extent that that is a sensible question, is static or dynamic. Things are much harder, but much more interesting if the topology is dynamic.

Final clue is the old, old issue of black holes and unitarity. I had a student look at that last year, a good student. Am still thinking about some of the things he pointed out, might be something there, and one of you may be lucky enough to get him for a PhD student someyear.
This is a problem that, strangely, I think has not been hammered on enough - in particular just how bad the possible violation of the various weak symmetries is when scattering through virtual black hole states is.

So, that's kinda weak, lot of pretty obvious stuff everyone really knows.

There are some amusing hybrid approaches that could be pushed - I like stringy LQG, require that the vertices be tied by strings - both open and closed - and constrain the propagators on the lattice to keep the string connected, see where that goes. Another thing to try is LQG on branes - restric the dimensionality but let the geometry be free.

Conversely, it would be fun to look at strings where the string manifold is it, see if you can let go of the background metric and just take a path integral over sheets of all topologies with no embedding geometry. That should lead to something like stringy LQG, might tie the two approaches together, or show they are really inconsistent.

Easy to say, hard to do.