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Diffcult for me to fully understand / believe in the holographic principle at macroscopical scales ... potentially it looks though as a revolutionary idea.....

never heard about it... seems interesting. At first sight it seems that it is based on fundamental principle that could lead to a new phenomenology, so that could be tested. Perhaps Luzi knows more about this ? Did we ever work on this concept ?

The paper is quite long and I don't have the time right now to read it in detail. Just a few comments: * We (ACT) definitely never did anything in this direction? But: is there a new phenomenology? I'm not sure, if the aim is just to get Einstein's theory as emergent theory, then GR should not change (or only change in extreme conditions.) * Emergent gravity is not new, also Erik admits that. The claim to have found a solution appears quite frequently, but most proposals actually are not emergent at all. At least, I have the impression that Erik is aware of the relevant steps to be performed. * It's very difficult to judge from a short glance at the paper, up to which point the claims are serious and where it just starts to be advertisments. Section 6 is pretty much a collection of self-praise. * Most importantly: I don't understand how exactly space and time should be emergent. I think it's not new to observe that space is related to special canonical variables in thermodynamics. If anybody can see anything "emergent" in the first paragraphs of section 3, then please explain me. For me, this is not emergent space, but space introduced with a "sledge hammer." Time anyway seems to be a precondition, else there is nothing like energy and nothing like dynamics. * Finally, holography appears to be a precondition, to my knowledge no proof exists that normal (non-supersymmetric, non-stringy, non-whatever) GR has a holographic dual.

Update: meanwhile I understood roughly what this should be about. It's well known that BH physics follow the laws of theormodynamics, suggesting the existence of underlying microstates. But if this is true, shouldn't the gravitational force then be emergent from these microstates in the same way as any theromdynamical effect is emergent from the behavior of its constituents (e.g. a gas)? If this can be prooven, then indeed gravity is emergent. Problem: one has to proof that *any* configuration in GR may be interpreted as thermodynamical, not just BHs. That's probably where holography comes into the play. To me this smells pretty much like N=4 SYM vs. QCD. The former is not QCD, but can be solved, so all stringy people study just that one and claim to learn something about QCD. Here, we look at holographic models, GR is not holographic, but who cares... Engineering problems...

is there any experimental or observational evidence that points to this "solution"?

Are you joking??? :D

I was a bit fast to say it could be tested... apparently we don't even know a theory that is holographic, perhaps a string theory (see http://arxiv.org/abs/hep-th/9409089v2). So very far from any test...

Luzi, I miss you!!!

we... the article is a bit overblown in my view ... except maybe the last paragraphs: "The collision between universe's is a variation on this theme. "The "colliding universe" scenario can be realized as a simple extension of our earlier experiments simulating the spacetime geometry in the vicinity of big bang," he says. He simulates an expanding universe using concetric rings of gold separated by a dielectric. "When the two concentric ring ("universe") patterns touch each other ("collide"), a Minkowski domain wall is created, in which the metallic stripes touch each other at a small angle," he says. Being able to recreate these exotic events in the lab is certainly interesting but it is beginning to lose its novelty. The problem is that this work is not telling us anything we didn't know--the universe behaves the same way inside a metamaterial as it does outside. What Smolyaninov needs is a way of using his exotic materials to do something interesting. In other words, he needs a killer app. Any ideas? "

formation flying around black holes... so practical...

Horava is a serious string theorist (if there is anything like that...) I like the last comment by Dvali: if the theory can be adjusted in such a way that it becomes indistinguishable from GR then it should be taken seriously. Gosh, am I glad to be among engineers now!!!