Re:Black holes are like a hologram
by hankmccoy78 on Friday June 05, 2020 @02:24PM
(#23431974)
For anyone who wants to dive deeper into the science of this stuff I highly recommend this playlist from PBS Spacetime: https://www.youtube.com/playlist?list=PLsPUh22kYmNCHVpiXDJyA...
Also, quick note: I think you're confusing anti-de Sitter space w/ de Sitter space? de Sitter has positive curvature (i.e. it curves back in on itself) whereas _anti_ de Sitter space has negative curvature.
I've really enjoyed PBS Spacetime - it's a great "more than layman" but "less than physicist" channel. They aren't afraid to show math, and explain hard concepts.
Additionally I've found this channel, from Anton Petrov, to be good in a similar vein:
Re:Black holes are like a hologram
by twelfthnight on Friday June 05, 2020 @10:37PM
(#23436326)
Love this show. Originally thought the title was a little misleading since it seemed to suggest "Black holes are like a hologram" was news. In fact, according to PBS Spacetime, the observation that black holes acted like holograms (in a very particular sense) was the impetus for the holographic principle in the first place:
As I understand it, this paper is novel because it has found a scenario, a set of rules, where the math shows that the universe could indeed work this way...but this particular set of rules doesn't seem to be the ones we see in this universe. (I'll get to the specifics in a moment)
Why is this still useful? Because it is a starting point, a model that confirms the theory is workable. If the result had been negative, then some parts of the theory could be ruled out.
Now to the specifics from the original paper's abstract:
> We study this issue in the context of gravity with a negative cosmological constant. We exploit the most basic example of the holographic description of gravity (AdS/CFT): type IIB string theory on AdS5×S5, equivalent to maximally supersymmetric Yang-Mills theory in four dimensions. We thus resolve a long-standing question: Does the four-dimensional N=4 SU(N) Super-Yang-Mills theory on S3 at large N contain enough states to account for the entropy of rotating electrically charged supersymmetric black holes in 5D anti–de Sitter space? Our answer is positive.
Lots of words. A few things to take away is that this paper talks about a universe with four spatial dimensions, not three, and it considers "anti-de Sitter space", which would be a universe that loops back on itself instead of being infinite and flat as our universe appears to be. Last thing is that because the rate of expansion of the universe is accelerating, the cosmological constant is probably greater than zero but this theory only considers a scenario where the cosmological constant is negative.