> "The 3-D space we experience might be generated by a two-dimensional reality or even a zero-dimensional system, one that cannot be thought of as residing in space at all."
But isn't this effectively saying that the dimensions-based model for universe is incorrect? I'm trying to understand the comparison when it seems to be saying the benchmark is wrong.
I read it as saying our 3-d world can be encoded in ways other than a stream of x y z coordinates. Possibly a stream of 1-d "a" coordinates, which are translated to our reality by folding the "a" stream in different directions like a physical hologram.
Maybe I'm just a practical, basic, person but I don't understand a single thing about that article. Then I read the HN comments hoping for clarity, and came out even more confused...
I'm honestly tired of the personal anecdotes in scientific articles. I don't want to have to scan 3 paragraphs through before I get the gist of the article.
I think the holographic principle and its, especially popular, interpretations are stretching things too far, way outside of the black hole as one can say. There is so far nothing to indicate that the specific conditions inside black hole giving rise to the observed "holographicity" of the entropy of the black hole are applicable outside of the black hole.
What we have - the space of possible states, i.e. entropy, inside a black hole has significantly reduced cardinality, i.e. it is equivalent to the cardinality of the black hole surface in this case. That means that either there is strong additional dependency/correlation arises between the states of the black hole components/particles (doesn't sound that unrealistic - we do have similar, using very wide notion of similarity of course :), process on the other side of the spectrum - Bose-Einstein condensate (and the similarity may be pretty high https://arxiv.org/pdf/0807.0315.pdf)), and which in effect is kind of equivalent to the loss of some degrees of freedom, or may be there is a loss of degrees of freedom due to the black hole spacetime distortion - gravity distorts the spacetime, and the black hole is the ultimate case of it with the local time basically disappearing for the external observer, and thus we have a perceived loss of degrees of freedom - as observed by external observer. I.e. it may as well be that the entropy inside, as would be perceived locally, may still be "normal 3D" in the local spacetime while it is basically frozen from the POV of external observer (and thus what we observe is the projection of the rest of that spacetime taken at the point where(when) a given dimension is "stuck"), and thus externally observed "2D" entropy is just stuck in time, ie. a projection of, the "normal" 3D entropy of the black hole insides. Drawing some parallel with light coming out of deep gravitational well - the lightwave is stretching like the time dimension is getting "slower" until it stops in the case of black hole. The stopped dimension and an absence of the dimension - not much difference math- and observation-wise.
If we can just name zero dimension space as 'not space,' we could solve the problem much more easily by renaming 'space' as 'not space' instead of relying on convoluted analogies with holograms.
I fail to see how the hologram concept explains anything. Is my OS bootup process a hologram? Is the evolution of the universe from the big bang a hologram? What is not a hologram?
'Hologram' just seems to be a loose analogy for the concept that 'something complex came from something simple.'
On the other hand, the holographic nail sounds pretty neat.
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"Science is prediction, not explanation" - Fred Hoyle.
But isn't this effectively saying that the dimensions-based model for universe is incorrect? I'm trying to understand the comparison when it seems to be saying the benchmark is wrong.
After reading the article and not understanding anything, I thought maybe someone at HN made more sense if it than me, so I checked the comments.
Glad to know I'm not the only one for whom this was incomprehensible!
Deleted Comment
What we have - the space of possible states, i.e. entropy, inside a black hole has significantly reduced cardinality, i.e. it is equivalent to the cardinality of the black hole surface in this case. That means that either there is strong additional dependency/correlation arises between the states of the black hole components/particles (doesn't sound that unrealistic - we do have similar, using very wide notion of similarity of course :), process on the other side of the spectrum - Bose-Einstein condensate (and the similarity may be pretty high https://arxiv.org/pdf/0807.0315.pdf)), and which in effect is kind of equivalent to the loss of some degrees of freedom, or may be there is a loss of degrees of freedom due to the black hole spacetime distortion - gravity distorts the spacetime, and the black hole is the ultimate case of it with the local time basically disappearing for the external observer, and thus we have a perceived loss of degrees of freedom - as observed by external observer. I.e. it may as well be that the entropy inside, as would be perceived locally, may still be "normal 3D" in the local spacetime while it is basically frozen from the POV of external observer (and thus what we observe is the projection of the rest of that spacetime taken at the point where(when) a given dimension is "stuck"), and thus externally observed "2D" entropy is just stuck in time, ie. a projection of, the "normal" 3D entropy of the black hole insides. Drawing some parallel with light coming out of deep gravitational well - the lightwave is stretching like the time dimension is getting "slower" until it stops in the case of black hole. The stopped dimension and an absence of the dimension - not much difference math- and observation-wise.
'Hologram' just seems to be a loose analogy for the concept that 'something complex came from something simple.'
On the other hand, the holographic nail sounds pretty neat.