"The holographic principle is a property of quantum gravity and string theories that states that the description of a volume of space can be thought of as encoded on a boundary to the region—preferably a light-like boundary like a gravitational horizon. First proposed by Gerard 't Hooft, it was given a precise string-theory interpretation by Leonard Susskind[1] who combined his ideas with previous ones of 't Hooft and Charles Thorn.[1][2] As pointed out by Raphael Bousso,[3] Thorn observed in 1978 that string theory admits a lower-dimensional description in which gravity emerges from it in what would now be called a holographic way.
In a larger sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon, such that the three dimensions we observe are only an effective description at macroscopic scales and at low energies."
So the analogy is that the field inside the volume can be completely described by some function over the bounding surface of the volume, similar to how the light field captured by a hologram is projected and recorded on a flat glass or film plane. I can visualize that pretty easily, but I don't know enough to tie that to some concrete relationship to the fundamental physical forces of the universe.
"In mathematics, Cauchy's integral formula, named after Augustin-Louis Cauchy, is a central statement in complex analysis. It expresses the fact that a holomorphic function defined on a disk is completely determined by its values on the boundary of the disk, and it provides integral formulas for all derivatives of a holomorphic function. Cauchy's formula shows that, in complex analysis, "differentiation is equivalent to integration": complex differentiation, like integration, behaves well under uniform limits – a result denied in real analysis."
Does anyone who knows this stuff better than me know if there's any meaningful connection?
It's similar to Green's Theorem, a special case of Stokes' Theorem. The latter is probably very closely related to the ideas underpinning the holographic principal (just guessing; my background is more math than physics, though I love both).
Short version: The bulk is encoded in the boundary.
Imagine a special circle. The border of this circle contains all the information of everything inside the circle, so the inside of the circle is a "holographic projection" of the information in the boundary.
In the same way that a holographic projection is physically two-dimensional, but contains enough data to appear three-dimensional from many different angles? (I'm guessing here, I don't really get holograms.)
A regular photograph captures the intensity pattern of light at a particular location at a particular time.
Holograms recreate the interference pattern of light in a volume of space. By interfering two coherent sources using a film that has the interference pattern captured, you recreate the interference pattern. Hence it exists in 3-D.
It means in essence, that we live in the two-dimensional space, which contains just enough information (thanks to interference patterns), to be projectable to the 3rd dimension. In holographic duality, this is a way to derive a more complex dimension from the next lowest dimension. It is thought that the four-dimensional space, which you may have just been thinking about, exists due to distant entangled quarks and may be the thing we call space-time. The holy grail every physicist is searching for is "gravity". Nobody on earth knows for sure what gravity exactly is. But it is thought to exist in the fifth-dimension "bends & shapes the our space-time.
Don't confuse this with the simulated universe theory, as I initially did. That's a whole nother story.
Time is believed to not exist as a separate dimension, but as a byproduct of gravity.
"Time is believed to not exist as a separate dimension, but as a byproduct of gravity."
I love this comment because I hadn't heard ^^ perspective before. Do you know what particular schools / models treat time this way, or are you inferring that this is the general conclusion of the field?
No, that is not what's believed in general, but gains in attractivity as a possible solution. That's because, it's simpler. I have read about it on various blogs and have also seen an inspiring TED talk about it, before it got removed.
i think its quite well established that space and time break down as approximations at the small scale.
i also think that gravity is interesting because in GR there really isn't such a thing - its an artefact of the geometry of space and time - because of how we perceive the passing of time.
i'm not sure exactly how time would fall out of gravity... afaik the quantum mechanical descriptions usually break the magic trick of GR and make it into a graviton field, which depends on some background time.
i do wonder why we pursue theories which our existing theories show to be unlikely to be fundamental... thinking about the limits, near the planck scale we find that it is impossible to tell if an event is before or after, or if a thing is one or two things, or if its seperated in x or y... the simple conclusion imo is that space and time are approximations that are useful at everyday scales, but have no physical reality.
> we live in the two-dimensional space, which contains just enough information
I would change "just enough information" to "much more than enough". If it was just enough, then the universe would be an enormous black hole. Note that I'm not an expert, and I could be wrong, but this is my interpretation.
Thinking about the universe as a massive black hole, whereas black holes are a concept that is still not entirely known makes thinking about this subject highly speculative. This list only adds salt to that wound: http://en.wikipedia.org/wiki/List_of_unsolved_problems_in_ph...
But to me Black Holes are spinning L-Systems which distribute information in the universe instantly by quantum teleportation. This is much simpler than other existing theories which leave open question like: http://en.wikipedia.org/wiki/Black_hole#Open_questions
Take this information with caution, but these paper supports such possibility:
When reading that article, while I don't have the background for all of it, I find that most of it sounds fairly plausible, until I get to this: "In 1995, Susskind, along with collaborators Tom Banks, Willy Fischler, and Stephen Shenker, presented a formulation of the new M-theory using a holographic description in terms of charged point black holes, the D0 branes of type IIA string theory. The Matrix theory they proposed was first suggested as a description of two branes in 11-dimensional supergravity by Bernard de Wit, Jens Hoppe, and Hermann Nicolai" at which point I start to suspect that this is all just made up technobabble.
"In a larger sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon"
True for an anti de Sitter space (thus ADS/CFT) but not for the one we live in which is a de Sitter space and lacks the requisite boundry. I wish someone could explain the relevance of ADS/CFT to this universe.
I once had the opportunity of being in a car alone with Juan Maldacena for an hour and asked him. He pretty much shrugged (probably meaning any attempt to explain that to me, a layman physics junkie, would be futile.) He's a really, really nice and personable guy so I'm sure that if there was anything I could have understood he would have tried.
Think of it this way de Sitter space is essentially analogous to living on a sphere. In that space any triangle on the sphere's surface has more than 180 degrees.
http://en.wikipedia.org/wiki/Spherical_geometry
In hyperbolic space any triangle on the hyperbolic surface has less than 180 degrees.
A sphere has no boundary (think invisible walls in video games). You can move over it for infinite time without encountering an invisible wall that says, you can't go further. Because it closes on itself. Contrast this with hyperbolic space, which must has such boundary, because it can't close on itself without becoming some other kind of space.
"The holographic principle is a property of quantum gravity and string theories that states that the description of a volume of space can be thought of as encoded on a boundary to the region—preferably a light-like boundary like a gravitational horizon. First proposed by Gerard 't Hooft, it was given a precise string-theory interpretation by Leonard Susskind[1] who combined his ideas with previous ones of 't Hooft and Charles Thorn.[1][2] As pointed out by Raphael Bousso,[3] Thorn observed in 1978 that string theory admits a lower-dimensional description in which gravity emerges from it in what would now be called a holographic way. In a larger sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon, such that the three dimensions we observe are only an effective description at macroscopic scales and at low energies."
So the analogy is that the field inside the volume can be completely described by some function over the bounding surface of the volume, similar to how the light field captured by a hologram is projected and recorded on a flat glass or film plane. I can visualize that pretty easily, but I don't know enough to tie that to some concrete relationship to the fundamental physical forces of the universe.