Holographic principle Definition and 18 Discussions

The holographic principle is a tenet of string theories and a supposed property of quantum gravity that states that the description of a volume of space can be thought of as encoded on a lower-dimensional boundary to the region—such as 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, who combined his ideas with previous ones of 't Hooft and Charles Thorn. As pointed out by Raphael Bousso, 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. The prime example of holography is the AdS/CFT correspondence.
The holographic principle was inspired by black hole thermodynamics, which conjectures that the maximal entropy in any region scales with the radius squared, and not cubed as might be expected. In the case of a black hole, the insight was that the informational content of all the objects that have fallen into the hole might be entirely contained in surface fluctuations of the event horizon. The holographic principle resolves the black hole information paradox within the framework of string theory.
However, there exist classical solutions to the Einstein equations that allow values of the entropy larger than those allowed by an area law, hence in principle larger than those of a black hole. These are the so-called "Wheeler's bags of gold". The existence of such solutions conflicts with the holographic interpretation, and their effects in a quantum theory of gravity including the holographic principle are not fully understood yet.

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  1. S

    I Multiple (Non-Interacting) Universes?

    Before anything, I would like to clarify that I am aware that this is speculative physics more than established mainstream physics (and Smoot is not claiming that his ideas are true). However I think that it is interesting to discuss these models even if they are not yet proven to be right. I...
  2. S

    I How many apparent horizons could the Universe have?

    I was reading a paper written by George Smoot [1], which assumes the holographic principle as true and conjectures that our universe would be encoded on the "surface" of an apparent horizon as the weighted average of all possible histories. In that way, there would be one world (or universe)...
  3. BiGyElLoWhAt

    B Looking for a specific paper on the Holographic Principal / Information theory

    The paper is reasonably old and was written as a phd thesis by (I believe) a man from china. It was basically the first paper on the subject and in it he effectively (from what I understand) dropped particles into a black hole, counting the information added, and saw that the black hole changed...
  4. nomadreid

    I What use is the AdS/CFT correspondence in a flat universe?

    All the accounts which I have read (and which are accessible to my limited knowledge of General Relativity and its mathematics) on the holographic principle says vaguely that the AdS/CFT correspondence is very enlightening, but with the caveat that, well, we don't happen to live in an AdS space...
  5. S

    A Is the Randall-Sundrum model background independent?

    Randall-Sundrum model (https://en.wikipedia.org/wiki/Randall%E2%80%93Sundrum_model) is related to string theory. String theory can be background independent (https://en.wikipedia.org/wiki/Background_independence): "String theory is usually formulated with perturbation theory around a fixed...
  6. S

    I Is the holographic principle based on fuzzy logic?

    Physicist Craig Hogan has proposed that the universe is based on holographic principle. To prove that the universe is a "hologram" he (and other physicists) have designed an experiment named "The Holometer" to measure quantum fluctuations that would become fuzzy at Planck scale...
  7. S

    A How does this study affect the holographic principle?

    In a recent study (https://phys.org/news/2018-08-flaw-emergent-gravity.html) it has been discovered an important flaw in Emergent/Entropic Gravity because it has been discovered that holographic screens cannot behave according to thermodynamics... But then, doesn't this also invalidate...
  8. nomadreid

    I ER=EPR baby steps: causation or not?

    The questions concern the extension of the holographic principle to the identification of a wormhole between two black holes with negative cosmological constant and an entangled pair on its boundary, included in the conjecture known as EPR=ER ( Maldacena, Susskind). I refer to...
  9. S

    A Could information in a boundary be modified once encoded?

    Could information in a boundary be modified once encoded in holographic principle? There are models of universes where holographic principle has a different correspondence (there is absolutely no reason to assume that this would hold true for all possible universes. You could have a universe...
  10. S

    A What does this article mean? (The holographic principle and M-cosmology)

    I was reading an article about holographic principle and M-cosmology and how could they be used to interpret QM mechanics. But there's a part where it talks about holographic principle in a strange way to me. What does this article mean with this?: "Since for the participant observer the...
  11. S

    A Information encoding in the Holographic principle

    Can whatever type of information be encoded in a boundary in holographic principle? in a question some years ago regarding holography (https://physics.stackexchange.com/questions/75436/are-stokes-theorem-and-gausss-theorem-examples-of-the-holographic-principle) It is said that AdS/CFT is the...
  12. S

    A Can a 3d holographic universe exist in 3d?

    In a holographic universe model, could our 3D universe be encoded in 3D and still be a holographic universe, instead of 3D information encoded in 2D space? Or is the standard model (non-holographic) of the universe already 3d information encoded into 3d space...
  13. Michael27

    B Can the Holographic Principle make predictions

    I have been following the online lectures of Leonard Susskind regarding the holographic principle and entanglement.see Holographic Principle Lecture Part2 The universe can be seen as two-dimensional information on a cosmological horizon. (see https://en.wikipedia.org/wiki/Holographic_principle)...
  14. nomadreid

    I Holographic principle versus no-cloning

    If I understand the holographic principle for black holes correctly (which is highly unlikely, but this is a start), the information of a particle falling into a black hole is encoded on the event horizon. But from the view of General Relativity, the particle will not notice a change upon...
  15. J

    Cosmology Book on Black Holes, Strings, AdS/CFT

    Hello, I would really like a book like Susskind's "An Introduction To Black Holes, Information And The String Theory Revolution: The Holographic Universe" but not so condensed. If you have anything to suggest please do so. Also, if you know of any book that contains any part of the above book in...

    B Is it possible Earth is a black hole?

    Yes I know. Sounds silly. I'm not a physicist, but it occurred to me to wonder: is it possible Earth is a black hole with data encoded in two dimensions on its surface? What would the proofs look like? Discuss.
  17. ohwilleke

    LQG has not been shown to violate the holographic principle

    Backreaction has the story: http://backreaction.blogspot.com/2015/09/no-loop-quantum-gravity-has-not-been.html debunking this article: Violation of the Holographic Principle in the Loop Quantum Gravity Ozan Sargın, Mir Faizal http://arxiv.org/abs/1509.00843 and also showing the authors behaving...
  18. Nim

    The Holographic Principle

    I first came across this concept in a Scientific American magazine. At the time it was nigh impossible to find much more information on it. Even now I am having a hard time wrapping my head around it. So I have a few questions. From what I understand, it basically says: Every single bit of...