# Talk:Holographic principle

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## Holographic Universe search go to Holographic principle

No it shouldn't. --Michael C. Price talk 18:49, 29 September 2009 (UTC)

Can we turn off the holograpic princible? Is it information imprinted on to a flat surface or is it information in an energy format, if so is it possible to turn that energy off?

I just had an interesting thought that I think could help a person grasp the holographic principle. Try to visualize 3-space as a gigantic sierpinski sponge (for those who aren't familiar with it: http://mathworld.wolfram.com/Tetrix.html ). The object *looks* 3-dimensional, but if you calculate its dimensionality, it's 2-dimensional. Also, it's worth noting that the little pyramids a sierpinski sponge is made of have 4 sides...analogous to the way a bit of information is encoded on 4 planck areas. Maybe it's just a coincidence, but I'd love to hear a physicist's take on this. - Waylon Rowley

The holographic principle is rather unintuitive, but I think I can picture it, if denser mass makes space more hyperbolic. Mind you, I don't really understand curved space very well yet. But in hyperbolic space, I believe the center of a volume is supposed to be closer to it's surface than in euclidian space. So as the mass gets denser, the center aproaches the surface. When it reaches critical density, the center *reaches* the surface (VERY unintuitive), and it becomes a black hole. Is this at all logical? Does dense mass make space hyperbolic? I know mass is supposed to bend space, but I don't know which way, positive (ball) or negative (hyperbolic), or some combination.

Some interesting thoughts, but I don't really understand what you're saying. I mean, space is not homogeneously curved in either direction, though you can approximate it as such depending on what your are talking about. I think you are perhaps speaking too generally? I mean, is the volume strictly hyperbolic, or are you dealing with some hyperbolic manifold embedded in some ambient space? I need some more orientation to understand the statement/question.
Anyway, I have a question to posit here. Is this idea restricted to dimension 3? -- and if not, then what is the boundary like? Moreso, why does information inherently carry mass? So, in other words, what is the inherent principle here that suggests that information has density. For example, how much does an infinite collection of ~0 energy photons (~0 frequency radio waves) weigh? Just trying to understand. Also, if i may, does the holopgraphic principle rely upon the information entropy hypothesis, or can they be thought of (formulated) separately? 66.141.54.43 05:17, 20 July 2005 (UTC)

Is this idea restricted to dimension 3? No. It is concretely realized in the AdS/CFT correspondence which is actually a higher dimensional correspondence. It is a relation between gravity in D dimensions and field theory in D-1.

Why does information inherently carry mass? Nobody knows. If information would ever be proven not to carry mass, it would be a problem for the correspondence.

An infinite collection of zero energy photons weighs nothing. On the other hand, it doesn't carry any information, because they are not localized. If you think of photons in a box, the minimum wavelength of a photon is the length of the box (well, twice the length of the box), which means that the photon has a minimum energy. It turns out that photons in a box seem to conspire in just such a way to preserve the holographic principle, but nobody really knows a deep reason why.

I think the holographic principle can be formulated seperately from these entropy bounds, but they are logically connected, because you need the entropy bounds to remove degrees of freedom from the gravity theory: that's how you lose a dimension, because the vast majority of states in the field theory are not accessible, as they would form black holes.

This is an article I would really like to expand, but I don't have the time at present. The review article by Bousso is great, but technical. –Joke137 18:46, 20 July 2005 (UTC)

Clearly I should probably just read the article, but a quick comment/question. So, in other words, we are relying fundamentally on the information entropy by this logic. For example, yes, nonlocal waves at ~0=E could carry information on the length scale of the universe, if you allow them to be out of phase with each other for example. Maybe impractical. I mean, I am trying to understand the base element construct. So clearly we are in some Boolean algebra over some profinite field? Forgive my ignorance, I tend to think in field extensions over Magmas too often I guess. Also, I do not understand this statement: "Is this idea restricted to dimension 3? No. It is concretely realized in the AdS/CFT correspondence which is actually a higher dimensional correspondence. It is a relation between gravity in D dimensions and field theory in D-1." I mean, dimension D<=26, I pressume? Which is fine. But then, what does the boundary look like on S^7, for example? 128.62.97.227 23:18, 20 July 2005 (UTC)

For the first question, I don't understand much of what you're saying about profinite fields, etc, but the basic argument is in the Bousso article, II.C.3. It turns out that for a gas of radiation, the so-called Bekenstein entropy bound is closer to being saturated for smaller boxes. The review says that the bound isn't particularly well defined, and proposes an alternate bound, called the covariant entropy bound. As for AdS/CFT, I think it is normally realized on ${\displaystyle AdS_{5}\times S^{5}}$ (although the S5 could be any compact five dimensional manifold and really it could be ${\displaystyle AdS_{d}\times S^{10-d}}$), and the boundary looks like ${\displaystyle M_{4}\times S^{5}}$, where ${\displaystyle M}$ is for Minkowski. If you object that anti-de Sitter space doesn't have a boundary, well, it's the conformal boundary. –Joke137 23:49, 20 July 2005 (UTC)

I see. So sorry, I guess I should, more correctly, say profinite topology. Sorry about that. But no, so yeah this AdS/CFT correspondence is interesting, and I probably should go read it (I keep saying that ;)), but here, this is a gendanken for the idea. So even in S^5, if you think of the construction of the tesseract from a cube. You have to extend each vertex, but then maintain the 90 degree angle, which bends or twists out of the parameter 3-space. So, likewise, intuitively, S^5 is going to bend and twist (possibly back on S^2) from the point of view of the intuition contrived in 3-dimensions. So, the boundary may striate and wrap back on S^2. So I've heard of strings talked about in this way. But now, think of your room as S^2, but bounded in some way by ${\displaystyle S^{5}}$. Well, then, the boundary is not strict in the same sense, no? So what about information packets acting (in the modular sense) as simple fibrations over S^2? Well then, your base elements are masked in the set X, and you can say that not only is your topology not profinite, but that in fact you are on an ultrafilter over X. No?

I'm having trouble reconciling a pair of statements. The author starts the paragraph with: "Black holes become more disordered as they absorb matter." Then the author ends the paragraph with "Black holes are thus the most disordered objects in the Universe." These two statements seem to contradict each-other.--Paul 21:30, September 11, 2005 (UTC)

The total entropy increases when the black hole expands by absorbing matter. It's not an addition of entropies. --Pjacobi 07:39, September 12, 2005 (UTC)

I think references [1], ... in article don't work, is that correct?

The relationship to the Sierpinski Sponge is misleading. Consider the Menger Sponge, a similar construction using a cubic geometry that has dimension of about 2.7. Unless I'm missing something entirely, the fractal dimension of the Sierpinski Sponge has nothing at the moment to do with this concept (though I concede that there is research connecting the two--consider [1]) SamuelRiv (talk) 07:58, 21 November 2007 (UTC)

References

1. ^ Bekenstein, Jacob D. (January 1981 (Revision: August 25, 1980.)). "Universal upper bound on the entropy-to-energy ratio for bounded systems". Physical Review DD. 23 (215). Check date values in: |year= (help)

## Article needs more on the AdS/CFT correspondence

Currently the article is almost entirely about black holes and the Bekenstein bound, but the essence of what physicists mean by the "holographic principle" goes beyond this, and says that the dynamics inside any volume should be understandable in terms of the boundary of that region or some corresponding region in a space with a different number of dimensions. As I understand it, the key piece of evidence for this is the finding in string theory that there is an exact equivalence between the dynamics predicted by string theory in a region of 5D anti-deSitter spacetime, and the dynamics predicted by ordinary quantum field theory on the 4D boundary of this region (the CFT stands for 'conformal field theory', which I gather is a specific class of quantum field theory). For a good layman's explanation of this stuff, see the Scientific American article by Bekenstein that I added to the external links section.

Without this sort of generalization, it seems like the holographic principle would be nothing more than a synonym for the Bekenstein bound, and most of the article at present is just duplicating stuff already seen in the Bekenstein bound article. If nothing else, the article at least needs to make it clear that the holographic principle is a hypothesis which goes beyond just talking about the boundaries of black holes. Hypnosifl 20:34, 2 December 2006 (UTC)

## Note about Scientific American Article

That link has a crackpot article about LSD research, past lives, and psychic claims that was just slapped on the end without notice of any kind. It would seem that a supporter of this latter essay used the credibility of Scientific American parasitically. The link I put in its place lacks a few sentences at the beginning, but seems to have all the rest. Scientific American article [New York] 12:40, August 13, 2007]

## Bekenstein Bound

I removed a statement saying that the bound of entropy in space is Bek. Bound. The Bekenstein bound - which is a bit controversial - is something else, a bound on the entropy of an obect of a given size AND energy. S<A/4 is now part of the Covariant Entropy Bound (aka Bousso Bound).PhysPhD 22:33, 17 April 2007 (UTC)

## Error found (bits and nats)

"One bit equals 2 nats" is false and must be fixed.

Done --Michael C. Price talk 00:31, 1 July 2007 (UTC)

## Feedback

This reads as a great science article and as a lay person with some grasp of physics, it makes no sense to me. I would encourage knowledgable people to re-write it so that it as encyclopedia article- accesible to everyone. Sethie 16:45, 13 August 2007 (UTC)

Agreed...I think the SciAm article (as stated above) is a good layman's reference, was written by Wheeler's student Bekenstein, and I will take a stab at paraphrasing in attempt not to re-write, but to add Beckenstein quotes here and there explain. riverguy42 aka WNDL42 (talk) 16:57, 30 January 2008 (UTC)
Second update to "High level overview just now, comments and suggestions? WNDL42 (talk) 17:45, 7 February 2008 (UTC)

Hi, I am adding this comment here as the title is just "feedback".

In the following statement the example seems to be anachronistic. As I understand, from the paragraph before the mentioned line, Shannon wrote the theory in the 1940´s and as you read the line below it is somehow implied that he was thinking in the quantity of the information that an email message carries when he must probably was thinking on letters or telegraphic messages.

"Shannon's efforts to find a way to quantify the information contained in, for example, an e-mail message, led him unexpectedly to a formula with the same form as Boltzmann's"

From an encyclopedic point of view this is misleading, as an analogy or example it will need to be rewritten to avoid the idea that Shannon was sending emails on 1948. Editions that may work:

"Shannon's efforts to find a way to quantify the information contained in, for example a letter, led him unexpectedly to a formula with the same form as Boltzmann's"

or

"Shannon's efforts to find a way to quantify the information contained in, for example in modern times e-mail messages, led him unexpectedly to a formula with the same form as Boltzmann's" — Preceding unsigned comment added by Mauvarca (talkcontribs) 05:16, 7 July 2012 (UTC)

I agree that the example is anachronistic and ahistorical, clearly. My understanding is that Shannon was working with encoding communications signals (historically relevant examples are Morse Code, FM and AM signals). I don't see any reason to dumb down the article to the point at which it becomes silly. Its like using GPS satellites as an "example" of what Einstein was working on 100 years ago.Abitslow (talk) 22:34, 1 March 2015 (UTC)

## Strong & Weak forms reversed?

Yo dawgs: it seems as though the strong and weak forms of the principle have been swapped! But I don't really know for sure. It just seems that way. CKL this signed entry was misinterpreted as unsigned by some bot several hours after everyone stopped caring

I thought so too, the strong form was both weaker than the weak form and not particularly illuminating, but I'd never heard of this before. The "weak form" is the only version that I know. I mean, in AdS/CFT, all the physics is contained in the boundary theory, there is no extra information, so there can't be any objective meaning to a statement like "there is still a particle behind the screen projecting its information", that's just a philosophical argument about whether something "exists", not a statement about the mathematical description of the object. Perhaps that section should be erased.Likebox (talk) 19:48, 13 August 2008 (UTC)
I agree. I'm going to go ahead and delete the section.PhysPhD (talk) 22:20, 13 August 2008 (UTC)
If anyone wants to see the old section, the diff is here.

## The Black Hole War

I would like to suggest adding a book to the references: "The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics“ by Leonard Susskind. This book gives a good overview and history by one authors of this priciple. —Preceding unsigned comment added by Leifshu (talkcontribs) 17:01, 17 August 2008 (UTC)

## possible evidence of holographic universe

http://www.newscientist.com/article/mg20126911.300-our-world-may-be-a-giant-hologram.html?full=true --Wongba (talk) 18:55, 15 January 2009 (UTC)

The connection of space-time "graininess" far above the Planck-scale, if I understand it correctly, is a forehead-slappingly obvious conclusion from this, it's just that nobody ever thought of it before. I suggest a reference to the GEO600 "noise-story" be added to this article. --dab (𒁳) 19:09, 24 January 2009 (UTC)

as an afterthought, there may be a new eschatology in this: the supposed "blur level" at 1E-16 m is disconcertingly close to the atomic scale. What if the universe expands any further, and the blur should rise to above atomic level? Will the universe die a "blur-out" death of being eaten up from the inside? Death by out-of-memory error, so to speak? --dab (𒁳) 19:56, 24 January 2009 (UTC)

I must read the paper and see how they derive this graininess -- IIUIC the holographic principle is subsumed by the more general Bekenstein bound, which requires the information density scales inversely with the scale of the universe -- which seems weird until we recall that, holding the total energy constant, that the matter density scales with the inverse cube of the scale factor. So there is more information per particle as the universe expands -- so no "blur out".--Michael C. Price talk 20:29, 24 January 2009 (UTC)

I do not understand your conclusion of "there is more information per particle as the universe expands" as a consequence of any of this. My understanding of this is that information scales with the sphere surface, not the sphere volume, and since the surface will scale more slowly than the volume (no matter how many dimensions you are looking at specifically), information density in the volume will decrease if you assume information density on the surface remain constant. The rest is a back-of-the-envelope calculation assuming that the "graininess" on the surface is limited by the Planck scale. --dab (𒁳) 13:16, 25 January 2009 (UTC)

We agree that information density is decreasing ; my point is that it is decreasing less quickly than particle density, hence "there is more information per particle as the universe expands"; not perhaps a very profound observation, but sufficient to avert "blur out".--Michael C. Price talk 16:55, 25 January 2009 (UTC)

## Planck length and the end of the world

Michael, according to your scenario, the vacuum expands (the Planck length increases), but the protons become more interconnected (informed) and thus avoid magnification and blurring. Thus the Planck length will eventually become equal to the radius (the Compton wavelength) of the proton, at which point the protons will become delocalised (dissolved in the ambient vacuum):
"In Section 3 we saw that at a time n = N (where n is the time in atomic time units, and N is the baryon number of the Universe), the evolution of the Universe reaches a state at which the Planck length is equal to the Compton wavelength of the proton. In other words, the scale factor of the Universe has evolved to the point where the radius of the proton exceeds the Schwarzschild radius corresponding to the proton mass. At this point the Universe effectively comes to an end as all protons simultaneously collapse into micro Black Holes." The ultimate fate of the Universe by Robin Booth (Theoretical Physics, The Blackett Laboratory, Imperial College, London)
The radius of the proton experimentally determined by Robert Hofstadter is 7 × 10-16 m."[2]
The Planck length inferred by Craig Hogan from the results of the Fermilab experiments is approximately equal to the radius of the proton: "So while the Planck length is too small for experiments to detect, the holographic "projection" of that graininess could be much, much larger, at around 10-16 metres."[3]
THEREFORE, THE WORLD IS ABOUT TO END.
During the transitional period immediately preceding the final dissolution of the protons, they will be in a semi-delocalised state, which will allow teleportation and psychokinesis. The semi-delocalised state of the protons means that the whole universe will be governed by a single wavefunction—the Universal Wavefunction, God. In religion, this transitional period before the end of the world is known as the Millennium. Systemizer (talk) 14:10, 19 March 2010 (UTC)

There are already particles where its Compton wavelength and Schwarzschild radius become approximately equal, its called wave-particle duality. It would approximately have a planck mass and radius of a planck length.

Furthermore, Planck Units are the smallest observable units, just within the explanation by relativity and just outside the need for quantum mechanics. EnemyTortoise15 (talk) 05:23, 01 May 2017

Uhhh.... No. Jersey John (talk) 10:21, 22 November 2011 (UTC)

## deWit/Hoppe/Nicolai Matrix Models and Matrix theory

This is a great reference, and it should be mentioned, and I haven't read it all yet. But my first impression after a cursory glance is that it is not completely fair to claim full priority for the earlier authors for the matrix formulation. But its unbelievable that they got so close so early, and they should definitely be mentioned.

The question is the physical interpretation. In the earlier paper, there's an interpretation that a certain large N limit of the matrix model will reproduce the membrane dynamics. I don't think you can say that this includes the holographic principle implicitly, although it might. It is motivated by string expansion, and this expansion contains some stunted version of holography inside, so it's hard to say "no this isn't holography" or "yes this holography" for sure.

The motivation is discrete chopping up of the M2 brane to get a good quantization, which does not give confidence that the matrix formulation will include the fivebranes and gravitons as well (but maybe the original authors understood it better). You could only be sure that everything is included by the holographic principle and by having a good black hole interpretation for the objects that are carrying the matrices around. That essential physical insight, that the D0 branes can serve as the "string bits" (or "membrane bits" in this case), came in 1995 from BFSS, immediately following Witten's famous analysis of D0 brane spectrum in IIA, and the D0-brane action was a reduction of more complicated D-brane actions in a light-cone way that has a physical interpretation which allows you to be sure that you can really reconstruct all the objects from the large N matrix model, and that the finite N part is also physical, not just the limit. This is exactly AdS/CFT, but a little earlier.

I have to admit that the BFSS paper seemed like magic to me. I couldn't understand how something like that could ever have been dreamed up. This earlier reference helps a lot to understand how this type of magic works. So maybe it should read "following an approach pioneered in early work of deWit Hoppe and Nicolai, BFSS were able to intepret the matrix models proposed by the earlier authors as holographic actions for a physical black hole type in string theory and thereby give the first arguments that these form a complete nonperturbative formulation of M-theory."

There's also the discrete string-bit approaches, which led to other matrix models in low dimensions. Maybe these should be mentioned as precursors too.Likebox (talk) 20:34, 20 May 2009 (UTC)

## 86 't Hooft work

The best reference for 'tHooft's ideas in a form closest to string theory is the stuff he did in the 80s regarding the black hole S-matrix and the deformation of the horizon for an infalling particle. One of these papers is reprinted in "Under the Spell of the Gauge Principle", and another is in some issue of Nuclear Physics B. The Nuclear Physics B article is better than the 1993 article, in my opinion, because it includes the "imaginary action" string action for radial black hole deformations from the analysis of small body impacts. While this is not precisely modern, its probably slightly wrong in details because the black hole is thermal, its close enough that the modern picture can be deduced from it. I don't know whether there is a good freely available link to these classic papers.Likebox (talk) 18:47, 27 May 2009 (UTC)

The current text suggests that Bekenstein's result of black-hole entropy being proportional to area (which, by the way, if true, then holds independently of the units chosen, Planck areas or ploughgates) was derived from an upper bound on the entropy in a region of space, and that this was published in:

Bekenstein, Jacob D. (January 1981). "Universal upper bound on the entropy-to-energy ratio for bounded systems". Physical Review D. 23 (215): 287–298. doi:10.1103/PhysRevD.23.287. Unknown parameter |month= ignored (help)CS1 maint: Date and year (link).

However, this publication assumes the Bekenstein–Hawking formula S = A/4 for black-hole entropy to be known. Bekenstein introduced the concept of black-hole entropy as the measure of information about a black-hole interior which is inaccessible to an exterior observer and derived SA already in:

Bekenstein, Jacob D. (1973). "Black holes and entropy". Physical Review D. 7 (8): 2333–2346. doi:10.1103/PhysRevD.7.2333. Unknown parameter |month= ignored (help).

I'm not sufficiently familiar with the physics to confidently make the requisite changes myself; in particular, I'm not sure I've fully grasped the relevance of this material for the holographic principle.  --Lambiam 18:29, 11 September 2009 (UTC)

Without looking at the sources I think you must be correct from the dates alone. Bekenstein made his initial conjecture about the proportionality between S and A before Hawking came up with the exact answer.
I've added a sentence to the lead making the relevance of black hole thermodynamics to the holographic principle a bit clearer. --Michael C. Price talk 19:07, 11 September 2009 (UTC)

## Holographic Universe and Spooky Action at a Distance

Would the Holographic Universe be an explanation for quantum entanglement? It strikes me rather simplistically that items can interact at a distance if they are really not at a distance, but only appear to be so - e.g. the location of the 'emitter' is given, the emitted particles appear to diverge, but in the "superbrane" they do not diverge until they are disturbed on a "superbrane" level. Until that point it should appear to us that finding state A of one "causes" the other to take on state B, while in reality you have simply pulled A out of an invisible bag meaning that B must remain. Could someone comment?158.143.136.205 (talk) 14:45, 29 October 2009 (UTC)

See some of the (mostly rejected) work of David Bohm - http://en.wikipedia.org/wiki/Implicate_and_explicate_order_according_to_David_Bohm Regardless of how deeply the original mistakes and misinterpretations in the creation of the theory may or may not cut into its conclusions, I find it quite an interesting read! Also quite interesting is the very different verbal attitude and points of view on this article, in comparison to the article on Bohm's Holographic_paradigm --80.6.149.158 (talk) 14:42, 21 March 2010 (UTC)

## Is this correct??

In this article it says that the holographic principle implies that "volume is illusory". Wouldn't it be more accurate to say that space becomes emergent, so that space is illusory? (or at least, not fundamental) I really don't think I understand this stuff, but it doesn't seem to jive on a conceptual level with what I've read before. Danski14(talk) 22:32, 8 September 2010 (UTC)

## Information

There is a fundamental flaw, possibly, in this interpretation of the relation between entropy and information. It is said that the entropy is proportional to the amount of information. However, the Shannon information is a measure of the amount of information MISSING in a message = uncertainty. This would imply that the amount of information (in the form of bits or nats) on the screen is actually decreasing (lost) as time evolves and the entropy increases, not the other way around. —Preceding unsigned comment added by 217.128.46.38 (talk) 18:00, 16 November 2010 (UTC) Magnaquantum (talk) 12:14, 20 November 2010 (UTC)

These are not in conflict. Per both entropy (information theory) and entropy (statistical thermodynamics), the entropy of a system is the amount of information encoded within the parts of the system state you're calling "missing information". Calling this "missing" is a misnomer, as the information is present. The "non-missing" information in your terms would be the macroscopic properties properties of a system such as temperature and pressure of a gas (for thermodynamics) or length and total number of 1s and 0s (for a bit stream). The "missing" information is encoded in a detailed description of the system's microstate (for thermodynamics) or the actual pattern of bits involved (for a bit stream). "Entropy" in this article is referring to the amount of information encoded in the choice of microstate. --Christopher Thomas (talk) 07:39, 21 November 2010 (UTC)

Well, something may escape me, quite likely, but I still argue that this interpretation that an increase in information leads equally to an increase in Entropy is flawed. Take the example of a colour photograph, a picture, the old fashion argental one. It contains billions of “pixels” and the amount of information on it is very big indeed. Now, place the photograph outside, exposed to the elements. The rays of the sun will bleach the colours and rain and wear erodes the picture and with time it will become increasingly difficult to see what the picture originally looked like. The information is lost. Simultaneously, the Entropy increases = proportional to the now missing information (according to some algorithm). The same should be true to a holographic picture or screen, wherever it may reside. Magnaquantum (talk) 12:35, 22 November 2010 (UTC)

You are thinking of information in human terms (a picture), not in terms of the number of microstates. The number of arrangements of atoms in which an uncorrupted photograph exists is much smaller than the number of arrangements of atoms in which a damaged photograph exists. To put it in terms of information storage, the universe is encoding information in exactly what damage occurs to the photograph. It isn't information we care about, but it's still there as part of the system microstate. As there are many more possible damaged phorographs than possible undamaged ones, the amount of information present (determined by selecting which damaged phorograph exists) has increased. --Christopher Thomas (talk) 19:21, 22 November 2010 (UTC)

Hello again- this is getting more interesting by the minute. First, the question of whether information exists also without me, a human (or any other so called conscious receiver) is indeed a philosophical question, which merits a separate discussion. Second, we are in full agreement that, according thermodynamic entropy concept, entropy is proportional to the number of degrees of freedom, or, with your terminology, number of arrangements of “microstates”.. Just to make things clear, a given surface (our picture) can harbour only a given number of “atoms”, Plank lengths or pixels or whatever discrete unit we decide to use. The number of positions of these is constant, regardless of in what order they are arranged. For the arrangements to have an effect on entropy, it would be required that we study one specific arrangement, i.e. the original one, which gave us an image, containing the information. When the image deteriorates, the “atoms” or pixels change position, whilst leaving the total number of positions unchanged, whereas the information is corroded and the Information Entropy increases. In this respect, I fail to see that Entropy = amount of Information (the more Information-the more Entropy). On the contrary. It is the other way around. Entropy = Uncertainty. Thus S= lack of Information of the nature of the original “message”. Lastly, your arguments seems to indicate that the amount of information, over which information is lost or missing, is increasing. Magnaquantum (talk) 16:01, 26 November 2010 (UTC) Magnaquantum (talk) 06:43, 27 November 2010 (UTC)

Entropy has been described by L.Susskind as "hidden information". It is a counter-intuitive fact (accepted by virtually all physicists; or rather corollaries of this 'fact' are generally accepted as being required for Physics to "work") that for ANY isolated system, the amount of information is constant. That is: information can be neither created nor destroyed. (As an arm-chair observer, I find this hard to buy, but there you go). Entropy is the information which isn't 'available', and can be described as the number of microstates which are indistinguishable from the given state divided by all possible states. Entropy is a better term than "information" because it is more specific. If someone uses the term "information" they may mean the ensemble of possible states OR the ensemble of indistinguishable states OR the total ensemble of possible states less the indistinguishable states OR.... They're completely different things. You can see how using the term often causes confusion. Your example of a photograph is fundamentally flawed: the weathering you describe is only possible in an open system. You failed to consider the ENTIRE (isolated) system (you MUST include the sunlight and rain, etc.!) The fact is that cause and effect require that any change to one silver particle (say) by one photon, could be "run backward" with the colloidal particle of silver emitting a photon and recovering its information (image pixel). IOW, the information encoded in the photo becomes encoded in the motions of the atoms and photons which interact with it. The information is NOT (in some theoretical sense) lost, but becomes hidden or unavailable. Its a subtle concept. It is even MORE difficult when dealing with quantum mechanics and the uncertainty principle. That's too complex to deal with here.(And I am not competent to deal with that, anyhoo.) And of course, talking about a "true" "isolated system" which isn't affected by external gravitational forces is fantasy...Abitslow (talk) 23:30, 1 March 2015 (UTC)

## Is this fact or conjecture?

"In a given volume, there is an upper limit to the density of information about the whereabouts of all the particles which compose matter in that volume..."

In its context in the article, the above reads like a statement of known fact. Is this actually the case, or is it really just an unproven claim of the theory? 86.183.171.111 (talk) 23:04, 3 February 2011 (UTC)

This is fact (the Bekenstein bound). If you see a way to make that clearer in the article, by all means tweak the phrasing. --Christopher Thomas (talk) 23:29, 3 February 2011 (UTC)
Thanks! I'm a bit puzzled, because does that not imply that space can't be continuous (else there would be an infinite number of possible configurations of particles)? And I thought that the question of whether space is continuous was unresolved? 86.183.171.111 (talk) 02:20, 4 February 2011 (UTC)
The uncertainty principle takes care of that. Without it, you could specify the location of a particle to arbitrary precision in continuous space, and store an arbitrarily large amount of information in that value. With uncertainty, you can still do that, but would have to make the momentum arbitrarily large (or at least the uncertainty in the momentum arbitrarily large) in order to do so. If you put a bound on both the volume and the momentum you're willing to deal with, you end up with a maximum amount of information you can represent (the Bekenstein bound).
The same applies if you try to use more than one particle (energy, mass, or momentum of the collection goes to infinity as the amount of information goes to infinity). --Christopher Thomas (talk) 05:19, 4 February 2011 (UTC)
I get it. Thanks for the clear explanation. 81.159.78.94 (talk) 12:28, 4 February 2011 (UTC).

## The shape is now a physical concept?

"That volume itself is illusory and the universe is really a hologram which is isomorphic to the information "inscribed" on the surface of its boundary"

Yes, in fact, we call this a shape and the Latin etymology of the word information means shaping or creating a shape.

We remark, indeed, at the quantum level, the macroscopic volume is an illusion; emptiness is the only true reality. Even universes composed of compact balls attached to each other obey to the holographic principle.

The introduction of the concept of "information" into physics is revolutionary but the shape... it has always existed in front of all physicists.

It's like the color of the wings of flies that remained hidden for 300 years just because we looked them on white cards... We had to watch them on black cards...or a black hole.

--Nipou (d) French Wiki — Preceding unsigned comment added by 96.20.8.46 (talk) 21:25, 19 June 2011 (UTC)

I don't see the relation you make with the concept of shape. (That would be more inline with a theory with conformal invariance.)TR 10:12, 20 June 2011 (UTC)
He appears to be confused about what the holographic principle actually is. From what I can tell, his argument boils down to "the holographic principle describes a surface that bounds a volume, but topologists have been doing that for ages, so it's trivial". This doesn't demonstrate any understanding of the key points of the holographic principle, which is why I didn't consider it useful to respond to his/her original post. --Christopher Thomas (talk) 22:39, 20 June 2011 (UTC)

## Mass, energy and shape

The great unification will be between theory of computability and physics. The mass is the amount of information stored in the space while energy is the potential for achieving deterministic phenomena (potential of calculation). Their strict equivalence is simply the consequence of the fact that there is equivalence between information (product of a deterministic phenomenon) and computational complexity (in the sense of Kolmogorov). The shape (equivalent to the mass) is simply the means by which the universe store information in space. Every phenomenon on the mass (inertia and gravitation) is, by logical consequence, the result of the constraints of representation of information in space. - Nipou (d) French Wiki October 15, 2011 at 17:28 (CEST)

Thus the sphere is the level zero of shape, any injection of energy absorbed by this sphere will be transformed into shape. For example, one mole of spherical metal is not the same mass that this same mole representing a Michelangelo statue (small variation in the level of mechanical energy). This variation of mass is also proportional to the algorithm of Kolmogorov complexity necessary to achieve this formatting- Nipou (d) French Wiki October 15, 2011

## Schrödinger's cat

Question: The limit to the density of information does not give us a formal limit to the largest buildable Schrödinger's cat? It would thus be a constraint on quantum entanglement.

--Nipou (d) French Wiki — Preceding unsigned comment added by 96.20.8.46 (talk) 21:33, 19 June 2011 (UTC)

## Bits or qunats?

I'm only a maths & theoretical physics undergrad, so I have no in-depth knowledge on this topic. I noticed the section Limit on information density says: “The holographic principle thus implies that the subdivisions must stop at some level, and that the fundamental particle is a bit (1 or 0) of information.”. Should this be qubit instead of bit? Wouldn't a quantum theory of thermodynamics presumably use qubits instead of bits? IMHO the use of "bit" in this context seems to me at odds with quantum mechanics and quantum information theory, which are surely essential to any fundamental description of reality, especially of the sort described in the above quote.

On a separate note, I wonder whether the more scientific terms "embedded" or "encoded" (the latter's used elsewhere in the article) might be more appropriate than the rather poetic terms "painted" and "inscribed" that the article occasionally uses: i.e. “the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon” and “the universe is really a hologram which is isomorphic to the information "inscribed" on the surface of its boundary”. IMHO it would also make the article more consistent in its use of terms as well as sounding more encyclopedic.

Anyway, just my two cents. Annoyamouse (talk) 20:45, 2 December 2011 (UTC)

On further thought, shouldn't this be a "qunat" (i.e. a quantum nat) since “The nat is the natural unit for information entropy.” (see Nat (information))? Personally, I've never seen the term "qunat" used on Wikipedia, though I guess it's just a special case of the qudit such that d = e. However, IMHO this seems to me to be the relevant unit of measure for what the article text is describing. As I'm only an undergrad, and have no knowledge of this field, it would be interesting to get an expert on this topic to give some feedback on what the correct unit is. By the way, I've retitled the section heading to "Bits or qunats?" instead of "Bits or qubits?" to reflect this second post. Annoyamouse (talk) 02:09, 7 December 2011 (UTC)

## All physics is two-dimensional.

Equations are written on, like, paper and stuff. 192.139.122.42 (talk) 22:41, 24 October 2012 (UTC)

you need better drugs yours are weak — Preceding unsigned comment added by 88.108.239.94 (talk) 01:53, 28 October 2013 (UTC)

## Hogan's Holographic Noise

I've recently edited this article, because of the undue weight given to Craig Hogan's claims. It is not justifiable to associate Hogan's claims with the whole holographic principle. If we leave aside the one self-cite and the 4 cites by experiments, this paper has earned exactly two citations since 2009, neither of which lend any credence to the idea that Hogan's idea is relevant to the whole holographic principle. In particular it doesn't seem to have anything to do with string theory, which makes the relevance of his claims for this page especially doubtful. Isocliff (talk) 18:50, 8 April 2013 (UTC)

## Recent Hyakutake Papers

Greetings, I find this fascinating. Apparently two papers came out in Japan recently which lend some mathematical plausibility to this theory. Someone smarter than me would have to do the heavy lifting of integrating the information into this page: http://www.nature.com/news/simulations-back-up-theory-that-universe-is-a-hologram-1.14328 Thanks! Joel J. Rane (talk) 10:00, 13 December 2013 (UTC)

Hi Joel, do you think I should add more information or is it comprehensible as it is? I can't tell. Thanks! (talk) Alma 12:52, 20 December 2013 (UTC)

## Recent Work

I question the wisdom of using "Recent" as a section title. It isn't a very good idea, unless this page is being frequently monitored and updated. What was recent in 2014 is going be NOT recent in a couple of years. I also question the relevance of the information in the section. A computer model of a Universe which isn't our Universe is hardly evidence AND CERTAINLY NOT EVIDENCE OF WHAT IS "TRUE"!! I'm out of my depth here, but our Universe is NOT AdS/CFT, is it? (I just read that Wikipedia article, which makes that very clear.) Somebody apparently believes that if the "right" result is obtained from a "toy model", then we can quote it as evidence. Rubbish. I don't see how it is even suggestive, since the holographic principle must at least be nearly as consistent as the theory (and speculations) used to obtain it in the first place, right? Starting with it, and modeling a toy Universe, is hardly meaningful. (Not saying it isn't worthwhile, but only to advance THE EXPERTS understanding. It doesn't significanly add to what we know. I think its counting angels dancing on the head of a pin: only of interest to fanboys and experts.)Abitslow (talk) 23:49, 1 March 2015 (UTC)

## Remove string theory primacy

The categorization of the article, and the introduction, talk a lot about string theory, as though the most important thing in the article is the relationship of the ideas to string theory. The rest of the article seems to say nothing at all about string theory. It looks like the results may be independent of string theory. If so then Occam's Razor tells us we should simplify by removing string theory from the central discussion. String theory could be perhaps referenced as a footnote to the article - nothing more. — Preceding unsigned comment added by 54.240.196.169 (talk) 08:15, 28 April 2015 (UTC)

## Assessment comment

The comment(s) below were originally left at Talk:Holographic principle/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

 It seems to me that if indeed the Holographic principle is a candidate for, or is an underlying basis of a "Theory of Everything", that it's importance should perhaps be "high" as opposed to "mid". Just curious about other opinions. WNDL42 (talk) 12:55, 17 March 2008 (UTC)

Last edited at 12:55, 17 March 2008 (UTC). Substituted at 18:10, 29 April 2016 (UTC)

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## What does this sentence mean ??

Here is the start of the second paragraph of the article. This sentence seems illogical to me. Can someone who knows what this is supposed to mean break it down in some way please?

"In a larger sense, the theory suggests that the entire universe can be seen as two-dimensional information on the cosmological horizon, the event horizon from which information may still be gathered and not lost due to the natural limitations of spacetime supporting a black hole, an observer and a given setting of these specific elements,[clarification needed] such that the three dimensions we observe are an effective description only at macroscopic scales and at low energies." — Preceding unsigned comment added by 82.72.139.164 (talk) 03:31, 20 June 2017 (UTC)

## If the holographic principle is true a classic computer may mimick a quantum one

Some have tried to create pixelated Bloch-like spheres, wired with many others - this requires a humongous amount of all possible connections; also that generates quantization noise, because the actual Bloch spheres aren't pixelated.

• this is a major question - if the holographic principle is true, then a classical computer may mimick (with bigger data) the quantum phenomena (it's not answered yet - some tried to use a noise generator - also we have to mimick all the quantum behavior, even the percentages of random non-entangled results versus random and entangled results) — Preceding unsigned comment added by 2A02:2149:8227:F600:2056:F713:B40A:C68E (talk) 00:33, 12 May 2018 (UTC)

## As pointed out

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.

Wearing my linguistic hat for a moment, the scope of this modifier is ambiguous. It could apply to the proposition that Thorn observed something in 1978 (or that Thorn observed something, not necessarily in 1978) or it could apply to how "string theory admits" or merely to the "lower-dimensional description" on its own terms, without necessarily going so far as to posit that "string theory admits" this.

Sentence modifiers do so love impersonating lazy, hazy writing. Furthermore, it glides unctuously over such details as when Bousso pointed this out, and to whom, and if he pointed it out to anyone important, as something thought to be important at the time, why he's now being tucked into this sentence as a murky afterthought. — MaxEnt 14:40, 16 December 2018 (UTC)

## Information is in superposition in 2D on the black hole hairy sphere, and inside

The information is not in both the 2D black hole sphere and the interior of the black hole.
It is in superposition and decides where to be materialized/reified/objectified after the measurement.
Measurement is to hit stuff with stuff; so natural "measurements" occur, because true black holes are hairy/imperfect and turbulent.

The higher the energy pressure, the more likely it gets to detect the particle moving afar from the holographic horizon it belonged. For a black hole the pressure is at the maximum. The "measured" particle appears as afar from the horizon as the energy of the measuring/hitting particle was. To measure = to be someone and to hit someone else. (Thus almost no particle becomes reified exactly at the horizon, because energies of measuring thrashers is usually high..... That's an issue. According to the standard view, no particle can ever reach an abolute zero energy when it acts a thrashing measurer of other particles in a black hole, so we have an eternal back and forward motion of particles which bounce off the black hole and immediately re-enter because all paths lead to the black hole... almost all, 99,999999...% with some Hawking radiation escaping. Actual black holes aren't as perfect as taught in universities.)

— Preceding unsigned comment added by 2a02:587:4111:8300:6c10:9423:59d1:91bc (talk) 09:14, 11 April 2019 (UTC)

## The black hole is a phenomenon which has components

It's constituents:

1. 1/10 of its mass (that is not a constant, it changes with the mass of the black hole) is a conveyer of particles relatively near the black hole atmosphere (billions of kilometers and more); particles collide with other particles and re-enter in a vortex and not in a straight path the surface
2. most of its mass, its dark energy; Dark energy is a phenomenon of space. It is not a weird particle, but a relativistic mechanism of spacetime. The extremely big black holes are 50/1 dark matter/matter and even more.

— Preceding unsigned comment added by 2a02:587:4123:6d00:6c10:9423:59d1:91bc (talk) 09:29, 11 April 2019 (UTC)

## The problem with non defining the lower possible amount of information/holographic information content

A system's lowers possible informational density is extremely crucial. If you try to delete or spread afar information at a very fast pace, the whole system explodes. Big Bang causality is linked to that. — Preceding unsigned comment added by 2A02:587:4102:B000:DC36:6B05:57BD:8DE7 (talk) 15:23, 26 April 2019 (UTC)

It appears that quite a few unusual ideas are being proposed in the above sections. What we need is references where people have published something about them. I suspect original research, in which case, Wikipedia is not the right venue. Graeme Bartlett (talk) 11:05, 28 April 2019 (UTC)

## Singularity isn't possible because there is a Plankian limit of compression (the holographic principle applies partially, so does the Schwarzschild radius; but not strictly for so small sizes [actuality is more unstable than these predictions, this means higher decay rate])

Travel to India; discuss to the professors and add here the link.
the Indian Institute of Science will do, but ask more professors

We cannot get content by asking people. Instead the references have to be recorded somehow so that others can verify them. Normally these would be written references, but video or sound recordings are OK too if they are reliable. Graeme Bartlett (talk) 11:50, 3 May 2019 (UTC)