# What is Holographic: Definition and 122 Discussions

Holography is a technique which enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating three-dimensional images but it also has a wide range of other applications. In principle, it is possible to make a hologram for any type of wave.
A hologram is made by superimposing a second wavefront (normally called the reference beam) on the wavefront of interest, thereby generating an interference pattern which is recorded on a physical medium. When only the second wavefront illuminates the interference pattern, it is diffracted to recreate the original wavefront. Holograms can also be computer-generated by modelling the two wavefronts and adding them together digitally. The resulting digital image is then printed onto a suitable mask or film and illuminated by a suitable source to reconstruct the wavefront of interest.

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1. ### A Current status of Tom Banks' Holographic space time?

Interested in Banks' HST these days, for discussion,here are some abstract and an email from L.Smolin. A recent conclusive paper as well https://arxiv.org/abs/2201.06988 The formalism of Holographic Space-time (HST) is a translation of the principles of Lorentzian geometry into the language...
2. ### "Holographic" Display with Rotating Blades

Video: I recently happened upon this holographic display design where a number of blades with led strips affixed rotate like a fan. It quite puzzles me how this such a design achieves the desired results. I am pretty confident that they use polar coordinates when mapping the pixels, but I am...
3. ### A Holographic Cosmology lecture of Leonard Susskind

In the following lectures: Prof. Susskind writes the terms ##\exp(3Ht_n)## and ##\exp(3ht_n)##. If I understand correctly he computes ##R(t)=R_0 \exp[\int^{t_n}H(t')dt']## where ##R(t)## is the scale factor of the Universe and ##H(t')## is Hubble's parameter. What I still don't understand is...
4. ### I Holographic Principle and/or implications of the entropy bound

Hi all, First post here. I'm a casual physics enthusiast, but I've been reading and thinking a lot about this topic lately. The thing I'm most interested in is the fact that black hole formation involves the simultaneous limits of two things: time dilation and the information bound. I find it...
5. ### A Holographic principle (I'm looking for a paper that I read)

I read a paper a long time ago. And i forgot who wrote it. The author said that information was not encoded on space time but on the boundaries of regions of space time. there was 3 parts on this boundaries. a space like part (for the initial conditions) . another one for the "out" state...
6. ### How to reflect light through a glass like those in holographic sight?

Hello everyone, Most of you know the Holographic Sights used on weapons to aim. I have a 3d printer and I will try to replicate one of them. I just wonder how the red dot/sight is reflected on the glass without making the light reflected anywhere else? It doesn't have to have exact same...
7. ### How Can Drones Create Holograms in the Sky?

Has anyone seen Spiderman: Far from Homes already? In it the drones can create holograms in the sky. Is there any proposal in real life of how these could be done? I guess by emitting some smokes and laser from many drones, perhaps some kind of holograms can be attempted? The following may be...
8. ### A Do Holographic Screens eliminate holographic dualities?

Do Holographic Screens eliminate the need of finding holographic dualities? There are various models in physics based on the famous holographic principle (https://en.wikipedia.org/wiki/Holographic_principle) This does not always work since in these models we must find a correlation between two...
9. ### I Is the Quantum State Holographic?

I'm reading Tim Maudlin latest book "Philosophy of Physics: Quantum Theory". In the following descriptions, it is not akin to holographic? "In the context of the quantum recipe, the mathematics of the wavefunction suggests that the quantum state (whatever it is) is a fundamentally global sort...
10. ### 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...
11. ### 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...
12. ### Controlling light diffraction angle with a holographic "lens"

I'm a physics student, and working on a class project that requires coming up with a method to control the exit angle (diffraction angle) of a monochromatic light source. For example, taking a laser (monochromatic, coherent light source), spreading the beam, and directing the light at a piece...
13. ### A Holographic Relations for OPE Blocks in Excited States

Holographic Relations for OPE Blocks in Excited States https://arxiv.org/pdf/1809.09107.pdf Jesse C. Cresswell†1 , Ian T. Jardine†2 , and Amanda W. Peet†§3 †Department of Physics, University of Toronto, Toronto, ON M5S 1A7, Canada §Department of Mathematics, University of Toronto, Toronto, ON...
14. ### B Please explain to me the 2d holographic universe

Hello, this idea of holographic universe is mind boggling to me. If we are 2d and everything we see is actully 2d hologram, like picture on the monitor https://metro.co.uk/2017/01/30/our-entire-universe-is-an-illusion-and-reality-is-actually-a-2d-hologram-say-scientists-6415724/. There is...
15. ### 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...
16. ### 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...
17. ### I Event Horizons - Holographic Principle

Another thread (now closed), got me thinking about the holographic principle. So I looked it up and found a couple of surprises. First it seems to be attached in some peculiar way to string theory. Second, it seems to be applied more restrictively than it I thought. It's especially that...
18. ### 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...
19. ### 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)...
20. ### 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...
21. ### Optics Lab Project Holographic Weapon Sight

Good evening everyone. For my third year optics course we have to do a research lab that includes a lab component for a project. Our prof has suggested we look into something that interests us an design a lab around it. Personally I have always had an interest in military technology and was...
22. ### Calculators Holographic Display for See-Through Imaging: A Closer Look

I am looking for a method that displays a see-through images of an object through an arbitrarily non-transparent surface. Suppose I have already the 3D tomographic information of an object inside a closed box and I am interested to have a holographic 3D view of that object just by looking at the...
23. ### A Argument for Holographic Principle

So around 44:00, Susskind begins his argument. He put a variety of items into a region of space, and the added a minimal shell of material surrounding the items, then squeezed that material to form a black hole around the item. Then he said that the amount of original information cannot be...
24. ### I Is the Holographic Principle the Key to Understanding Our Universe?

I have just come across the following on the Astronomy Picture of the Day. https://apod.nasa.gov/apod/ap170423.html Here is a quote that I would like to learn more about. The Holographic Principle, yet unproven, states that there is a maximum amount of information content held by regions...
25. ### B Holographic Principle and the Description of Higher Dimensional Universes

I thought that the holographic idea had been ruled out, But this article shows that it could be ruled in again. https://www.sciencedaily.com/releases/2017/03/170321110344.htm And this new research has implications for some fundamental problems in physics. So far, the study of gravity has...
26. ### B Perhaps a silly analogy - hologram light source retreating?

Hi everyone I would love to get some feedback on this silly idea I had when thinking of the balloon analogy. Another way to achieve the same effect - at least in 2 dimensions - is to move a projector further away from a screen - everything expands relatively. If the universe is a 2d hologram...
27. ### B What is the Holographic Universe Theory and What Are Its Implications?

My understanding of physics and mathematics and what nots is self taught and frankly really rather amateur compared to the people who use this forum, but one thing that really fascinates me is the holographic universe theory. Would you be able to explain the pros and cons of the arguments and...
28. ### B Holographic universe is it real

I am not a proponent of holographic principle, I believe the universe is infinite, one will start off and not come back to the same starting point , my question is how popular is the holographic principle? and why? Not that my views mean any thing...
29. ### I How does the Holographic Principle relate to 11 dimensions?

So the Holographic Principle says that our 3 dimensonal world is encoded in the 2d surface of the cosmological horizon. What about the remaining dimensions? Are they there in the regular 3space or are they also encoded?
30. ### I Holographic principle, non-locality, and Lorentz invariance

Hi all, Some recent comments from the forums here led me to do a bit of reading on the holographic principle, and to a posting on "The Reference Frame" by Lubos Moti about the (likely lack of) 'holographic noise' in the experiment by Craig Hogan at Fermilab...
31. J

### Exploring the Mysteries of Holographic Duality and String Theory

Hello, I had recently created an account. I'm Justin and perhaps am a physics student studying holographic duality and string theory, hopefully my colleagues were right in having me be forming an account in regards to this website. Anyways, pretty much it.
32. ### B Create Your Own Hologram: A Step-by-Step Guide for Beginners

hello! i am trying to make a hologram. buy lasers, isolation table, spreading optic, etc... I have no idea of phisics or maths, i study photography but the subject interests me so much. I have a few books about it. Do you think it is possible to make a simple hologram without any knowledge of...
33. ### A Problem with fields and operators in holographic duality

I'm reading McGreevy's lecture notes on holographic duality but I have two problems now: (See here!) 1) The author considers a matrix field theory for large N expansion. At first I thought its just a theory considered as a simple example and has nothing to do with the ## \mathcal N=4 ## SYM...
34. ### I Holographic Principle discussion in Sean Carroll's book

am reading Sean Carroll's pop-science book 'From Eternity to Here' and am having trouble connecting the links in his discussion of the Holographic Principle. At the outset, I would ask that you try to answer in terms of Carroll's discussion and without moving into concepts much more advanced...
35. ### B So the holographic principle doesn't have much evidence?

I heard the holographic principle is a sham and that there is no evidence to back it up and that 99% of physicists don't accept the idea as credible. Is this true?
36. ### 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...
37. ### Holographic and trapped surfaces

This the breaktrhough by bousso, which was a student from Hawking. It sees it was accepted under peer review magazines in 2 months. You can find the versions at: 1. arXiv:1504.07660 [pdf, other] Proof of a New Area Law in General Relativity Raphael Bousso, Netta Engelhardt Comments: 15 pages...
38. ### How Holography Works: Explained

To make a hologram a film is exposed to an incident plane wave and wave from the object to record the interference pattern on the film. The principle is commonly explained in a way like that in p.1212 of "University Physics" (...
39. ### Question about Holograms and 3D mid air images, videos, etc.

I am very curious about holograms and if there is a possible way to project 3D , mid-air images and videos on air with no holographic screen (The Princess Leia hologram in Star Wars). If it is not possible, how long till they actually start arriving to the world and how will they work/operate?
40. ### Black hole information : Holographic theory question.

Question! So Alice falls into a black hole, instead of the volume increasing for the black hole, it actually increases proportional to it's area. Thus one can draw the conclusion that 3 dimensional information can be fully explained by the information encoded on the surface area at the boundary...
41. ### Holographic Universe. 2D Universe = Matrix?

Hi people. I just read some articles about physicist starting to gain more and more evidence for the Universe to be a 3D Hologram of a 2D world (or that's how I understood it). And apparently for us living in a "Matrix", like the one in the movie. Now I would like to understand the relation...
42. ### Exploring Holographic Theory: Quantum Physics and the Nature of Reality

[broken link deleted by moderator] Does this proves the theory of the holographic universe? I saw video on youtube, a guy called "Stephen Davis" who says that is "fanatic about quantum physics", he created a model of the "holographic universe" which he says that everyone is a player, and every...
43. ### Is there a holographic principle in loop quantum gravity?

for example, is loop quantum gravity/SF in 4 dimensions dual to a CFT in 3 dimensions? does a serious proposal of QG have to respect the holographic principle?
44. ### Exploring the Holographic Universe Theory: Fact or Fiction?

This theory was accepted? Is it more to be correct or more to be wrong?
45. ### The Holographic Principle: Separating Fact from Fiction

I saw some videos about the Holographic Universe and I found a big problem, has some people (non-physicists) that create videos saying the Holographic Universe is created by our brain (to hold religious beliefs), they say that people, objects, etc are made of waves and frequencies (sounds)...and...
46. ### David Bohm Holographic Universe

"Energy fields are decoded by the brain into a 3D image, to give the illusion of a physical world." - David Bohm It's OK to believe in the holographic theory, but to believe that OUR BRAINS do that converting energy into a 3d image is completely nonsense. He tried to fit the 'observer effect'...
47. ### Holographic Principle question

So I've been looking up things on the Holographic Principle for a while now, but there's still a few questions I have. As I understand it, the Principle says that if I drop a book into a black hole the book's information would be 3D inside the black hole and it would also be 2D on the event...
48. ### Holographic principle and string theory

Hi. I am no physicist but I am trying to know something about the holographic principle. As I understand, everything is happening in a surface and our three-dimensionality is an illusion of our senses. On the other side, string theory assume the existence of 11 dimensions. Are the two theories...
49. ### How does the Holographic Principle apply to different scenarios and dimensions?

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...
50. ### Very small holographic laser projectors and diffraction.

In thinking about what it would take to make a feasible invisibility cloak or holographic disguise or perfect hologram room, I've imagined something that works like this: A light beam "image" is projected onto a device designed to refract or reflect it in all directions, but only 1 color in any...