Penrose Definition and 91 Threads

The Penrose triangle, also known as the Penrose tribar, the impossible tribar, or the impossible triangle, is a triangular impossible object, an optical illusion consisting of an object which can be depicted in a perspective drawing, but cannot exist as a solid object. It was first created by the Swedish artist Oscar Reutersvärd in 1934. Independently from Reutersvärd, the triangle was devised and popularized in the 1950s by psychiatrist Lionel Penrose and his son, prominent Nobel Prize-winning mathematician Sir Roger Penrose, who described it as "impossibility in its purest form". It is featured prominently in the works of artist M. C. Escher, whose earlier depictions of impossible objects partly inspired it.

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  1. J

    Penrose zigzag model of Higgs-electron interaction

    Roger Penrose in Chapter 25 of his book The Road to Reality describes a "zigzag" model of the electron that consists of a pair of massless components one with a left-handed spin (the zig) and the other with a right-handed spin (the zag). He says that the Dirac equation can be written as a pair...
  2. P

    Why Does Penrose's Singularity Theorem Not Apply to Certain Spacetimes?

    Can anyone help me with this? Homework Statement Explain why Penrose's singularity theorem does not apply to each of the following geodesi- cally complete Lorentzian manifolds: (a) Minkowski's spacetime; (b) Einstein's universe; (c) de Sitter's universe; (d) Anti-de Sitter spacetime.2...
  3. tom.stoer

    Singularity theorems (Hawkign & Penrose)

    Does anybody kow about a good summary (online) of the singularity theorems?
  4. S

    Updates on Penrose Quantum Mirror Experiment

    http://discovermagazine.com/2005/jun/cover/article_view?b_start:int=3&-C= Any updates on the mirror experiment depicted in the above drawing to refute or proof Penrose theory?
  5. M

    Penrose diagrams, reference request.

    Where can one find a general and detailed exposition of Penrose diagrams? What I have seen so far, in the books, are relatively brief general comments and a couple of specific examples. Usually Minkowski and Schwarzschild metrics, sometimes one or two more.
  6. L

    Penrose Diagram for Anti de Sitter Spacetime - Explained

    Consider the penrose diagram for anti de sitter spacetime. It looks like the picture at the bottom of this wikipedia page: http://en.wikipedia.org/wiki/Anti_de_Sitter_space but sandwiched down I guess. Anyway, the bit I've just been reading claims that \mathcal{I} (null and spacelike) infinity...
  7. marcus

    Latest Penrose video on Conformal Cyclic Cosmology

    http://pirsa.org/11040063/ Big Perimeter audience, appreciative interest, long question period after. He undercuts his critics (who said the concentric circles could have appeared by chance) by criticising their methods and makes at least one valid point. I would say that the critics still...
  8. D

    Roger Penrose's Crazy Idea on the Big Bang

    I was watching a show recently where Roger Penrose explained a new idea he had on the Big Bang. It was very interesting, and I thought I was recording it. Of course, it didn't, now I can't remember exactly what he said, and of course, can't find it anywhere else. Perhaps somebody can feel in...
  9. B

    Phase-Space volume V - Roger Penrose

    I've heard a lot about fine tuning but Roger Penrose on this website http://www.ws5.com/Penrose/ which is an excerpt from his book the Emperor's New Mind claims that the phase-space volume must be accurate to within 10^10^123. I can't understand the following lines. If someone could make...
  10. Y

    What is Newman Penrose Formalism?

    What is Newman Penrose Formalism? Are there any easy-to-read references? I find their original work on N-P Formalism, but only find it is a bit difficult for me... Thank you.
  11. marcus

    Penrose Gurzadyan fire back: new paper today

    Penrose and Gurzadyan are not giving up without a fight. They posted a second paper today, answering their critics: http://arxiv.org/abs/1012.1486 More on the low variance circles in CMB sky V.G.Gurzadyan, R.Penrose 2 pages (Submitted on 7 Dec 2010) "Two groups [3,4] have confirmed the...
  12. nicksauce

    No evidence for circles in the CMB; contrary to claims by Penrose and Gurzadyan

    http://arxiv.org/abs/1012.1268 http://arxiv.org/abs/1012.1305 These papers seem to claim that the circles found by Penrose and Gurzadyan in the WMAP data, which were presented as evidence of pre-big bang activity, are entirely consistent with what we would expect the CMB to look like from...
  13. G

    Penrose: WMAP Shows Evidence of ‘Activity’ Before Big Bang

    Here's some strange stuff coming from Penrose... An article on Universe Today: http://www.universetoday.com/79750/penrose-wmap-shows-evidence-of-%E2%80%98activity%E2%80%99-before-big-bang/ And the paper: http://arxiv.org/abs/1011.3706 Okaaaay... Granted, I need to actually pore over...
  14. bcrowell

    Choice of scaling function for Penrose diagrams

    The standard definition of coordinates on Penrose diagrams seems to be something like \tan(u\pm v)=x\pm t. This is what Wikipedia gives, and Hawking and Ellis also give a transformation involving a tangent function, although I haven't checked whether the factors of 2, etc. agree. Neither source...
  15. R

    Penrose interpretation of quantum gravity

    hi, what do you think of the Penrose interpretation of quantum gravity, that gravity is responsible of the transitions between the quantum world and the macroscopic world?
  16. R

    Rotating black holes in Penrose diagrams

    hello, in Penrose diagrams it says that once you have crossed a first Cauchy horizon(of a rotating black hole) , then, with the repulsive singularity, it is possible to cross another Cauchy horizon, and then another event horizon to escape the black hole and go into another universe. so I...
  17. M

    Can Every Spherically Symmetric Spacetime Be Represented by a Penrose Diagram?

    Can you recommend a good book or pdf file to learn how to draw Penrose diagrams in general cases? It is possible to draw "precise" well-defined Penrose diagrams for every spacetimes?
  18. T

    Penrose's "The Road to Reality" - Objection to Broken Electroweak Symmetry?

    Hi! This is for those who have read Penrose's "The Road to Reality" (btw, fantastic book). In paragraph 25.8, on page 651, he writes something that I interpret as a critical remark regarding the spontaneous broken electroweak gauge symmetry. Quote ( btw, he writes U(2) instead of the usual...
  19. J

    Kruskal and Penrose diagrams for a Minkosky spacetime

    Hello I'm looking for diagrams (Kruskal and Penrose diagrams) representing Minkosky spacetime. I found two diagrams at http://nrumiano.free.fr/Estars/int_bh.html (the two first diagrams of the page). Do they represent a Minkowski spacetime ? Thanks, Jeff
  20. S

    Roger Penrose - Before the Big Bang

    http://www.youtube.com/watch?v=fJ-D5AUGVcI&hl=de" http://www.youtube.com/watch?v=inzgHjEVxAc&feature=channel" http://www.youtube.com/watch?v=WD3BWt85bxA&feature=channel" http://www.youtube.com/watch?v=YXDSCEX5wE8&feature=channel" http://www.youtube.com/watch?v=YX30dxKdJkc&NR=1"...
  21. B

    Understanding Penrose Diagrams - Insight & Explanation

    Hey. I was hoping that someone(s) could give me some explanation and insight into the Penrose Diagram shown below. Any links to good sites would be great, as I have not found what I am looking for. I guess, one of the things I am really wondering is: why is there a circular like...
  22. N

    Drawing Penrose diagram figures

    I need to create a figure of a Penrose diagram and I wonder if there is a dedicated program to this task. I know it's only a bunch of nested squares and lines but some people like me are simply uncapable of drawing anything by hand!
  23. marcus

    Penrose on YouTube, before bang cosmology, eight episodes October 2007

    Penrose has given this Before the Big Bang talk repeatedly over several years and it has developed. Some new thoughts, new cartoon drawings. Here on YouTube is a version he gave 31 October 2007 at George Mason University (Fairfax, Virginia, near Washington DC). It comes in several segments. The...
  24. Peeter

    Moore penrose inverse expressed as geometric product?

    I getting far enough into my geometric algebra books now that I'm at linear transformations, including the result showing how a linear transformation inverse can be expressed directly as a geometric product, using the adjoint and pseudoscalar multiplication, instead of using matrix inversion...
  25. M

    Fine literature on penrose diagrams?

    So here I'm begging for your suggestions. Thanks.
  26. nicksauce

    Is The Road to Reality Too Difficult for Undergraduates?

    I just borrowed this book, and am about to start reading it. However, I am a just a third year undergraduate, and flipping through the book, there looks like there is going to be a lot of new material, and some difficult math. How hard do you think it will be for me to get through it? Is it...
  27. S

    Penrose Lecture: Find Web Address for Lecture

    Greetings, In one of these threads, somebody commenting on the original thread provided a link to a Penrose lecture. I now cannot find which thread it was in. I'm also not sure - it was either in Genral Relativity or Cosmology threads. Does this ring a bell with anybody. What I'm...
  28. S

    Where Can I Find the Penrose Lecture Link Mentioned in the Forum?

    Greetings, In one of these threads, somebody commenting on the original thread provided a link to a Penrose lecture. I now cannot find which thread it was in. I'm also not sure - it was either in Genral Relativity or Cosmology threads. Does this ring a bell with anybody. What I'm...
  29. K

    Does Penrose theorem about Space-time forbid 'Strings'

    Penrose proved that a more than 4-dimensional spacetime would be unstable.. does this mean that String theory is completely wrong?? (since this only works on 11 dimensions). Also without offending nobody's beliefs .. .what're the proofs for the existence of String theory ??, its math elegance...
  30. George Jones

    Do Penrose and Carroll Agree on the Specialness of Conditions for Inflation?

    Without inflation, only extremely special conditions in the past produce the universe we now see. Or so the story goes. Penrose has long argued that conditions necessary for inflation are actually more special that the necessary past conditions without inflation. Its seems that Sean Carroll...
  31. A

    Question on Penrose diagram for Schwazschild metric

    Hi, I am just learning about Penrose diagrams and got confused: Why is the singularity r=0 in the Schwarzschild spacetime depicted by a horizontal line in the Penrose diagram? I thought a surface like r=0 would be timeike(as in the Reisner-Nordstrom case) rather than spacelike but obviously I...
  32. marcus

    Penrose: Outrageous Solution to Big Bang Cosmology Puzzle

    Penrose: Before the Big Bang--Outrageous Solution to a Profound Cosmological Puzzle a video of a talk given at Perimeter Institute recently by Sir Roger Penrose Before the Big Bang: an Outrageous Solution to a Profound Cosmological Puzzle go here...
  33. H

    The Road To Reality - Roger Penrose

    I was wondering if anyone had read this book and if it was a good book to read if you are not familiar with physics. I looked at the book at a bookstore and it seemed lengthy and filled with formulae. However the preface painted a very different picture so I was just wondering what other thought...
  34. C

    Penrose Diagram for Schwarzschild

    Hi. I've got a quick question on Penrose diagrams for the Schwarzschild space-time that I'd appreciate some comments on. In standard (t,r,\theta,\phi) coordinates the Schwarzschild metric is ds^2 = -\left(1-\frac{2M}{r}\right)dt^2 + \left(1-\frac{2M}{r}\right)^{-1}dr^2 + r^2 d\Omega^2. The...
  35. R

    G Penrose: Quantum vs. Gravity Experiment on Page 35

    Anyone else see the Penrose article in DISCOVER? "Two places at once" Not sure what he’s thinking with the “Experiment” he’s proposing on page 35. He seems to be claim that any interference between “states” or parts of an individual photon when if they come back together will always be...
  36. E

    Is the Schrodinger Cat Paradox an Indication of a Fundamental Flaw in Science?

    Roger Penrose suggests in his new book that the schrodinger cat paradox is an indication of the largest fundamental flaw in science as it now exists. He arrives at the conclusion that the particle/wave duality is not acceptable as a valid reality. Is anyone familiar with any of this? Does anyone...
  37. G

    The Road to Reality By Penrose?

    "The Road to Reality" By Penrose? i live in the US and decided to get this book off of amazon.com. i was wondering if anyone has read, or atleast skimmed (its pretty big) through it and would mind telling me if its a good buy(although if it isnt, its a little late now :-p). also, I am...
  38. marcus

    Penrose book #14 on Amazon in Britain

    Penrose book #3 on Amazon in Britain [edit: as of 5PM GMT-8, Friday 6August, Penrose book had risen to THIRD on amazon.com best seller list http://www.amazon.com/exec/obidos/tg/stores/static/-/books/amazon-bestsellers/ref=cs_nav_sn_4/202-5121337-2949434&tag= It is topped only a diet book...
  39. N

    Will Hawking or Penrose ever win Nobel Prize?

    my question is simple: Will Hawking or Penrose ever win Nobel Prize? And if yes, when do you think it will come.
  40. S

    Penrose Altered Smolin's Thinking?

    Why the work of LQG from a SRian approach is considered? Ths distilliation process was good for Smolin as it helped me to understand from his examples as to how the formation of the "new logic" might have extended from this head shaking that went on. This to me lead into other issues of...
  41. marcus

    Penrose: Road to Reality, just out

    On friday 23July Penrose new book came out "The Road to Reality" Three hour-and-half lectures he gave on separate evenings last October at Princeton are online and very likely share key ideas with the book. I will get the links for those lectures. The series was called something like...
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