Diagrams Definition and 689 Threads

A diagram is a symbolic representation of information using visualization techniques. Diagrams have been used since ancient times on walls of caves, but became more prevalent during the Enlightenment. Sometimes, the technique uses a three-dimensional visualization which is then projected onto a two-dimensional surface. The word graph is sometimes used as a synonym for diagram.

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  1. 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...
  2. A

    Molecular Orbital Diagrams, learning how to draw?

    Hi, So I'm a phd student of physics, but my research overlaps a little with inorganic chemistry, specifically transition metal oxides and spectroscopies of them. I can glean some information MO diagrams and find them quite useful when writing about what I'm doing... however it's difficult to...
  3. P

    Why Does the Metal Fermi Level Remain Constant in Schottky Barriers?

    Dear All I am having problems with how to draw band diagrams with band bending for Schottky Barriers and PN junctions. My issue is that I don't know how you determine which Fermi level remains fixed at its equilibrium level and which Fermi level moves to align with it when the two materials...
  4. P

    Why is kinetic friction always lower than maximum static friction?

    I was reading about those in my textbook and they drew an example of a block resting on a ramp. The diagram showed the force of friction. How is there friction if the block is not moving? Thanks, Peter G.
  5. M

    Weight diagrams and Lie algebras

    Very often we've identified sets of particles with the weights of a semi-simple Lie algebra - for example, the 8 particles of the baryon octet with the weights of the 8 representation of SU(3) global flavour symmetry (in the old days of the Eightfold Way), or the 3 weak bosons with the weights...
  6. L

    What are the rules for drawing molecular diagrams?

    If I have a molecule of pb2SO4 for example, how would I draw that? What are the rules that tell me what attaches to what? When it's only 3 or 4 atoms, it's pretty easy to draw them, but when it's more than that, I have no clue what to do.
  7. Femme_physics

    Binary phase diagrams - understanding the eutectic point

    1) So, does the binary phase always represent the materials 100% on each end? That is to say, if you have lead and antimony, the right side will always represent 100% of one of the two, and the other side will present 100% of the other. If we look in the middle of the diagram, it's 50-50%...
  8. M

    LaTeX Can I use feynmf to generate sums of Feynman diagrams?

    Does anyone here use the package feynmf to generate feynman diagrams? I can use it to build diagrams, but I don't know how to build sums of diagrams i.e. diagramA + diagram B + diagram C Does anyone know how to do this? Thanks
  9. S

    Circuit Diagrams in technical writing

    I am writing a paper for a journal. The paper is supposed to have quite a few circuit diagrams. What software should I use to draw the circuit diagrams?
  10. ?

    Phase Diagrams and Phase tranformations

    i need some read up material regarding the title any links or references please?
  11. F

    Seeking Alternatives for Microsoft Visio 2010 for Detailed Computer Logic Diagrams

    Hello, I want to draw the detailed logic level diagram for a basic computer. For this i found a software that will work which is microsoft visio 2010. But i m not satisfied with that because it has some limitations. Such as re-arranging the wires automatically and also the simulation...
  12. D

    How to Clean Up Circuit Diagrams Without Contact?

    Homework Statement Essentially I am pursuing clues as to what I should do in order to clean up the following circuit: . I'm kind of confused regarding the portion where it says "no contact". Help?
  13. D

    Help with Ray Diagrams for Lens and Mirror Systems

    hello, my professer has been getting us to draw ray diagrams of two lens systems and diagrams of a lens and mirror system. these are two situations that i can not seem to figure out for my self two lens system : diverging lens to converging lens (pictures would be ideal)...
  14. D

    Ray diagrams (lenses) problem. I need full explanations.

    Ray diagrams (lenses) urgent problem. I need full explanations. 1. The question An object of height 2cm is placed 15 cm from a thin converging lens of focal length 10cm. Complete the paths of two rays on the figure to show their passage through the lens to the image formed. 2. The...
  15. S

    Feynman diagrams: Planar Vs Non-Planar topologies

    Hi everybody, as usual I need help with some definitions regarding many-loop calculations. In particular what do we mean with planar and non-planar topologies exactly? I have an idea but I'm really not sure how to formalize it for an arbitrary big number of loops and legs. Second, once...
  16. W

    Analyzing Spacetime Diagrams: Finding Coordinates and Checking Invariance

    Homework Statement Two rockets are sent off at t=0, one from x=0 and the other at x=4. The rocket leaving from x=0 is moving at .8c and the rocket leaving x=4 is moving at .2c. When the paths of the two rockets meet, they send a light signal to x=0. Read off the coordinates in the S frame...
  17. L

    U-Channel Diagrams in QFT: A Closer Look

    In these notes: http://www.damtp.cam.ac.uk/user/tong/qft/qft.pdf Why can we not have a u-channel diagram in Figure 13 on p64?
  18. MysticDude

    Drawing Free Body Diagrams for Acceleration Problems

    Homework Statement Draw free body diagrams: A rectangular block being accelerated on a horizontal, frictionless surface. A skydiver who had just jumped from a plane and hasn't reached terminal velocity. A cube being accelerated up a 30° incline with μk > 0. A pendulum bob that has just been...
  19. J

    On Feynman diagrams, why do antiparticles have their arrows pointing backwards

    ...compared to normal particles? I was told this was something about, for a particle moving forward in spacetime, its antiparticle can be considered as moving backwards in space time. but that really doesn't mean anything to me. what's wrong with putting a forward arrow on an...
  20. N

    Conserved quantities in the Feynman diagrams.

    I'm currently reading Griffiths book (I'm at chapter 4) on Particle physics, and I had a question about Feynman diagrams. In every "node" of a Feynman diagram, what quantities are conserved? Further, what quantities are conserved over the entire diagram?
  21. T

    Free body diagrams for springs and dampers in torsion

    Homework Statement I have been having a little discussion with a friend. We both know that for a spring/damper system in parallel like shown below, the associated free body diagram is correct. http://img337.imageshack.us/img337/2023/para0.jpg But when it comes to the same system in...
  22. M

    Can someone me out with free body diagrams

    **a horizontal force with magnitude A is acting on a pulley as shown. the two masses p and P are moving together, same acceleration. p is trying to fall to the left but the tension from the rope and the static friction is keeping it in place. Everything else you need to know is in my two...
  23. 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...
  24. N

    Plotting Phase Diagrams (Temperature vs Composition)

    I'm planning to plot phase diagrams of Temperature vs Composition. I found the formula ln(x) = \frac{\Delta H}{R} (\frac{1}{T_A} - \frac{1}{T}) from the Clapeyron equation. Its a ideal solution of 2 metals in L state and regular solution in S state. Eutectic temperature is at 850C and enthalpy...
  25. Y

    How to determine direction of forces in free body diagrams?

    For instance, in the below diagram: [PLAIN]http://img101.imageshack.us/img101/3205/59914396.png How do you know if the reaction force on the beam is in Direction A or B? How do you determine the correction direction?
  26. D

    Determining if force is attractive/repulsive from Energy diagrams

    Homework Statement The potential energy of a pair of atoms separated by a large distance x is given by U(x) = -C6/x6, where C6 is a positive constant. What is the force that one atom exerts on the other? Is this force attractive or repulsive? Homework Equations F(x) = -dU/dx...
  27. T

    Counting and Grouping Feynman Diagrams

    I'm working through Srednicki's QFT text, and I'm continuously vexed by the various numerical factors in diagrams and vertices, as well as the grouping of diagrams. For example, in Chapter 10 (pg 75) Srednicki treats basic \phi\phi\rightarrow\phi\phi scattering processes in \phi^3. He claims...
  28. F

    Creating S-N Diagrams with Excel

    Hello, I need help with plotting a S-N curve using Excel given the data below I know how to plot using the scatter function in excel but i am confused on what values should go on the y-axis...i.e S...it is clear that the number of cycles will obviously go onto the x-axis...Please explain what...
  29. A

    Is My Tension Calculation Correct in Mechanics Problem?

    Homework Statement Please see the attachment, Q2 Homework Equations \sumFx = 0 \sumMA = 0 The Attempt at a Solution for part A, i get 14123N as the tension, moment at C about B, 9.8x1000x5 = 49050 49050/7 = 7007N tan-1 (4/7) = 29.74o TSin(29.74) - 7007 = 0 TSin(29.74) = 7007...
  30. N

    Help with drawing free-body diagrams?

    Homework Statement Bobo decides to go skydiving. When he jumps from the plane, his mass combines with the mass of his chute is 75.4kg, which means that the force of gravity on him is 739N. A. Before he opens the chute, the wind resistance on Bobo gives him an upward force of 10N. Draw a force...
  31. V

    Creating a Bit Detector with Mealy Machine: State Diagrams & Tables

    Homework Statement I have to make a scheme of a bit detector that detects the bit "1101" with a Mealy Machine. So I have made the following state diagram and state table(picture 1 and picture 2) http://img215.imageshack.us/g/picture1jf.png/" Now I don't know what happens in picture 3. How...
  32. 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...
  33. M

    Representation of covariant and contravariant vectors on spacetime diagrams

    Hi, How can we represent covariant and contravariant vectors on curved spacetime diagrams? How can we draw these vectors on a spacetime diagram? Contravariant vectors are really vectors, therefore we can represent them on the diagram with directed line elements. Covariant vectors are...
  34. S

    Where Can I Find Phase Diagrams for Substances Other Than Water or CO2?

    Where can I find phase diagrams for things other than water or CO2? I'm looking for pressure/temperature ones.
  35. D

    Free Body Diagrams on friction less surface

    1. A frictionless surface is inclined at an angle of 34.4° to the horizontal. A 270-g block on the ramp is attached to a 75.0-g block using a pulley, as shown in the figure below. (a) Draw two free-body diagrams, one for the 270-g block and the other for the 75.0-g block. (b) Find the tension...
  36. P

    Draw diagrams in th plane of Cartesian products

    Homework Statement In the attachments, you will see the problem and my answer. Is my answer correct?
  37. N

    Scalar field theory - Feynman diagrams and anti-particles

    I'm working on a "draw all possible Feynman diagrams up to order 2" problem for a scalar field that obeys the Klein-Gordon equation, and I'm wondering about a few things. When I did a course on particle physics and was first introduced to Feynman diagrams in the context of QED (but not QED...
  38. C

    Internal energy and pv diagrams

    http://img689.imageshack.us/img689/511/pistonquerstion.jpg This is my part attempt... [PLAIN][PLAIN]http://img830.imageshack.us/img830/7342/internalenergyanswer.jpg And ideas on how I can do the rest of it?
  39. I

    What is the origin of the 1/2 symmetry factor in Feynman diagrams?

    I was suddenly confused by the calculation of symmetry factors of Feynman diagrams. For example, in Peskin's textbook, as the attached pdf file, Below eq(4.45), he calculated the symmetry factor in detail, however, I was confused by the last 1/2 factor. I'm trying to realize this...
  40. 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?
  41. S

    Shear & Bending Moment Diagrams

    I apologize for not using the template, but my question is more of a conceptual question than anything else. The only thing so far that confuses me with Shear and Bending Moment Diagrams is when, in some cases, it is easier to approach the beam from the right side instead of the left...
  42. E

    Where do you put the angle in force diagrams?

    Homework Statement Ok, so I'm in college now. However, I'm having the same problem i did when I was in high school. When your doing a problem that has let's say a truck on a 30 degree incline, how do you decide whether that angle will be touching the y component of the angle or the x? The...
  43. R

    Are Feynman diagrams evaluated using the residue theorem or Wick rotation?

    Say you want to evaluate this integral: \int^{\infty}_{-\infty} \frac{dx}{x^2-A} Since the bottom factors into \frac{1}{(x-\sqrt{A})(x+\sqrt{A})} , using the theorem of residues, the integral is \pm 2\pi i (\frac{1}{2\sqrt{A}}) (where \pm is + if Im \{\sqrt{A} \}>0 and - otherwise, but...
  44. marcus

    Spinfoams are the Feynman diagrams of GFT (V. Rivasseau)

    Vincent Rivasseau and four others just posted "July3150" (I mean 1007.3150, just easier to remember that way for some reason) where they made the observation in effect that spinfoams are the Feynman diagrams of GFT. It's not a new thing to point out, but it is very helpful to mention...
  45. A

    Shear and Bending Moment Diagrams for a Ski

    Homework Statement The ski supports the 900N weight of a person. If the snow loading on its bottom surface is trapezoidal determine the intensity w (N/m). Draw the shear and bending moment diagrams for the ski. The ski has an overall length of 2m. The force arrows 'hang' of the bottom of...
  46. N

    E vs K Diagrams: Understanding Crystal Momentum & Velocity

    *Hope this is in the right forum* This upcoming semester I'll be taking my first course in Semiconductor physics and I'm studying out of the textbook independently this summer to prepare myself. I've been learning about energy bands and I wanted to clarify a couple of concepts that my text...
  47. E

    LaTeX Drawing Braid diagrams in Latex

    I hope this is the right forum to ask this question. I am looking for a Latex package that is able to draw Braid diagrams without too much trouble. See for example http://arxiv.org/abs/0707.1889v2" (figure 2, page 3). Any suggestions? Thanks in advance.
  48. J

    Calculation of neutral Kaon Box Diagrams

    Hi everybody,i'm worried about some calculation. I have to write down the amplitude for the neutral Kaon oscillation. There are two Box diagrams which are depicted here: http://upload.wikimedia.org/wikipedia/de/9/92/FeynmanKaon.png The two diagrams come along with a combinatorical factor of...
  49. A

    Medical Find Diagrams from a Book: An Internet Search

    Does anyone know where, on the internet, I can find a bunch of the diagrams from the book? Google images didn't really have any decent sized ones.
  50. N

    Explaining Diagrams using Physic concepts

    Here I have a question which I'm unfamilar with. I'm not sure how to answer the question by explaining what is involved with the diagram. Discuss the following pictures in terms of work and power outlining any assumptions that you make.
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