What is Feynman: Definition and 646 Discussions

Richard Phillips Feynman (; May 11, 1918 – February 15, 1988) was an American theoretical physicist, known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of the superfluidity of supercooled liquid helium, as well as his work in particle physics for which he proposed the parton model. For contributions to the development of quantum electrodynamics, Feynman received the Nobel Prize in Physics in 1965 jointly with Julian Schwinger and Shin'ichirō Tomonaga.
Feynman developed a widely used pictorial representation scheme for the mathematical expressions describing the behavior of subatomic particles, which later became known as Feynman diagrams. During his lifetime, Feynman became one of the best-known scientists in the world. In a 1999 poll of 130 leading physicists worldwide by the British journal Physics World, he was ranked the seventh greatest physicist of all time.He assisted in the development of the atomic bomb during World War II and became known to a wide public in the 1980s as a member of the Rogers Commission, the panel that investigated the Space Shuttle Challenger disaster. Along with his work in theoretical physics, Feynman has been credited with pioneering the field of quantum computing and introducing the concept of nanotechnology. He held the Richard C. Tolman professorship in theoretical physics at the California Institute of Technology.
Feynman was a keen popularizer of physics through both books and lectures, including a 1959 talk on top-down nanotechnology called There's Plenty of Room at the Bottom and the three-volume publication of his undergraduate lectures, The Feynman Lectures on Physics. Feynman also became known through his semi-autobiographical books Surely You're Joking, Mr. Feynman! and What Do You Care What Other People Think?, and books written about him such as Tuva or Bust! by Ralph Leighton and the biography Genius: The Life and Science of Richard Feynman by James Gleick.

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  1. mgkii

    Exploring Feynman's Tidal Forces: A Deeper Look

    I used to think I understood this - big mistake! I've just watched a great classic Feynman lecture posted by another PF user (a superb way to spend 50 mins of you can spare the time) https://www.physicsforums.com/threads/i-found-the-best-teacher-of-physics.855335/ In that lecture, Feynman...
  2. hubot

    Feynman exercise - container with steel balls

    Homework Statement You received many steel balls of the same diameter d and container of known volume V. All dimensions of the container are much greater than balls diameter. How many balls can be placed in a container? Homework Equations (\frac{4}{3}\pi)(\frac{d^3}{8})\approx0,52d^3 The...
  3. hubot

    Intro Physics What do you think about the Feynman lectures?

    Hi! I've bought book Feynman lectures, Feynman exercises and Physics Jay Orear. Is worthwhile to buy Landau and Lifshitz books? I'm beginner in physics. I'm not sure what to school textbooks. School programme is too easy for me. I need more accurate source to learn physics. Although in my school...
  4. H

    Where Does Feynman Get This Equation For E Field?

    http://www.feynmanlectures.caltech.edu/I_28.html#mjx-eqn-EqI283 It's Coulomb's law with retarded positions for the charges. Or something like that. How is it derived, please? Oh, never mind. I found some nice instructive materials from U Texas.
  5. P

    Feynman diagram; ##\pi^0+\pi^0\rightarrow \pi^++\pi^-##

    Homework Statement For the reaction below draw three Feynman diagrams, one that proceeds through exchange of a gluon, one through a photon and one exchanging a weak W-Boson. ##\pi^0+\pi^0\rightarrow \pi^++\pi^-## Which diagram provides the dominant contribution for this reaction? Explain how...
  6. FrancescoS

    Dyson equation and Feynman diagrams: a brief explain

    Hi! I have found a note about Generating functionals that seems to be very direct. Since I faced a difficulty many times without solve it, I would like if anyone can explain me my troubles. You can fine the note here (link). In the following figure, the author describes the 3-point green...
  7. H

    Feynman Lectures in Physics Available Free

    Since August 2014 the Feynman lectures have been available free of charge. They are direct from Cal Tech online, so one may rest assured they are not pirated. They are also available as a pdf download. Best introductory text I've found. The online site has better layout than the pdf, but is...
  8. Immortalis

    Learning Feynman Diagrams: Matrices & Dirac Adjoints

    I am trying to learn about Feynman diagrams and am confused by some of the notation. In particular, what do matrices, in particular the Dirac adjoint, have to do with Feynman propogators and why are they in imaginary terms?
  9. H

    Using Feynman rules to calculate amplitude

    Given a diagram, how is one supposed to apply the feynman rules to calculate the feynman amplitude?
  10. H

    How to calculate Feynman diagrams in phi^4

    For quartic scalar field theory these are some of the lowest order diagrams (taken from the solutions to 9.2 srednicki). I'm wondering if someone can give me an intuition of how to actually calculate them. What I'm thinking is that vertices are $$\int \frac{d^{4}x}{(2\pi)^{4}}$$ and for the...
  11. H

    Order of scalar interaction impact Feynman diagrams

    On page 60 of srednicki (72 for online version) for the $$\phi^{3}$$ interaction for scalar fields he defines $$Z_{1}(J) \propto exp\left[\frac{i}{6}Z_{g}g\int d^{4}x(\frac{1}{i}\frac{\delta}{\delta J})^{3}\right]Z_0(J)$$ Where does this come from? I.e for the quartic interaction does this...
  12. T

    ELI5: Antiparticles in Feynman Diagrams

    Hi!, I am studying for an introductory course in QED and Feynman Diagrams. Everything we see is like a first order approach and I am having some trouble understanding antiparticles in Feynman Diagrams: Why is it that we put an antiparticle that is leaving as if it is entering the interaction...
  13. Andrea M.

    Drawing Feynman diagrams with feynarts

    I'm trying to draw Feynman diagrams with the feynarts.sty package for LaTex. The problem is that if I write the following code \begin{feynartspicture}(150,150)(1,1) \FADiagram{} \FAProp(0.,10.)(6.,10.)(0.,){/Straight}{0} \FALabel(3.,9.18)[t]{$1$}...
  14. T

    Feynman Diagrams in MWI: Exploring Reality

    Please check my logic. 1. Feynman diagram is a tool to calculate 'final state' from an 'original state'. It is mostly used for simple processes, like scattering. 2. 'Final state' usually have a precise meaning due to observation of particles trajectories. 3. However, in MWI there is nothing...
  15. C

    IBP Relations in Feynman integrals

    I am wondering if anyone has experience in using IBP( Integration by parts) identities in the evaluation of Feynman diagrams via differential equations? My question is that I can't seem to understand where equation (4.8) on P.8 of this paper: http://arxiv.org/pdf/hep-ph/9912329.pdf comes from...
  16. S

    Feynman diagrams for phi phi -> phi phi

    Homework Statement Compute the matrix element for the scattering process \phi \phi \to \phi \phi Homework Equations The Lagrangian is given by L = \frac{1}{2} \partial_{\mu} \phi \partial^{\mu} \phi + \frac{\alpha}{2} \phi \partial_{\mu} \phi \partial^{\mu} \phi + \frac{\beta}{2} \phi^2...
  17. S

    Feynman rules for Lagrangian with derivative Interaction

    Homework Statement The lagrangian is given by: L = \frac{1}{2} \partial_{\mu} \phi \partial^{\mu} \phi + \frac{\alpha}{2} \phi \partial_{\mu} \phi \partial^{\mu} \phi And the question is to find the feynman rules. Homework EquationsThe Attempt at a Solution I started by using the...
  18. M

    Can anybody confirm the following Feynman slash identity?

    I want to compute the following when the 4-vectors are already given i.e x^{\mu},y^{\mu} are given and are orthonormal ( x, y are complex vectors); \begin{eqnarray} \left(/\negmedspace\negmedspace x/\negmedspace\negmedspace y\right)^{2} & = & /\negmedspace\negmedspace...
  19. Biscuit

    How to prepare for the Feynman Lectures

    I'm in the 11th grade and have little education of college level mathematics. I individually find myself studying one section of it but hardly have a grasp. I really want to read the Feynman Lectures to further my education of physics, but as I read over the pdf it looks like there is a lot of...
  20. A

    Bohmian trajectories vs. Feynman paths, always continuous?

    After reading some of the other posts on the Forum, I'm clear on the fact that Bohmian trajectories (of the de Broglie Bohm formulation) and the paths of the Feynman path integral formulation are very different things. I'm wondering (and it's a naive question, no doubt), when talking about...
  21. throneoo

    Feynman diagram of annihilation-pair production question

    Consider the lowest order interaction e.g. e- e+ -> virtual photon-> muon anti muon. I appreciate that the electron-positron pair cannot annihilate into a real photon due to conservation of 4-momentum, but why is the pair permitted to produce a virtual photon? I know that virtual particles...
  22. S

    Quantum Functional Integration and Feynman rules

    Hallo Everybody, I am searching for a book (or lecture notes) that details the calculations that lead me from a given Lagrangian to the Feynman rules of the theory. It should not be rigouros, just the main steps to get the Feynman rules. Thanks for your help!
  23. M

    What Are the Feynman Rules for Bremsstrahlung with Vector Particle Production?

    So this isn't a homework problem really, but based on the posting rules for the HEP section this seems to fit better here. My issue is that I'm trying to use a Feynman diagram to represent a Bremsstrahlung process in which a vector particle is produced: $$ Z + e^- \rightarrow Z + e^- + v. $$...
  24. A

    How to prepare for the Calculus BC and Physics C Exam?

    Firstly, let me talk about my BC exam situation first and then the Physics C exam secondly. I just recently downloaded a PDF full of released BC exams from 1969 to 1998. Is there any PDF for a fully released BC exam from last year(2015)? What is the best textbook that is oriented towards this...
  25. C

    Cuts of a Feynman diagram and the massless limit

    Consider a ##j## point all massive leg one loop polygonal Feynman diagram ##P## representing some scattering process cut on a particular mass channel ##s_i##. Invoking the relevant Feynman rules and proceeding with the integration via dimensional regularisation for example gives me an expression...
  26. N

    Heads or tails? (Question from Feynman lectures)

    I have been going through feynmans lectures on probability and have a few questions that i can't answer ; in the part regarding fluctuations he introduces us to tree diagrams(pascals triangle ) and gives an example regarding the toss of a coin If we consider the no. Of tosses as n and no. Of...
  27. G

    Lagrangian of fields from Feynman diagrams

    ¿How is possible deduce the Lagrangian of the fields of a theory knowing only his Feynman Diagrams?
  28. C

    How to draw Feynman diagrams

    I am reading the book tilted "quantum field theory in a nutshell(second version)" by A.Zee. On the page 45, for example there is a term \frac{1}{m^2}λJ^4. The question is that how to related it to the Figure 1.7.1. or that, How can I draw the three diagrams in Figure 1.7.1 from the term...
  29. A

    Extracting a Feynman diagram from a lagrangian?

    Hi everyone, sorry if this is not the right place to post that question but I'm new to this forum, i'll delete if necessary. I am currently trying to learn QFT from Matthew Schwartz's "Quantum field theory and the standard model", quite clear during the first chapters, but i have been...
  30. Perry

    A prank by Richard Feynman - How to"understand" physics and mathematics?

    I am not sure if this is the right part of the forums to post this, but I was reading the book Surely you're joking Mr Feynman when i reached this part: This got me thinking. How does one "understand" physics and mathematics? It's certainly more than remembering some formulas. What do you think?
  31. andrex904

    Euclidean Feynman rules for QED

    Hi, i have some trouble with feynman rules after wick's rotation. I don't understand how the propagators transform. In particular if i take the photon's propagator in minkowskian coordinates i don't understand where the factor "-i" goes after the transformation. ## \frac{-i\eta_{\mu\nu}}{p^2}...
  32. A

    Feynman lectures electric dipole question

    For some reason, I'm having trouble with what I feel should be a relatively simple derivative to take. Feynman is differentiating the potential to find the z-component of the electric field. He has: -\frac{\partial \phi}{\partial z} = - \frac{p}{4 \pi \epsilon_0} \frac{\partial }{\partial z}...
  33. Safinaz

    Understanding Color Factors in Feynman Diagrams

    Hi there, In paper as : http://authors.library.caltech.edu/8947/1/GREprd07.pdf I don't understand the colour factor associated with two gluons and single octet scalar as the first Feynman diagram in fig. 3 ? In eq. 27, this colour factor is given by ## (d^{abc})^2 ## .. so, how did this come...
  34. rolotomassi

    Green's Functions and Feynman Diagrams

    I've been learning about Greens functions. I'm familiar with how to find them for different differential operators and situations but far from fully understanding them. We were shown in lecture how they can be used to obtain a perturbation series, leading to Feynman diagrams which represent...
  35. H

    Feynman rules for nonlinear sigma models

    Nonlinear sigma models are particular field theories in which the fields take values in some nontrivial manifold. In the simplest cases this is equivalent to saying that the fields appearing in the lagrangian are subject to a number of constraints. Since the lagrangian fields are not independent...
  36. L

    Feynman rules for Yukawa theory

    Hi. Do you know any book/paper/lecture notes where I can find complete derivation of Feynman rules for both scalar and pseudo-scalar Yukawa theory, and maybe an example of application to decay of fermion?
  37. 1

    Feynman Diagram Help: Decay of ∆+ to n + π+

    Homework Statement :[/B] For the decay of the ∆+ → n + π+, sketch an appropriate quark-level Feynman diagram. State which interaction is responsible for this decay. 3. The Attempt at a Solution This is more of a question to see if I'm doing it right more than anything. The first Feynman...
  38. Greg Bernhardt

    Insights Think you know Richard Feynman? - comments

    Greg Bernhardt submitted a new PF Insights post Think You Know Richard Feynman? Continue reading the Original PF Insights Post.
  39. A

    Condensed matter problem with Feynman integral

    Im working on deriving the final expression on the attached picture. The problem is that of a particle in a potential coupled to a "bath" of harmonic oscillators but I'm not sure how you arrive at the final expression. First of all, why are you allowed to assume that q is periodic on the...
  40. S

    Why Does Feynman Use a Single Electron Charge for Dipole Calculations?

    Hello, I am reading the volume 2 of the Feynman's Lectures on Physics, and something is bothering me when he calculates the dipole moment of a single atom induced by an extern field ...
  41. S

    Why Does Feynman Use a Single Electron Charge in Dipole Calculations?

    Hello, I am reading the volume 2 of the Feynman's Lectures on Physics, and something is bothering me when he calculates the dipole moment of a single atom induced by an extern field ...
  42. zthompson47

    Relativistic mass in Six Not-so-easy Pieces (Feynman)

    I'm hoping that someone can help me understand a topic on page 86 of Feynman's "Six Not-so-easy-pieces", in the "4-4 Relativistic mass" section. He says, "It is an interesting exercise to now check whether or not Eq.(4.9) is indeed true for arbitrary values of w, assuming that Eq.(4.10) is the...
  43. MidgetDwarf

    Intro Physics Feynman Lectures millenium Edition questions.

    Looking to buy a copy of the Feynman lectures and the millenium edition is the one I am going to buy. I remember reading, maybe I am mistaken, that there was reprint of the 2011 millenium edition. If I am correct, this reprint fixed errors that were found in the 2011 editipn. However, when I...
  44. Telemachus

    Feynman Expression for the field of a point charge

    Hi there. I'm reading Jackson's Classical Electrodynamics. 1. Homework Statement In chapter 6, the equation for the electric field of a moving point charge is derived. I could follow the mathematics to get the electric field for the moving charge, which is given in equation 6.57 in Jackson...
  45. C

    Proton Collision Feynman Diagram

    Supposed to represent a relativistic proton colliding with a stationary proton, leading to changes in the momentum of both and the production of a neutral pion. The pion then decays into two photons. No clue if this is right. I've never drawn anything much more complicated than...
  46. D

    Antiparticles are regular particles going backward in time?

    First I would like to say that I'm sorry if this question has been asked before- I'm new here. I was reading QED by Richard Feynman, and he mentioned that any given antiparticle is just it's regular particle counterpart moving backwards in time. How is this possible? I thought that it was only...
  47. thegirl

    Why do neutrons and neutrinos have arrows in Feynman diagrams?

    The arrows in a Feynman diagram represent electric current. right? If this is the case then why do neutrons and neutrinos have arrows. How do they have an electric current?
  48. Z

    From Effective Lagrangian to Feynman Rule

    In this process: N*→N+photon If we want to calculate the amplitude with the following interaction Lagrangian: (http://arxiv.org/abs/nucl-th/0205052) If we use functional method,the field operator is not polynomial,how to use "center formula"to bring functional derivative in? Or we must...
  49. CAH

    Feynman Diagrams, exchange particle?

    Exchange Particles are to show the transfer of (for example) +/- charge to the other side so the charges balance. But I don't understand... Beta plus decay: p → n + e+ + νe. This is just an example, the Feynman diagram shows a W+ boson transferring the positive charge to the right hand side...
  50. K

    Left/Right Communication with Alien Race by Richard Feynman

    Hi all, I was thinking about the problem and can someone verify my solution : 1) Set up a Magnetic field going from down to up, i.e north pole is at the bottom. 2) Use the triboelectric series to charge some small particle positive (hair or glass with teflon) 3) Throw that particle in forward...
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