What is Feynman: Definition and 647 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. J

    I Did Feynman make a mistake in the drawing of moving charges?

    This is from Feynman's lectures: https://www.feynmanlectures.caltech.edu/II_26.html Should the (b) say F1=q1E2 and F2=q2E1?
  2. S

    Question about Feynman diagram showing annihilation

    This is Feynman diagram of annihilation I get from wikipedia https://en.wikipedia.org/wiki/Annihilation I don't understand what the middle line with arrow to the right is. If I consider the left vertex and conservation of charge, it means the horizontal line with arrow to the right should carry...
  3. D

    I Your Favorite Feynman Diagram?

    Working on an art project using Feynman diagrams ... I'm curious if there are any that you consider to be particularly relevant to everyday human experience or particularly beautiful (according to any criteria you wish). Thanks!
  4. S

    Feynman Diagram of Meson decay

    I have trouble understanding the diagram and the answer key. 1) I am thinking time is the horizontal axis. Since A is π+, the quark composition will be ##u## and ##\bar{d}##. There are 2 vertices, let say P (on the left) and Q (on the right). I don't understand the conservation of charge at...
  5. Y

    I Feynman lectures on physics: random walk

    I do not understand the formulas (6.11) and (6.12) in volume 1 of the Feynman lectures on physics, the entire paragraph between equations (6.10) and (6.12) is generally not very clear. Please explain (preferably in simple language, I'm 13). Thanks!
  6. elou

    I Feynman discussion of electron diffraction

    Feynman, in the third volume of his Lectures on Physics, chapter 1, presents bullets and waves in two different diagrams, Fig 1-1 and 1-2 respectively. https://www.feynmanlectures.caltech.edu/III_01.html It is obvious that bullets are counted individually, the detector registering each hit...
  7. T

    Feynman lectures question where he explains math in terms of nuts

    Feynman lectures question where he explains math in terms of nuts. Feynman has a few lectures where he explained math numbers with Mayan counting as an example. I am not looking for that example. The example I am looking for is where he just uses nuts to give examples of math, add...
  8. J

    Revisiting the Feynman Ball on an Inclined Plane Problem

    Fw = sec(alpha) * kg-wt Fp = tan(alpha) * kg-wt
  9. R

    Expressing Feynman Green's function as a 4-momentum integral

    I am a bit confused on how we can just say that (z',p) form a 4-vector. In my head, four vectors are sacred objects that are Lorentz covariant, but now we introduced some new variable and say it forms a 4-vector with momentum. I understand that these are just integration variables but I still do...
  10. N

    Feynman diagram for ##\mu^+\mu^-## production in ##p\bar{p}## reaction

    I was able to solve b) but I am confused for a). I understand that in the proton-antiproton collision, only two quarks (one from proton and other from anti-proton) can be combined to get a virtual photon that in turn creates muon and anti-muon. I don't understand what would happen to the other...
  11. M

    I The Feynman way of explaining Symmetry in Physical laws

    So on this page https://www.feynmanlectures.caltech.edu/I_11.html under heading 11-2 Translations first he tries to proof that there is no origin in space. Joe writes newtons laws after measuring quantities from some origin. $$m(d^2x/dt^2)=F_x$$ $$m(d^2y/dt^2)=F_y$$ $$m(d^2z/dt^2)=F_z$$ We need...
  12. suh112

    Problem involving Torque and a Derrick from Feynman Exercises

    I attempted to solve this problem by considering the torque caused by the perpendicular components of the tension and weight with respect to the derrick. $$ Tcos\theta x = Wsin\theta L$$ $$T = \frac L x Wtan\theta$$ Using the principle of virtual work I also arrived at the same answer by...
  13. paulimerci

    Intro Physics Where can I find The Feynman Lectures on Physics at a discount?

    Hello everyone, I'm looking for The Feynman Lectures on Physics including Feynman's Tips on Physics: The Definitive and Extended Edition (2nd edition, 2005) for a discounted price. Any suggestions where I might look for one?
  14. P

    Which Feynman diagram or diagrams include feasible processes?

    Hello friends. I couldn't do it. Which Feynman diagram or diagrams has include feasible process?
  15. H

    I Feynman diagrams and sum over paths

    Hi ! In a Feynman diagram, can we consider that the propagator specifying the transition amplitude of a particle (let's say, of a "real" electron, or of a "virtual" photon) between two points or two vertices, is in fact itself the sum of a multiplicity of probability amplitudes, each one...
  16. N

    Is my Feynman diagram for production of ##W^-## boson correct?

    I think ##X## appears to be ##\pi^{+}## because it is light and energetically more favourable. Pion should be positive to ensure charge conservation. I am stuck at drawing a Feynman diagram for $$p+\bar{p} \to W^- + \pi^+$$. Is this correct? Is this the leading order diagram or is there a...
  17. PhysicsRock

    LaTeX LaTeX formatting Feynman Diagrams incorrectly

    I've been trying to get Feynman Diagrams to work in my LaTeX code, however, the output is not what it is supposed to be. I'm using TeXMaker and TikZ-Feynman to draw the diagrams. My code looks like this: \feynmandiagram [horizontal=a to b] { i1 -- [fermion] a -- [fermion] i2, a -- [photon] b...
  18. 4

    I Richard Feynman: Deriving Lorentz Mass Transformation

    In section 3.8, Feynman does a derivation of the Lorentz transformation for mass starting from $$\frac{d}{dt}E=F \cdot v \hspace{1cm}(1) $$ But is this a valid starting point if you are going to show mass changes with velocity? He says (1) comes from chapter 13 of his Lectures which he...
  19. apostolosdt

    Is Feynman the "wise guy" in Zee's QFT book?

    Zee, in his QFT in a nutshell, tells that beautiful story about a "wise guy" who, through his annoying questions to the professor, actually describes a fundamental principle of quantum mechanics, essential to Feynman's approach to quantum phenomena (pp. 9 in Zee's). Now, Zee appears to imply...
  20. jedishrfu

    Quora question: Did Richard Muller ever meet Richard Feynman?

    Great question answered by Prof Richard Muller with a joke on the one time gravity killed a man...
  21. C

    Studying About Richard Feynman lectures

    I was wondering if anyone else had trouble with reading Richard Feynman's lectures on physics. I think he's a good man and had fundamental contributions to science, but has anyone noticed that it is sometimes hard to follow what he is saying? I was reading his chapter about psuedo forces and...
  22. A

    A Feynman parametrization integration by parts

    How can i move from this expression: $$\frac{4}{\pi^{4}} \int dk \frac{1}{k^2} \frac{1}{(1+i(k-k_{f}))^3} \frac{1}{(1+i(k-k_{i}))^3}$$ to this one: $$\frac{4}{\pi^{4}} \int dk \frac{1}{k^2} \frac{1}{(1+|k-k_{i}|^2)^2} \frac{1}{(1+|k-k_{f}|^2)^2}$$ using Feynman parametrization (Integration by...
  23. codelieb

    Classical FLP Original Course Handouts at The Feynman Lectures Website

    Hello, everyone. The first large collection of FLP-related content posted at The Feynman Lectures Website was 744 pages of FLP classroom handouts (including laboratory guidelines, descriptions of experiments, homework, quizzes and exams, lecture summaries and outlines) donated by one of...
  24. E

    I Schwartz derivation of the Feynman rules for scalar fields

    Hi everyone, In his book "Quantum field theory and the standard model", Schwartz derives the position-space Feynman rules starting from the Schwinger-Dyson formula (section 7.1.1). I have two questions about his derivation. 1) As a first step, he rewrites the correlation function as $$...
  25. E

    A HQET Feynman Rule: QCD Interaction Vertex Explained

    Several texts state the vertex HQET Feynman rule as : igTijvμ\frac{1}{1+\slashed{v}} with the reasoning for vμ presented as being due to the QCD interaction vertex being between two heavy quark propagators, which are \frac{1+\slashed{v}}{2v.k}, giving ...
  26. E

    I When to use Feynman or Schwinger Parametrization

    I had been doing some calculations involving propagators with both a quadratic and a linear power of loop momentum in the denominator. In the context of HQET and QCD with strategy of regions. The texts which I am following sometimes tend to straightaway use Schwinger and I am just wondering if...
  27. ergospherical

    Quantum Is Feynman's Statistical Mechanics Suitable for a First Introduction?

    I found this little book titled “Statistical Mechanics; A set of lectures” by Feynman in the library. I’m not taking Stat Mech until Easter so I’d just be reading for interest at this stage, although the content looks fairly involved. Is it suitable for a first introduction?
  28. G

    I Exploring the Feynman Diagram of γ+γ→γ+γ: What Does It Reveal?

    If you have γ+γ→γ+γ what would the Feynman diagram look like (time-ordering implied). I think it will be a square with four photons on each vertex but is this all there is to it or am I missing something?
  29. Dr. Courtney

    The Feynman Lectures: Physics Gift for Your Son

    When your son puts "The Feynman Lectures in Physics" on his gift list.
  30. M

    Feynman rules and the tree level cross section of two scalar fields

    Hi there. I'm trying to solve the problem mentioned above, the thing is I'm truly lost and I don't know how to start solving this problem. Sorry if I don't have a concrete attempt at a solution. How do I derive the Feynman rules for this Lagrangian? What I think happens is that in momentum...
  31. rudransh verma

    B A Question about a Quote from the Feynman lectures

    “incidentally, to a good approximation we have another law, which says that the change in distance of a moving point is the velocity times the time interval, Deltas=vdeltat This statement is true only iF the Velocity is not changing during that time interval, and this condition is true only in...
  32. W

    A Measurement from Feynman diagram

    hi, can anyone please give me the list of measurement we can do ON Feynman diagram? Like , branching ratio, cross-section etc
  33. rudransh verma

    Intro Physics Exploring Potential Errors in Feynman Lectures on Physics: A Scientific Inquiry

    I was reading Motion chapter 8 in Vol 1 and I came across a line in speed topic which seemed confusing. So I checked with others and we concluded that its a mistake. Are there printing mistakes in this book? I will be surprised. Its pearson.
  34. K

    I Feynman path integral and events beyond the speed of light

    In Richard Feynman's book "The Strange Theory of Light and Matter", in chapter 2, he explains how to calculate the probability that light from some source will be reflected by a mirror and be detected at some location. He explains how you sum up all of the probability amplitudes (represented...
  35. E

    I Opaque-wall-with-hole argument from Feynman lectures

    In Feynman lectures vol I, last part of chapter 31, there was this argument about electric field on the other side of the opaque wall with holes. The argument is attached below. I'm having a hard time understanding the claim in the red box. In particular, I failed to see how "fields arrive at...
  36. J

    A Feynman diagram for bound particle output

    I am interested on how Feynman diagram is formed from a differential equation model of particle interaction wherein the incoming particles are not bound (e.g., separated neutron, proton and electron) and one or more of the outgoing particles are bound (e.g., hydrogen atom). However, I had never...
  37. T

    Question on problem 2.16 (a) of the Feynman Lectures (two-mass pulley)

    My attempt was to calculate the acceleration of M2 as the acceleration of M2 if it were the only mass in the system, minus the component of M1's acceleration along the slope. And then I would divide the whole thing by 2 to get the acceleration for just one of the two masses@ a = 1/2 ( g -...
  38. J

    A QM is Feynman path ensemble - is QFT Feynman field ensemble?

    While classical mechanics uses single action optimizing trajectory, QM can be formulated as Feynman ensemble of trajectories. As in derivation of Brownian motion, mathematically it is convenient to use nonphysical: nowhere differentiable trajectories - should it be so? Can this connection be...
  39. codelieb

    Intro Physics Feynman Lectures on Physics Tape Recordings Online for Free Listening

    Hello, everyone. I've made a number of announcements in this Forum about publications at The Feynman Lectures Website, but this is one I've long anticipated and am particularly happy to make: You can now listen to the original tape recordings of Feynman's famous Caltech Introductory Physics...
  40. G

    I Feynman diagram for scalar - vector interaction

    The term for the electromagnetic interaction of a Fermion is ##g \bar{\Psi} \gamma_\mu \Psi A^\mu##, where ##g## is a dimensionless coupling constant, ##\Psi## is the wave function of the Fermion, ##\gamma## are the gamma matrices and ##A## is the electromagnetic field. One can quite simply see...
  41. N

    Feynman Diagrams, are these allowed?

    These are my attempts, I have found two possibilities for each, but have no idea if they're 'legal'... Thanks in advance!
  42. snypehype46

    Amplitude of Feynman diagram in ##\phi^4## interactions

    This is not really homework assigned to me but I wasn't sure where to post this. I'm trying to work through the book "Quantum Field Theory for Gifted Amateurs" by Tom Lancaster. I'm doing the questions on Chapter 19 to understand how to draw Feynman diagrams and work out their amplitude. One of...
  43. JD_PM

    Deriving Feynman rules out of a generating functional

    To approach the problem I first studied section 1.3 and, more importantly, 1.4 of Osborn's notes. We first need to compute ##\partial_j \omega_i (x)## and ##\omega_i (x)\omega_i (x)## \begin{equation*} \partial_j \omega_i (x) = \delta_{ij} + \underbrace{\partial_j (g_{ilm})}_{=0}x_l x_m +...
  44. codelieb

    Intro Physics Messenger Lectures at The Feynman Lectures Website

    Hello everyone, You can now watch Feynman's Messenger Lectures in Full HD video with a searchable autoscrolling transcript (and other cool features) at The Feynman Lectures Website. Here are some useful links: information about Feynman's Messenger Lectures with links to videos ...
  45. JD_PM

    I Understanding how to derive the Feynman rules out of the path integral

    I am studying interacting scalar fields (from Osborn) using the path integral approach. We define the functional integral \begin{equation*} Z[J] := \int d[\phi] e^{iS[\phi] + i\int d^d x J(x) \phi(x)} \tag{1} \end{equation*} The idea is to differentiate ##Z[J]## with respect to ##J## and end...
  46. E

    Feynman irreversible and reversible weightlifting machine

    i have tried to understand Feynman's words i think i finally understands what he means by "we must add a little extra to get it to run" he refers to the "inversion" of the process, that's when we need to add extra work (lifting up a little mass) please correct me if I am wrong, this is something...
  47. JD_PM

    Loop Feynman diagram contributions to correlation functions

    My understanding of the n-correlation function is \begin{equation*} \langle \phi(x_1) \phi(x_2) ... \phi(x_n)\rangle = i \Delta_F (x_1-x_2-...-x_n) \end{equation*} Where ##\Delta_F## is known as the Feynman propagator (in Mathematics is better known as Green's function). Let us analyze...
  48. LCSphysicist

    I General relativity, Electromagnetism and Feynman Diagrams

    We are discussing the introduction to Einstein field equation, so he start talk about the linearity in Newtonian gravity and the non linearity in GR. But there is somethings I am missing: > " (...) in GR the gravitational field couples to itself (...) A nice way to think about this is provided...
  49. A

    Are the Feynman lectures on physics good?

    I've been reading a lot of stuff around physics as of late, and I was wondering if the "The Feynman Lectures on Physics: Volumes I, II, III." are a good thing to read? I'm asking as the price for these books aren't cheap, and I want to make sure they are worth the buy.