Feynman Definition and 617 Threads

Dear collegues, I want to share with you a little idea which permits to obtain (almost apparently) renormalizable Feynman diagrams for General Relativity. (See attached file) This idea exchanges renormalizability with non-locality. I'll vary fain if someone of you will try to calculate any...

Hello I have not familiarised myself with the mathematics etc I merely have the conceptual idea that, for example, with the two slit experiement and electron is permitted to take "all possible paths" from the electron gun to the detector screen. The thought occurred (and as will all thoughts...

Feynman checkerboard as a model of discrete space-time Back in 2006 Ed Hanna posted an interesting thread about this topic and I would really like to discuss it with him. Are you out there Ed - or does anyone know how to contact him? Thanks, John Wellings

Hello to everyone! What are the feynman diagramms for the three basic photon interactions? Photelectric Compton(compton, Rayleigh and Thomsom scattering) Pair Production Thank you in advance!

if possible could you tag some good video lectures may be feymann or any other good source..thanks...!

Hi there everyone. I'll try to keep this short. I'm currently a sophomore at a local college. I'm in Honors Calculus 1 and part of the honors course requires a research project at the end of the semester. I'm studying to be an ER Doctor/Particle Physicist, yes I know this will take some...

Hello, I'm wondering if there are a series of books, analogous to the Feynman Lectures, for Electrical Engineering. The Feynman Lectures (as many of you know) are clear and concise, and nutshell a great deal of typical undergraduate study. A student can read these lectures from cover to...

Feynman Diagrams! Please Help! Hi guys! I've been asked to draw a scattering and annihilation Feynman diagram for the following scenario: e+e- → VeVe (The second Ve is an anti-neutrino just couldn't figure how to put the bar on! :P I've tried it and I'm convinced the mediating...

Relationship between "Bohmian trajectories" and "Feynman paths"? Can someone summarize what (if any) relationship there is between these two? I've read that Bohmian trajectories are very different than Feynman paths but I've also come across papers suggesting that "Feynman method of summing...

The Feynman diagram you'd naively draw for a beta decay such as p\rightarrow n + e^++\bar{\nu} would have four lines joined at a vertex, but in reality there's a virtual W or Z involved, which makes it into two 3-vertices. Is there any fundamental reason why all the vertices in a field theory...

Homework Statement I don't really know where to post this but I chose this section. I need help finding the source of this Feynman Quote "The probability of detecting a photon at any point is the sum of all the probabilities of the photon being detected at that point by any path" Homework...

Hi all, I am learning Feynman diagrams, and I have a quick question: in diagrams such as the one for electron-positron annihilation (see http://en.wikipedia.org/wiki/Feynman_diagram#Electron-positron_annihilation_example) why is it that the line "in the middle" is that of an...

feynmf returns "Feynman graph:\Delta", no diagram I recently installed the package feynmf for drawing Feynman diagrams (or at least I think I did -- my MiKTex Package Manager says so). When I compile\documentclass{article} \usepackage{feynmf} \begin{document}\setlength{\unitlength}{1mm}...

did feynman unify special relativity with QM or was it mostly a group effort and he just made some important contributions? did he make the decisive step just as leibniz and Newton made the decisive step with calculus? i watched a documentary about him and i couldn't get what his central claim...

Are the Feynman lectures supposed to have problems in the end of the chapters? Because I am looking at some previews and it doesn't seem that they have problems to solve? I always thought that it would have challenging problems, perhaps I am confusing it with a different book.

Hello all! I'm just out of high school and have got a few months before college begins. I think I'm fairly good in high school math, and now I've just started self-learning Single Variable Calculus (Calc I) from MIT OCW Scholar. I love Physics, and aim to be a physicist someday. I...

I didn't know where to put this, because it isn't a homework or coursework I have to do but just a thing I'm trying to understand. Anyway, I have attached the problem as an image. We have a scalar quartic lagrangian in d dimensions. It says that the number of vacuum Feynman diagrams, at a...

Hi, I'm reading Appendix 1 of Section N2 (Gluon Scattering) in "Quantum Field Theory in a Nutshell" by Anthony Zee. The generators for SU(N) have the usual algebra [T^a, T^b] = i \epsilon^{a b c}T^c Suppose we adopt the following normalization \text{tr}(T^a T^b) = \frac{1}{2}\delta^{a b}...

Do you think Hamilton's principle from classical mechanics can be deduced from Feynman's path integral in quantum mechanics? (We get across this question in another discussion: https://www.physicsforums.com/showthread.php?t=609087&page=5) Of course, there is a loose connection, since...

Feynman Diagram: Simga+ --> p + gamma? Hi, Can anyone give me some indications as to how to draw the feynman diagram for the following decay? Ʃ+ → p + \gamma Should I consider the quark composition of the sigma first? Thanks a lot.

I know the generalized formula for Feynman parameters, my problem is in simplifying. What I mean is something like this: Take the simplest 3 parameter equation \frac{1}{ABC} = 2 \int_0^1 dx \int_0^1 dy \int_0^1 dz \frac{ \delta \left( 1-x-y-z \right)}{(xA+yB+zC)^3} And you can take this...

Hi all After many months of contemplating, coming up with tattoo ideas, waiting a few months to see if I still like that idea, etc etc, I've settled on getting a Feynman diagram for many reasons, but having a but of trouble settling on one in particular. I've seen a few with the standard...

Hello, The Feynman graph of muon decay is and I asked my professor if we could also write and he said no, because then out of nothingness an electron and an (anti)electron-neutrino would appear and send out a boson to the muon. However, I was not very convinced, so I wanted to double...

I think I have a pretty good handle on how scalar field scattering works in QFT, so now I'm trying to wrap my head around spin 1/2 particles, and I'm having a bit of trouble with it. For instance, in N + \phi \rightarrow N + \phi scattering, an application of the Feynman rules leads to an...

I'm trying to follow Feynman's explanation on page 9-3 of Volume 3 of The Feynman Lectures on Physics. I've attached a copy of the section in question. To normalize CII he notes that < II | II > = < II | 1 >< 1 | II > + < II | 2 >< 2 | II > = 1 I am not clear how he derives the conclusion...

This isn't really a 'problem', I'm just trying to follow Feynman's reasoning in section 18-2 of Volume 1 The Feynman Lectures on Physics. I've attached a png of the paragraph in question. I have 2 issues with this: 1. If the length OQ = OP, how can there be a right angle at P(x,y)? 2. I...

Can a vertex of a Feynman diagram have more than three particles going in or out from it? Assuming all other conservation laws are obeyed, of course. I haven't seen this being explicitly stated but all the Feynman vertices I have seen have three arms attached. Thank you.

I did not find wikipedia article to be quiet intuitive. Any online sources or your own descriptions. I would be greatful.

Are the Feynman diagrams still applicable to more than two particles interactions? This would be very helpful in modelling many-body scattering cross-sections.

In 15-4,Feynman tried to explain why the rod perpendicular to the motion does not shrink."How do we know that perpendicular lengths do not change? The men can agree to make marks on each other's y-meter stick as they pass each other.By symmetry, the two marks must come at the same y- and y'-...

In 2-5, an analogy is given for electromagnetic field: two corks in water, and the effect of jiggling one cork on the other (probably the up and down motion). Now, that sounded more like water is a medium propagating the energy. But the electromagnetic waves require no medium for propagation...

Hi, this is probably very simple but what is the difference between these two Feynman propagators: \frac{i}{q^2-m^2} \frac{i(p/+m)}{p^2-m^2} E.g. Is one used for the invariant amplitude and the other for loop integrals? Or is one for a fermion and the other for a boson? =s Thanks!

in chapter 32 section 4 on electromagnetic waves, near the end he writes since \lambda = \frac{2\pi c}{\omega} then \Delta\lambda = \frac{2 \pi c \Delta \omega}{{\omega}^2}. i understand the first equation he writes but then the second one i am having trouble convincing myself how he came up...

Hi all, I am looking for some more information about the experiments that Feynman describes during the lectures that he gave in Auckland which can be viewed on the vega science trust website. The first experiment is where photons are transmitted or reflected by one surface with a second similar...

Homework Statement For a real scalar field \phi, the propagator is \frac{i}{(k^2-m_\phi^2)}. If we instead assume a complex scalar field, \phi = \frac{1}{\sqrt{2}} (\phi_1 + i \phi_2), where \phi_1,\phi_2 are real fields with masses m_{\phi 1},m_{\phi 2}, what is the propagator...

Please teach me this: Does a symmetry of Lagrangian be reserved in each Feynman diagram of perturbative QFT,because even Ward Identity still deduces from U(1) symmetry that we consider each diagram has?. By the way, does effective action reserve the symmetry that Lagrangian has?. Thank...

I'm trying to do the following problem: ie. I'm trying to use the Feynman rules for momentum space to write down the mathematical expression that the diagram is supposed to represent. However, I don't feel very confident in what I've managed so far. Now as I understand it, these diagrams...

Homework Statement I need to construct the Feynman loop integral for the following diagram: (*) where \nuL is the left-handed neutrino, \phi is a scalar particle and N is a heavy neutrino with a Majorana mass. Homework Equations N/A The Attempt at a Solution I'm trying to determine it...

There are all these Feynman YouTubes. Does anybody have a full listing? Or a favorite 10 or 20 of them? Can you list them with suggestive topic names to make it easy to find one you want? Feynman is more than physics. I'll try to start the list Different ways of thinking (counting and...

This seems to contradict the very tools we use to perform the scientific method. Immediately after performing any experiment, the measurement becomes a historical event, and this says that we cannot say that any historical event has actually occurred. Thus, I cannot actually say that I...

The Feynman slash \slashed{a}=\gamma^\mu a_\mu maps a four-vector a to its Clifford algebra-representation. This is a linear combination of the gamma matrices with the components of a acting as expansion coefficients. What physical significance does this new object have? The gamma...

Homework Statement With the time evolution time operator, where there is time dependent hamiltonian, show the new form of the feynman propagator between two states. Consider the Weyl Integral. 2. Equations from \newcommand{\mean}[1]{{<\!\!{#1}\!\!>}}...

Can someone refer me to Feynman rules for electroweak interactions in the general case of SU(2) multiplets of weak isospin n and weak hypercharge Y interacting with EW gauge bosons? I can only find the standard rules for SU(2) doublet electron - neutrino. Thanks!

Can someone describe the Feynman diagram for the Sigma plus decay to a positive pion and a neutron? I'm fine with the primary decay to the neutral pion and a proton. There appears to be insufficient down quarks created.

Hi, I am wondering how different the Feynman Lectures editions are. I have the option of getting the 1964,1965, 1970, and 1989 editions. Obviously getting the latest of those editions is the best, however I heard that the 2005 edition is the best edition with all the corrections and the one...

Hi, what do you think are the most important Feynman diagrams (or probably better: what do you think are the most important processes in particle physics)? Thanks, Quantum Cosmo

Hello, all. My colleagues and I are currently working on an exercise book for The Feynman Lectures on Physics (FLP). This book will include about 1000 exercises from the original Feynman Lectures course as taught at Caltech, covering pretty much the entire range of topics in all three volumes...

In the subject accelerometer (see link) the answer given is a = kgx. I get a = 2kgx. I'm wondering if anyone cares to discuss this problem. The answerer used an energy argument that I'm not sure I followed, whereas I used a simpler force-balance method. F = force on bead by parabola and is...

Hi all, I've been reading the Feynman Lectures on Physics and I've stumbled on something. I understand the theory but not how they arrived at the answer. It's to do with firing a bullet from a gun and working out the speed it would need to travel in a curve around the Earth's surface in order...

Hi all, I'm trying to calculate the Feynman Rules for the effective electroweak chiral Lagrangian. For example, this is the first term in the Lagrangian: \begin{eqnarray} \mathcal{L}=\frac{v^2}{4}\text{Tr}(D_{\mu}U D^{\mu}U^{\dagger}) \end{eqnarray} where \begin{eqnarray}...