Feynman diagrams Definition and 150 Threads

I need to put some Feynman Diagrams in a paper that I'm writing on my Mac (Lion) with Texpad, but I don't know how to create them in Latex (I tried it with some things I found on google [feynmf], but it didn't work). So I need a way to create them online, if you know one. I hope this is the...

Hey, I was wondering what exactly a loop is of this kind : I understand the initial & final four momentums to be the same and so there is no boundary on the possible allowed momentums in the loop. My professor said the loop is equal to (or can be modeled as) the self-interaction by...

Hey again, I have a question on a couple of things related to feynman diagrams but also the relativistic scalar propagator term. First of all, this interaction: The cross represents a self-interaction via the mass and characterised by the term: -im^2, is this just some initial state...

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...

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...

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...

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...

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...

Homework Statement Draw the Feynman diagram vertex corresponding to the interaction Lint = eAμJμ, where Aμ is the electromagnetic field and e is the coupling constant. Draw all the Feynman diagrams in quantum electrodynamics to O(e2) describing the processes: (i) e+e- ----> e+e-, (ii)...

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.

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

Hi, the breaking radiation emitted by the scattering of an electron with an external field is described by the hamiltonian: H=\bar \Psi^- (\displaystyle{\not}{A}_e + \displaystyle{\not}A) \Psi^+ where A_e is the external static classical field, while A is the quantized field. The...

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

I am reading Srednicki's Quantum Field Theory recently. I have thought over the descriptions of the Feynman Diagrams on his book in chapter 9, but I still can not understand what these diagrams mean and how do they help us to calculate the right-hand side of the equation 9.11 on the book. Is...

I'm reading QED. At first I thought I understood Feynman diagrams, but due to ones like these I'm not so sure anymore. In either of these diagrams, the photon "curves" around in space time. Why would it travel in anything BUT a straight line if nothing is influencing it? I liked to picture these...

Hey there, this isn't a homework / coursework question so I didn't think it should be posted in that section. I can't seem to find a source which explicitly tells you how to determine which bosons are used in reactions. I understand how to work out if a reaction is legal or not by using charge...

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

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...

...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...

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?

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...

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...

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...

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...

Homework Statement I need to draw a series of Feynman diagrams to show some processes, but I'm unsure if I'm doing these correctly. I've put them together in this one post and detailed each below in turn, hopefully this is going to make sense. I know there's a few, but I want to make sure I'm...

I'm learning how to do Feynman diagrams for an exam coming up, and have come across diagrams in both position and momentum space. If I'm asked to draw a Feynman diagram without specifying which kind, is it generally assumed that it's in position space? If I label the the incoming and outgoing...

I have a two point Green's Function with a phi^4 interacting Hamiltonian and am considering the second order of pertubation, and must work out the following: T[\phi(x_1) \phi(x_2) \phi(y_1)^4 \phi(y_2)^4] = T[\phi(x_1) \phi(x_2) \phi(y_1) \phi(y_1) \phi(y_1) \phi(y_1) \phi(y_2) \phi(y_2)...

I have spent a while trying to get to grips with the building blocks used for constructing feynman diagrams, below is my attempt at a set of reactions, how am I doing so far? I don't think e^{+}e^{-}\rightarrow\mu^{+}\mu^{-} can happen since a gluon only interacts on particles with a...

I have some well ordered feyman diagrams which have an incoming neutrino interacting at a vertex with a w boson and emitting an electron. since a neutrino can pass through some 18 light years of led without interacting, I'm wandering how a single neutrino interacts at this vertex?

Is this right? To calculate a scattering amplitude for a certain scattering event, you take the term in the wick's expansion of the S-Matrix that suits your situation best. Then you draw a Feynman Diagram that corresponds to the term in the wick's expansion, then just use the Feynman Rules to...

Hey all, I am just wondering if one can directly calculate the Einstein coefficient in spontaneous emission of, say, two-level atoms through feynman diagrams? I searched for sources in google but could not find anything. Thanks a lot for an answer! Wit best regards, blue2script

Hi everybody! I'm a new Physics Forums user and hope someone could help me out with my minor dilemma. I'm a PhD student in mathematical/theoretical physics and I' working on the Boltzmann equation in QFT. Up to now, there was no major emphasis on Feynamn diagrams - the approach was rather more...

hello, I am trying to follow the arguments in Peskin pages 96-97 where the exponentiation of disconnected diagrams are performed. I think the 'proof' is too 'not detailed' and was wondering if there exists a better explanation elsewhere? My biggest question is the sentence on page 97 "The sum...

I'm trying to learn Feynman diagrams from Srednicki's QFT book! Could someone retell and summarize in his or her own words what Srednicki is saying in the three paragraphs after equation 9.11? (I don't understand what the (2P)!/(2P-3V)! different combinations are, how Feynman diagrams are...

Hello I have to calculate symmetry factors for the following feynman diagrams for my qft class, and would be hugely grateful if anyone could point out any mistakes (I'm sure there are lots!) that I've made. http://picasaweb.google.com/jessicagreerstanley/Physics#5259179071440262450"...

I would like to clearify the connection between n-point functions, Feynman diagrams and S-matrix. I do not want ( yet) to understand the detailed derivation of the LSZ reduction formula, just the rough connection between the n-point function on the one side and the S- matrix on the other...

Homework Statement I’m trying to learn Feynman diagrams from Peskin and Schroeder. I’m stuck right now on page 91-93, especially about constant factors and symmetry factors. Equation 4.44 and the two constants 3 and 12 in it make perfect sense to me. The trouble starts with 4.45. I understand...

1. Feynman says all of electromagnetism follows from Maxwell equations. 2. Somebody (Pointing to a Feynman diagram of a photon/electron reaction) said all of electromagnetism is in that one diagram. So, can anyone help me with these two questions: how does point 1 come from point 2. And, how...

What distinguishes Fermions form Bosons in Feynman diagrams?

Hi everybody, I am a MAC OS X user, and I have a trouble with feynmf package in latex. I have downloaded the package from CTAN website and followed the instructions for installation. Then in my latex file I coded a generic 2-body scattering process labeled as "generic", after typesetting...

I have posted a question on the Tutorial subforum because there was already a thread on that subject but I figured that people here may be more likely to be able to help me out https://www.physicsforums.com/showthread.php?p=1313121#post1313121 Thanks! Patrick

http://arxiv.org/abs/hep-th/0611042 Hidden Quantum Gravity in 4d Feynman diagrams: Emergence of spin foams Aristide Baratin, Laurent Freidel 28 pages, 7 figures "We show how Feynman amplitudes of standard QFT on flat and homogeneous space can naturally be recast as the evaluation of...

Could anyone direct me to a coherent tutorial for drawing simple Feynman diagrams in Latex (I use TeXnicCentre) using the Feynmf package? The only ones I've found are rather complicated, given that I don't have a huge deal of experience with the writing of lengthy 'tex. Cheers, guys. [If this...

http://arxiv.org/abs/gr-qc/0604016 Hidden Quantum Gravity in 3d Feynman diagrams Aristide Baratin, Laurent Freidel 35 pages, 4 figures "In this work we show that 3d Feynman amplitudes of standard QFT in flat and homogeneous space can be naturally expressed as expectation values of a specific...

Hey, I was wandering if anyone knew if the Feynman diagrams could be created in Latex or in threads like this? If not then maybe it would be an interesting development avenue...

Is there a systematical way to count all the possible feynman diagram with vertices less than or equal to n...

Hi, I'm seeking for a software, witch will alow me to easily draw Feynman diagrams. I have currently found: FeynMF: LaTeX package. Not very nice to use, but very good quality diagrams FeynmanDraw: Very primitive WIN software. Not fine diagrams. FeynDiagram: C++ source for drawing...

Hi, I'm seeking for a software, witch will alow me to easily draw Feynman diagrams. I have currently found: FeynMF: LaTeX package. Not very nice to use, but good quality diagrams FeynmanDraw: Very primitive WIN software. Not fine diagrams. FeynDiagram: C++ source for drawing. Complicated...

I'm looking for some excellent references on Feynman diagrams, from an overview of the basics to a description of the relation between the diagrams and the heavy duty mathematics that they represent. Any information would be appreciated.

Richard Feynman in his Physics lectures and diagrams show a free electron emitting a photo and/ or absorbing a photon. He (They?) always show the electron being deflected. My question is if the photon has no mass how can or why does the electron react by being deflected in motion? If it is a...