Feynman Definition and 617 Threads

A recent Veritasium video demonstrates via experiment that light from a laser pointer takes every possible.path from source to destination, as promulgated by Richard Feynman. These paths need not be straight lines and thus can wander all of spacetime. That implies light is taking an infinite, or...

In Feynman's The Strange Theory of Light and Matter the simple technique for calculating quantum amplitudes for simple optical phenomenon by adding arrows is given. Could that same technique in principle be used to calculate the amplitude for a photon to arrive at the detector port of the LIGO...

Mint condition. Happy to up load a list of the chapters papers. The font is small in places, looks like word processing in places I can image that too.

In his lecture 26 vol 2 Feynman discusses charges moving at right angles shown in fig 26-2. As Feynman states "It appears that action is not equal to reaction." He states it will be discussed further but I cannot find that. My question is what is the most updated thought on this 60 year old...

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

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...

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!

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...

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!

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...

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...

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

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...

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...

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...

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...

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?

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

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...

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...

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...

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...

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...

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

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...

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...

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...

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 $$...

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 ...

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...

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?

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?

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

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...

“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...

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

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.

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...

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...

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...

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 -...

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...

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...

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...

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

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...

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 ...

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...

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...