Feynman Definition and 649 Threads

New member here, who decided four years ago to look into quantum gravity. My original intentions were pure: really, how hard could quantum gravity be? My current intentions are: to empathize with those who have approached this subject, spent hours, days, months pulling their hair out, yet...

Homework Statement The density of air is given as .001g/cm^-3 and the density of liquid air 1g/cm^-3 A.) Estimate the number of air molecules per cm^3 B.) Estimate the Mass of a single molecule. C.) Estimate the average distance L an air molecule should travel between collisions at normal...

A talk (audio only) of Feynman on problem solving: and Bill Gates on Feynman:

A long time ago I read an explanation Richard Feynman did on how the concepts of arithmetic can be derived from basic principles, along the lines of Peano's axioms, but I don't remember where it was. Thanks.

The Feynman Lectures on Gravitation is a famous book. There are originally 27 lectures but only the first 16 has been published. The remaining 11 lectures can only be found in the first edition (1962-63). It is very rare but is there a (possible) way to read the content, provided that my...

Hi. I'm self-studying particle physics.Just been looking at some questions where a reaction is listed and the questions asks to draw a Feynman diagram for the reaction and state which force is involved. I have the answers but they all seem so random and I would like to know how to decide which...

This Feynman diagram accompanied the announcement on the public LHCb site. How would you describe the origins of the up and down quark anti-quark pairs that that contribute to the decay of the ##\Xi_{cc}^{++}##?

Hi, I would like to ask you how to properly describe the Feynman diagram of the Vector Boson Fusion where the Higgs boson is produced. Two quarks scatters two vector bosons (that means boson W or Z) at some moment which influence each other and produce the Higgs boson. Is that right...

I'd appreciate it very much if someone told me if there is any free software to (draw and) calculate the amplitudes of simple (tree and one loop) Feynman diagrams. I'm hesitating because I don't know if this is the right place to ask. If it's not, I apologize in advance.

I am in the process of reducing tensor integrals down to a sum of scalar ones with the tensor structure factored out in some basis of decomposition. I am able to write some scalar products in terms of appearing propagators but I encountered one where I have something like $$\int_k...

I was wondering if anyone knows how to set up a procedure in REDUZE that will decompose tensor integrals appearing in QCD loop calculations into a sum of scalar topologies with the tensor structure factored out? I've had a look at the appropriate manual but I am not entirely sure how to...

Consider the diagram attached for the process quark + quark -> photon + quark + quark. I want to check I have the correct expression for the amplitude for this process by using the Feynman rules. ##i,j,m,n,l,p## are colour indices. ##k## is the loop momentum. I don't care about overall factors...

Is it because it is more rigorous than books like Halliday and Resnick? Or maybe you need to digest those books as a prerequisite for the feynman lectures? Or maybe people don't believe a regular person could digest the feynman lectures as a introductory level physics book? If someone is a...

I'm studying Quantum Field Theory and the main books I'm reading (Peskin and Schwartz) present Feynman diagrams something like this: one first derive how to express with perturbation theory the n-point correlation functions, and then represent each term by a diagram. It is then derived the...

I am looking at Appendix A Equation 52 (Loop Integrals and Dimensional Regularization) in Peskin and Schroeder's book. ∫ddk/(2π)d1/(k2 - Δ)2 = Γ(2-d/2)/(4π)2(1/Δ)2-d/2 = (1/4π)2(2/ε - logΔ - γ + log4π) Can somebody explain how this equation is derived? I would also like to know what the...

Hello! I hope this is the proper forum for my question(s). English is not my native language, so I apologize in advance for language mistakes. In Feynman Lectures on Physics, there is a chapter about the conservation of energy. The first part, which deals with the definition of energy, I...

Hi all, I have a little problem while reading Feynman lecture note volume 2, chapter 40, section 40-3. In that section Mr Feynman talked about Bernoulli equation and a example of a filled water container. In high school we learned that if we drill a hole near bottom of container, we can get...

Was listening to a Charlie Munger interview: At time 1:55, Charlie mentions Feynman used to sleep with wives of his undergraduate students. I never knew about this personal side of him.

One of the Feynman rules of QED is the following: For a closed fermionic loop, the Feynman rule is to start at an arbitrary vertex or propagator, follow the line until we get back to the starting point, multiply all the vertices and the propagators in the order of the line, then take the trace...

Hello everyone, I am currently trying to understand how we can use feynman diagrams to estimate the matrix element of a process to be used in fermi's golden rule so that we can estimate decay rates. I am trying to learn by going through solved examples, but I am struggling to follow the logic...

The decay processes of the ##W## bosons are completely governed by the charged current interaction terms of the Standard model: $$\mathcal{L}_{cc} = ie_{W}\big[W_{\mu}^{+}(\bar{\nu}_{m}\gamma^{\mu}(1-\gamma_{5})e_{m} + V_{mn}\bar{u}_{m}\gamma^{\mu}(1-\gamma_{5})d_{n})\\...

Hi all, It's written in QFT books, see for instance George_W._S. book "Flavor Physics and the TeV Scale" that the following Feynman diagram (1) is the dominant Feynman diagram for ## b \to s ~l^+l^− ## decay. Actually I compare this diagram via another possible diagram (2) Both (1) and...

Consider the process in the picture below where an ##r \bar r## state goes to an ##r \bar r## state through mediation of a gluon. The gluon may carry the colour anticolour combination ##r \bar r##. I'm just wondering... 1) Can we have a gluon with the colour assignments just ##r \bar r##? If...

I have some difficulty understanding how to go about with this problem: I came up with several graphs, you can see them in the attached picture (they are up to ~g^4 order). I am not sure about the self-interaction diagrams, but I think they are considered in the connected graphs (they are not...

In order to compute the scattering probability that two particles of type 1 (associated to ##\phi_1(x)##) which come from the far past with the momenta ##p1## and## p2##, to scatter and evolve into two particles of type 2 (associated to ##\phi_2(x)##) with the momenta ##p3## and ##p4## , I am...

I couldn't understand the physical meaning of this equation.Could anyone please tell me?(the last equation)

Hello everyone, I am trying to compute the ΔF=2 box diagrams in SUSY with gluinos. The relevant diagrams are the following: I want to use the Dirac formalism and NOT the Weyl one. So, the only reference that I have for Feynman rules with Majorana spinors is the old but good SUSY review from...

I am wanting to get the expression up to ##O(\epsilon^{2}) ## : To show that ##\frac{1}{2w_{k}} (\frac{1}{w_{k}-k_{0}-i\epsilon} + \frac{1}{w_{k}+k_{0}-i\epsilon})## ##=## ## \frac{1}{k_{v}k^{v} + m^{2} - i\epsilon}##, [2] where ##w_{k}^{2}=k^{2}+m^{2}##, ##k## the variable, and (this seemed...

Consider the process of electron-positron annihilation into muons as given by $$e^{+}e^{-}\rightarrow \mu^{+}\mu^{-}.$$ The Feynman diagrams for this process to lowest-order are given by This is an s-channel diagram.Why are there no t-channel or u-channel diagrams for this process?

Homework Statement Consider a real scalar field with a derivative interaction $$\mathcal{L} = \frac{1}{2}\left((\partial\phi)^{2}-m^{2}\phi^{2}\right)+\frac{g}{2}\phi\partial^{\mu}\phi\partial_{\mu}\phi.$$ What are the momentum-space Feynman rules for this theory? Homework Equations The...

Question: Draw the lowest-order Feynman diagrams for the e+e- --> W+W-process The answer gives three diagrams. I understand the first two, but the third makes no sense to me. Here it is: So this is a t-channel Feynman diagram. As far as I can tell regarding how these types of Feynman diagrams...

Hi all! I'm a senior philosophy/economics undergrad and I'm recently finding myself very interested in physics. For several reasons, I'm not able to take physics courses in college, but I wanted to introduce myself to the "corpus" of the undergrad physics. I'm willing to invest time and have...

I have found this article on the net, which is fun to read. At least to all who are interested in Feynman's habits and attitudes. In the end it is about the "current state of geology", but it can be read as a reminder on how to do science in general...

Consider the partition function ##Z(\lambda)## of the ##0##-dimensional scalar ##\phi^{4}## theory ##Z(\lambda)=\frac{1}{\sqrt{2\pi}}\int^{\infty}_{-\infty}d\phi\ \exp\{-\frac{1}{2}\phi^{2}-\frac{\lambda}{4!}\phi^{4}\}.## It can be shown that...

Hi all , I try to calculate the squared amplitude of the following self energy digram : where se is massless Dirac fermion , and vrm is massless right handed neutrino. x is a scalar with mass m .. I wrote the nominator of this process as: N = ## \bar{u}(p) (1-\gamma_5) (p\!\!\!/ +k\!\!\!/ )...

Homework Statement Compute ##\displaystyle{\int\ \frac{d^{4}p}{(2\pi)^{4}}} \frac{i}{p^{2}-m^{2}+i\epsilon}e^{-ip \cdot{(x-y)}}## in terms of the invariant interval. Interpret your answer in the limit of small and large invariant intervals and for zero mass. Homework Equations The Attempt...

Interesting and humorous lecture by Prof RP Feynman: http://www.cornell.edu/video/richard-feynman-messenger-lecture-1-law-of-gravitation The first few minutes capture Feynman's unique character.

Back again. This time I'm looking to build a small catalog of Feynman diagrams for my own use (and when I'm done to put it on the Internet in PDF format). I need your help to get a list of URLs together that I can download the required PDF's off the internet, bring them into Illustrator and have...

I'm reading Srednicki's Quantum Field Theory. I 'm trying to read Srednicki's presentation of Feynman Diagrams in the chapter Path Integral for the Interacting Field Theory. Link to the book: The path integral for the phi-cubed theory is equation 9.11 in the book. Please read that. I get the...

Why doesn't The Feynman Lectures consider the possibility of negative ##\alpha## when it says that ##e^{+2\alpha\rho}## is a rapidly increasing exponential (just below http://feynmanlectures.caltech.edu/III_19.html#mjx-eqn-EqIII1923) ?

Years ago someone asked Bill Gates who his hero was. It was Feynman (as he is one of mine along with Von Neumann and Lev Landau). He has done an interesting post about Feynman's teaching: https://www.gatesnotes.com/Education/The-Best-Teacher-I-Never-Had Feynman was a great scientist and...

Hello, Consider the the following Lagrangian of the $\phi ^4$ theory: $$\begin{align*} \mathcal{L} = \frac{1}{2} [\partial ^{\mu} \phi \partial _{\mu} \phi - m^2 \phi ^2] - \frac{\lambda}{4!} \phi ^4 \end{align*}$$ Now I'm interested in Feynman diagrams. 1. The second term gives the...

Hello there. I'm attending an introductory course in particle physics. We're supposed to know how to draw first-order tree level Feynman diagrams for simple reactions. I've been struggling to understand the method I should follow in order to correctly draw them. As I understand it now, we can...

Homework Statement Reading Feynman The Principle of Least Action out of The Feynman Lectures on Physics, Vol 2. Link to text http://www.feynmanlectures.caltech.edu/II_19.html So I'm having a problem proving that, section 19-2 5th paragraf, that "Now the mean square of something that deviates...

Hello everyone. I'm studying Mechanical engineering but I'm at Foreign language preparation class. My area is Space and aircraft. I'm studying Aircraft Deisgn (Daniel P. Raymer) and I think I've to improve myself in physics area. I thought that Feynman lectures on physics can be good start. What...

Hi everyone! In an exam on particle physics there has been a problem where for a number of decays we were asked to either reason their non-existence (i.e. name a conservation law that it contradicts to) or draw a Feynman diagram. However, with one of those decays I have a problem: \gamma + p...

Is the Hamiltonian matrix that is constructed in Ch 8 of the Feynman lectures the Heisenberg matrix picture, or is it something else? I am just curious. Thanks, Chris Maness

Consider a real scalar field described through the following lagrangian $$\mathcal L = \frac{1}{2} \partial_{\mu} \phi \partial^{\mu} \phi - \frac{1}{2}m^2 \phi^2 - \frac{g}{3!}\phi^3$$ The second order term in the S matrix expansion produces the diagrams in which we have a ##2 \rightarrow 2##...

I know that the Millennium Edition of FLP is supposed to be the most up-to-date and corrected, however, I have read (in amazon) really less than ideal reviews on how glossy the pages are, how light the printed text are, and how the texts go inside the left margin making it very difficult to...

Hello guys. I've seen a lot of differing opinions on this site. I'm a middle schooler with a decent understanding of basic calculus, trig, and algebra. I want to learn physics, and am wondering if The Feynman Lectures supplemented with problems from Irodov and some of Walter Lewin's lectures...