Diagrams Definition and 659 Threads

I wanted to ask, about the ##6##-dimensional ##\phi ^3 ## theory... The Lagrangian is: $$ L = \frac{1}{2} (\partial \phi)^2 - c \phi - \frac{m^2}{2} \phi^2 + \frac{g}{3!} \phi^3$$ When I want to draw all the 1-loop 1PI diagrams, should I make something like these: ?

I'm currently going through the interaction part of Tong's lecture notes on quantum field theory, and I'm a bit confused about how many Feynman diagrams I need to draw in order to compute the amplitude of various interaction terms. Tong presents Feynman diagrams through a series of examples. For...

Homework Statement Can anyone provide me a good tutorial link on drawing the vector diagrams for a transformer on load, when the load is a)Inductive b)Capacitive c)Resistive Capacitive ? Homework EquationsThe Attempt at a Solution

Homework Statement I have a rectangular PV diagram of a heat engine. Like this one: I have to show why this cannot work in reverse as a refrigerator. Homework Equations U = 0.5fnRT (U = internal energy, f = degrees of freedom, n = number of moles of gas, R = ideal gas constant, T =...

Anyone can show me how the velocity diagram at the inlet and outlet of a airfoil section ceiling fan blade?

Has anyone of you tried to work with creating Feynman Graphs in LaTeX? I tried using the feynmf package, as explained here: https://www.sharelatex.com/learn/Feynman_diagrams and used the same introductory script: \begin{fmffile*}{diagram} \begin{fmfgraph}(40,25) \fmfleft{i1,i2} \fmfright{o1,o2}...

Homework Statement Homework Equations w=(2/3)x The Attempt at a Solution So integrating w to get V (1/3)x^2 +C Then Sum in the Y-direction should be 9-(2/3)x+18=0 Somebody tell me what in god's name is going on here. It seems like they are ignoring the 18kN force and then plugging in my...

Hello, I am learning Feynman diagrams and I still do not understad quite well the symmetry factor idea. The equation is: $$ \frac{1}{O(G)} = \frac{M}{n!(4!)^n} $$ I was trying the next example: If I am not wrong it is O(G) = 10 taking care of the asymmetry of each pair of internal lines...

Hi there, I have created lots of shear force and bending moment diagrams for simply supported beams. I have used the maximum value on the bending mement diagram for bending and stress equations, but I have never found any real use for the shear force diagram. Yes they tell you the distribution...

Homework Statement Hi everyone, I am trying to construct qualitative band diagrams and I think I have confused myself. I am not sure on how to figure out what the electron configurations are of the orbitals when k=0. I get that at k=π/2 it is the opposite state but I can't seem to figure out...

Homework Statement Which of these diagrams represent the same circuit? Homework EquationsThe Attempt at a Solution I thought it was A and D because it seems to me that in both cases the current is going splitting into two different paths. Also it seems to me that in A and D the potential...

I am looking for phase diagrams for Mag-Thor alloys and would also like to get some information on how they are typically processed. Are these alloys typically made by diffusion of Th in the Mg and then thermally homogenized? Or are they usually cast? Perhaps made by some other process all...

Hello folks, I've just started to read "An Introduction to Quantum Field Theory by Peskin and Schroeder" and at the end of 6th page I could read: "... Since H_I should conserve angular momentum, the photon to which these particles couple must have the correct polarization vector to give it...

Hi everyone. I'm working on getting together some notes on school maths and of course I'd like to include some diagrams. The usual stuff, graphs of things like parabolas, circle geometry, etc. But I'm also skint. So I'm looking for some open source programs that can do that, and they need to be...

In Introduction to QFT (peskin) 4.5, he writes: The computation for M, of course, will be quite different when identical particles are present. However, I have finished reading the first part of the book and found no special treatment for identical particles. Can anybody tell me how to...

Hello, I am wanting to write a math/physics book or possibly a PDF online book and I'm wondering if anyone knows of any programs that exists for making pictures and drawing diagrams. I not just looking for something to make x-y graphs or 3-D graphs, I'm looking for something that designed...

Homework Statement Imagine a graph of pressure in kPa (y-axis) against volume in L (x-axis). There is a straight line moving from point A at 300kPa, 0.5L to point B at 500kPa, 1L. The false origin on this graph is 200kPa, 0L. What is the work done by the gas? Homework Equations W=pV...

Homework Statement For the following reactions draw Feynman diagrams, clearly labelling all the quarks, leptons and exchanged particles and stating the type of interaction involved (if more than one interaction could be involved give the most likely): (i) ##\pi^0 \to \gamma + \gamma##...

[SIZE="4"]Definition/Summary Feynman diagrams are a combinatorial device for enumerating a sum of integrals of products of delta functions. Feynman diagrams are a mathematical tool with no physical significance. In particular, no single Feynman diagram is intended to represent any physical...

Hi all, I've been reading about biconvex lenses, drawing ray diagrams and real/virtual images. I'm now trying to translate this into how an image is formed in a compound infinity optics microscope. And this has raised some questions: -In an infinity optical system the object is placed at a...

4m3 rigid tank contains saturated H2O vapour at 3.5 bar. When this tank is left for a long time in a laboratory at 25.4oC, its temperatures reduces to this temperature. The thermodynamic properties of H2O is attached. Questions What would the boundary of the system be and what would the...

Let's use the material brass as an example. My problem is that I have no understanding of the concept of "phases". In the phase diagram for brass, we have α, β, γ, δ, ε, and η phases as well as the liquid phase (L). My question is, how do I interpret these phases? What is the difference...

Hi folks, I'm assured that scattering cross-sections in QFT computed at tree level correspond to cross-sections in the classical theory. For example the tree level cross-section for electron-electron scaterring in QED corresponds to scattering of classical point charges. But I'm not sure I...

Draw the shear and moment diagrams for the beam in the figure. Clearly show all values, including the maximum shear and maximum moment and their positions on the diagrams. Assume the supports at A and C are rollers and D is a pin support. note there is a hinge at point B. I am having trouble...

Question: A) Explain what happens when a gas is kept in a cylinder under constant pressure while being cooled. Assume that constant pressure is less than critical pressure. Draw PT and VT diagrams for this? B) Describe and explain what is seen when a strong transparent container of constant...

Homework Statement An object with a mass of 300 kg is suspended between two cables which sag at an angle of 40ᴼ below horizontal, on either side. Draw a free-body diagram. While driving in your car, you notice that the string holding the rosary to your rear-view mirror makes an angle...

Homework Statement An object with a mass of 5 kg is suspended between 2 strings which sags at an angle of 52° Below horizontal on either sides. Draw a force diagram. 2. Attempt

Hi everyone. I have been studying CP violation in kaon systems. I would like to know is someone can explain why, to leading order, strong penguin diagrams (i.e. involving a gluon) only contribute to the K\to (\pi\pi)_{I=0} amplitude, while the isospin 2 amplitude is given by the electro-weak...

Hi Folks, Have a task , but no idea how to resolve. Will appreciate any help. Consider the function f: {5,6,7} →{A,B,C} given by f(5)=A, f(6)=C, and f(7)=B Draw its arrow diagram and state its domain, codomain and range. Is it (i) onto and (ii) one-to-one ? Explain. Does it have...

I'm trying to understand how to draw MO diagram for molecules such as CO, HF, and NO. I am finding so much conflicting information on how to order the σ and pi boxes in the diagram. Now, I know that the more electronegative atom's orbitals are going to be lower in energy than the less...

Homework Statement I am trying to write a block diagram as a transfer function. Homework Equations The Attempt at a Solution Let ##G = \frac{1}{s}##, ##H = \frac{K}{Js + a}##, and ##L= K_f##. Then wouldn't the closed loop transfer function be written as $$...

A 60kg student is standing on a scale in an elevator that measures weight in Newtons. Calculate the reading on the scale if the elevator is accelerating down at 4 m/s^2...when the elevator is accelerating up at 4 m/s^2... and in free fall. Not sure if my work/answer is correct accelerating...

If we scatter unpolarized electrons off each other and we calculate the amplitude for electrons to scatter into final states and one photon to be emitted do we get destructive interference because the photon can be emitted by either electron? Is one photon emission suppressed in favor of an even...

Homework Statement So in my notes we have the following example: So I decided to try to solve it another way, this time I flipped the figure and here is my attempt: I got the correct moment but then the signs on my shear is flipped. Does anyone know why?

For a 2nd order electron-positron scattering, the following diagrams are possible: http://www.quantumdiaries.org/wp-content/uploads/2010/02/eepp-1024x228.png My question is: What is the meaning of the right diagram - is a photon created and annihilated instantaneously? how is this possible?

I need help :( How can I draw a Feynman Diagram, starting with a Lagrangian?

I am starting to learn Special and General realitivity by reading through Bernard F. Schutz's book "A First Course in General Realitivity". However I can't seem to grasp the relationship between two reference frames as compared with a Space-Time diagram. I understand the geometry of the diagrams...

Homework Statement Show that the S' axes, x' and ct', are nonorthogonal in a spacetime diagram. Assume that t = t' = 0 when x = x' = 0. (Hint: use the fact that the ct' axis is the world line of the origin of S' to show that the ct' axis is inclined with respect to the ct' axis. Next, note...

Would someone please tell me how I would show Strontium-90 decay into Yttrium 90(and emitting Beta particles)? Would I need to use a Feynman diagram? Thank you!

I read the book of "quantum field theory in nutshell" by A. Zee. There is a "baby problem" in Page 44. I can't understand how to get the diagrams of Figure 1.7.1 from the calculation of -(\lambda/4!)(d/dJ)^4 differentiating [1/4!(2m^2)^4]J^8. How to associate this term to the three diagrams...

I met a problem when I read the textbook "Relativistic Quantum Mechanics" by J.D.Bjorken. He said we can get the potential V(r_1,r_2)=\frac{f^{2}}{\mu^{2}}(1-P_{ex})(\tau_1\cdot\tau_2)(\sigma_1\cdot\nabla_1)(\sigma_2\cdot\nabla_1)\frac{e^{-\mu|r_1-r_{2}|}}{|r_1-r_{2}|} (10.51) from the...

I understand that Feynman diagrams can be expressed either in the position or momentum representation. Is the 4-momentum conserved at the vertices in each case or only in the momentum representation?

Problem: Write the equations as a set of two, second-order ordinary differential equations. My attempt…does it look correct? Thanks in advance!

Hi, I am drawing Feynman diagrams for various Higgs decay channels. There are two diagrams I am stuck on and there aren't many examples online. They are H→gg and H→Z\gamma For the H→gg decay I had a stab at drawing the reverse of the gluon fusion diagram. Higgs decaying to two gluons via a...

Homework Statement For the beam shown in the figure: a) Draw necessary free body diagrams b) Calculate support reactions c) Draw the shear force and bending moments Homework Equations ∑Fy = 0; ∑M = 0; V(x) = ∫ L(x) ; M(x) = ∫ V(x) The Attempt at a...

A standard way of plotting an S-N (fatigue strength vs no of cycles) graph is to start off by taking a value of Sm (for N=1000) cycles and joining it to the point depicting Se(Endurance Limit). Now we commonly take Sm= 0.9Sut for steels. Now I was wandering, before you actually get to use the...

I recently graduated with a bachelors in Mech Eng and have been asked to create some wiring and line diagrams for UL approved industrial control panels for my first job. I need some good resources to guide me through this... Any suggestions would be greatly appreciated. Thanks!

Hi All, I'm really curious to know how we can predict the shapes of constant property lines (isenthalpic/constant internal energy/isotherms/isentropes/isobars) on any given plot, such as T-s and P-v or even u-s diagrams. Is there a rule to do so? Usually in practice we deal with p-v and T-s...

I wasn't sure which section to post this, I was going to put this in learning materials: https://www.physicsforums.com/forumdisplay.php?f=151 But it says I cannot post there...anyway, Are there any good programs, preferably free or inexpensive, that are useful for drawing professional...

Homework Statement http://postimg.org/image/4lvunjeoz/ Solution: http://postimg.org/image/v1d7gilef/ When you have to calculate the internal forces at a point, how do you decide which forces are included in the free body diagram? For D, why isn't the rectangular bit of the distributed load...