Interaction Definition and 713 Threads

I have attached the pages in Kittel's book (pages 417-420) regarding my question. My question is simply based off of the second to last photo, where e_f = 5*10^4 K and e_1 = 1K. e_2<e_f and |e_2|<e_1. So how can (e_1/e_f)^2 be less than 1? The energy of the free flowing electron is assumed to...

If there are three bodies A, B, and C arranged linearly, and B is free falling towards C, will the gravitational presence of A affect the rate of free fall of B towards C?

When introducing renormalization of fields, we define the "free Lagrangian" to be the kinetic and mass terms, using the renormalized fields. The remaining kinetic term is treated as an "interaction" counterterm. If we write down the Hamiltonian, the split between "free" and "interaction" terms...

Part a was not much of a problem. I got that $$m=QR\omega \hat{z}$$. From that, I get $$A_{dip}=\frac{\mu_0}{4\pi}\frac{QR\omega}{r^2}\hat{\phi}$$ (using $$\theta=\frac{pi}{2}$$. My problem occurs in part b. I know there is a potential energy relation for two dipoles, but what would I use for a...

A textbook gives an example of an ideal mass striking an ideal string here: This is drawn as an equivalent electrical circuit as follows, where each R represents one of the two string segments the mass interacts with (ie. the string segment to the left of the mass and the string segment to...

When is weak interaction actually a force, rather than merely cause of some process? Not in beta decay - it is process. There are simpler weak interaction processes around: elastic scatterings that change only momentum but not taste. But those are still processes and are over as the particles...

For a system of interacting particles, is it possible to define single-particle phase spaces? If not, why?

While writing out the Dyson series due to the time ordering above I encountered the two expressions $$T(\mathcal{L}_{int}(x))\quad \text{and}\quad T(\mathcal{L}_{int}(x)\mathcal{L}_{int}(y))$$ I was able to write out the first term in terms of contractions using Wick's theorem and then finally...

When working on the interaction picture you can show that in a certain rotating frame the Hamiltonian of a 2-level system (for example) becomes uncoupled. This implies that in such frame there are no Rabi oscillations or other dynamical phenomena, this seems weird to me and I would like to know...

I want to understand this topic but I can not understand very well so please suggest any reading for good conceptual grasp of this topic.

Let there be four spin (1/2) particles at the corners of a tetrahedron, coupled such that the total hamiltonian is given by $$H=\sum_{i\neq j} S_{i} \cdot S_{J}$$. How would I go about showing that each component of the total spin $$\sum_{i} S_{i}$$ commutes with the hamiltonian. Work so far...

Hi I'm looking at David Tong notes on QHE http://www.damtp.cam.ac.uk/user/tong/qhe/two.pdf (page 56), I've attached the relevant screenshot below also. I understand we are working in the interaction picture whereby states evolve via the Unitary Operataor EQ 2.10 in the notes(I think this is...

I tried an approach where I build the interactions one by one and then add them all to find the total potential energy. The electric field of particle 1 induces a dipole moment on particle 2 given by ## \mu_2 = \alpha_2 E_q(2) ##(by ##E(2)## I mean the field evaluated at the position of particle...

Greeting all! So I apologize if this has been explained to death and if so, please advise as I do not want to clog up the forums with the same questions over and over. A little background first, a coworker and I routinely talk about astrophysics and quantum mechanics( yes, somewhere out there...

For Elastic neutron interactions with matter, they mentioned that the neutron will collide with atomic nucleus and the recoil nuclei quickly become ion pairs and loose energy through excitation and ionization. How does this nuclei become ion pair? It is when the neutron interact with it and...

One description of the interaction light with atoms states "Light waves incident on a material induce small oscillations in the atoms, causing each to radiate a small secondary wave in all directions". And another that "A photon with the right energy causes an electron to jump up to the next...

Are the interaction path and mean free path of a particle the same thing?

I'm studying the electron-proton deep inelastic scattering. In the notes that I'm studying from the author states that the time-scale for a virtual photon to interact with a proton is ##τ\sim\frac{1}{Q}##, where ##Q## is the momentum transfer with ##Q\gg M##, which is the mass of the proton. I...

Summary: specific modulation of lasers will cause ionisation, how is this being used in plasma physics? Just a simple question

I've been reading Griffths' intro to elementary particles and I encountered this symbol that looks similar to "M" called amplitude, which can be calculated by analyzing the Feynman diagram of an interaction. What exactly is it? When I hear amplitude I imagine waves, but not sure what this one's...

Can the electron-electron interaction have an impact on the conductivity? Google seems to point out that yes for some 2d materials such as graphene. But what about 3d materials? Intuitively, any lost momentum by an electron would be gained by another electron, so in average, this e-e...

I am wondering if there is a book with solved example problems I can follow so that I can carry out the following calculation: I have a set of unperturbed electron Green functions $g^{r0},g^{a0},g^{<0},g^{>0}$ and phonon Green functions $d^{r0},d^{a0},d^{<0},d^{>0}$ which are for a central...

How will the repulsion of electrons occur in the simulation hypothesis? The electrons will also create electrostatic fields around yourself ?

https://arxiv.org/abs/1512.06471 In the paper, dark plasma (that is, NOT baryonic plasma) was suggested. I'd like to know if it is compatible with many cosmic phenomena (like bullet clusters). Can you think of one where the data (especially new ones) don't support it? In baryonic matter...

Don't know how to relate the equations. Thanks for your help.

The two electrons will be repelled by electrostatic force, but they interact with weak force, means that in addition to the electrostatic force between the electrons there will be weak force?

Why do you need a weak spin orbit interactions in individual electrons in order to use the LS coupling? From what I know, we are free to combined angular momentum whenever [L1, L2]=0 and this should be true on the orbital angular momentum (and spin) of the electrons because they are...

The Standard Model Lagrangian contains terms like these: ##-\partial_\mu \phi^+ \partial_\mu\phi^-## ##-\frac{1}{2}\partial_\nu Z^0_\mu\partial_\nu Z^0_\mu## ##-igc_w\partial_\nu Z^0(W^+_\mu W^-_\nu-W^+_\nu W^-_\mu)## How should one interpret the "derivative particle fields" like...

Can the suns photons accelerate the plasma/solar wind away from the sun? or is there no interaction between them?

Hello! I attached a picture of the LHC main rings. I see 8 interactions points labeled, even if there are only 4 experiments (and the other 4 points don't even intersect). What are these 4 other points? Thank you!

We know the on-site interaction in optical lattice can be expressed as U=4pi*ħ2 a/m ∫d3x |w(x)|4 It's simply understood in a 3d system. But how to calculate this term in 1d and 2d system?

Do we know if entanglement between two entangled particles is completely severed after the particles interact? By interact I am generally thinking of interacting with the measurement device. Maybe another way of asking my question: In an EPR like experiment, if you put one of the entangled...

Consider, two fields interact with each other and the interaction term of the action is given. Now the Lagrangian density is Fourier transformed and the interaction term of the action is expressed as an integral over the momentum space. How is the integrand related to the form factor?

I am still confused about the difference between measurement and interaction. I mean when electrons are traveling from source to the screen through the slits, there are air molecules in their way. And even if the electron double slit experiment is carried out in total vacuum in a completely...

Stiff soil like tuff rock is said to be in resonance with short storey buildings (like 2 to 3 storey).. meaning during seismic movement the response in the short storey buildings would be greater. Is there any formula that can relate the two... like does stiff soil has the same frequency as...

The longer-range inter-nucleon force is not a direct result of the gluon field, but is indirectly affected by a quark-antiquark pair (meson). If this ‘residual’ strong interaction between nucleons is mediated by a π-meson, then what is the maximum time period in which the interaction takes...

The (residual) strong force between nucleons can be desribed as - The exchange of a meson (from a nucleon to the other), as in picture b) - The exchange of a quark and an antiquark: in picture a) one nucleon "gives" a quark and receive an antiquark and it's the opposite for the other I do...

A friend, well-read in popular accounts of physics, posted the following question to me: is the weak force attractive or repulsive? Now I have read about the weak interaction. I know that it violates parity, that it is involved in beta decay, that it unifies with the electromagnetic interaction...

Consider a scattering between two particles a and b that produces two particles c and d: d is stable, while c decays in two other different particles e and f. The first interaction is by strong force (time of interaction ##t_1\sim 10^{-23}s##, which is also the time of generation of c and d)...

Good evening. I'm currently studing dense matter and nuclear matter above 10^8 g/cm^3, and i know well how to insert a beta equilibirum condition in a free Fermi gás at T=0. \sqrt{K^2_{F,n}+m^2_n}=\sqrt{K^2_{F,p}+m^2_p}+\sqrt{K^2_{F,e}+m^2_e} But how do i insert the same condition of...

So I'v been told that this interaction : e- + e+ = mu- + e+ isn't allowed. Why not? I thought maybe because the mass of the muon is so much bigger, so would violate energy conservation, but the electron/positron could be moving relativistically and thus have enough energy. Apparently the...

I always struggle to know which force (strong nuclear, electromagnetic, weak, gravity) is responsible for an interaction. For example, pi+ + pi- = neutron + pi0 I would say its strong force responsible, because quarks are involved. But the pions are also charged, so how do I know it's not...

My unreliable memory is that although Schrödinger's equation treats the interaction between an electron and the nucleus as unquantised, it is more generally thought to be mediated by an exchange of quanta between electron and nucleus. I want to check on this and get a better understanding. Can...

We have the electric charge for the electromagnetic force, the color charge for the strong force. What is the charge for the weak force? Thank you. :)

Hello together, I'm interested in the electron-hole exchange energy. I would like to see how and have a proof why electron-hole exchange works. Is it symmetric or antisymmetric? More specific, I would like to have a proof that exchange with paired electrons in a molecule can be neglected...

Hi, I was wondering that if there is some kind of interaction time between two charged particles. Imagine an electron shoot to ionize an atom. This electron interacts one of the electrons in the atom. Does the ionization depend on the velocity of the incoming electron? Is it possible that when...

https://www.space.com/39837-first-stars-universe-fingerprints-dark-matter.html...

Most QFT texts, such as Peskin&Schroeder and D. Tong's lecture notes, contain a mention that the renormalizability of an interacting theory requires the coupling constants to have correct dimensions, making scalar fields with ##\phi^5 , \phi^6, \dots## interactions uninteresting. Maybe there are...

Not the best at physics but trying to understand the standard model. So can someone please tell me if this is right or not and if not, can you explain me why? Higgs bosons reacts with everything that has mass. Electromagnetic force reacts with everything that has charge. Weak force reacts with...

For a school project, I've got to choose a subject. I chose "Emergence", but I have to narrow it down a little bit. So, that's why I'm creating this topic. The definition of emergence that I use: By emergence, I mean the fact that proprieties of one scale implies other proprieties by changing...