Interaction Definition and 653 Threads

Can someone please tell me the name of the theory describing the interaction of photons with charged particles eg electrons, protons? Can you also suggest a good introductory web page describing that theory at First Year University level for self study? Better still, a good VIDEO lecture on...

Hi, I have been getting a little confused; the textbook (and from what i can see on-line) are saying that Hadrons only interact through the strong interaction (along with the electromagnetic force if charged Q) and yet K Mesons decay through the weak interaction. If my understanding is correct...

To whom is able to answer this: I think that when radiant energy get in contact with matter three basic phenomena take place: 1.- Transmission 2.- Reflection 3.-Absorption and emission I think this three basic phenomena enclose all phenomena that can occur after the interaction I wait for...

hi, I'm a student and i have an electromagnet and a bar magnet paced head on coaxially and i want to calculate the force between these two when the distance is around 0.5 cm. please help I'm unable to find anything useful after browsing various websites. Thanks in advance.

Hi, In many quantum physics books I see questions such as "what is the spin-orbit interaction in this case?" Sorry if this seems like a dumb question, but what do they mean by this? Do they mean the ENERGY of the spin-orbit interaction or something else? Also, could anyone give (or write a...

Hey has anyone had experience with a good book on Laser-Plasma interaction at a graduate level? I've seen a few on amazon and the like but they rarely have reviews so I have no idea how good they are. Thanks you!

One of the observation noted in connection with coulomb interaction is that, it is not affected by the presence of other charges. Why? Thanks.

If one has a 4-fermion vertex, like in Fermi theory : ##G_f (f_1 \Gamma f_2)(l_1 \Gamma l_2)## And you are calculating a one-loop diagram where you have the diagram of : f1-> f2,l1,l2 -> f1 (used for dispersive/unitarity approach) Where in the end you'll use Cutkosky rules to calculate...

Coming from a Chemistry background, the Uncertainty Principle always seemed to be described as an inability of precision due to strictly physical and real reasons (i.e. you have to interact with an object to measure something about it, and this certainly will alter the object). It seems as if...

How does a moving point charge affect another point charge moving at the same velocity and separated by some distance in one direction relative to an observer whom the charge are moving? What formula describes that interaction?

dear sir i want to know theoritically what would happen when three black holes are near by and exert influence on each other.

Hi everyone. I have been studying the Heavy Quark Effective Theory and at a certain point we have a Lagrangian like: $$ \mathcal{L}=\bar h_v iD\cdot v h_v+\bar h_vi\gamma_\mu D^\mu_\perp\frac{1}{iD\cdot v+2m_Q}i\gamma_\nu D_\perp^\nu h_v. $$ h_v is the field representing the heavy quark, v...

Dear All, I have read many posts on this forums about the interaction of photons with the atoms of transparent materials. The point that I was searching for in particular was "why is the speed of light in transparent material less than c". The explanations given by many about the absorption...

When we describe the amplitude of two interacting particles, we are integrating w.r.t the relative momentum of the particles. Why we do this? Thank you all of you.

Hi guys, I need some help on this question: Derive the van der Waal interaction potential between 2 spheres of radius R_1 and R_2 using the Hamaker approach. Take the distance between the center of each sphere to be D. Thank you very much for your help!

Homework Statement The interaction between the spins of the two particles in a hydrogenic atom can be described by the interaction Hamiltonian $$\hat{H_I} = A \hat{S_1} \cdot \hat{S_2}.$$ Compute the splitting of the ground state due to ##\hat{H_I}##. Both particles have spin 1/2. Homework...

I came across a worked example question in a particle physics book this morning that had a beam of neutrinos of energy 2.3MeV incident on a lead target. The point of the question was calculating the thickness of lead needed to reduce the beam intensity by a certain fraction - and the solution...

In SM, people say the ##SU(2)\otimes U(1)## theory unify the EM and weak interaction. I understand that the two interactions both originate from the electroweak theory in a mixed way. But does this mean they are unified? Since when we talk about unification like GUT, we require the couplings run...

How can we determine the ranges of strong interactions and weak interactions? Can calculations of relevant scattering cross sections do this? Thanks.

Homework Statement Homework Equations The Attempt at a Solution I can extend the bigger cap with charge density ##\rho_2## and make it a complete sphere. If I do this, I must replace the smaller cap of charge density ##\rho_1## with a cap (of same dimensions) of charge density...

Hi all, could you suggest me references that can help me in the following calculation? I would like to see how to describe microscopically the interaction of light (or in general of an external field) with a disordered system such as glass ( I can find literature only for materials modeled...

Fron wiki: [SIZE="1"] spin–orbit interaction causes shifts in an electron's atomic energy levels due to electromagnetic interaction between the electron's spin and the magnetic field generated by the electron's orbit around the nucleus. This is detectable as a splitting of spectral lines...

Homework Statement Consider a time-dependent harmonic oscillator with Hamiltonian \hat{H}(t)=\hat{H}_0+\hat{V}(t) \hat{H}_0=\hbar \omega \left( \hat{a}^{\dagger}\hat{a}+\frac{1}{2} \right) \hat{V}(t)=\lambda \left( e^{i\Omega t}\hat{a}^{\dagger}+e^{-i\Omega t}\hat{a} \right) (i)...

A bird perches on a bare high power line and nothing happens to it. A man standing on the ground touches the same line and gets a fatal shock. This is supposed to be because there is potential difference between the ground and the line which the man touches but similarly, isn't there also a...

i guess in the wigner crystal, the exchange interaction between the electrons can be neglected. What is your opinion?

Hello, I just read a question about the Ising model, and this reminds me of an old interrogation I had long ago. It is simply that: The Ising model deals with spins interacting only with close neighbors. I would be interested in a model where all spins interact with each other in exactly the...

We have a system of two orbitals 'a' and 'b'. The Hamiltonian is given as: $$H=\sum_{\sigma=\uparrow,\downarrow}(\epsilon_a A_\sigma^\dagger A_\sigma+\epsilon_b B_\sigma^\dagger B_\sigma) -t\sum_{\sigma=\uparrow,\downarrow}(A_\sigma^\dagger B_\sigma+B_\sigma^\dagger A_\sigma)+U...

A beta particle consists of a fast moving electron emitted from the nucleus of an atom. Beta particles can pass through the palm of a human hand. My question is .. Being a particle how can it pass through the palm of a hand? I still haven't done quantum Physics but I suspect that it has...

Hi! I would really appreciate you to help me answer this question: What is the physical meaning of coherent interaction (in the Dicke model for example)? I mean, coherence is well defined in classical optics, but what does it means when you ask for a system of N atomic dipoles to interact...

In every source I've checked so far, we make the assumption that we can neglect electron-electron interaction in this model but they always fail to give any reason to answer why this is plausible. Does anyone know how physicists convinced themselves of this at the time and even now (other than...

What is the Lagrangian of interaction of photon and spin zero charge scalar?The vertex of photon and spin 1/2 charge fermion is proportional with e multiplied vertor gamma matrix,but I do not know what is the vertex of photon and charge scalar.I hear that a vertex is proportional with polynomial...

Hi, please could someone help as I have got myself desperately confused with how radiation interacts with matter largely because of conflicting sources on the internet. Apparently there are 2 main types of interaction of radiation with matter; atomic/molecular vibrations and electron...

Well, I was doing a problem the other day, inserting the complete interaction QED Lagrangian into the Euler-Lagrange equations, in order to obtain the field equation governing the interacting electromagnetic field, with the Dirac field. The problem is that, by doing so, I got the equation, but...

First of all, I'm not sure if this thread belongs here or at the "Special & General Relativity" sub-forum, if I posted at the wrong place please move it. Homework Statement I encountered this problem working in my master's degree. I need to find the stress-energy tensor of the following...

Charge attraction Hi I googled why different charges attrack each other and I found severel answer but I guess this answers are not true because there is no info about in wikipedia or there is no mathematicaal explanation.I want to know these theories are true or not or this theory is just...

In my lecture notes, there is a slide about an external field interacting with a system of electron spins. In this situation can we assume that B=B_0 ( or in other words that μ_0*M =0)? I would think so, but does a system of electron spins imply that these electrons belong to some matter...

Hello, I am facing a paradox, well it seems like one, resolving the interaction force between two equally charged plates each bearing a positive charge. Let us assume this as Q, and plates having area A. On one hand , we can claim the force = Q^2/2Ae0 where e0 is the vacuum permittivity...

Hello I read the follow paper about van del waals interaction in quantum mechanics http://www.damtp.cam.ac.uk/user/gold/pdfs/teaching/van_der_waals.pdf In this paper the potential V= e^2/R + e^2/(R+y)+e^2/(R-x)+ e^2/(R+y-x) is aproximated to V \approx -2 e^2/R^3 xy with R>>|x|,|y| why...

Imagine that two electrons interact by exchanging a virtual photon. Electron A gains momentum ##-\vec{p}## and electron B gains momentum ##\vec{p}##. If the two momentum vectors are not collinear then there will be extra angular momentum left over from the interaction. In a simple Coulomb...

Hi people, I have one question, leptons and quarks are electromagnetically charged particles. Is there an electromagnetic interaction between them? Thank you for the help!

According to Fleming's left hand rule, if the direction of a current that is running through a wire is perpendicular to the direction of the magnetic field that it is in, a force is acted on a wire that moves it in a direction that is both perpendicular to the wire and the field. Why does the...

What I am trying to find out is: whether the superposition of a singe photon (across the all the paths --that the photon can possibly take) interfere/interact with the superposition of another single photon... assuming that the superimposed paths of both the photons are close enough to...

Assumptions: 1] I'm an observer at inertial rest 2] Light is going c 3] Gravitational interaction can't exceed c I'm going to use "photon" and "graviton" as shorthand to pose the questions initially. Maybe correcting the form or assumptions of the questions will provide the answer...

electromagnetism -- interaction between the electron and the quarks Which theory explains the electromagnetic interaction between the electron and the quarks within a hydrogen atom ? Is it QED or should I look at Standard Model ?

1. Problem statement i am trying to calculate the momentum and energy of the products in the reaction 7Be4 + e -----> 7Li3 + neutrino 2. Relavant equations p = mv mass of 7Be = 7.016929 u mass of 7Li = 7.016004 u 3. The attempt at a solution i know that after the electron capture, the...

Ok so I have few question and would be happy if someone could answer them or reassure me of the way I think is right, thank you. First of all do electrons that have higher energy levels can attract two ions closer than electron with lower energy? Or is it a fundamental property that has to...

Dear Physics Forum, can anyone tell me which of the fundamental interactions is involved in the Higgs Field? Or is it a new and unique type of interaction apart from the fundamental 4?

There are numerous threads here about ball lightning but I am not exactly sure have any of those addressed this issue? Now a ball lightning even though haven't been duplicated in the lab is most likely a some sort of sphere or form of a plasma or ionized gas that has to do with charges and...

Hi.. I was reading about the special theory of relativity, and was thinking about interactions and speed of source retained by the body getting ejected from the body. As per the classical idea, imagine an airplane dropping something on the ground, then the dropped object acquires the speed of...

when we say two masses or charges or particles interacts with each other, we have used the word interacts, what does that mean, does that mean a physical contact or something of that kind?