Interaction Definition and 713 Threads

Consider the S-matrix: <f|U(t,-t)|i> When going into the interaction picture, this becomes: <f_I|U_I(t,-t)|i_I> where the propagator is the interaction picture propagator, and the states are interaction states. Can you say that: <f_I|U_I(t,-t)|i_I>= <f|U_I(t,-t)|i> ? It...

S-Matrix is calculated in that the interaction at infinite past and future time is zero.Then how can we solve the problem of ''scattering'' where the interaction presents at all time(e.g considering interaction of electron in an atom) with QFT?

Homework Statement Object A of mass 10 kg moving at 10 m/s [E] interacts with (but does not touch) Object B of mass 8 kg moving at 12 m/s [N]. What is the minimum possible kinetic energy of the system after the collision? Homework Equations M1V1o + M2V2o = M1V1f + M2V2f KE = (.5)(m)(v2)...

Let's consider a mach-zehnder apparatus The picture is below: http://en.wikipedia.org/wiki/File:Mach-zender-interferometer.png 1. When the photon encounters (and emerges from) a half-silvered mirror does it loose any energy? The photon does change phase when it moves through a half...

Hi, I just started self studying solid state and I'm having trouble figuring out what the hamiltonian for a square lattice would be when considering the Heisenberg interaction. I reformulated the dot product into 1/2( Si+Si+δ+ +Si+δ+S-- ) + SizSi+δz and use Siz = S-ai+ai Si+ =...

Two permanent magnets are on the table some distance apart and having some arbitrary orientation relative to each other. When we let go of them they will rotate and translate until they stick together. I am looking for suitable equations to model this interaction on a computer. Also, if anyone...

Is there any other software to visualise n-body interaction of charged particles in real time by modelling both electric AND magnetic forces, like this: "Virtual Bubble Chamber" Electric and Magnetic Fields: Positron & Electron do the helix dance...

Okay, I am not an electrical engineer but I dabble with circuits, electronics, and electromagnets. Id like to know if it is possible to measure the voltage, or current (not sure sure which is applicable here) using the measurement of interaction between one small magnetic field produced, and...

I know that the generators of the Poncaire group that are associated with *orbital* angular momentum belong to an infinite dimensional representation, i.e. \begin{equation} L = \frac{\partial}{\partial \theta} \end{equation} Also the spin generators are associated with some finite...

I'm just wondering... Regarding the single & double slit experiments... Why does every interpretation say that the photographic screen is 'measuring' the position of the particle traveling towards it? Why not say that the photographic screen interacts with an electron that is spread out...

hello! I want to know which factors determine the strength of interactions between two atoms (which both or one or none can be a part of a bigger molecule) thanks

The strong interaction has color ''charge'',the electromagnetic interaction has electric charge,the gravity interaction has mass ''charge'',then what is the charge in weak interaction? Each interaction corresponds to a symmetry.Symmetry SU(3) for strong interaction, SU(2)xU(1) for...

Question on Molecular Orbital Theory (and the "dot" that represents no interaction) I have a question about the "dot" that represents no interaction between orbitals. For example, in the molecular orbitals of H3, there is the lowest energy molecular orbital that has two bonding interactions...

hello! which equation descripts the electrostatic interaction between two non-point (ie. that have dimensions) charged particles? thanks!

I can't find sth about self interaction which tells for sure in what situations we should consider it and how to manipulate it! Can we talk about self interaction for e.g. a single electric charge?Or it appears only in certain cases?How should we calculate it? Thanks

How does light cause matter to move? For example, when a photon collides with an atom, an electron absorbs the photon and moves to a higher energy state. If the energy is not used then the electron falls back to a lower energy state and emits radiation. I am unsure of how the photon in the above...

Ok so I was wondering, let's say I have a device (eg., shaped like a toothpaste box with the two square ends cut off). I make 2 of the opposite faces from copper plate and the other 2 from iron plate (for example). I then generate an electric field in the box with the copper plates, and a...

hello! which factors determine, which parameters affect, the strength of an atomic interaction or bond? thanks!

For my understanding of electron-phonon interaction is that when electron moves across a lattice, it distorts charges and it leads to a higher density of positive charge at an instance of a second. As the electron leaves the region of high positive charge, another electron will jump into...

Let's suppose, we have two ideal point charges q_{1}, m_{1} and q_{2}, m_{2}. One of them comes from almost infinite distance with relative velocity v_{0}, w.r.t another charge. I'm curious how can we analyze this situation mathematically, i.e the equations of the motions of these particles...

Hi, there are two material points with unitary mass that can move on a stright line. They are subject to a potential of mutual interaction V which depends on x and y and it's not symmetric, where x and y are the coordinates of the two points. I can choose in the istant 0 v1,v2,x and y. How...

Roger Penrose in Chapter 25 of his book The Road to Reality describes a "zigzag" model of the electron that consists of a pair of massless components one with a left-handed spin (the zig) and the other with a right-handed spin (the zag). He says that the Dirac equation can be written as a pair...

Recently, I was surfing Youtube looking for scientific videos, and I came across one on black holes. Naturally, I figured I'd already heard it all before, but decided i might as well watch it anyways. At one point, it talked about black holes making "dents" in space-time due to its its gigantic...

Is the wave function, an unreal (but a useful mathematical) tool, to partially model a real interaction? i.e. can probabilities have an existence of their own? i.e. exist by themselves without referring to some underlying phenomena? The wave function is a mathematical/probability tool. It is...

Both the strong and weak interactions are short range forces of approximately 1 fm. Two protons are separated by this distance. Which equation should i use for these two question? i) The strength of the electrical and gravitational interactions that influence each of these protons. ii)...

Hi, I'm reading ad article of Lal et al (junction of several weakly interaction quantum wires: a renormalization group study). It's quite cleare but there are some row I'm not good to understand. Could someone help me to understand how obtain equation (6) from equation (4)? I don't know how to...

I was reading a description of the many-worlds interpretation and it stated that the separate universes cannot interact with each other. But in the double slit experiment isn't the interference pattern that is seen when both slits are open, specifically caused by this interference? How can...

I guess it does not produce any field in 2nd coil because there's no change in current in coil right?So there won't be any emf .. but coil 2 has magnetic field passing through it which results in current in coil(by forcing movement of electrons of coil 2 SINCE ELECTRONS ARE ALREADY IN MOTION...

Hi, It never occurred to me before, but when you derive the spin-orbit Hamiltonian as a perturbation to the hydrogen Hamiltonian, you imagine your electron orbiting around the nucleus, and of course that's not the correct picture because of the electromagnetic radiation that leaks out. So I...

Question about this "interaction" in QFT Hi, I started two months ago my course in QFT, and since I heard about the fact that the bare mass appearing in the Lagrangian of a theory isn't the physical mass of a particle (due to self interaction, I guess), I tried to find an example explicitly...

I'm currently doing a project on how the solar wind interacts with the Earth's magnetic field, but I'm having a hard time grasping the concept of the plasma emitted by the Sun and how it shapes the Earth's magnetic field. I read somewhere about a simple mirror dipole approximation (I'm guessing...

Homework Statement A supernova can produce a neutron star with typical radius 10km. Assume the neutron star matter consists of iron nuclei (A=56), produced by the electron capture reaction: e^{-}+Co\rightarrowFe+\nu_{e} The matter density is \rho=10^{5} tonne mm^{-3} and the neutrino...

Well, I would like to know the interaction process of an x-ray photon with ice? Thanks in advance.

First of all, I've already had and scheduled SEVERAL appointments with a psychiatrist, and I'm not asking for self-diagnosing advice - I'm simply wondering what I should look forward to after all the checking is done.So let me begin with a list of symptoms that I'm experiencing, or have...

Lets say, we have a cathode that emits electrons into the space under field emission and create a space charge in air.There is no arching of electrons to anode.We have hot dense gas which blow on space charge in certain direction.What would be the most likely outcome of interaction between...

Homework Statement Initially the three spheres are uncharged; then sphere A is dragged across a t.v. screen with an excess charge, giving (A) an excess negative charge. Then (A) is placed next to (B) and all three spheres lie on a line. There is a wire connecting (B) and (C). We want to...

2 questions on symmetries: "conserved in interaction => eigenstate in interaction"? Hello, I'm currently taking an introductory course in elementary particles (level: Griffiths) and I have 2 questions that are severely bothering me; all help is appreciated! They are related to Griffiths'...

I need to report about the Van der Waals interaction in our Quantum Mechanics class. Can someone please help me sort things out about Van der Waals interaction? How do go think should I go about it? In our book, the only thing discussed is the Van der Waals interaction between two hydrogen atom...

; Can someone explain to me (in layman's terms,) how it might be possible to associate the interactions of the up/down quarks in the strong nuclear force as analogous to the way electrons and photons interact in quantum electrodynamics ?

Hi Say I want to describe the interaction between a free atom atom and a classical EM field. The full Hamiltonian for the problem must be H = (H_0 + p^2/2m) + (H_V + H_E) + H_D where H0 denotes the internal levels of the atom, HV the vacuum field, HE the energy density of the classical...

What kind of force mediates the reaction: K- + alpha(ppnn) -> pi- + "hypernucleus"(ppn lambda) s(u) + (uud + uud + udd + udd) -> d(u) + (uud + uud + udd + uds) (u) is anti u We need to explain which force mediates this reaction. I am pretty sure it does not involve the weak force...

This is a follow-up of the following thread on refraction: https://www.physicsforums.com/showthread.php?t=576212&highlight=photon In a nutshell, an optical photon that traverses a solid dielectric extends over many atoms. While the photon traverses the dielectric, it continuously transmits...

There is given two neutral parallel plates, distance between them is d. Between them is putted insulating plate with a thikness of d. After that one of two plates was charged positively. How can I find electrostatic interaction force?

Hi all, While the articles I have been reading are about a year old (which can be considered relatively outdated in terms of particle physics) I have been looking at the possibility of Neutrinos being able to travel at FTL (Experiments conducted by CERN and OPERA). I understand in the articles...

Hi When looking at the interaction between an EM-wave/field E with an isolated atom, we know that they interact via the time-dependent dipole interaction V = dE. This can be derived by looking at an electron bound to an atom, and it is used in systems, where the atom can be rightfully...

Hello, as far I understand wavefunction collapse (or decoherence or whatever stops particles from acting as waves) is initiated through something referred to as a measurement. These measurements are thought of as interactions. Now the question I have is, why are some interactions measurements...

I am currently reading E=Mc^2 and have a quick question regarding some of the nuclear fusion they describe that takes place in stars: When proton fusion occurs, one of the protons decays into a neutron + positron + neutrino – due to the weak interaction. And the proton and neutron , acted...

Please teach me this: Why is CP symmetry violated in electro-weak interaction? Is it correct that because of the mass of neutrino is zero(so that the left and righ neutrinos do not mix with each other)? Thank you very much in advance.

According to the mathematics of sub-atomic particles, unless your force parameters on them, their wave function extends indefinitely through space, so why is it that interactions only happen at certain distances? Is there some kind of critical boson exchange rate?

Hi all, I am doing a masters in SSSI and I am a mechanical engineer so a lot of this stuff is all new to me (manly civil engineering based masters) so I have a question for the pros. (I will also do some analysis on SSI (soil-structure interaction) What is a good software to use to analyse...