Interactions Definition and 281 Threads

Suppose you have a container with perfectly reflecting walls, containing electromagnetic radiation that is not in equilibrium (i.e. does not have a Planck distribution of energies.) Will photon-photon interactions (QED and/or gravitational) produce a Planckian distribution after a sufficiently...

Homework Statement Derive an expression for the rate of interactions in a fixed target experiment, for which the beam of incoming protons has a current I, the target density is ρ(g/cm^{3}), the target thickness is d and the interaction cross-section is σ. You assume that the beam particles...

Let me start off by saying that I am no professor of any kind, i am simply a high school student in way over his head concerning particle interactions. Without a class to teach me, i have used the magic of the internet to attempt to get a rudimentary understanding of these interactions. I...

Homework Statement i need help with this problem (Online HW) If the force of attraction between a 1035 kg sports car and a 10680 kg cement truck is 3.930×10-6 N, how far are they apart? Homework Equations F = Gm_1m_2/r^2 The Attempt at a Solution

If it is electrical, why is there attraction between atoms? Shouldn't they repel each other due to outer electrons?

When I start DrJava in Eclipse the Interactions Pane gives me this: "Could not creat the view: Wait for interpreter to register was interrupted (probably timed out): java.lang.InterruptedException" What does this mean and what do I do to fix it? Thanks

hi i have a question about excited state: let me say you have an atom and then you use light to get the electron to a higher energy level. does this mean, that there is always a spin change, cause as far as i know the spin of a photon is 1. but what happens if you have an electron...

Hi all, I've been having a problem with understanding some of the van der Waals forces. I understand that the polarizability of a induced-fixed dipole interation is: \begin{equation}\alpha =4\pi\epsilon r^{3} \end{equation} Which leads to the potential field (assuming two different...

Homework Statement The question was, you have a Helium ion with one electron in its ground state. Then a second electron is added to the n = 10 level. What effect does the second electron have the first electron that is nearest the nucleus? Is the energy increased or decreased? Homework...

Please teach me whether this is correct: It seem to me that the velocity of propagating of all type of interaction is the same value c as the velocity of light.Because equation of propagating of phase p.x=0 leads to v=E/p^(where p^-modul of spacelike-momentum)=square(c)/v then v=c.Where p is...

Are there any W^\pm or Z^0 interactions that change lepton flavor? For example, turn an electron into a muon or vice versa? Thanks!

Im having a little bit of trouble with SuperSymmerty. I understand all the basics with the sparticles and gauginos being -1/2 less and how their properties change to boson-like and fermion-like respectively. What i don't understand is how do the interact exactly. i know none have been found in...

Sorry if I posted this in the wrong forum, to me it looks like this forum is for high energy, nuclear, OR particle physics. I was wondering if anybody could help me with this. I was trying to ask my teacher about the nature of energy transfer, and she said something that I really believe is...

Homework Statement The proposed maximum colliding beam energy, Ec, in the Large Hadron Collider is 7TeV per beam (proton-proton collisions). By a Lorenz transformation, show clearly that to produce the same centre of mass energy in a 'fixed target' interaction, the beam energy woulr have to...

I have heard that social skills are very important. (I'm an engineering major.) What kind of social skills, specifically, are important? I have no problem carrying a conversation with an intelligent person about either a common interest we share or about an idea. This ranges from...

I am deeply confused about the following and I'd really appreciate it if anyone could help! Consider a charged hadron such as a proton. Amongst the state-independent properties that define a proton are strong isospin Iz=1/2 and charge Q=e. Now, the total Hamiltonian for a proton is Hs...

I'm wondering if the potential term in the Lagrangian for a single particle is just an approximate way to summarize all the interactions of virtual particles created by the potential at every point. For example, the EM field is mediated by photons at every point in space. In reality an electron...

I'm just curious, as space offers the huge length scales that could substantially lengthen the attractive interaction between positive and negative charges (although charges will still be repelled from other like charges)

Is there any science out there that associates electrons with having different frequencies of their own (like light has different frequencies) depending on where they are in which atom? I'm just wondering why electrons have particular quantum jump differences between the different types of...

Hi all, I have (what might be a rather odd) question about the interactions between real and virtual particles. Let's say we have an isolated proton, moving slowly through space. There will be virtual proton/anti-proton pairs popping in and out of existence in the surrounding space. On...

Hello. One confusion regarding the explanation of electromagnetic [EM] interactions through photons. Conisder the water jug example given in this wikipedia http://en.wikipedia.org/wiki/Fundamental_interaction#Electromagnetism". It says - "if we place two such jugs a meter apart, the...

Homework Statement How do we determine whether we have a strong or a weak interaction? (for the following processes) For example we have a reaction K^{-}+p\Rightarrow \Xi^{-}+K^{+} or another example K^{+}\Rightarrow \pi^{+}+\pi^{0} thanks!

I'm not using the template because, again, it's not a question I need help with, it's understanding the topic so I can actually do the homework. :P First of all, is interaction completely different to decay? Because all hadrons interact by the strong interaction, and yet they can decay into...

My question is how to compute the ratio of cross section (mediate by charge current) of neutrino/ anti neutrino of electron in a nuclei which is made of an equal number of proton's and neutrons The same question to neutral current. I have to deliver soon my work. I hope you can answer...

Can someone point me to a reference that explains how the (effective) running coupling behaves in the weak interactions(at 1-loop order). I couldn't find it... If I understand correctly, than the coupling is g = \frac{e}{sin(\theta_W)} where e is the QED coupling, which increases with energy...

Hi, I keep reading about particles being produced in certain interactions, but I'm not completely clear on what this means. The image I have in my head is this. Say two protons collide with each other and move off with less energy than they started with, and the energy deficit goes into creating...

hi, it is a known fact that quarks are the most massive particles, and they interact with the 4 forces. then electrons, muons, and tauons are less massive, and interact with 3 forces. finally neutrinos are even less massive and interact with only 2 forces. I wonder if there is any...

hi, I wonder if the electromagnetic force is the force that expresses how pressure interacts. I mean, a pressure is a force divided by a surface. is that force the electromagnetic force, that would be the consequence of an increased kinetic energy?

Is the Jellium model only suitable for an electron gas of infinite volume? If I confined a gas to a finite volume using an infinite potential well, is there still a way to cancel out the infinities in the coulomb interactions between electrons?

Homework Statement So basically I'm sort of unclear as to what van der walls interactions are and how they occur...like I know that they're a type of noncovalent bond that occurs between identical groups in two molecules. Like, how do the partial charges appear? (e.g. let's say there are 2...

I would like to do some reading about how EM waves interact with each other via internet. Upon googling "EM wave interaction," I got some general links about EM radiation and some book titles but I didn't see any websites. Does anyone know one or more good online sources that give an overview...

Hello, First of all, sorry if my question is trivial but I'm not a physicist ;-) I heard a lot about the Ising model used to compute the energy of a system with 2 states. This model seems to be a bit "simple" because it assumes that particles interact with their nearest neighbors only. I was...

I know that particles don't have much mass and that the "force" of gravity is weaker than elecromagneitic or nuclear force, but gravity isn't really a force, it's a warping of space time related to energy density. Particles are quite dense so they should significantly warp space on a small...

I understand that the Colour Force is described by Quantum Chromodynamics, Electromagnetism is described by Quantum Electrodynamics and Gravity will hopefully be described by a Quantum Gravity Theory but currently General Relativity. But what Theory describes the Electroweak Interaction? Is...

hello I'm studying nuclear physics and I have a lot of questions which I can't figure out. The first thing has been thrown in my mind by a colleague of mine about propagators of particle interactions. It has been said that, for example, photons are the mediators for the electromagnetic...

Homework Statement three distiguishable spin 1/2 particles interact via H = \lamda ( S_1 \cdot S_2 + S_2 \cdot S_3 + S_3 \cdot S_1 ) a) What is the demension of the hilbert space? b) Express H in terms of J^2 where J = S_1 + S_2 + S_3 c) I then need to find the energy and...

What does it mean for the contact between two surfaces to be "perfectly rough"?

"interactions between polar materials and electric field" sorry typing error.polar materials are those who have a permanent dipole ( like water molecules ) but these dipoles doesn't appear on the macroscopic scale due to their random orientation , so what if this polar medium is subjected to...

Homework Statement Shown at right is a cross-sectional view of two long straight wires that are parallel to one another. One wire carries a current out of the page; the other carries an equal current into the page. I don't know how to show the diagrams, but the current into the page is at...

I did not quite understand the "stimulation" part. How does the photon coming near the excited atom force this atom to emit another, identical (from the physical properties point of view) photon? More precisely, how do the stimulating photon and the atom interact?

Hi folks, I have a question about virtual particles, and so far I haven't been able to find an answer. Do virtual particles ever annihilate with real particles? (Black hole evaporation aside) For example, let's say we have a (real) electron, floating in space, and a virtual...

I was listening to the regional NPR station yesterday and hear a brief discussion of two binary systems. http://stardate.org/radio/program.php?f=detail&id=2009-12-26 Is this common? Is it plausible? I presume that some how the velocity of Mu Columbae and the other star traveling 'north'...

Homework Statement Just a quick question, the Z can couple to leptons and there antiLeptons and quarks and there corresponding antiquark. Is the coupling constant just Gz for all these interactions? Or is it Gz.Sin(z) for some and not for others? Iv seen different notation and am wondering...

I'm struggling a bit with my module on particle physics. This is only part of the problem set, but I need it for the rest (which is asking whether or not some particular decays are possible). My problem is: How can you tell which is the most likely interaction for certain processes? For...

I have some well ordered feyman diagrams which have an incoming neutrino interacting at a vertex with a w boson and emitting an electron. since a neutrino can pass through some 18 light years of led without interacting, I'm wandering how a single neutrino interacts at this vertex?

If we consider a system of N suspended particles diffusing through a narrow channel. What happened if the hydrodynamic interactions are neglected? Is there only flow? How can the particles diffusse without flow?

Homework Statement The tungsten cathode in an electron microscope has a work function of 4.5 eV and is heated to release electrons that are initially at rest (near the cathode). The electrons are accelerated by a potential difference that creates a beam with a de Broglie wavelength of 0.040...

Hello, I know that Wen might be able to get W Z gauge bosons and chiral neutrinos using his lattice bosonic models he is unable to get chiral interactions using standard bosonic lattice on minkowski space. If instead he used Connes' noncommutative space would he be able to get chiral...

For the process where two neutral pions turn into two charged pions, I noticed that this can occur through both the strong and weak interactions. Through the strong interaction it is a 4-pion vertex, and through the weak interaction it involves a virtual W-particle. If I were asked on a quiz...

So I was studying in the library, and I noticed this very beautiful girl a few rows down, and I was kinda staring at her (... ok yes, I was staring), and then she looked up and caught me staring at her. I mean, it's only natural to stare at attractive people, isn't it? It's their fault their so...