Interactions Definition and 281 Threads

John Wheeler made the statement - “Time is what prevents everything from happening at once” However, at a quantum level (and other levels too, but let's focus on quantum and disregard gravity for now) particles can only change state if they interact with other particles. The particles that...

Hi, I'm trying to calculate the distance between Earth and moon and how the other planets and sun interfere in this system. I would like to know how can I solve this. What equations should I use? Will this also make me able to know how far the moon is "going away" from us? Thank you

A. Garrett Lisi, L. Smolin and S. Speziale, “Unification of gravity, gauge interactions and Higgs bosons in the extended Plebanski formalism,” to appear. This interesting reference was found in a recently posted preprint by Smolin and Speziale. (thanks to MTd2 for spotting the Smolin...

The production of a muon/antimuon pair from an electron and positron or... The production of a neutrino/antineutrino pair from an electron and a positron? The only weak interactions I know of are beta-minus decay, beta-plus decay and electron capture. All the sources I've found say they...

A completely positively ionized material would be practically invisible? Normally it interacts with electrons, witch tell them what to do next (reflect, pass trough..), but a completely positively ionized matter wouldn't have any electrons to interact with. Of course they can still interact...

I have always wondered about this particular problem, when three electrons are arranged in a triangle and the question was to calculate the force experienced by one of the electrons. My physics teacher taught us that we only care about the forces colored in red and blue, totally ignoring the...

soo... this is my first post and I'd like to start out by thanking the PF people for existing and helping the resting of us out. =P I'd also like to preface my post with, I took physics in high school and that was it. i remember that i really liked it but my career path has taken me more...

Homework Statement Shown at right is 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. Draw a vector on the diagram to show the direction of the magnetic field, if any...

The "Strand Model" of fundamental interactions [Mentor's note: This thread is a consolidation of three different threads which were started in our Beyond the Standard Model forum. They were moved to our former Independent Research forum, because in our view this represents a "new" or "personal"...

I was wondering the following: Does time effect the nucleus and Electron differently? Since Electrons travel at extreme speeds while the nucleus is almost static? How does time effect the area between the two?

Hi, I'm an undergraduate physics student and I'd like to know more about interactions of light with matter. Since I haven't studied Quantum Physics yet, I'd like to know what happen on a microscopic scale, when e-m radiation passes through a material (transmission), when it's...

Is there a collection somewhere of particle interaction descriptions? For example, if I'm wondering what an electron-positron interaction does, what website can I type "electron positron" into and get back a handful of Feynman diagrams of relevant interactions? If that's too idealistic, is...

Recently I have read some non-technical publication and books on strings (ex. The elegant universe by B. Greene). Greene says that the string theory unifies all interactions and explains their nature. In fact I haven’t found any explanation why do particles / strings interact. I mean – why do...

Hi Friends, I am an undergrad currently taking my first course in particle physics. In thinking about various possible reactions, I have run across what appears to be a rather basic question: Why are reactions of the form e^- + e^+ \rightarrow \gamma \rightarrow q + q^' where q and q' are...

This is not possible because lepton number is not conserved. The lepton number of the LHS is 1, while the lepton number on the right is 2. I would say this is possible. My Feynman diagram is mediated by the z^0 boson, I'm pretty sure I've put the arrows in correctly. I would say this...

I was reading a paper on yeast two hybrid, and I was wondering why a bait protein and GAL4 activation domain show growth on Leu- medium. I thought there should be no interaction since there is no prey protein?

Hello, I want to derive the connected two point function for the interacting boson-fermion theory. I know that the generating functional is Z(J, \overline{\eta}, \eta) = N \; exp \left( \int d^4 z \; L_{int} \left(-i \frac{\delta}{\delta J(z)} \right) \left(-i \frac{\delta}{\delta...

please help me with optics and wave interactions! 1). A 12 cm tall object is placed 16 cm to the left of a convex lens which has a focal length of 9 cm. a). Where will the image form? (image distance) b). What kind of image is formed? 2). A 15 cm tall object is placed 30 cm to the...

When 2 electrons come close the "throw" photons at each other causing them to move to opposite way. All I want to know is if you had a proton and electron coming close, do they "throw" photons outwards to come closer? Sorry this is probably an easy question!

Hi everyone, So, I've got some questions that fall into the category of social etiquette. I'm an undergrad, will graduate this year, and am looking at potential graduate programs, so hopefully I'll be visiting a few schools in the spring. I might also be attending a conference in my field...

From Wikipedia: "Phonons are not always in local thermal equilibrium; they move along the thermal gradient. They lose momentum by interacting with electrons (or other carriers) and imperfections in the crystal. If the phonon-electron interaction is predominant, the phonons will tend to push the...

Some Fundamental Interactions Of Matter Found To Be Fundamentally Different Than Thought ScienceDaily (July 2, 2008) — Collisions have consequences. Everyone knows that. Whether it's between trains, planes, automobiles or atoms, there are always repercussions. But while macroscale collisions...

Hi, Atmospheric gamma-ray extensive air showers are induced by pair-production interactions. The equation that governs pair production is: \gamma + \gamma = e^- + e^+ My understanding of the interaction is that a gamma passes "close" to the electric field of a nucleus. The nucleus acts...

If the polarity of the organoclay sufficiently matches the monomer or prepolymer，it will intercalate into the galleries,futher spreading clay layers apart.For long chain onium-exchanged organoclays,the galleries swollen by these precursors show a d-spacing indicative of a paraffin monolayer...

This animation is amazing! It shows molecular interactions between DNA and other molecules. http://uk.youtube.com/watch?v=4PKjF7OumYo&feature=related How do you think they were able to get the information to create this animation? The molecular interactions could be mathematically...

Suppose I couple a fermion field to a scalar field using \mathrm{i} g \bar{\psi}\psi \varphi and \mathrm{i} g \bar{\psi}\gamma_5\psi\varphi. I'm trying to understand what would be the physical difference between these interactions. I know that (1/2)(1\pm \gamma_5) approximately projects out...

I'm having a lot of difficulty finding info on the properties of virtual photons - things like their polarization when exchanged between positively and negatively charged particles. Feynman says, in his book QED: the strange thory of light and matter, at p. 120: Photons, it turns out...

I have just read, in general, weak interactions, have the lowest Q values; meaning they have the smallest cross sections, which means they control processes in stars at some time in the early universe. What would be the next relative strength? Cheers

I would like to know what are some examples of what two nuclei would have to experience in order to become entangled. Could being part of the same molecule yield such a state? or would they have to be, say, daughter products of a nuclear reaction, etc? big thanks, Mark

Hi, We are learning particle physics at the moment in school. My teacher was telling me that when matter meets anti matter, they annihilate each other out. My question is what happens when an anti proton meets a positron or when an anti neutrino meets an electron. Would they annihilate each...

Are medication interactions much more likely to occur between two medications than among three?

What is the justification behind these models to assume electrons as non-interacting? Because it is clearly not the case when considering coloumbic interactions.

Imagine that you never heard about particle before. For you the all the forces in nature are described by scalar,vector etc fields. now you calculate the hamilton of the field and the momentum of the field and you ill replace the the field say phi and its momentum by operators which...

Particles having mass=m and charge = Q travel parallel to the z axis, forming a beam of radius = R and uniform charge density = p. To keep the beam focused, an external uniform magnetic field, B, parallel to the z axis is provided, and the beam is made to rotate with a constant, uniform angular...

Are the coefficients of the CKM matrix the same for all interactions? If yes, why does the CP violation occur only in very specific interactions and not in all of then? If no, why does the coupling between family quarks interaction dependent? Thanks

Homework Statement I had a whole list of reactions and had to show whether or not they could occur... I understood most of the reasons, bar the following, but was more confused about whether or not a reaction was strong or weak... I know that if the reaction involves a lepton its weak, and if...

I originally posted this in the homework section until I realized the homework section only covers through undergraduate courses. The course I am currently in is a graduate level Medical Physics course. So if you don't mind, here is the thread I posted in the homework section. I am...

Someone is proposing to coin a new phrase to popularize technology based on quantum interaction: http://physicsworld.com/cws/article/news/31499 Is this phrase a useful one? A pointless buzzword? Or even a misnomer?

What is the basis for the sixth root dependancy on the inverse of the distance between the dipoles (in any dipole-dipole interaction)? Is it empirical or can it be mathematically derived?

At a macroscopic level it appears that when two objects collide, they physically interact and the atoms touch. However the charges of the electrons actually repel one another and they don't physically touch. Correct? A neutron however has no charge so what happens when a neutron collides with...

Homework Statement Each part of this problem describes an object in a specific physical context in which it interacts with other objects. In each case, use the macroscopic interaction categories to list the ways that the object interacts with its surroundings; and for each listed...

Hello everyone, I am kind of new to this forum. If this post belongs elsewhere, please tell me, thanks. 1. What are mediators? Are they particles? Why does the four fundamental interactions each have one or more associated mediators? Moore (my textbook's author) writes: “Each interaction as one...

Homework Statement Imagine that I throw a ball toward the floor. It hits the floor and rebounds upward. What type of fundamental interaction between the atoms of the floor and the ball causes the ball to rebound upward? a. Strong nuclear b. Electromagnetic c. Weak nuclear...

Hi, I am looking for table or something that gives a tumb of rule for van der Waals distances - I have some C C spatial interactions which I would like to determine if their interaction contributes to the total energy or should I calculate it with a Lennard-Jones potential to get an...

Before someone accuses me of being a half-wit attemtping to explore fields way beyond my intelligence, I'll just come straight out right now and say: "My highest level of education is that of a high school graduate"! I am however, on a very serious trip to learn as much as I can about the...

Whenever a process yields a photon, an electromagnetic interaction is involved. If a neutrino comes out, a weak interaction is responsible. Is there any way to see from the ingoing and outgoing particles if a strong interaction is involved?

Homework Statement A magnet is hung by a string and then placed near a wire as shown. When the switch is closed, the magnet rotates such that the ends of the magnet move as indicated by the arrows. At the instant the switch is closed determine: a) the direction of the current through the wire...

Say you (somehow) constructed a very long, sturdy rod, about a light year in length. Say it was made of unobtanium, so it has the same mass as a relatively short steel rod. Now say there are two astronauts, one at each end, and one of the astronauts gives the rod a firm push in the direction...

Hello! I was wondering if anyone could provide me with any advice on a better interatomic potential than the Lennard-Jones (Mie 6-12) potential for carbon-carbon interactions. I know that L-J fails for metals, but I am not sure how good it would be for carbon-carbon interactions. Are there any...

Can QFT be used to anything else but particle collisions? Particle collisions seem to be the major application of the theory, but it hasn't become clear to me if it works for anything else.