Interaction Definition and 713 Threads

Homework Statement So like let's say oil and water are interacting together. I know that they do not readily interact together and so water aggregates in a more ordered state around the oil. But then this is where I'm confused; -They say that the delta G (change in free energy) is...

simple question from a beginner to physics, in wikipedia it states that a magnetic field can be detected by its affects on a moving electrical charge, but does "not" go onto say how an electrical charge is affected by magnetic fields, is the current weakened/distorted or am i swinging in the...

Homework Statement What is the direction of the force \vec{F} on the -10 nC charge in the figure? Give your answer as an angle measured cw from the +x-axis. Problem 26.39 in Physics for Scientists and Engineers Second Edition by Knight Magnitude of the force is 4.3E-3 N Homework Equations As...

If a (charged) particle is in superposition of two different positions A and B is it interacting with itself by electric forces (and gravitational force)? Is it true that the particle is in both places A and B simultaneously?

Hello all, This is my first post on this forum, I am trying to find out about Fluid Surface Interaction (FSI), but have not found much information on it, I have two questions at the moment: 1) Can anyone recommend any literature/books on Fluid Surface Interaction? 2) I know that FSI...

I have started to learn BCS theory and I am not been able to find a derivation of the effective attractive electron-electron interaction which is assumed to explain the Cooper pairing. Can anyone point me to a reference where I can find this derivation? Jan.

Lets say i had a black hole out in space , and then i had another black hole made out of anti-matter , and they came together after they annihilated each other and produced photons , would the photons kind of orbit each other because they could not escape the intense G field , i realize...

From my understanding decoherence occurs whenever a quantum object interacts with a macroscopic sized object. So for instance a measurement involving a photographic plate registering a particle will cause decoherence of the wavefunction, which appears to us as the wavefunction collapsing...

I have heard that the coupling between Higgs to matter is weak, that it is a correspondingly weak effect. If this is true, is there any way that that effect can be made weaker or stronger? Or asked another way, what is it that sets the magnitude of the level of effect? Thanks

In textbooks one is told that, two beams of light shall propagate independently without any interactions. However, from QED, we have learned that, they can actually interact with each other, but the effective strength is remarkably tiny and hardly discernible. This insignificance is largely due...

Homework Statement So this is not really a homework problem, but it is an academic-related problem which I want to solve. Suppose in my current research position, I'm making synthetic Collagen heterotrimers, composed of A,B,C monomers, which form into a triple helix arrangement. Each monomer...

It strikes me that this may well be fairly easy, but i can't quite get my head round the correct way to lay this problem out (at least in a mathematical sense). If you are considering a neutron flux onto a fully understood material, and you also know the neutron interaction cross section of...

I have the next decay: B^0 \rightarrow D^+ e^- \nu_e The question is: employ CP symmetry on the particles in this process, what reaction would you get? and what would happen if CP symmetry breaks? Now if I employ CP symmetry I get: B^0 \rightarrow D^- e^+ \bar{\nu_e} But in my...

hey, i want to find the lowest order strong interaction feynman diagram for the following process: \Sigma^{++}_c \rightarrow \Lambda^+_c \pi^+ the quark composition is: \Sigma^{++}_c = (c u u) \ \Lambda^+_c = (c u d). \pi^+ =( \bar{d} u ) an image of a correct process is attached...

The problem: http://www.gobigbang.nl/cft/cft.jpg An attempt of the solution: http://www.gobigbang.nl/cft/DSCN2722.JPG My problem is question c. I don't have a clue how to see that the improved current is conserved... Can anyone help me? Update I managed to solve the question by using the...

Hi all I have been searching the internet but not with much luck. What can be expected to happen when a tritium is bombarded with a neutron of suitable energy? Will a neutron be knocked off or not? Regards bmeagle

Hello, my name is Artemis. These days I study at University of Science and Technology in Cracow. Due to the fact that semester is almost over one of my tutors asked me to do a quick presentation about "Ways of measuring hyperfine interactions". I would appreciate it a lot if anyone of you could...

Homework Statement Given a permanent dipole, call it pNO, at the origin pointing along r1 (general vector, not along any particular axis). A polarizable atom as at position r2. What is the induced dipole moment, call it pHe, of this atom in terms of pNO and r2? Homework Equations...

Homework Statement My problem is on questions like "say if the following interactions are allowed or prohibited, and explain why." where the interactions are something like p + p -> K^+ + K^- or e^- + p -> n + \nu_e The Attempt at a Solution Now the first one is not allowed...

Last week I posted the following question here: https://www.physicsforums.com/printthread.php?p=2735375 "Is it possible to predict the color of a solid object based on its molecular formula?" It wasn't completely ignored but the thread did come to an abrupt end after only three...

One has to wonder about photon interaction, and when to think of them as a particle and when as simply a wave. A friend of mine told me to think of them as a wave, because they are without mass. But why should I view it that way, when even theoretical mass is mass, such as weak force. So how...

When radio waves go through certain walls , I was reading about this , do they go through the wall because their wavelength is too long to interact with the matter in the wall , Does it haft to do with the crystal spacing in the matter , and in some cases is it like light going through...

"Prior interaction" as an unwarranted assumption of EPR I think it should be understood that the concept of "entanglement" is not native to the mathematical formalism of QM, but only comes to us with Einstein's assumption (in the EPR paper) that there is an initial, composite wavefunction that...

Homework Statement I have a question that says: What is the equation of motion for a general operator in the interaction picture. I.e. how does the time derivative of the operators behaves ? Show this. And then I have to find the time development for the annihilation and creation operator...

what makes a metal sheet to reflect light? why doesn't individual metal atom reflects light?

Towards the end of my atomic and quantum course my lecturer makes a note of residual Coulomb interaction and does a few graphs to show the concequences of it are (such as some states not being allowed do to symmetry) and that they favour larger values of angular momentum, but doesn't really...

Why according to QED two electrons repel each oteher while electron and proton attract. What are Feynman diagrams for these proceses. Thanks for help.

Homework Statement If there was a hypothetical interaction that occurs on, say, a scale of 10^{}-30m, where would one look for signatures of boson associated with this interaction. By that I mean what would the minimum energy be approximately where I would look for those signatures. Also...

Let's assume that we have two fields which doesn't interact at the beginning. But after some time this fields start to weakly interact. Interaction lasts only finite period of time. The density of lagrangian is: L = \partial_{\mu} \psi \partial^{\mu} \psi + m^2 \psi^2 + \partial_{\mu} \phi...

I hope someone can help me out here. I am having difficulty understanding what the difference is between the spin orbit interaction and LS coupling scheme in atoms. I know the spin orbit interaction (or spin orbit coupling) is due to the interaction of say an electron's spin with it's orbital...

I have read that charge is supposed to be invariant under time reversal. Now, if I consider two like charges placed some distance from each other, I expect them to repel and go away from each other. In a time-reversed frame, I expect them to approach each other. Since the separation is...

What is the most general reasonable form of the Lorentz invariant interaction term between a fermion field \psi and a scalar field \phi? A common choice for the interaction is something like \psi^{\dagger}A\psi\phi, with A being a Lorentz invariant matrix (like \gamma^{5}). However, I don't...

Homework Statement List all of the elements through calcium that you would expect not to have a spin-orbit interaction that splits the ground state energy. Explain. Homework Equations Not quite sure, but I'll list a few. If there are two electrons: L=|l1-l2| to |l1+l2| S=|s1-s2| to...

Homework Statement I was trying to work through some quantum physics questions and I was getting a bit confused. I know that for fermions the wavefunction must consist of spin and spatial parts of the fermionic wavefunction with opposite exchange symmetry (ie antisymmetric spin and symmetric...

Hi, I'm just trying to convince myself that the field in the interaction picture (IP) \phi_I(x,t)=e^{iH_0t}\phi(x,0)e^{-iH_0t} satisfies the Klein Gordan equation: (\tfrac{\partial^2}{\partial t^2}-\nabla^2+m^2)\phi_I(x,t)=0 . I have so far worked out that the time derivative is...

Homework Statement What is the force of attraction between a uranium nucleus(atomic number 92) and an electron at a distance of 0.1 nm? Homework Equations F = kQ1Q2/r2 The Attempt at a Solution F= 8.99*109*92*1.6*10-19*(-1.6*10-19)/0.1*10-9 Please let me know the attempt at a...

Homework Statement A particle is in a box of length L on x-axis. 0<x<L. What is the first order shift due to V(x) of the wavefunction? Homework Equations H=p2/2m Sin=sqrt(2/L)cos(npix/L) En=n2pi2hbar2/2mL2 V(x)=kx2/2 The Attempt at a Solution I'm super confused because the shift in the...

hi physicists, i have a gnawing question that could be put to rest with experiment but i lack the tools and challenged in ideas. we all know that the speed of light in vacuum is the maximum that can be attained in the universe. also light does not accelerate to that speed, it just begin to exist...

Ok, I was thinking about this the day. Let me know how far off I am on this. As we go smaller and smaller on physical scales we find that 'solid' objects are actually comprised of 'atoms' and 'empty space' <--- loose definition, the relationship of which is in proportion to the density. Like...

Hi, I am a young physics student who wonders a lot about the atom, especially it's nucleus. I thought about the atom and realized that there could never be a nucleus of two protons because they both would reject each other. I have made some calculations and realized that the gravitational force...

There are three kinds of light-cone string diagrams for four closed string interactions. As displayed by fig. 26.10, 26.11 and 26.12 of section 26.5 of Zwiebach's book. For each light-cone string diagram, it is characterized by two parameters, the time difference of the two interaction...

I have a question regarding the Coulomb interaction in spaces with non-trivial topology. Suppose we have D large spatial dimensions (D>2). Then the Coulomb potential is VC(r) ~ 1/rD-2. Usually one shows in three dimensions that the Coulomb potential VC(r) is nothing else but the Fourier...

For a particular energy level in hydrogen, with quantum numbers n and l, one will find when considering the spin-orbit interaction, the level is split into two fine structure levels with energy separation: \Delta E_{s.o.}=\beta_{nl}(l+1/2) I was trying to prove this result. The spin of an...

Hi everyone, I'm studying electron-electron scattering, starting with the Dirac equation it ends up calculating the invariant transition amplitude, defined as: -iM=(ie{\overline{u}^f}_A}\gamma^\mu u^i}_A) \frac{-ig_{\mu\nu}}{q^2}(ie{\overline{u}^f}_B}\gamma^\nu u^i}_B) With u_A and u_B the...

Homework Statement Write out: H_{SE}(\left|\right\beta,i_{\beta}\rangle\otimes\left|\right e_{j}\rangle) and exp(-iH_{SE}t)(\left|\right\beta,i_{\beta}\rangle\otimes\left|\right e_{j}\rangle) Where...

This is going to be a very elementary question, but I am having a hard time wrapping my head around it for whatever reason. In static equilibrium, like a book on a table, I have no problem seeing that the force exerted on the table by the book is equal and opposite to the force exerted on the...

I've had trouble understanding how the weak interaction could be field based, like classical gravity, or electromagnetism. My limited understanding of the interaction so far had been that left handed leptons and quarks would have an event spontaneously happen to them (such as decay). I thought...

Please see the diagram attached, I don't understand how my lecturer is resolving the E-field in the perpendicular case. He obtains: E_i = \bold{y} e^{-i\omega(t - \frac{n_1}{c} (-xsin \theta_i - z cos \theta_i))} How has he obtained the (-xsin \theta_i - z cos \theta_i) part from that...

What choices do we make about our language use?

I (moderately) understand the basics of the electromagnetic and weak nuclear forces, but I recently heard of a combined electro-weak theory. It apparently states that two forces are different manifestations of a single force at very high temperatures. Does this mean that the photon...