Interaction Definition and 713 Threads

Homework Statement (a)Find splitting between F=0 and F=1 in hydrogen (b) Find the constant ##A## and nuclear magnetic moment Homework EquationsThe Attempt at a Solution Hyperfine splitting is given by: H_{hf} = \frac{A}{2} \left[ F(F+1) - I(I+1) - J(J+1) \right] The intervals are given by...

Homework Statement I am trying to calculate the following quantity: $$<0|T\{\phi^\dagger(x_1) \phi(x_2) exp[i\int{L_1(x)dx}]\}|0>$$ where: $$ L_1(x) = -ieA_{\mu}[\phi^* (\partial_\mu \phi ) - (\partial_\mu \phi^*)\phi] $$[/B] I am trying to find an expression including the propagators...

In all the places where Spin-Orbit interaction is discussed, the equations are derived by going to electron's rest frame and considering the interaction of nucleus' magnetic field with electrons spin magnetic moment. But from SR, we know that there as to be an explantion from the nucleus's rest...

The corrections to the energy per electron in a jellium model (uniform distribution of positive ion charge approximation to the regulated long range order ionic array) is given by (in units of Ry) $$E/N = \frac{2.21}{(r_s/a_o)^2} - \frac{0.916}{(r_s/a_o)} + 0.0622 \ln (r_s/a_o) - 0.096 +...

Hello! This is my first time posting, so please correct me if I have done anything incorrectly. There's something that I don't understand about the spin-orbit interaction. First of all I know that [\hat{S} \cdot \hat{L}, \hat{L_z}] \ne 0 [\hat{S} \cdot \hat{L}, \hat{S_z}] \ne 0 so this means...

I have been asked to determine the "shock regime" of a oblique shock / bow shock interaction based on the angle of the impinging shock and flow conditions. What does this mean? My initial thoughts were that I was being asked to determine whether the shock was strong or weak, but since the...

Hi. In this video: he ignores the magnetic field from current 2(I2). Could anyone give me a good explanation why?

Recently it struck me that I'm not sure I understand the weak interaction at all. What causes it to happen? I know that its mediated by the W and Z bosons and has a short range as a result of the large mass these bosons posses, but what does that range refer to? Range from what?!

Could an energetic neutrino (of any flavor), on passing near an electron, nucleon, or nucleus, be stimulated to emit a neutrino pair (of any flavor)? An example might be an energetic electron-neutrino, passing close to a nucleus, and emitting a muon-neutrino/muon-antineutrino pair., with the...

If a symmetric distribution of charge has no electric dipole moment, where does the \mu term we write in the part of the hamiltonian representing interaction with light come from? We suppose it is induced by the electric field of the light?

Anyone can help me how to argue that interaction lagrangian is invariant under gauge transformation?

Homework Statement Consider two spin 1/2 particles interacting through a dipole-dipole potential \hat{V} = A\frac{(\hat{\sigma_1} \cdot \hat{\sigma_2})r^2 - (\sigma_1 \cdot \vec{r})(\sigma_2 \cdot \vec{r})}{r^5} If both spins are fixed at a distance d between each other, and at t = 0 one of...

I have personally been deeply fascinated by the processes and principles that underlie the QED and have done some recent research myself. However, recently my teacher posted me a question that stunned me. He went,"Why do like charges repel and unlike attract?" In QED I understand that this is...

Homework Statement This is not homework but relevant to an interaction model that I am developing. I assume an even distribution of sources on a spherical 3d-hypersurface, the sources having a potential as a function of pairwise 4-distance between any two sources. I wish to obtain the sum...

Homework Statement A 0.62-kg basketball dropped on a hardwood floor rises back up to 64% of its original height. If the basketball is dropped from a height of 1.6m , how much energy is dissipated in the first bounce? How much energy is dissipated in the fourth bounce? Homework Equations U(x) =...

Homework Statement Hey guys! I'm not convinced by what I obtained so far, please tell me whether I'm in the right or wrong direction. The Hamiltonian has the form ##H=-h\sum _i s_i## where ##s_i=\pm 1## and ##h=kT##. 1)Calculate the partition function and the Gibbs free energy. 2)Calculate the...

Can you look at an interaction term in your lagrangian or hamiltonian, like L_{\rm int} or H_{\rm int}, and say immediately how its diagrams will diverge (as in quartic, quadratic, linear, log, etc.)?

Homework Statement Thin rod of the length l is placed with one of its ends placed at the center Oof the thin ring of radius R as shown, perpendicular to the plane of the ring. Rod is charged with total charge Q that is distributed along the rod’s length with the linear charge density...

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: 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. The...

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)...

Hello, I have a homework problem posing the following hypothetical situation Imagine a hypothetical universe in which weak interactions do not exist and only first-generation quarks and leptons are present (i.e. there are no charm, strange, top or bottom quarks, and no muons, muon...

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'd like to calculate magnetic dipole-dipole interaction energy. Actually, I've tried to find models for the calculation, but most of them are just a simple point dipole-dipole interaction model. I can't utilize this simple point dipole-dipole interaction model directly because...

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...