Spin Definition and 1000 Threads

Homework Statement Let's consider conduction electrons (at T=0K) that are put in a magnetic field. The electrons can have spin that is parallel or antiparallel to the magnetic field. Below is the density of occupied states for such a system (horizontally) as a function of energy (vertically)...

Homework Statement Write down a spinor that represents the spin state of the particle at any time t > 0. Use the expression to find the expectation values of ##S_x## and ##S_y## Homework Equations The particle is a spin-##\frac 1 2## particle, the gyromagnetic ratio is ##\gamma_s \lt 0##, and...

Homework Statement Earlier my teacher put this equation on the board, π_0 --> γ+γ It appears to work until you consider spin. Homework Equations a quick google search reveals that the spin of a photon is +1 and the spin of a pi meson is 0 The Attempt at a Solution This appears to work for...

I've got to explain how spin art works to some 5th graders tomorrow. Basic setup: Paper is attached to center of a horizontal disk. Paint droplets are placed at different places on the paper. Disk is spun which causes paint to produce a pattern flowing away from the center of the disk/paper...

How can we be so sure? I know it's fast ..but, what if it swaps by the speed of light instead? I know there are some experiments that try to rule this out, however, I don't think they take into consideration that the signal to swap may be initiated by the action that observes one of the...

This is not part of my coursework but a question from a past paper (that we don't have solutions to). 1. Homework Statement Construct the matrix ##\sigma_{-} = \sigma_{x} - i\sigma_{y}## and show that the states resulting from ##\sigma_{-}## acting on the eigenstates of ##\sigma_{z} ## are...

If a space station has artificial gravity created by spinning, how can it best be spun up to speed? Little attitude rockets could do it, but they would use up fuel, and limit your ability to change the spin rate in future. What if you had an external wheel that you spin up very fast in the...

What is the basic concept which decides the spin of a particle. Like, electron has a spin of +- 1/2... What do this 1/2 signifies. Other spins are also there like 1 and 2. What do they signify? Is there any possibility of any particle with spin other than 1/2, 1 or 2?

So, we can break down the Dirac equation into 4 "component" equations for the wave function. I was going to post a question here a few days ago asking if a fermion (electron) could possesses a "spin" even if it were at rest, I.e., p=0. I did an internet scan, though, and found out that...

I have previously read that the spin of a particle is comparable to angular momentum of a system or object on the macroscopic level. However, the quantum world is much different and all I can imagine is a minuscule ball rotating on it's axis.

I am having difficulty thinking through how a ferromagnetic substance is permanently magnetized. I think I understand that when for example a sample of iron is heated above it curie temperature and then exposed to an external magnetic field , the sample will become permanently magnetized. The...

Hi guys! I'm struggling with the following problem: Consider two distinguishable (not interacting) particles in a quadratic 2 dimensional potential well. So ## V(x,y)=\left\{\begin{matrix} 0,\quad\quad-\frac { L }{ 2 } \le \quad x\quad \le \quad \frac { L }{ 2 } \quad and\quad -\frac { L }{...

So I am in an introductory modern physics class and we discussed how intrinsic spin can be a linear combination of the spin basis. I am a bit confused on the physical representation of this and whether or not there are different basis to represent spin. If it is possible, what would be the point...

Homework Statement Hello, I'm asked to show the equivalence of the given Hamiltonian below which describes the interaction between an electron and a nucleus and the following Hamiltonian The Attempt at a Solution [/B] I've simply written down each Hamiltonian as a sum of four tensor...

I have two questions... I'm sorry for my bad English. - Is it correct to think of the Higgs Boson as a quantization of the Higgs Field, as the photon is the quanta of Electromagnetic Field? - The property we call spin appears when we analyze electrons interacting with a magnetic field. But...

Homework Statement Consider an ensemble of spin 1 systems (a mixed state made of the spin 1 system). The density matrix is now a 3x3 matrix. How many independent parameters are needed to characterize the density matrix? What must we know in addition to Sx, Sy and Sz to characterize the mixed...

I've been doing some research on this but I've been seeing conflicting answers. 1 group of answers says an electron's spin can be changed using a magnetic field. Is the same thing true for quarks?(like the up down quarks in protons and neutrons?). Another set of answers are saying it's...

When we are measuring the spin of the electron in the experiment, we choose the spin property as its eigen state for the measurement. The eigen vectors corresponding to these states could be time dependent. Can we still break the problem into solving time independent Schrodinger Equation and...

Assume both billiard balls have same mass and same radius. So situation 1: ball 1 is moving forward without slipping on a surface and collides elastically with ball 2 which is stationary on that same surface. I read that immediately after the impact, ball 1 stops and keeps spinning with its...

I read that the stoichiometric half-metallic compound has integer spin moment. For this, n(up)-n(down) should be integer. Since n(up) +n(down) is always integer, either n(up) or n(down) should be integer to make total spin moment integer. I could not understand how the presence of energy gap in...

Hello good people! If i liftoff from the Earth in a helicopter and continually ascend slowly, at that moment i have beat gravity(i realize it is still hanging on to me, however the rotorforce/upforce is greater than it), therefore gravity should no longer hold me to the ballearth(because it has...

Physical polarization vectors are transverse, ##p\cdot{\epsilon}=0##, where ##p## is the momentum of a photon and ##\epsilon## is a polarization vector. Physical polarization vectors are unchanged under a gauge transformation ##\epsilon + a\cdot{p}=\epsilon##, where ##a## is some arbitrary...

Homework Statement Consider eigenstates of the total angular momentum $$\vec{J}=\vec{J}_1+\vec{J}_2+\vec{J}_3$$ where all of the \vec{J}_i are for j=1 , and let J(J+1) be the eigenvalue of \vec{J}^2. a) What are the possible values of J? How many linearly independent states are there for...

What would be the ramifications of discovering that a) dark matter radiates something non-electromagnetic, and that b) this radiation always travels at a constant velocity according to all inertial reference frames, but c) this constant velocity is equal to, say, c times pi?

Hello, I am learning about electron spin resonance and I just want to see if my understanding is correct. From what I gathered, if you place a paramagnetic material in a magnetic field, the electron energy levels split, and when you then apply EM radiation (generally microwave frequency) that...

Hey all, Is it correct to say that magnetic moment of particles with spin is because of the spin itself, and has nothing to do with any moving charge? The exception here would be the photon of course, but I'm not sure whether "photon spin" is the same kind of angular momentum as the spin of...

Homework Statement Starting from the proca lagrangian $$L=-\frac14 F_{uv}F^{uv}+\frac12 m^2 A_uA^u$$ Homework Equations $$H=\sum p_i\dot{q_i}-L$$ The Attempt at a Solution $$L=-\frac14F_{uv}F^{uv}+\frac12m^2A_uA^u\rightarrow\partial_uF^{uv}+m^2A^v=0$$ $$p^i=\frac{\partial L}{\partial...

Loop Quantum Gravity, Exact Holographic Mapping, and Holographic Entanglement Entropy Muxin Han, Ling-Yan Hung (Submitted on 7 Oct 2016) The relation between Loop Quantum Gravity (LQG) and tensor network is explored from the perspectives of bulk-boundary duality and holographic entanglement...

A photon has a spin of 1, while an electron is 1/2. I've heard it said that the electron needs to spin 720 degrees to complete a full cycle. Is there any proof that the electron is spinning 720 degrees and not just spinning 360 degrees, but at a lower harmonic of the photon-- 1/2 the photon's...

Hi all, I fairly basic question about spin foam models in loop quantum gravity. I just want to verify that spin foams represent effectively represent all of spacetime (in a quantum form), and that the idea is that general relativity can be obtained in the classical limit? Not sure if that's...

I was referring a lecture series by Professor Hong Liu. In his first lecture on Emergence of gravity he says, "massless spin-2 particles (gravitons) can arise as bound states in a theory of massless spin-1 (photons, gluons) and spin- 1 particles (protons, electrons)". What does it exactly...

I understand a helicopter in spin would mean a stabilizer is gone and the helicopter cannot maintain its stable altitude. However, I've noticed that helicopters have a tendency not to dip in free fall. I mention that bc I am curious as to what force is at play when objects and people (sorry...

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I know that I'm kinda asking for a lot here, but can any of you give me, a person with lesser experience in physics, a basic explanation of spin? I've found out that a particle's spin can be compared to a transistor, but that didn't really tell me what it actually is. What does it define? For...

When considering the 2 eigenvectors of the Sz operator the | + > eigenvector points in the positive z direction and the | - > points in the negative z direction ; so is it correct to write | + > = - | - > ? And similarly for the eigenvectors of the Sx and Sy operators ? Thanks

Homework Statement Consider a spin state |n; +> where n is the unit vector defined by the polar and azimuthal angles θ and φ and the spin state |n'; +> where n' is the unit vector defined by the polar and azimuthal angles θ' and φ'. Let γ denote the angle between the vectors n and n': n⋅n' =...

So I have previously learned how to discretize the Schrödinger equation on the form: (p^2/2m + V)ψ = Eψ , where the second order derivative is approximated as: (ψi+1+ψi-1-2ψi)/2Δx Such that the whole equation can be translated into a matrix eigenvalue-equation. The problem is that I am now...

Spin current is defined as ##I_s=I_\uparrow -I_\downarrow## in which ##I_\uparrow## and ##I_\downarrow##are the currents of spin up and down electrons respectively. One of the advantages of the spin current is that if ##I_\uparrow =-I_\downarrow##, then the charge current ##I_C=I_\uparrow...

Homework Statement We have got two particles with S_1=1 and S_2=1. We know that S_{1z}|\psi_1\rangle=\hbar |\psi_1\rangle and S_{2x}|\psi_2\rangle = \hbar |\psi_2\rangle. a) Find wave function |\psi_1\rangle in S_{1z} basis and |\psi_2\rangle in S_{2z} basis. b) We measure S^2 of total...

Jupiter's spins the same way the Earth does, so the Coriolis effect should make the Great Red Spot spin clockwise, but it's an anti-cyclone. Why is that?

I am relatively well versed when it comes to systems of spin, or doing the maths for them at least, but am unsure whether all of the {L2, Lz, (other required quantum numbers)} basis eigenstates for a general system of n particles of spins si, where si is the spin of the ith particle, can...

As I understand it (e.g. from discussions around the Fermi field theory of the nuclear force), a spin 1/2 particle can emit a spin-1 particle and simultaneously flip its spin (say, spin +1/2 -> photon +1 & spin -1/2); but how does this work with spin-2 particles? Does it need to emit pairs in...

The spin exchange operator would have the property $$\begin{align*}P\mid \chi_{\uparrow\downarrow} \rangle = \mid\chi_{\downarrow\uparrow} \rangle & &P\mid \chi_{\downarrow\uparrow} \rangle =\mid \chi_{\uparrow\downarrow} \rangle \end{align*}$$ This also implies ##P\mid \chi_{\text{sym.}}...

I've read that this is one of the meaning that define a lepton and I was curious to see what this means. Other resources aren't being very clear.

Gluons are spin 1 particles so the Strong Force can both attract and repulse. The constituent partons of a meson are a quark and an antiquark so they must carry a given color and its anticolor, respectively, in order that there is no net color carried by the parton. In that case, the force...

Hi is there any device or experiment, which could measure Earth spin vector and magnitude, centrifugal/centripetal forces, so i could derive from it, where is west and east , what's the vector of Earth rotation and what's my lattitude. Im assuming these forces and effects has to be...

Perhaps a silly question, but... As I understand it, if a particle has a 1/2 spin, it must be spun 720 degrees for it to arrive at its original orientation. What experiment spins a particle like this? Has there been one that actually spins a particle 720 degrees and checks its orientation? Or...

I know that magnetic fields can align objects with spin. In that case, if we suspend an object and turn on a magnetic field such that a significant number of electrons become aligned with the field, could we observe a macroscopic change in angular momentum?

Hi folks, A simple question, in classical mechanics for example you have: -Because of the speed --> Kinetic energy =1/2 m v^2 -Because of position in a gravitational field ---> Potential energy In quantum mechanics, let's talk about an electron on an hydrogen atom. From the point of view of...

I was wondering just what physical properties of an electron influence it's probability of being detected in a certain spin state? For example, if I prepare an electron in the spin up state along say the way y-axis (vertical axis) and pass it through a detector that is at 0 degrees, then using...