What is Spin: Definition and 1000 Discussions

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...

I have two photons that are entangled and exist in all possible states simultaneously. By measuring photon A, I cause the superposition to collapse, and i can see that it has a certain spin (say left). This measurement also causes photon B's superposition to collapse, but will it be spinning...

Hi, I'm recently reading Krane's nuclear physics textbook, and in the meson physics chapter there is a section about the spin and parity of pions. He demonstrated a way to find out the parity of the pion by investigating a pion decay(as in the attached images). I think I understand what he's...

A nice discussion of the density operator for a qubit can be found here: http://www.vcpc.univie.ac.at/~ian/hotlist/qc/talks/bloch-sphere-rotations.pdf

Say I have {S_{x}=\frac{1}{\sqrt{2}}\left(\begin{array}{ccc} 0 & 1 & 0\\ 1 & 0 & 1\\ 0 & 1 & 0\\ \end{array}\right)} Right now, this spin operator is in the Cartesian basis. I want to transform it into the spherical basis. Since, {\vec{S}} acts like a vector I think that I only need to...

If we use the Weyl representation the solutions to the Dirac equation turn out to be eigenfunctions of the S3 operator with eigenvalues 1/2 and -1/2, so we say that the field has spin 1/2. But what about other fields? Why do we say the scalar real and complex field have spin 0? I tried...

I am currently reading Prof.Leonard Susskind's Lecture on Quantum Mechanics. In the Chapter: Spin in the arbitrary directions, in the subdivision Eigenstates In case $$\lambda=1$$ Prof states that measuring spin in arbitrary +n state gives me +1 as eigenvalue, what I don't understand is the next...

Hello everyone, How come the electron wave energy states are different for spin -½ and +½ values? What causes this asymmetry?

Ok, so I know I'm missing something here. But, you know how pool balls that rotate opposite direction increase the speed of one of them through kinetic transfer? Why don't we build a launch platform based on this approach and use the orbital spin of the Sun, Jupiter, and Saturn (gaining speed...

Dear All in the idea of gauging Poincare group i am trying to find the equation of motion of the spin connection w_mu^ab using Euler Lagrange equation. but it seems that i am not getting the same terms can i have a help. I know that this equation is equivalent to the torsionless condition, but...

http://arxiv.org/abs/1105.3735 I have a question about the paper that haushofer mentioned. In the paper, the author states that Moving on to helicity 2, the required gauge symmetry is linearized general coordinate invariance. Asking for consistent self interactions leads essentially uniquely...

Is there any experimental evidence that neutrino spin is equal to the electron spin ( I think h/4pi, right?) If it is just an assumed intrinsic property,can you explain on what grounds it is assumed as such, is it juas a matter of parity?

If a top has angular momentum of 12 units and the Earth has angular momentum of 100. Does this mean that Earth is spinning faster than the top since it has more angular momentum? The answer is there at the back of my head but can't articulate it.