Spin Definition and 1000 Threads

With no applied moments, it is asked to prove that a gyroscope Fermi-Walker transports its spin vector ##S_{\alpha} = - \dfrac{1}{2} \epsilon_{\alpha \beta \gamma \delta} J^{\beta \gamma} u^{\delta}##. In a local inertial frame ##u^{\alpha} = (1, \mathbf{0}) = \delta^{\alpha}_0## and...

Hi, can somebody explain the spin structure factor (static and dynamic)? how is it related to the lattice symmetry(I m working with honeycomb)? How could I implement it easily? Thanks :)

Hi, I want to measure spin components of a ground state of some models. These ground states are obtained by ED. The states for constructing the Hamiltonian are integers representing spins in binary. As the ground state (and the other eigenvectors) are now not anymore in a suitable representation...

I have this homework: consider the case of two spin half particles. Use the basis: |++>, |+->, |-+>, |--> to find the matrices representing the operators S^2 and S_z. My idea for the solution for S_z is: S_z=S_z(1)+S_z(2) where S_z(1) is the operator for the first particle ... etc So I...

The other day I found a fascinating video on geometric algebra: At 34:50, after showing how to rotate a vector in three dimensions, he says, "wait a minute, this looks like a spinor from quantum mechanics. The way that spinors rotate is always said to be a part of so-called 'quantum...

An electron beam with the spin state ## |\psi\rangle = \frac{1}{\sqrt{3}}|+\rangle+\sqrt{\frac{2}{3}}|-\rangle##, where ##\{|+\rangle,|-\rangle\}## is the eigenstates of ##\hat S_z##, passes through a Stern-Gerlach device with the magnetic field oriented in the ##Z## axis. Afterwards, it goes...

Greetings, I'm new here, I have an interest in the nature of reality, and a question. Does the quantum spin of a particle (its intrinsic angular momentum) have anything to do with its wavelength and frequency? One of the experts on Quora said no, and I cannot find anything about it on the web...

I am trying to understand how do we see the spin accumulation due to Rashba-Edelstein effect. I mean everywhere I look people just say a shift in the bands due to e-field which results in spin accumulation in the transverse direction (y in this case) as shown Can somebody explain how to see...

While physics is generally believed to be CPT symmetric, there are processes for which such symmetry is being questioned - especially the measurement. One of examples of (allegedly?) going out of QM unitary evolution is atom deexcitation - we can save its reversibility by remembering about...

What is the quantum spin of the valence electron in the silver atom in the furnace in the Stern-Gerlach experiment? . Up, down, at random, alternating, in a (quantum) superposition (of both), or none? Does it even have/get one until it's measured/observed /needed? . Does the second electron, in...

So...I have a home spin bike which unfortunately lacks the sensors of some of the more expensive models. What I'm trying to do is work out if I can dynamically calculate my power output. The spin bike itself has: - An 18kg flywheel of radius 30cm - Direct drive between the crank and the...

How do I determine the required combination of spin rate and disc mass to counteract the inertia of a second spinning disc? I have complete knowledge of and control over both disc masses and spin rate and geometry. Let's say Disc A geometry, mass and spin rate are fixed and constant, so I can...

> Consider two particle with spin 1/2 interacting via the hamiltonian $H = \frac{A}{\hbar^2}S_{1}.S_{2}$, Where A is a constant. What aare the eigenstates, eigenvalues and its multicplity? $H = \frac{A}{\hbar^2}S_{1}.S_{2} = A\frac{(SS-S_{1}S_{1}-S_{2}S_{2})}{2\hbar^2 } =...

Hi guys, I don't have much knowledge of physics sadly, and I want to build a machine that can spin a disk. My question is - How can I know the weight I can spin on a motor? I need to be able to spin around 5-6kg, for 350 RPM, and I'm not sure I'm aiming for the correct motor. I'm thinking of...

From the relevant equation above, there is not imaginary part in the |+> state, so I multiplied the state by (1-i). The state is then : ##\Psi=(2)|+>-(1+\sqrt{3})+i(\sqrt{3}-1)|->## Then I normalize it : ##\Psi=(\frac{1}{\sqrt{3}})|+>-\frac{1}{2\sqrt{3}}(1+\sqrt{3})+i(\sqrt{3}-1)|->## From the...

I have been reading 2010: The Year We Make Contact, a sci-fi book belonging to a classic series by Arthur Clarke. The book involves a myraid of scientific concepts so I think it is worth it to verify if the scenes would be feasible in the real word. In this thread I'd like to focus on the scene...

From what I understand, electrons are negatively charged, however, I have recently come to learn that electrons also have a spin which creates a magnetic field around each electron. I don't understand how the electron can be a negative monopole, yet have a completely independent magnetic field...

I am taking a course on General Relativity. Recently, I was given the following homework assignment, which reads > Derive the following transformation rules for vielbein and spin connection: $$\delta e_a^\mu=(\lambda^\nu\partial_\nu e_a^\mu-e_a^\nu\partial_\nu\lambda^\mu)+\lambda_a^b e_b^\mu$$...

I am having trouble with the normalization part. To get a spin ##|32>## state I could have the following possibilities ##C_1|111110> + C_2|111011> + C_3|101111>## This should be equivalent to ##C_1|11>|21> + C_2|11>|21> + C_3|10>|22>## That is a spin 1 particle and a spin 2 particle that need...

Hello! The isotope shift for an atomic transition is usually parameterized as: $$\delta\nu = K\frac{m_1m_2}{m_1-m_2}+F\delta<r^2>$$ where ##m_{1,2}## are the masses of the 2 isotopes, ##\delta<r^2>## is the change in the mean square charge radius between the 2 isotopes and K and F are some...

Hi! I'm trying to understand the dependence of spin hall voltage on various parameters of the material. I have been going through this paper, and it is mentioned that $$V_{SH} = 2 \pi R_s L j_x n \mu_B$$ In the equation, only ##L## and ##j_x## seem to be the variables. Does increasing ##L##...

So what I'm not sure on, is calculating the matrix elements for part (iii) with Pauli spinors and Pauli matrices, and then finding the form of the corresponding states. As I don't see how using the hint helps. The following is using the eigenvalues of the spin-operators. Provided what I...

Good Morning Suppose, for the sake of this question, the following Euler rotations for a gyroscope) A precession about the vertical 3-axis (like with a top, going around a vertical) Then, a nutation (a leaning over) about the 1-axis Then, back to the spin itself of the top body about the...

If I were viewing the Earth from high above the North pole, I would notice it spinning in an anti clockwise direction BUT when viewed from the South pole it would be spinning in a clockwise direction. If I were high above the equator oriented in a "North up" position I would observe the globe...

Does the Higgs Boson really have 0 spin or is the spin between 0 and 1/2 x (1.054 571 817... x 10-34 J s)?

I am confused about why spin down has a lower energy than spin up. What is the correct interpretation of the equations? If we have a spin ##\frac{1}{2}## particle in a magnetic field ##B_0## that is applied in the positive z direction The spin states of the particle are $$\ket{up} =...

The 1D transverse field Ising model $$ H(\sigma)=-J\sum_{i\in \mathbb{Z}} \sigma^x_i \sigma^x_{i+1} -h \sum_{i \in \mathbb{Z}} \sigma^z_i$$ is usually solved in quantum way, but we can also solve it classically - e.g. parametrize angles of spins ##\sigma^x_i = \cos(\alpha_i)...

Is the Reduced Planck Constant the minimum frequently/movement/spin matter can have to exist? So if a matter were to spin lower than 1.054 571 817... x 10-34 J s, it when cease to exist? Or would matter falling below the Reduced Planck Constant by classified as Dark Matter? I heard that Higgs...

Basic descriptions of spin such as the beginning of Lindley's "Where does the weirdness go" state that an electron's spin doesn't exist or is "indeterminant" until measured (e.g. passed through a Stern-Gerlach field). However, isn't the magnetic field nonzero essentially everywhere (albeit...

Hello! Assuming we use a laser of frequency very close to resonance, in the Ramsey technique (say for 2 level atoms) the ##\pi/2## pulse would put the Bloch vector in the equatorial plane, along the y axis, then in the free region the vector will rotate around the z axis accumulating a phase of...

To show that when ##[J^2, H]=0 ## the propagator vanishes unless ##j_1 = j_2## , I did (##\hbar =1##) $$ K(j_1, m_1, j_2 m_2; t) = [jm, e^{-iHt}]= e^{iHt} (e^{iHt} jm e^{-iHt}) - e^{-iHt} jm $$ $$ = e^{iHt}[jm_H - jm] $$ So we have $$ \langle j_1 m_1 | [jm, e^{-iHt} ] | j_2 m_2 \rangle $$ $$ =...

I can't why there are four elements in each ket instead of only two

I am having trouble to understand what it means by "physically relevant real parameters" and how does it help us to specify a quantum system. Let say, we have a state of k half spin electrons? My guess is about the local phase of the spin, and this would make it 2^k parameters since each...

It's been troubling me for a while, is there some kind of intuitive heuristic picture of why the electron spin g-factor is 2? I remembered this question because of the thread about the nature of spin. One of the early models of spin that were proposed was that it represented the electrons...

Some texts say quantum spin is analogous to the spin of a planet in that it gives a particle angular momentum and a magnetic moment. However, as subatomic particles are tiny, the surfaces of charged particles would have to be moving faster than the speed of light in order to produce the measured...

1) Can the contact between two pool balls impart any kind of spin, other that about its horizontal axis due friction contact with the table surface? 2) If a ball is in motion (traveling in a straight line) and contacts a cushion, can that contact impart spin to the ball such that when leaving...

I have some difficulties interpreting an exercise. It states that the dibaryon H is made of uuddss, with total spin zero, and relative angular momentum 0 as well. It then proceeds to use that the spin of every pair of particles uu, dd, and ss is equal to 1. Why is that the case? It seems obvious...

In this lecture Lenny Susskind describes a spin in a magnetic field precesses around the axis of the direction of the magnetic field. This description is also frequently found in NMR theory which is a semi-classical theory. Lenny says if the magnetic field ##B_o## is applied in the ##z##...

Is it possible that dark matter has Planckmass and Spin two?

Which tends to fill first: p3/2 or p1/2? d5/2 or d3/2? And why is there no spin orbit coupling in the nucleus?

I've harvested a motor from a cordless drill and connected it to a belt which turns a rotating shaft. The motor pulley and the pulley on the other side of the belt are roughly the same size, which a fairly small radius (5 mm maybe?). The issue I'm running into, which I don't fully understand...

I know that in QM, there is LS coupling. So the interaction is there. But is such an interaction possible in macroscopic objects like a planet?

If the nuclear spin quantum number of a particular type of nucleus is ##I##, then the ##z##-component of spin can take values ##m_I = -I, \dots, I##, and since the energy of a dipole is ##E = - \vec{\mu} \cdot \vec{B} = - \gamma m_I \hbar B_0## (with ##\vec{B} = B_0 \hat{z}##), you end up with...

Well, this calculation is straightforward in the Heisenberg picture. After finding the eigen values and eigen vectors of the total Hamiltonian, I found the explicit form for the exponential of the integral of the matrix and then did the matrix multiplication and calculated its expectation value...

Starting with finding the probability of getting one of the states will make finding the other trivial, as the sum of their probabilities would be 1. Some confusion came because I never represented the states ##|\pm \textbf{z}\rangle## as a superposition of other states, but I guess you would...

In 2016, https://en.wikipedia.org/w/index.php?title=Norman_Yao&action=edit&redlink=1 et al. proposed a different way to create discrete time crystals in spin systems. From there, Christopher Monroe and Mikhail Lukin independently confirmed this in their labs. Both experiments were published in...

Is there a way to translate a quantum particle's spin into regular motion in any of the directions?

i recently read about the stern-gerlach experiment and found out that they did it in the first place to verify the principle of the "space quantization " introduced by Bohr , and they thought they did detect the quantization of the orbital angular momentum of ( L = 1 , m = 1,-1 ) neglecting the...

I'm just starting my undergraduate Quantum Mechanics course. I had a homework problem to show that \Delta S_x = \sqrt{\langle S_x^2 \rangle - \langle S_x \rangle ^2} = 0 , S_x being the spin in the x direction. I managed to solve it, but the physical interpretation is confusing me. If I...