What is Spin: Definition and 1000 Discussions

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...

I recently came across a paper (referenced below) containing the statement that:"The differential form notation is much more concise and elegant than the tensor notation, but both contain the same information.", and the paper left me with a desire to understand the notation of differential...

This question is beyond my level of understanding, nonetheless I feel it can’t be right. I have been studying Geometric algebra and was thinking about (6-component) bivectors in spacetime, (specifically the electromagnetic field and 4D-angular-momentum). The conventional perspective is to...

Some time ago, before particles turned out to be mutable wave excitations (making Alchemist's dreams sound nicer, I guess :-) ) , to say that something was an "elementary particle" meant that it couldn't be broken down further. OK, that idea bit the dust, but now there are intrinsic...

Given a pair of Spin ##1/2## entangled particles created in the ##z^→## direction according to the following equation ##Ψ=1/√2(\uparrow\uparrow+\downarrow\downarrow)##. One entangled particle is sent to Alice and another to Bob. Now if Alice measures her particle in the ##z^→## direction she...

In reading around, it seems that in the case of entangled particles, it is the measurement of one of the particles that causes the other one to be it's opposite spin and that there's some means of info transfer going on caused by the measurement. I'm not understanding why it would not be that...

Hello, So I know that the magnetic moments of atoms are dependent on the spin and orbital angular momenta of its electrons. Both of these quantities are limited by the uncertainty principle so that neither of their direction and magnitude can be known simultaneously with arbitrary precision...

The Wikipedia page for angular velocity makes a big fuss over "spin" and "orbital" angular velocities, but I have checked through Gregory and Morin's textbooks on classical mechanics and haven't found any reference to them at all. They just work with a single quantity, the angular velocity...

I was thinking to myself, how come are particles coming from the sun gets deflected the way they do due to Earth's magnetic field? They are getting pulled toward the poles, but if we think in terms of classical Lorentz force, they should not just follow the magnetic field lines, but rather start...

Imagine laying a pencil down, and spinning it on its own graphite. What do you call that, "spinning" or "rotating"?

Hi, When a quantum entangled photon is measured to determine spin does it's spin stay in that orientation as long as it's measured it or does it immediately go back to a superpositioned state? In other words if you determined the spin of a quantum entangled particle at say 12:00 pm and...

Practically it is said that, given two spin states |u⟩ (up) and |d⟩ (down) - which are the spin measured along the +z and -z semiaxes - such that they are orthogonal ( ⟨u|d⟩ = ⟨d|u⟩ = 0), it is possible to write any other spin states using a linear combination of these two (because they are a...

For high temperature superconductivity, people usually say two quasifree electrons are pairing, one is spin up and the other one is spin down. So, if that is the case, each two electrons will have zero spin angular momentum. Since the superconductivity is the magnetic properties and spin is the...

If the spin space is independent of the real space, what is the meaning of, for example, the z-component of the spin?

For a 1/2 spin particle, every pure spin state may be represented as a superposition of two states of spin parallel to some arbitrary Z axis. (Upd) Particularly: $$|\uparrow_{x}>=\frac{1}{\sqrt{2}}(|\uparrow_{z}>+|\downarrow_{z}>)$$ I then wonder, if we chose the Z axis, how the X axis should...