Spin Definition and 1000 Threads

I have two questions, but the second is only worth asking if the answer to the first is yes: Are the spin matrices for three particles, with the same spin, σ ⊗ I ⊗ I, I ⊗ σ ⊗ I and I ⊗ I ⊗ σ for particles 1, 2 and 3 respectively, where σ is the spin matrix for a single one of the particles? I...

Homework Statement I am trying to solve the model analitically just for 2 sites to have a comparison between computational results. The problem is my professor keeps saying that the result should be a singlet ground state and a triplet of excited states, but when I compute it explicitally I...

I know how to solve "typical" Kepler problem but I'm interested in a global view to "binary" systems. For example Earth - Moon. If I set lagrangian of system as ##L=\frac{1}{2}(m_1\dot{r}_1^2 + m_2\dot{r}_2^2)-V(|r_2-r_1|)## there isn't included a spin. My questions are: 1) If it is solved as...

I have been learning about precession lately. Suppose there is a pole with a rope on it (like the things they used to hang people), and there is a wheel hung on the rope. The wheel spins and it precesses around the rope, now suppose there are no air friction or friction within the system, will...

I know that the sun is a gas, but like the earth, no matter how hot the core, the enormous weight would turn it to a solid. So the suns core is a solid and would it spin on an axis? Or just randomly?

Hi, I have learned about how to find the 4 spin states of 2 spin 1/2 particles, and how to find them by using the lowering operator twice on |1/2, 1/2> to find the triplet, then simply finding the orthogonal singlet state, |0, 0>. I started to attempt finding the states of 3 spin 1/2...

Neutrinos are always left handed* and so, if you set up a coordinate system with the z-axis pointing in the direction of a neutrino's momentum, any measurement of its spin's z-component will always yield ##-\hbar/2##. What if you measured the spin of the neutrino along the x or y axes? Or is...

I have been following a series of Leonard Susskind's lectures called 'Quantum Entanglements' (Part 1). In general, he explains how to find the probabilities of measurements of spin ½ particles' states, both single particles and pairs of them. I have learned the following: how to use the 2x2 spin...

I am hesitant to write this post. I am a bit overwhelmed that many members have questions of a higher level. They may be reading scientific journals. My question is very basic. I might be called stupid. Coming to the question. Is angular momentum same as spin of an electron?. But I read that...

Hello, I've worked through most of Carroll's appendix on the non-coordinate basis. I see and agree how the spin connection and tetrad one-forms are useful while calculating. However as an example he sets out to apply the formalism to a spatially flat, expanding universe. ds^2 = -dt^2...

Hello dear physics masters on earth, I am very grateful to be priviliged to ask you a question regarding electric fields and potential of a single-cpin helix. It is portrayed as below. It is a line of uniform charge, and 1-turn helix with radius R and height H. I have came to ugly answers, and...

Hello everyone. Let us consider two fermions whose spin state wave functions are certain (normalized) ##\psi_{1}## and ##\psi_{2}##. So the overall normalized spin state wave function of this system is of the form: ##\psi = (1/\sqrt{2})(\psi_{1} \psi_{2} - \psi_{2} \psi_{1})## Is there any...

Spin is an intrinsic property of particles meaning that they have it naturally. Electrons can have either +1/2 spin or -1/2, what dictates that it is one instead of the other?

Hello, this is my first post, i only have what we call an O Level Physics here in the UK, but i have a strong layperson's interest in the subject, so I'm looking forward to picking the brains of the more educated people here. My friend's professor showed him something very interesting, all to...

Homework Statement A singly ionized atom exhibits hyperfine structure in a ##^3P_1 \rightarrow ^3S_1## transition. Assuming ##I## is greater than ##J## and given that the ##^3S_1## levels are split by ##66~GHz## and ##54~GHz##, find the nuclear spin ##I##. Homework Equations E_{HFS} =...

How would someone measure the Higgs spin? I have a feeling that the spin would somehow affect the symmetry of the decays...? A spin zero would have to show a spherically symmetric distribution of decay products (independent on ##\theta##, maybe a little dependent on ##\eta## due to the...

Hi, I was looking at the wikipedia article for spin 1/2 http://en.wikipedia.org/wiki/Spin-%C2%BD and it stated that √(½(½+1))ħ=√3/2ħ. According to my math it is √¾ħ. Is this just a typo or am I missing something?

Homework Statement I have the following massive spin-1 propagator- $$ D^{\mu\nu}(k)=\frac{\eta^{\mu\nu}-\frac{k^{\mu}k^{\nu}}{m^2}}{k^2 - m^2} $$ I want to write down the propagator in the imaginary time formalism commonly used in thermal field theories. Homework EquationsThe Attempt at a...

The spin observable for spin 1/2 particles is represented by Pauli Matrices acting upon a 2-dimensional Hilbert Space. In RQM, forgetting about the matter-antimatter duality for the moment, that TWO-state Hilbert Space is directly related, through the Lorentz Group, to the TWO separate...

What If the universe has a spin, was it causing the similar results like dark energy?

1. Problem: Determine the final translational speed of a spinning disc that is dropped on an infinite horizontal plane. Think of spinning up an automobile wheel suspended over a road (wheel spinning normal to the road), then dropping the wheel on the road. When the wheel rim touches the road...

I have been looking at the solution to a question and I don't understand how the eigenstates are calculated. The question concerns a 3-state spin-1-system with angular momentum l=1. The 3 eigenstates of L3 are given as ## \begin{pmatrix} 1 \\ 0 \\ 0 \end{pmatrix} ## , ## \begin{pmatrix} 0 \\ 1...

baryon decuplet and octet have same quark content, but has spin 1/2 and 3/2. So what gives octet the extra spin?

I wish to imagine Spin connection on a 2-sphere. Now, I am reading Carroll's http://arxiv.org/abs/gr-qc/9712019. He begins to write about spin connections in page 88. Calculations of ##\Gamma## on sphere are evident in page 84. Can you help me, how spin connection on a 2-sphere look like and...

I just need a simple confermation, when the outermost shells of an atom have unpaired electrons is it the pairing of electrons between two different atoms say oxygen and two hydrogens that causes them to bond together? I keep going back to counting subshells and their spins? my mind went...

Homework Statement Use the shell model to determine the parity and spin assignments for all the stable isotopes of calcium. Homework Equations n/a The Attempt at a Solution The stable isotopes seem to be 40Ca, 42Ca, 43Ca, 44Ca, 46Ca, and 48Ca I believe all of those isotopes except 43Ca are...

Hi pf, Please could someone kindly answer a few questions about proton spin in the context of MRI. As I understand it when an external static magnetic field is applied to a patient the magnetic dipole moments of the protons in the hydrogen nuclei will experience a torque causing them to align...

Hello, For the spin angular momentum operator, the eigenvalue problem can be formed into matrix form. I will use ##S_{z}## as my example $$S_{z} | \uparrow \rangle = \begin{pmatrix} a & b \\ c & d \end{pmatrix} \begin{pmatrix} 1 \\ 0 \end{pmatrix} = \frac {\hbar}{2} \begin{pmatrix} 1 \\ 0...

Homework Statement Set |Ψ> = (1/√ 2) | ↑, z> + (eiθ / √ 2) | ↓, z>. Find the probability of measuring the spin component of sz to be up the z-axis. Find the probability of measuring the spin component of sx to be up the x axis. Homework Equations I'm not sure. The Attempt at a Solution I...

In A. Zee "QFT in a nutshell" in chapter I.5 Exercise 1.5.1 on page 39 for spin 2 massive propagator. I know I’m missing something very simple (self-taught beginner). I'm trying to derive equation (13) on page 35, which is G_{\mu\nu,\lambda\sigma} = G_{\mu\lambda}G_{\nu\sigma} +...

I just want to know what is the effect of proton spin & coloumbs repulsive force & nuclear interaction on binding energy. Plzz explain with derivation.

I just want to know what is the effect of proton spin & coloumbs repulsive force & nuclear interaction on binding energy. Please explain with derivation.

Homework Statement a) If a spin-1/2 particle is in the up spin state along z, what is the probability that if its spin along the y-direction is measured it will be found to be pointing in the “up” direction along y? (b) Calculate the expectation values of the components of S, i.e. {Sx, Sy...

Homework Statement I am currently working on a seemingly straightforward eigenvalue problem appearing as problem 1.8 in Sakurai's Modern QM. He asks us to find an eigenket \vert\vec S\cdot\hat n;+\rangle with \vec S\cdot\hat n\vert\vec S\cdot\hat n;+\rangle = \frac\hbar 2\vert\vec S\cdot\hat...

Does spin up mean which way the magnetic field is pointed in relation it's environment (so when do you know if it is up or down, or does that depend on the enviroment?) So if it is spin up, it means the field lines go from up to down, and vice versa. So spin pretty much means where the poles...

So, my current understanding of spin is that when particles with a certain spin state hit a stern gerlach device, their wavefunction is split into components, deflection associated with one of the pure spin states aligned with the device. For spin 1/2 particles, there are only supposed to be two...

I was trying to understand the QM tests done to show the violation of Bell’s inequality. In the example given this was done by testing the polarization of entangled photons which were positively correlated. So in the example Alice and Bob are detecting the polarisation for the two entangled...

Hey guys I was wondering what would happen if: took a ball neo magnet, balanced it on a few other magnets to basically make it a frictionless bearing. Then spin the ball magnet to 10k rpm. But do all this in a box that's a vacuum. Would the neo ball magnet spin basically for a VERY long...

What subatomic particle is emitted when a diatomic Hydrogen molecule transitions from Orthohydrogen to Parahydrogen? e.g. during cooling And why can you cool a sample of Hydrogen to assure that all H2 molecules are para-, but you cannot heat to have any more than 3:1 ortho-:para- ?

Can you have a left handed pion? i.e. it's spin is opposite to its direction of flight

Homework Statement I have a B field initially in the x-direction, and its constant: \widehat{H}= - (\dfrac{e}{mc})\overrightarrow{B} \dot{} \overrightarrow{S} At t=0 it was prepared so that Sz has an eigenvalue of + hbar/2 I want to show the time evolution of the initial state. Homework...

As I understand it, there is a certain probability associated with detecting spin states. Which if the spin state is unknown prior to testing is 0.5. But if I prepare an electron with say spin up, then measure it again for spin up I will detected spin up 100% of the time. Also, if I prepare...

Homework Statement [/B] Just trying to find the spin 3/2 rotation matrix, I've found spin 1/2 and spin 1. This isn't a homework problem just studying some other spins. Homework Equations For spin 1/2: Rn(Φ) = cos(Φ/2)1ˆ − isin(Φ/2)σn For spin 1: Un(Φ) = e −iΦSn = 1ˆ − isin(Φ) · Sn − (1ˆ −...

I just want to clear up something about electron spin to see if I have it correctly. As far as I understand it is it not really spinning but it's just a convenient word and what it denotes is the the particular quantum number is either up or down. Now I think I've got it right to say that this...

Homework Statement Spin can be represented by matrices. For example, a spin half particle can be described by the following Pauli spin matrices s_x = \frac{\hbar} {2} \begin{pmatrix} 0 & 1 \\ 1 & 0 \end{pmatrix} , s_y = \frac{\hbar} {2} \begin{pmatrix} 0 & -i \\ i & 0 \end{pmatrix} , s_z =...

Hey I'm curious if it would be possible to measure if a particle's spin is in a superstate similar to how the double slit experiment can show whether or not an electron's location is in a superstate. Wouldn't such a machine allow for FTL communications, since if we measure one of two entangled...

how fast does an electron spin? if an electron has no volume and is a point, then surly speed would have no meaning. So could it spin at what ever speed it likes? would it just be pure spin (think of a square, it has 4 corners and 4 sides, if the length of the sides were zero, then it would be...

ok i just learned that spin comes up when l (azimuthal quantum number) is half integer but then my book says that each elementary particle has a specific and immutable value of spin. Ok now does this mean that l (azimuth quantum number) takes two values at once - One value corresponding to spin...

When trying to solve ##\mathbb{S}^2 =\hbar^2s(s+1)\mathbb{I},## I got that ##\mathbb{S}^2 = \mathbb{S}^2 _x+\mathbb{S}^2_y+\mathbb{S}^2_z = \frac{3\hbar^2}{4} \left[\begin{array}{ c c }1 & 0\\0 & 1\end{array} \right] = \frac{3\hbar^2}{4}\mathbb{I},## but how does ##\frac{3\hbar^2}{4} =...

Homework Statement On an ice rink two skaters of equal mass grab hands and spin in a mutual circle once every 2.5s. If we assume their arms are each 0.80m long and their individual masses are 55.0kg , how hard are they pulling on one another? Homework Equations ## a_c = \frac {v^2}{R} ## ## v...