Spin Definition and 1000 Threads

Does anyone know why time reversal requires spin to be flipped? It seems like my book assumes that, but I have no idea why.

Hi everybody. I have been reading about the Stern Gerlach experiment lately and a doubt has came to my mind. Is there any way to know the spin of an electron without forcing it to interact with a magnetic field? Thanks for reading.

Homework Statement Show that the determinant of a ##2 \times 2 ## matrix ## \vec\sigma \cdot \vec a ## is invariant under ## \vec \sigma\cdot \vec a \rightarrow \vec \sigma\cdot \vec a' \equiv \exp(\frac{i\vec \sigma \cdot \hat n \phi}{2})\vec \sigma\cdot \vec a \exp(\frac{-i\vec \sigma \cdot...

If spin is a quantum degree of freedom represented out of real space, why the real coordinates (x,y,z) are attributed to it? In other words, how can one say s_x, s_y, s_z?

Homework Statement Two particles, their spin are 1/2. The hamiltonian is ##H=\gamma s_1 \cdot s_2## At t=0, the state ##|\alpha(0)>## is such as ##s_{1z}|\alpha(0)>=\hbar/2 |\alpha(0)>## and ##s_{2z}|\alpha(0)>=\hbar/2 |\alpha(0)>##. Find the state ##|\alpha(0)>##.2. The attempt at a...

We know Sz = h/2 [1 0 // 0 -1] for up spin.So can we say that the energy of the electron in this state is h/2 ? (since Sz |up> = h/2 |up>)Now we consider a Hamiltonian H = [1 0 // 0 -1] which has eigen values +1, -1 and the respective states are (1 0) and (0 1). If we see the...

Homework Statement The momentum carried by an electromagnetic field is [;\vec{P}(\vec{x}, t) = \frac{1}{4\pi c} \int d\vec{x}\vec{E}(\vec{x},t) \times \vec{B}(\vec{x},t);] show that for a finite field extension [;\vec{J}(\vec{x}, t) = \frac{1}{4\pi c}\int -i...

What does and does not have intrinsic spin? Wikipedia Spin (Physics) https://en.wikipedia.org/wiki/Spin_(physics ) says: “In quantummechanicsand particlephysics, spinis an intrinsic form of angularmomentumcarried by elementaryparticles, composite particles (hadrons), and atomicnuclei.”But it...

Homework Statement How can I solve this hamiltonian equation? H= p2/2m +α/ħ (σxpy - σypx) + γ/ħ (σxpx - σypy) + βxσx + βyσy Homework Equations Rashba coupling effect equation: HR=α(σykx - σxky) The Attempt at a Solution H0=ħ2k2/2m + HR+ HD

okay , this question might look a little silly .. But i have been wondering about this for a while .. i know electrons move around the orbit because of the electrostatic force between electron and proton .. But what what makes an electron rotate about its axis ? i believe even without the spin...

Just reviewing some QM again and I think I'm forgetting something basic. Just consider a qubit with basis {0, 1}. On the one hand I thought 0 and -0 are NOT the same state as demonstrated in interference experiments, but on the other hand the literature seems to say the state space is...

Does a Buckyball spin like an electron or like a baseball? We are often told that an electron does not really spin like a baseball. Only one (or two, if you count up and down) spin states, for example. How about a Buckyball? Does it spin more like an electron, or more like a baseball? Where...

Assuming R-pairity and thus the creation/destruction of supersymmetric particles happens in pairs, how is angular momentum conserved when a particle and its supersymmetric partner have different spin by 1/2?

I'm a litte confused about spin triplet and singlet states. How do we know that for ↑↓+↓↑ the total spin S is 1, and for ↑↓-↓↑ the total spin S is 0? Also, how is total ms computed for these two states? (I understand that they are both 0, but not sure where that comes from) Thank you very much...

In my book (Griffiths) it is said : A particle is in ↑ state. The z-component of the particle's spin angular momentum [Sz] is h bar/2. The x- component of the particle's spin angular momentum [Sx] can be either h bar/2 or...

I have just started to study quantum mechanics, so I have some doubts. 1) if I consider the base given by the eigenstates of s_z s_z | \pm >=\pm \frac{\hbar}{2} |\pm> the spin operators are represented by the matrices s_x= \frac {\hbar}{2} (|+><-|+|-><+|) s_y= i \frac...

What does 'high spin' mean? I have heard of mono atomic gold having unusual properties. What is going on inside the atom?

Hello, I have read about Schrodinger's cat saying we do not know whether or not a particle has a spin up or spin down. It is only when we check it that we know which one it is. I understand the concept however I do not understand what do scientists mean when they say "spin up/down". What...

Does the orbital of an electron change when it experiences a spin-orbit interaction, and if so, how?

since a massless spin 2 field when perturbatively quantized gives rise to gravitons, which couple to everything and is identical to gravitation, is spacetime itself massless spin 2 field? do virtual graviton exchange also modify time and space?

In the stern-gerlach experiment, silver atoms with a +1/2 would be deflected up, and atoms with a -1/2 spin would be deflected down. With that in mind, would electrons' orbitals within an atom be affected by its spin?

Hey guys, I really need your help. I have an exam tomorrow and no idea how to solve this task. Sorry for my bad english (did not use it for a long time). I hope that I translated the task correctly so that you might be able to help me. So We have two particles with spin=1 which means they have...

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...

Homework Statement So I'm given a spin 1/2 particle in a rotating magnetic field in the (x,y) direction and a constant field, B_0, in the z direction and am asked to find the S matrix describing it. Given is: B(t) = [B_1 \cos(\omega t), B_1 \sin(\omega t), B_0] Homework Equations H = \sum...

Assume String Theory is headed in the right direction, can one understand electron (or any Standard Model particle spin for that matter) spin roughly in terms of some small spinning string? If so, would you consider that a selling point of the theory as it provides an explanation for intrinsic...

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...