What is Spin: Definition and 1000 Discussions

Good day everyone, The question is as following: Consider an electron gas with Hamiltonian: \mathcal{H} = -\frac{\hbar^2 \nabla^2}{2m} + \alpha (\boldsymbol{\sigma} \cdot \nabla) where α parameterizes a model spin-orbit interaction. Compute the eigenvalues and eigenvectors of wave vector k...

A system consisting of two spins is described by the Hamiltonian (b>0) H = aσ1 ⋅ σ2 + b(σ1z - σ2z) where a and b are constants. (a) Is the total spin S = ½ (σ1 + σ2) conserved? Which components of S, if any, are conserved? (b) Find the eigenvalues of H and the corresponding...

Homework Statement Not exactly a homework problem but I tried to predict the spin and parity of (the ground states of) ##^{89}Sr##,##^{97}Zr## and ##^{137}Ba## using the shell model and my results seem to differ from the tables. Homework Equations Parity ##\pi = (-1)^l## Figure 4 seems to...

Why can’t force-carrying particles (spin 0, 1, 2) be detected by particle detector? Some have masses!

Homework Statement So I have to do a report about tennis and about the spin. I understand how the magnus effect works and how the ball will bounce but am still unable to figure out how the actual spin is created by the contact with the racquet and the moving ball Homework Equations T=Fr The...

Suppose we confine a spin 1/2 particle to an infinite annular region, in cylindrical coordinates, defined by the two cylinders r=a and r=b with a<b. How does such a region constrain possible spin and angular momentum? Thanks!

I've just come across the spin states of a two electron system. There are 4 states possible and I am a little confused as to why the state below has values of s=1 m_s=0? [1/√2]{α(1)β(2)+α(2)β(1)} where α(i) and β(i) tell us if the particle has +ve or -ve z component of spin respectively. I...

Homework Statement It was noted that <00|Su11Su22|00> = -ħ2/4 * u1⋅u2. where u1 and us are unit vectors along which the two spin operators are measured and θ is the angle between. |00> is the singlet state that the two electrons are entangled in (corresponding to total spin values ). Prove...

Homework Statement I want to find the matrix representation of the ##\hat{S}_x,\hat{S}_y,\hat{S}_z## and ##\hat{S}^2## operators in the ##S_x## basis (is it more correct to say the ##x## basis, ##S_x## basis or the ##\hat{S}_x## basis?). Homework Equations...

Dear All I am trying to find the equation of motion of the spin connection out of the einstein hilbert action written in terms of the vielbeins. Can anyone help me to do? Thank you

Hello, I am a 40 year old Computer Scientist by education and profession. Education in general is my hobby. I am currently listening to a lecture on quantum mechanics: The Teaching Company's Quantum Mechanics Physics of the Microscopic World. Very good. So please excuse my nievity and ignorance...

I just read an article stating physicists have discovered a new state of matter. What is a quantum spin liquid?

Homework Statement A yo-yo has a moment of inertia of 75.0 g-cm2 about its rotation axis. What is the constant torque required to make it spin to 300 rev/min in one second, starting from rest? Homework Equations ∑ = Iα The Attempt at a Solution I was thinking since the question is asking for...

I have a basic question about what spin invariance means. If we were to use a classical example, if the spin of a basketball was invariant, what would that mean? Would every frame measure the same revs/min? Newtonian mechanics predicts that every frame would measure the same revs/min, but sr...

Homework Statement Describe, with examples, what is meant by magnetic moment. What gives rise to a magnetic moment in a proton/neutron? Homework Equations The Attempt at a Solution I know what a magnetic moment is, just struggling with the other parts of the question. So what I'm thinking is...

Homework Statement Consider a particle of spin 3/2. Find the matrix for the component of the spin along a unit vector with arbitrary direction n. Find its eigenvalues and eigenvectors. Homework Equations I know that the general spin operator is \begin{equation} \widehat{S} = a\cdot...

Homework Statement Consider a spin system with noninteracting spin 1/2 particles. The magnetic moment of the system is written as: μ = (ħq/2mc)σ Where σ = (σx, σy, σz) is the Pauli spin operator of the particle. A magnetic field of strength Bz is applied along the z direction and a second...

So I was wandering why it is not possible to use quantum particles to communicate across vast distances. As I understand it we cannot send information using this as it would break the laws of physics but what I was wandering is why can't we us entangled particles in a binary why by changing the...

How does one go about finding the spin number for a molecule like water for example? Do we consider the spin of the nuclei (e.g. proton, neutrons), and also look at which electrons are shared and not?

My question is, how does one get a wave function for a 'combined' spin-1 and a spin-0 field? How is this possible? I have only been able to find combined states for equal spin identical particles. If you don't understand my question, I'll be glad to reword it.

If an atom described by spin-orbit coupling is in a 4P state, why is the spin quantum number s=3/2?

the vw type 1 engine comes with flaps that close when the engine is cold. i know the flow through the fan doesn't completely stop but for the sake off argument let's assume that is does. the fan is spinning but there is no flow. what power is required to maintain the pressure differential...

The triplet spin state with a normalisation constant of 1/√2 and the singlet spin state with the same normalisation constant... Where on Earth is this normalisation constant derived from? I've been scouring the Griffiths intro to quantum mechanics textbook and can't find info on it.

Spin up and spin down states in the x direction can be written as |Upx> = 1/ √2 ( |Upz> + |Downz> ) and |Downx> = 1/ √2 ( - |Upz> + |Downz> ) My textbook just stated the above facts without referencing why and I've been going through the spin chapter for a while now and I can't see it. Why...

Equation (8) defines the conditional wave function of a microscopic physical system in terms of the wave function of the universe and the true positions of the particles in the environment (= the universe except the microscopic system). Such a definition is essential for the interpretation of...

Im having trouble with my thought process for spin states of a system of two electrons Using Total Spin 'S' and Total spin mag quantum numbers 'MS' as state ket |S MS> My textbook states... " Three Symmetric Spin states Triplet spin stats for twin identical spin -1/2 particles | Up Up> = |S...

Now, how did the particle spin numbering system come about? What I'm referring to is, why are bosons integer spins, while fermions are half-spins? Is this just a convention that we got stuck with since the early days of quantum theory? For example, instead of having half-spins, could they have...

This has always bugged me, but it appears that the answer is out there via this: "But deep theoretical reasons having to do with the rotational symmetry of nature lead to the existence of spins for elementary objects and to their quantization." The sentence before says this: "A simple answer...

Homework Statement I have a spin operator and have to find the eigenstates from it and then calculate the eigenvalues. I think I managed to get the eigenvalues but am not sure how to get the eigenstates.Homework Equations The Attempt at a Solution I think I managed to get the eigenvalues out...

As I understand, two electrons may be found (close) together providing they are of opposite spin. How does this occur ? How does the character of opposite spin offset the impact of the electromagnetic force repelling these two particles of the same charge ?

Homework Statement The problem is given above. I am struggling on the first two parts, where I am tasked with finding gamma and beta. Homework Equations For spin one half states in arbitrary directions, I know that psi = a*|n;+> + b*|n;-> . |n;+> = cos(theta/2)|+> +sin(theta/2)*ei*phi|->...

Let ##\alpha(n)## and ##\beta(n)## be the eigenfunctions of ##S_z## that correspond to "spin up" and "spin down" for electron ##n## respectively. (a) Suppose we prepare electron ##1## to have its spin aligned along the ##x## axis. Is its spin wave function...

I have been under the impression that application of a magnetic field will quantise the z component of an electrons spin in that direction. I see this as a physical process, but Is this incorrect as it is often described as a measurement of a random variable/ wavefunction collapse? I am familiar...

In a covalent bonded molecule, what is the force responsible for the molecule staying together. To my knowledge it's to do with electrons of opposite spins and being at a lower energy with valence shells filled but what is the force itself that pulls a second atom along if the atom it's bonded...

Sorry. I lost the text of the post while trying to edit it. I will abandon this for a while.

Homework Statement Question: http://imgur.com/YzexPKl (only part c) Homework Equations From part a) I got |psi> = (1/sqrt(2))(e^(iwt/2)|z-up> + ie^(-iwt/2)|z-down> I expanded this wave function in the x-spin basis and got, |psi> = (1/(2))[(e^(iwt/2)+ie^(-iwt/2))|x-up> +...

How do we get (6.265)? Shouldn't we have ##exp(-i\frac{\alpha}{2}\hat{n}.\sigma)=\cos(\frac{\alpha}{2}\hat{n}.\sigma)-i\sin(\frac{\alpha}{2}\hat{n}.\sigma)##?

So far I have seen Sakurai, Townsend, Cohen Tannoudji, Feynman, and McIntyre. Are there any other books that take this approach? Just curious.

Homework Statement If an object is hanging by a thread, how fast must it be twirled around in order to break the thread? (must also provide explanation of why this is the velocity). As a part of a lab, pick a certain mass. Attach to light string (easily breaks) and pull the string through a...

I have a magnet that has a cylindrical shape, where the center is slightly larger than its outer sides. I was wondering why it beings to spin on its outer end when spun very fast (on its long edge). Whereas if its spun not too fast, it stays on its axis. I have included a photo for further...

Say we have a Helium atom with the first electron in 1s orbital and second electron in 2s orbital, and if these electrons have parallel spin so that the total spin of the system is S=1, then is this a triplet or a singlet state? According to LS coupling, multiplicity is defined as: 2S+1 (if...

Hey, I am new to the forum, and would certainly appreciate help in understanding spin - although I realize that perhaps no one really understands spin. If a beam of spin polarized electrons are absorbed in a target, then the target will start to rotate. This kind of makes sense on a...

Homework Statement Find spin only magnetic moment of ##[Fe(H2O)5NO]^{2+}## Homework Equations None The Attempt at a Solution When I used Google, the magnetic moment in 3.87 ##Fe## is in +1 oxidation state. So configuration is $$[Ar]3d^64s^1$$ There are 5 unpaired electrons. How does magnetic...

Homework Statement Hello all, Im asked to construct the state | \frac{5}{2} , \frac{3}{2} \rangle from the eigenfunctions | L, L_z\rangle and the electron states | \uparrow \rangle and | \downarrow \rangle . Homework Equations Clebsch Gordon Coefficient's table The Attempt at a...

Help. I'm really struggling with the general idea here. The intricacies of the theory are hopelessly beyond my cognitive reach. I'm just trying to get a general handle on the big picture concept. I read a bit where Lee Smolin referred to this model as a leading theory that characterized space...

The intricacies of the theory are hopelessly over my head. But I'm trying to clarify my understanding of the Spin Foam cosmological model in very basic and generalized terms. The logical starting point might be in understanding what the SPIN in spin foam refers to. My cursory scan of web...

I was wondering it the projection of the measurement axes onto a spinning vector modeled by a plane would produce correlations of entangled particles in line with what is found by experiment. Does anyone know of any discussions on this subject? Would this lead to stronger correlations than spin...

Our moon rotates around Earth in such a way that we always see the same face. But Earth orbits Sun in a different way. It keeps spinning. My question is, If I were to go to space and put a basketball in a circular orbit around Earth in such a way that at the time I throw it a particular face is...

In chapter 1 of Peskin and Schroeder, the reaction ##e^{+}e^{-}\rightarrow \mu^{+}\mu^{-}## is studied in detail. The related following paragraph is taken from page 4 of Peskin and Schroeder: Both the electron and the muon have spin ##1/2##, so their spin orientations must be specified. It is...

Hi everyone, Firstly, sorry if this seems a bit rushed, I don’t have much time in between shifts at work. You may have to refer to my links. But if needed, I will add more information later on. I've been racking my head over this for the last month or so. I’m kinda doing a private personal...