Spin Definition and 1000 Threads

I have two photons that are entangled and exist in all possible states simultaneously. By measuring photon A, I cause the superposition to collapse, and i can see that it has a certain spin (say left). This measurement also causes photon B's superposition to collapse, but will it be spinning...

Hi, I'm recently reading Krane's nuclear physics textbook, and in the meson physics chapter there is a section about the spin and parity of pions. He demonstrated a way to find out the parity of the pion by investigating a pion decay(as in the attached images). I think I understand what he's...

A nice discussion of the density operator for a qubit can be found here: http://www.vcpc.univie.ac.at/~ian/hotlist/qc/talks/bloch-sphere-rotations.pdf

Say I have {S_{x}=\frac{1}{\sqrt{2}}\left(\begin{array}{ccc} 0 & 1 & 0\\ 1 & 0 & 1\\ 0 & 1 & 0\\ \end{array}\right)} Right now, this spin operator is in the Cartesian basis. I want to transform it into the spherical basis. Since, {\vec{S}} acts like a vector I think that I only need to...

If we use the Weyl representation the solutions to the Dirac equation turn out to be eigenfunctions of the S3 operator with eigenvalues 1/2 and -1/2, so we say that the field has spin 1/2. But what about other fields? Why do we say the scalar real and complex field have spin 0? I tried...

I am currently reading Prof.Leonard Susskind's Lecture on Quantum Mechanics. In the Chapter: Spin in the arbitrary directions, in the subdivision Eigenstates In case $$\lambda=1$$ Prof states that measuring spin in arbitrary +n state gives me +1 as eigenvalue, what I don't understand is the next...

Hello everyone, How come the electron wave energy states are different for spin -½ and +½ values? What causes this asymmetry?

Ok, so I know I'm missing something here. But, you know how pool balls that rotate opposite direction increase the speed of one of them through kinetic transfer? Why don't we build a launch platform based on this approach and use the orbital spin of the Sun, Jupiter, and Saturn (gaining speed...

Dear All in the idea of gauging Poincare group i am trying to find the equation of motion of the spin connection w_mu^ab using Euler Lagrange equation. but it seems that i am not getting the same terms can i have a help. I know that this equation is equivalent to the torsionless condition, but...

http://arxiv.org/abs/1105.3735 I have a question about the paper that haushofer mentioned. In the paper, the author states that Moving on to helicity 2, the required gauge symmetry is linearized general coordinate invariance. Asking for consistent self interactions leads essentially uniquely...

Is there any experimental evidence that neutrino spin is equal to the electron spin ( I think h/4pi, right?) If it is just an assumed intrinsic property,can you explain on what grounds it is assumed as such, is it juas a matter of parity?

If a top has angular momentum of 12 units and the Earth has angular momentum of 100. Does this mean that Earth is spinning faster than the top since it has more angular momentum? The answer is there at the back of my head but can't articulate it.

Just curious. Any answers would be appreciated. Thanks!

Homework Statement Consider the following example from a previous exam. We are to predict the spin and parity for F(A=17,Z=9), Florine, in the ground state and the first two excited states using the shell model. Ground state: Neutrons: (1s 1/2)^2 (1p 3/2)^4 (1p 1/2)^2 Protons: (1s 1/2)^2...

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> +...