States Definition and 1000 Threads

Okay, here goes... Our teacher set a question in the last test which asked us to show that if a system initially be in a stationary state, it will remain in a stationary state even if the system evolves according to the time dependent Schrodinger equation. What I did was show that the...

The question is for which of the ##1P## meson states - ##1^{1}P_{1}, 1^{3}P_{0},1^{3}P_{1}, 1^{3}P_{2} ## ##D_{s}## states decaying to a ##1S## state is the decay: ##D_{s}**^{+} -> D_{s}^{+}\pi^{0} ## possible? Solution So the strong interaction conserves parity. Parity of meson is given by...

Hi all, In Charles Kittel (Introduction to Solid State Physics) He writes : U (Total Phonon Energy ) = Σk∑p((ħ*ωk,p)/((exp(ħ*ωk,p/τ))-1)) I understand this, but then he integrate over k and multiply by density of states : U (Total Phonon Energy ) = ∑p∫dω*Dp(ω)*((ħ*ωk,p)/((exp(ħ*ωk,p/τ))-1))...

I have looked around for help with this, including on existing threads, but I can't quite find what I'm looking for. I know that in the nuclear shell model we fill the shells in the same way as with electrons, so 2 protons in the first and 6 in the second etc, with the same being true for...

Homework Statement When calculating expectation values for spin states I encountered ##\langle \hat{\mathbb{S}}_+\rangle = \langle+z|\hat{\mathbb{S}}_+|+z\rangle = \frac12\langle+z|\hat{\mathbb{S}}_++\hat{\mathbb{S}}_-|+z\rangle.## How do we compute...

Folks were celebrating when these states joined the EU. http://www.dw.de/the-baltic-states-from-soviet-to-european/a-17872310 But now, folks are wearily eyeing a more aggressive Russia next door, especially after the Russian annexation of Crimea and invasion of Ukraine's territory. Meanwhile...

It is stated that classical states are robust against decoherence.. what would happen if classical states can decohere too? Or how do you imagine it for example occurring to a table.. How would the table look like if it suffers decoherence too? Would you fall down if you sit on one?

I've been following the EdX course on Quantum Computing by Prof. Vazirani and I don't understand how one physically can create a superimposed state of the ground and 1st excited state of an hydrogen atom. He mentions "the use of light," but doesn't explain the frequency of the light, nor the...

I think I have read that massless fermionic states can be used (as a basis?) to build up massive fermionic states. Is that true? If so, could you please give me a very short outline of how this is done, or maybe better, a mathematical statement that "says" the same thing? Thanks for any help!

Homework Statement Consider three electrons in three different orbital levels n, m and p. We assume that there is one electron in each orbital level. How many states are then possible? Homework Equations Equations for constructing symmetric and asymmetric wavefunctions: Symmetric under pair...

Are there any known (collective spin) operators to raise or lower the quantum number s in \left|{s,m}\right> spin states? I'm trying to construct coherent states varying the quantum number s instead of the well known spin coherent states varying m. I found a coherent-like state similar to the...

Things I don't understand: What do they mean by "two spin-1/2 doublets and a spin-3/2 quadruplet"? Why do they use the two flavours "+2/3e and -1/3e" ?

While browsing Wikipedia I bumped into this sentence that seemed partially wrong to me but maybe I didn't understand what it is referring to so would like for some expert to help me elucidate it: "Even if an elementary particle has a delocalized wavepacket, the wavepacket is in fact a quantum...

Homework Statement Evaluate the matrix elements ## {\mathbb S}=\left( \begin{array}{cc} \langle x|\mathbb{\hat J}_z|x\rangle& \langle x|\mathbb{\hat J}_z|y\rangle\\ \langle y|\mathbb{\hat J}_z|x\rangle &\langle y|\mathbb{\hat J}_z|y\rangle\end{array}\right)## by expressing the linear...

Homework Statement I'm curious in proving that expectation value of momentum for any bound state is zero. So the problem is how to prove this.Homework Equations $$ \langle \mathbf{p_n} \rangle \propto \int \psi^*(\mathbf{r_1}, \dots ,\mathbf{r_N}) \nabla_n \psi(\mathbf{r_1}, \dots...

I know that matter can only exist in one state at a time; however at the quantum level knowing what state it is in at a set time is impossible to know for sure until you look at the system. Like with how Schrodinger cat is in a state of randomness between the two states of dead and alive until...

Is it possible, in principle, for an experiment to distinguish between an ensemble of pure states and an ensemble of mixed states? If so, how? In particular, I am thinking of an ensemble of particles whose spin has been measured, one at a time, on the "Vertical" axis. The ensemble consists of...

How do you understand pointer states? I was trying to comprehend Zurek papers that without Einselection, Decoherence can even affect classical states and every tourist who looks at the Statue of Liberty would see different thing because its state was affected by the previous tourist. So he...

I have a theoretical question, I just recently learned that the spin triplet S=1 of helium in the state 1s2s is lower in energy than the 1s2 state due to the exchange interaction. I then learned that this 1s2s state has a shorter lifetime than the 1s2 state, can anyone explain why this occurs...

In The Theoritical Minimum we shown all spins states use just two states up and down. How can we do that.? I am confused about the directions of states and normal coordinate system Can somebody help me ? Thanks

I am reading a book The Theoretical Minimum I didnt understand spin and quantum states "All possible spin states can be represented in a two dimensional vector space." What it means ?

I have a question concerning the paper "Quantum imaging with undetected photons". http://arxiv.org/abs/1401.4318 In the schematic (Fig. 1) a photon (idler) is created at NL1 and passing the object at O to be reflected further to NL2. It is then stated in the paper "By reflection at dichroic...

Hello, I am calculating the potential energy surface of an iron slab, once with a ferro magnetic behavior and later anti ferromagnetic behavior, I know for ferromagnetic I multiply the number of atoms by its magnetic moment (I use 3 that must be a little higher than its real value), my...

Homework Statement http://web.phys.ntnu.no/~kolausen/TFY4230/.oldExams/17_eksdes12.en.pdf solution: http://web.phys.ntnu.no/~kolausen/TFY4230/.oldExams/18_losdes12.en.pdf Look at problem 4a, formula (27) or the expression between (29) and (30). My professor keeps converting sums into...

(This though came up while learning about band structure, so that is how I am going to explain it, but I think it applies equally well to a square well, for example). Say you have an electron at the Fermi level of an insulator. Then, you apply an electric field. No current flows, because all...

Ok, so what I considered to be true for quite some time now has been somewhat tarnished after something that was said recently in a lecture, so I am looking for some insight. Basically, I was told several times by several teachers/professors over the years that when an electron absorbs a...

Homework Statement Given the coherent state of the harmonic oscillator |z>=e^{-\frac{|z|^2}{2}}\sum_{n=0}^\infty\frac{z^{n}}{\sqrt{n!}}|n> compute the probability for finding n quanta in the sate |z> and the average excitation number <z|n|z>Homework Equations...

A voltaic cell is composed with reactants and products in their standard states.So when it operates,the concentration of all substance must change,it should no be hold.Am i right?

Is there any state of matter for fire or electricity ? If yes, then what is the state of matter ?

Homework Statement The wavelength of the radiation emitted when the outermost electron of Al (Aluminum) falls from the 4s state to the ground state is about 395 nm. Calculate the energy separation (in joules) between these two states in the Al atom. Draw an energy level diagram of the states...

In basic chemistry, we "fill up" the energy levels of an atom by putting two electrons in each energy level. The justification for this (that I've seen) is that the Pauli exclusion principle only allows one electron per state and there are two states in each energy level (spin up and spin down)...

Homework Statement I'm supposed to calculate all the states for a system with ##l=1## and ##s=1/2##. Let's say ##\vec{J} = \vec{L} + \vec{S}##. I want to find the Klebsch-Gordon coefficients. I know that said system has 2 towers, one with ##j=3/2## and the other with ##j=1/2##. I've...

Homework Statement The emission spectrum of thermally excited sodium atoms practically consists of a single intensive line at 589 nm wavelength. What is the energy difference (in eV units) between the excited and ground states of the sodium atom? Homework Equations E = hc/lambda, we also know...

Hello I'm trying to work through a see-saw model derivation and I've become a bit stuck. I've tried lots of sources but the difference in conventions doesn't fill me with confidence when combining these sources. I need to get from ## \overline{ \nu_L^c } \nu_R^c + h.c ## to ## \overline{...

Let: $$x_1=A\sin{\omega t}$$ $$x_2=\dot{x}_1=A\omega \cos{\omega t}$$ $$y=A\omega$$ We want to represent this system in a state space model. The state transition matrix read: $$A=\begin{bmatrix} 0 & 1 &\\ -\omega^2 & 0 \\ \end{bmatrix}$$ I am not sure what the output matrix will be like. Can we...

Homework Statement A certain system has 6 × 10^24 degrees of freedom. Its internal energy increases by 1%. By what factor does the number of accessible states increase? Homework Equations \Omega = E^{N\nu/2} \nu is the degrees of freedom, and N is just 1, so we can ignore that. So the exponent...

In my particles course, it says we will use Fermi's golden rule to work out rates. FGR is: Γ=2π|Mfi|ρ For the case of non-relativistic phase space, my notes say the density of states can be found as follows (pretty much word for word): Apply boundary conditions Wave-function vanishing at box...

Tell me if the following is correct. For a simple infinite square well potential, the solutions to the Schrodinger equation are \Psi_n(x)=\sqrt{\frac{2}{a}}sin(\frac{n\pi x}{a}), then you plug in the appropriate value for n and operate on the function accordingly to get your observables. Then...

Homework Statement (a) the density of k-states g(k) = L^2*k/2*Pi. (b) the density of states g(E) = L^2*m/Pi*h^2 (c)The density of states per area n2D(E)=m*/Pi*h^2 (d) Sketch a graph of n2D(E) vs E. (e) Calculate n2D(E) as a quantity. The questions don't have to be answered in full a...

1)So from my understanding, as long as ##E>0## you will have scattering states and these scattering states will always result in an imaginary ##\psi##, but bound states can also have an imaginary ##\psi##? Is this correct and or is there a better way of looking at this maybe more conceptually...

I'm working on a problem out of Griffith's Intro to QM 2nd Ed. and it's asking to find the bound states for for the potential ##V(x)=-\alpha[\delta(x+a)+\delta(x-a)]## This is what I'm doing so far: $$ \mbox{for $x\lt-a$:}\hspace{1cm}\psi=Ae^{\kappa a}\\ \mbox{for $-a\lt x\lt...

I am a little confused about exercise 1.2 in the book "Quantum Computation And Quantum Information" By Michael Nielson. The question is: Explain how a device which, upon input of one of two non-orthogonal quantum states |a> or |b> correctly identified the state, could be used to build a device...

Homework Statement Consider a particle of mass m in the ground state of a potential well of width 2 a and depth. the particle was in the ground state of the potential well with V0 < Vcritical, which means the well is a narrow one. At t = 0 the bottom of the potential well is shifted down to Vo'...

In some quantum textbooks [1], the tunneling transmission formula depends only on the density of states of 2 regions (DOS) involved in tunneling. (T(E)=C×DOS1(E)×DOS2(E), where C is constant). However, in Landauer transmission formula (without tunneling) the transmission depends on both DOS and...

Hi, Following electromegnetic field quantization, one ends up with the fock states as the energy eigenstates of the quantized field. Considering a single mode field, the set of fock states are the single-mode energy eigenstates. Yes, these fock (or number) states are just the eigenstates of the...

I am writing a book, and since I am a science layman, just wanted to check to see if you find the following paragraph I wrote to be correct from a physics standpoint. The idea here is that "a single, simple substance or field can contain regions which are in different states." I would greatly...

I have learned the fact from Peskin QFT book,that one-particle state presents a delta function form in spectral function at s=m^2,while multiparticle states present a continuous form begin at s=4m^2,but i don't really understand the reason.What cause the difference between one-particle state and...

Homework Statement For an electron in a uniform magnetic field, say B\hat{z} with no angular momentum, the Hamiltonian can be expressed as \hat{H}=\frac{1}{2m}\Big(\hat{p}_x^2+\frac{mω^2}{2}\hat{x}^2\Big)+\frac{1}{2m}\Big(\hat{p}_y^2+\frac{mω^2}{2}\hat{y}^2\Big) Which is equivalent to two...

Homework Statement A particle is moving in one dimension, estimate the number of quantum states available to that particle if it is an electron confined in a region 10-9m long with speed less than 107 m/s (less than meaning velocity is between 107 and -107 m/s) Homework Equations...

Homework Statement These are rather simple questions but the rules for all of this are not quite clear to me yet. I'm to determine whether or not the following states are "legal" and if not I should normalize them. a. ##\frac{1}{√385} ∑_{x=1}^{10}x^2 |x>## b. ##\frac{1}{√2}...