Quantum mechanics describes the microscopic properties of nature in a regime where classical mechanics no longer applies. It explains phenomena such as the wave-particle duality, quantization of energy and the uncertainty principle and is generally used in single body systems. Use the ...

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How to arrive on the diffraction pattern for the double slit experiment using path integrals for the Gaussian slit case?

I wish to take the path integral route to derive the diffraction pattern for the double slit experiment using the Gaussian slits as the nature of the slits. The kernel looks like: \begin{equation} ...
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64 views

Can the wall in the double-slit experiment be considered to perform a “half measurement”?

When talking about the double-slit experiment, most physics books consider the wall to be a infinitely high potential, so that the photon is either reflected or transmitted through one of the slits. ...
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59 views

How would the frequency of particle spin be estimated if it really was rotation?

I understand from reading that particle spin is not real spin as the globe spins. from what I have read particle spin came about because of the magnetic field of a particle. If I understand the text ...
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50 views

Eigenstates of a harmonic oscillator

Using ladder operators, I can find eigenstates $\psi_n$ with eigenenergies $$E_n=\hbar\omega\left(n+\frac{1}{2}\right). $$ In my textbook, ladder operators work like $$ a\psi_n = c_n \psi_{n-1}$$ $$ ...
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60 views

Photon Absorption vs. Photoelectric Effect

USually, photons are absorbed by substances only if their energies coincide with the orbital transitions of that particle. However, in the photoelectric effect, it seems that you can take the energy ...
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47 views

Evolution of a 'state' in the Heisenberg picture

Suppose that we have a Hamiltonian, $\hat{H}$, and an operator $\hat{A}$ which satisfies the Heisenberg equation$^{[a]}$ $$i \frac{d}{dt} \hat{A} = [\hat{A},\hat{H}].$$ Can we create a 'state' by ...
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64 views

Schrodinger equation contains two pieces of information?

I've read that Schrödinger equation contains two pieces of information: about amplitudes and about phases. I know continuity eqn. for probability which is nice expression of former. I wanted to ...
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1answer
31 views

Mean squared velocity of a particle moving in a logarithmic potential [closed]

A particle of mass $m$ moves in the logarithmic potential $V(r)= C\ln(ar)$. $C$ and $a$ are constants. What is the mean squared velocity of the particle? Do I have to solve this in ...
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1answer
43 views

Find the expression of $j_+$ and $j_-$operators [closed]

I have just started to do exercises about quantum mechanics and I have some difficulties. I have a particle with spin $j=1$ and the Hamiltonian is $H=\gamma(j_xj_y+j_y j_x)$ (where $\gamma$ is a ...
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39 views

Is the connection of two spin-zero projectors with a singlet again a projector?

Let me pose a question that popped up in my research. Consider a square lattice, where each of the lattice sites is associated to 4 spin 1/2 particles. Now let the single-site projector $P_{(1,1)}$ be ...
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1answer
55 views

What is the relationship between quantum physics and chaos theory?

I am not a physicist, I am looking for a non-technical explanation. Articles such as this one seem to hint at the fact that "macro reality" regulated by classical mechanics is somehow a pattern ...
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1answer
74 views

Width of a 1 dimensional box with same ground state energy as hydrogen atom [closed]

I am trying to find the width $L$ of a one-dimensional box for which the ground state energy of an electron in the box equals the absolute value of the ground state of a hydrogen atom. No ...
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2answers
67 views

How can a solution of the time-independent Schrödinger equation evolve in space?

I understand that if the Hamiltonian does not depend on the time, the Schrödinger Equation becomes separable, so you get $$ H \psi(x) = E \psi(x) $$ and $$ \Psi(x,t) = ...
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1answer
27 views

Mass eigenstates and occupied physical volume?

I recently read about atom lasers and it made me wonder about something I recalled from my limited experience with quantum (two undergraduate and two graduate level classes). I recall that some ...
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1answer
70 views

No two identical fermions can have the same quantum state at once?

This is the Pauli Exclusion Principle, but I have a question about it... It states that no two identical fermions can have the same quantum state, but what about different fermions having the same ...
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21 views

Ramsey pulse versus optical pumping: what's the difference?

A Ramsey pulse is a coherent process, where the electronic states of for example an ion (or some other two-level-system) are coupled to a laser field. By tuning the laser precisely, we can coherently ...
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1answer
36 views

Potential energy function for high energy continuum?

For the hydrogen atom the quantised energy levels are: $$E_n = \frac{- 13.6 eV}{n^2}\quad\text{with}\quad n = 1,2,3...$$ One peculiar property of this quantisation is that for large $n$ the energy ...
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67 views

Can't a hydrogen electron have net positive energy?

This page http://www.physicspages.com/2011/06/07/hydrogen-atom-series-solution/ is the 2nd half of a solution to the hydrogen atom Schrödinger equation. They derive that $E = -1/n^2 *$ (bunch of ...
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1answer
99 views

Definition of probablity current in dirac space not including spatial dimension?

I'm currently reviewing (basic) relativistic quantum mechanics and stumbled upon the probability current in "dirac space", defined as $j^μ = (j^0,\vec j)^\mathrm T$ with $j^0 = c\,ρ = c\,ψ^+ψ$ and ...
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1answer
70 views

Can Schroedinger equation be derived from the unitary representation of Galilean group?

I have been trying to understand quantum mechanics as a unitary representation of spacetime symmetries. My first question is: Can Schroedinger equation be derived from the unitary representation of ...
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1answer
86 views

Derivation of time-dependent Schrödinger equation from De Broglie hypothesis

In a quantum mechanics script I'm reading, the Schrödinger equation is "derived" (more precisely, motivated) by the De Broglie hypothesis. It starts at $$ \lambda = \frac{2\pi h}{p} $$ $$ \omega = ...
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1answer
76 views

Effective hamiltonian for the second-order degenerate perturbation theory

I'm currently trying to figure out the way we arrive to the Hamiltonian of a topological insulator. In an article by Xiao-Liang Qi (arXiv: http://arxiv.org/abs/1005.1682) in a process of arriving to ...
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333 views

Confusion about 1-forms as introduced in “Gravitation” (Kip S. Thorne,…)

In the book Gravitation in chapter 2, paragraph 5, they introduce the concept of 1-forms by thinking about the momentum 4-vector differently. They first introduce the de Broglie 1-form as follows (I ...
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302 views

Are quantum numbers always integers?

Quantum numbers are integers for lots of systems. For example, for a particle in an infinite well $$E_n = E_1 n^2 \text{ with } n = 1, 2, 3\ldots$$ for a quantum harmonic oscillator $$E_n = (n + ...
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36 views

How photons get distributed in a system?

Let's say I'm in a room, and there are plenty of things in my room like carpet,mirrors,glass and other stuff.And I see there are shadow regions and fully bright regions, and I want to know how photons ...
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1answer
54 views

Positive Partial Transposition in Fano form

Cite from "Geometry of Quantum States: An Introduction to Quantum Entanglement 1st Edition by Ingemar Bengtsson (Author), Karol Zyczkowski (Author)": "Partial transposition applied on a density ...
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1answer
51 views

In path integrals, why is phase defined the way it is? [duplicate]

In reading from the book, there's a peculiar definition of the phase, stating: \begin{align} K[a,b] &= \sum_{\text{All paths from $a$ to $b$}} \phi [x(t)]\\ \phi [x(t)] &= \text{const} ...
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27 views

What is the kernel for a double slit experiment? [duplicate]

In the book path integrals by Feynman and Hibbs, the author has established the kernel for a single slit in the Gaussian form. How can I find the kernel for a double slit in a similar fashion as ...
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8 views

trace of spherical components of an angular momentum multiplet

My basic mathematical question is whether or not there exist selection rules regarding the traces of the spherical tensor components of some operator acting on some subspace of definite total angular ...
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1answer
30 views

Why photons don't have or match the energy difference of atom in order to pass thought that material?

Rule I learned: only photons with quanta of energy match matching the exact difference between energy levels can be absorbed/ reemitted. But to me optical density works opposite to this rule. ...
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28 views

What happens to quantum fluctuations near the schwarzschild radius?

I was reading about Feynman Diagrams and have gotten the impression that particle/anti-particle pairs are created fairly often given a large space. The surface area of a sphere with a radius equal to ...
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16 views

the difference between magnetic neutron scattering and polarization neutron scattering

recently I have been reading some papers about neutron scattering in High-Tc SC. I'm a little confused by the method of neutron scattering, especially about magnetic neutron scattering and ...
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17 views

What is the electron barrier tunneling mass, and why it is necessary? What is the ebarrier tunneling mass of AlGaAs?

I am doing solar cell simulations in synopsys software. I am getting a persistent error saying ebarrier tunneling mass has not been defined. Is anyone familiar with this error? What is this ...
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152 views

Does the spin of a particle change if observed from an accelerating reference frame?

If we consider a spin-$\frac12$ particle at rest in the absence of any potentials, we can use the Pauli spin operators and an associated basis to describe the observable. Let's arbitrarily choose the ...
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12 views

Relaxation time approximation in anisotropic potential scattering event

In relaxation time approximation (RTA) of Boltzmann transport theory, the relaxation time is calculated by $\frac{1}{\tau(\mathbf{k})}=\frac{2 \pi}{\hbar V}\sum_{\mathbf{k^{'}}} \delta ...
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2answers
97 views

Do Entangled Particles communicate through Wormholes? [closed]

If so, would this “spooky action at a distance” still be spooky if that “distance” is actually shorter than it appears? Sorry if this is a Noob question. Just trying to understand how Entangled ...
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1answer
66 views

Wouldn't the cat observe what happened?

Put a cat in a sealed box, Schrödinger said, with a gun that has a 50/50 chance of shooting the cat in response to an unpredictable, random quantum event. Because the box is built so solidly that no ...
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1answer
35 views

Do I have some freedom when I define the quantum SHO ladder operators? [closed]

I tried to solve the quantum harmonic oscillator via the operator method. After doing it and looking up the solution I noticed that for some reason the ladder operators got an additional factor of (i) ...
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10 views

Long delay in the delayed choice quantum eraser experiment

As I understand it, the which-path information of the entangled particle is observed after the particle passes through the slit but before it hits the screen (detector D0). I guess there is some flaw ...
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20 views

Evaluation of a probability from Fermi Golden rule

In Marc Bee's book, he has described the principle of spectroscopy with reservoir (the material) and the probe as interacting systems with their own hamiltonians $H_R$ and $H_p$ respectively and $H_c$ ...
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1answer
34 views

particles from waves?

If you slide a styrofoam cup containing milky coffee accross a formica tabletop, the friction of the styrofoam on the formica, will produce a wave interference pattern on the surface of the coffee. ...
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53 views

Would a time difference allow identification of the path in the two-path experiment in quantum mechanics?

In the two-path (or color-hardness) experiment as described in this link (experiment #3), what would happen if we make one of the paths much longer than the other one. In this way, we would be able to ...
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3answers
124 views

What is the physical meaning of the Lindblad operator?

I read the wikipedia article on the Lindblad operator, but I still don't understand what this operator is supposed to describe. I therefore considered setting up an example in order to get the idea. ...
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44 views

Is there a difference between two of the same fundamental particle?

Is there a difference between two of the same fundamental particle? For example, is there a difference between two electrons or two protons, or quarks or gluons? If there is a difference then how ...
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2answers
77 views

How to predict bound states in a 1 D triangular well?

Assume we have a (single) particle in a potential well of the following shape: For $x \leq 0$, $V = \infty$ (Region I) For $x \geq L$, $V = 0$ (Region III) For the interval $x > 0$ to $x < ...
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3answers
172 views

Why the nonexistence of a “one sentence layman phrase” for the de Broglie relation $p=\hbar k$? [closed]

(My question seems most likely will be considered a duplicate of OP (and possibly 1, 2, 3), but it turns out to be WAY TOO LONG as a comment in OP, and the system has deleted the corresponding chat ...
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1answer
52 views

How can a two-state ammonia molecule have more than two states?

[...]this molecule, like any other, has an infinite number of states. It can spin around any possible axis; it can be moving in any direction; it can be vibrating inside, and so on, and so on. It ...
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1answer
87 views

Continuous spectrum of hydrogen atom

I wonder if there is a nice treatment of the continuous spectrum of hydrogen atom in the physics literature--showing how the spectrum decomposition looks and how to derive it.
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2answers
92 views

Why is there an energy gap in superconductors?

I'm a little out of my depth here... I'm trying to understand quasiparticle tunnelling in superconductor-insulator-superconductor junctions. Many books use the "semiconductor model" to explain this: ...
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1answer
79 views

What's Wrong With This Quantum Analogy?

"Sometimes the idea of the quantum is compared to the units we use for money. A dollar can be divided into smaller units, where the cent is the smallest possible unit." A question I came ...