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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60 views
A general wavefunction in a square lattice
Suppose we have a square lattice with periodic condition in both $x$ and $y$ direction with four atoms per unit cell, the configuration of the four atoms has $C_4$ symmetry. What will be a general ...
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51 views
Standard Quantum Mechanics representation as a constrained 2 + 1 space-time (membrane) theory?
Could a particular Standard Quantum Mechanics representation be a constrained 2 + 1 space-time theory (membrane theory) ?
(i) This question is motivated by a possible (approximative) analogy with ...
2
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32 views
Perturbation in Supersymmetric Quantum Mechanics.
To do perturbation analysis of Supersymmetric Quantum Mechanical Hamiltonian, the superpotential is first scaled by a constant $\lambda >> 1$ and then expanded about it's critical point. Finally ...
2
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61 views
Relativistic genarization of Quantum Harmonic Oscillator
I am trying to find out relativistic description of a quantum harmonic oscillator.
For a classical relativistic oscillator mass is a function of co-ordinates(http://arxiv.org/abs/1209.2876).
...
2
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84 views
Infinite degeneracy
Is something special for a quantum system with infinite degeneracy like free particle levels?
$E=\frac{\hbar^2 \vec{k}.\vec{k}}{2m}$
Edit: I mean what is physical (or mathematical) significance of ...
2
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42 views
Analytical solution of two level system driving by a sinusoidal potential beyond rotating wave approximation
A quantum mechanical two-level system driving by a constant sinusoidal external potential is very useful in varies areas of physics. Although the wildly used rotating-wave approximation(RWA) is very ...
2
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33 views
When is classical mechanics valid for describing motion of atoms?
In Molecular Dynamics simulations, the Newton's equation of motion is used to calculate the time evolution of system. Once, I read in an introductory text that when the thermal de Broglie wavelength ...
2
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42 views
Boundary condition Hamiltonian with point tinteractions
I`m studying the Hamiltonian with point interaction centered in $y$ in three dimensions.
I know that the elements in the domain of the Hamiltonian are of the form
$$\psi=\phi+qG^z(\cdot-y)$$
where ...
2
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91 views
Black & Scholes and the Quantum Mechanics
I am interested in the link between the Black & Scholes equation and quantum mechanics.
I start from the Black & Scholes PDE
$$
\frac{\partial C}{\partial t} = -\frac{1}{2}\sigma^2 S^2 ...
2
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44 views
Why should multiple versions of a weak measurement preclude it from being a measurement of intrinsic properties of some system
I've been trying to understand Stephen Parrott's criticisms of weak measurement, outlined most concisely here: http://arxiv.org/abs/0909.0295
One of his major criticisms is that weak measurement is ...
2
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0answers
144 views
How is parity relevant to determining angular momentum?
Question:
Particle A, whose spin $\mathbf{J}$ is less than 2, decays into two identical spin-1/2 particles of type B.
What are the allowed values of the orbital angular momentum $\mathbf{L}$, ...
2
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69 views
Is that true that real quantum chaos doesn't exist?
I read several books and papers on quantum chaos, to my understanding they all emphases that the quantum chaos does not really exist because the linearity of the Schrodinger equation. Some works were ...
2
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0answers
31 views
Why the peak of spectrum gets vague when the dimension is lower?
In a many-body system, we can know the spectrum function at a particular temperature from Green function. It means density of states. A peak of spectrum represents one mode. My question is that in the ...
2
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38 views
Scattering in quantum wires
I'm working on a project involving scattering of particles in networks of quantum wires off of point scatterers. The problem that I am having is that even in fairly simple configurations of quantum ...
2
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0answers
44 views
Topological Solitons and the Higgs Condensate entanglement
While focusing on resolutions to the Firewall controversy, and the possible implications of the Higgs field as it relates to the issue, the possibility of using EPR correlations in the Higgs ...
2
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0answers
37 views
How large would the electric field need to be to split the mj -/+1 626.6 nm line of neon?
I am an undergraduate considering an extension on a quantum beats experiment with neon. The premise is to excite neon atoms coherently from a metastable 'ground' state into a superposition of excited ...
2
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0answers
76 views
What is Z3 exciton?
I am searching and studying excitons and I confronted with a term named Z3 exciton. What is it? And what is its difference with, for instance Z1 or Z2 exciton?
2
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0answers
57 views
How to make timelike entanglement in the laboratory?
http://io9.com/5744143/particles-can-be-quantum-entangled-through-time-as-well-as-space
http://arxiv.org/abs/1101.2565
How to make timelike entanglement in the laboratory?
How to test whether mixed ...
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0answers
59 views
How to explain Tsirelson's inequality using extended probabilities?
How to explain Tsirelson's inequality using extended probabilities?
Some people have tried explaining the Bell inequalities using extended probabilities.
For instance, a pair of entangled photons ...
2
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0answers
123 views
Angular momentum confusion
Could somebody please explain what is going on here?
We have a system of two indistinguishable spin-1 bosons. We shall adopt the center of mass frame.
Let
$S$ = total spin
$L$ = relative orbital ...
2
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132 views
What is the relationship between consistent histories and path integrals?
As can for example be learned from chapter I.2 of Anthony Zee's Quantum field theory in a nutshell, path integrals can be used to to calculate the amplitude for a system to transition from one state ...
2
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0answers
69 views
decoherence free subspace of a single photon
Take the state vector for a single photon as
$\psi = \int \gamma_{\omega} | \omega \rangle \otimes (\alpha |H \rangle + \beta | V \rangle )d \omega$
$H, V, \omega$ are the horizontal polarization, ...
2
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94 views
Eternal clocks and 4D spacetime crystals
There was a recent article about the creation of 4D spacetime crystals based on recent theory proposed by Frank Wilczek. This theory is based on breaking time translational symmetry which basically ...
2
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0answers
120 views
quantum field theoretic models of decoherence
I am interested in whether there is a field theoretic description (there is, so what is it?) of the tensor product (aka density matrix) model of open quantum systems. In particular, I am interested in ...
2
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53 views
Beginning with an arbitrary classical equation for energy, how do I get the QM Hamiltonian?
For linear momentum I can use the de Broglie equation, but what about energy in terms of moment of inertia or some other form?
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47 views
dynamical operator and $SU(n+1)$
I want to know precisely by example
what is dynamical operator?
what is the relationship between dynamical operators and the $SU(n+1)$
How to show all the eigen states of a dynamical operator form ...
2
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0answers
204 views
What is effective mass approximation
Currently i am studing about quantum confinement in semiconductors and came across effective mass approximation.but i am unable to understand this concept. what is the use of effective mass ...
2
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0answers
79 views
After quantization of electron vibrations, do we need electrons anyway?
The title question is not ment in a general context, but one in which goes to the plasmon theory.
In that case, how is are the statistics (boson vs. fermions) of plasmons determined?
And is there an ...
2
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0answers
98 views
Separable states of maximum non-classical correlations
Although there is no standard measure of entanglement, the GHZ states
$|GHZ\rangle=\frac{1}{\sqrt{2}}(|0\rangle^{\otimes n}+|1\rangle^{\otimes n})$
are often deemed as maximally entangled states of ...
2
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0answers
53 views
Are there any connections between James–Stein estimator and quantum mechanics?
Very nice statement from wiki:
When three or more unrelated parameters are measured, their total MSE can be reduced by using a combined estimator such as the James–Stein estimator; whereas when ...
2
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0answers
80 views
What can tunnel through a graphene sheet?
In popularizations, people tunnel through walls or doors. But what can really tunnel through a graphene sheet without tearing it?
According to Wikipedia, a single layer of graphene absorbs 2.3 % ...
2
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0answers
149 views
Comparison of different ab-initio codes
One may find on the web a lot of different computational packages to perform "ab-initio" calculations of electron structure of the solids. Usually, the documentation is not quite transparent about the ...
2
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0answers
73 views
Factorization of fermionic scattering integral in 2d momentum rep
the scattering integrals for fermions involves both momentum ($k$) and energy ($k^2$) conservation and a nonlinear phase space factor of a distribution function $f(k)$.
$$\begin{multline}I(k) = ...
2
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0answers
160 views
A solvable model for the finite rectangular potential well with a bump in the middle
A well known example in quantum mechanics is that of a finite rectangular potential well with a rectangular bump in the middle. I guess this closely approximates the "umbrella" effect of the $NH_3$ ...
2
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0answers
182 views
In Scully and Druhl delayed choice quantum eraser experiment, are there limits to the lengths of the delay?
I'm in humanities, not physics, so please bear with me. I am trying to understand this experiment and have a few unanswered questions. I have read the other posts on this site that discuss the ...
2
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0answers
80 views
Derivation of Brillouin-Wigner theory for coupled subpaces
I recall faintly from my quantum theory lecture that there was a really neat way to derive Brillouin-Wigner perturbation theory for the special case of two coupled subspaces that involved a geometric ...
2
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0answers
84 views
How can one trace out polaritonic degrees of freedom?
I have read the paper "Steady state entanglement between hybrid light-matter qubits", arXiv:0711.1830v2.
There, writers obtained density operator in matrix form after solving steady state equation ...
2
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0answers
267 views
Gauge invariance and Feynman path-integrals
Let me look at the Hamiltonian of a charged particle in a plane in a constant magnetic field ($\vec{B}$) pointing upwards - then in usual notation it is,
$$\hat{H} = \frac{1}{2m}\biggl(\hat{p} + ...
2
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0answers
132 views
Can the time direction of wave function collapse be reversed?
The laws of physics are invariant under CPT transformations reversing time, inverting space and flipping charges. Almost so. The collapse of the wave function is the odd man out. Can the time ...
2
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0answers
118 views
Do Bell inequality violations appear instantly when the source is turned on, or do they increase over time?
This experimental Question is a result of reading a particular article on Bell violations. I addressed the e-mail below to the corresponding authors —because who knows, they might reply— but it is not ...
1
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0answers
24 views
Clarification of Landauer approach
I am trying to understand the Landauer approach. Consider the setup: (left contact)-(conductor)-(right contact). For simplicity, the conductor is a 1d wire (the transverse part is not relevant for ...
1
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0answers
27 views
Is it possible to detect subjective decoherence? If yes, how?
In his paper from 1994 Thomas Breuer describes a phenomenon of subjective decoherence (p. 43). I wonder whether it can be measured, and if yes, how.
I also wonder whether it would allow to create an ...
1
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0answers
24 views
How does a state vector change under an exchange of a boson and a fermion?
How does a state vector change under an exchange of a boson and a fermion ? That's how is $\Psi_{\alpha,\beta}$ related to $\Psi_{\beta,\alpha}$ where $\alpha$ and $\beta$ are a boson and a fermion ...
1
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0answers
28 views
Non reciprocal light propagation
In search for some explanation in why magneto-optical materials (like the one used in the Faraday rotator and, consequently, in the "optical diode") act in such a "strange" way, I saw that this kind ...
1
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0answers
34 views
What is the difference between Cramer and Vaidman?
Two very interesting new papers on arXiv last night by Lev Vaidman and friends lead me to ask about the differences between Cramer's transactional interpretation of quantum mechanics (TIQM) and the ...
1
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0answers
23 views
Laughlin state unique ground state?
In the FQHE, one typically encounters the statement that the $\nu = 1/3$ Laughlin state is a unique exact ground state of a model Hamiltonian where the Haldane pseudopotentials $V_1 \neq 0$ and $V_m = ...
1
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0answers
54 views
Helicity operator in Non relativistic limit
Helicity operator in Dirac equation is given by
$$H=\frac{\vec{S}\times \vec{P}}{P^{2}}$$
This operator commutes with dirac hamiltonian.We can also define a helicity(with same form) operator in case ...
1
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0answers
26 views
Quantum graph theory: complex spectra
In quantum graph theory, what are the properties of a given graph to own complex conjugated complex eigenvalues, either finite or infinite? Spectral graph theory is as far as I know a not completely ...
1
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0answers
91 views
Is there a physical reason for level repulsion and avoided crossings?
Suppose we have a Hamiltonian that depends on various real parameters. When tuning the values of these parameters, the energy eigenvalues will often avoid crossing each other. Why?
Is there a ...
1
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0answers
77 views
Unitary Operator apply to Entangled vector
I am trying of resolve this exercise: Show that if $|\psi \rangle$ is an entangled state of two Qbits, then the application of a unitary operator of the form $U_1 \otimes U_2$ necessarily generates an ...
