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Nov
23
comment Do photons age in a medium?
What is the difference between field velocity and photon velocity? If you quantize a field that propagates with velocity $v<c$, would you still get photons propagating with velocity $c$? How can we see this mathematically?
Nov
21
comment Explaining chirality for spin 1/2 particle
Calling the two states of chirality left and right gives the impression that it has an intuitive meaning similar to helicity, and this intuitive meaning is what I couldn't grasp till now. In nonrelativistic quantum mechanics, the phase associated with rotating around the z-axis depends only on the angle of rotation (the sense of rotation and hence the sign of the phase is encoded in the angle). In relativistic QM, I don't know how this works since I don't know how a relativistic spin operator is defined.
Nov
21
comment Explaining chirality for spin 1/2 particle
Thanks Flip for the answer. It seems from the first part of your answer that you consider chirality just as another quantum number that has different values for particles and anti-particles. Is that true? Otherwise, is it possible to explain chirality without referring to anti-particles at all?
Nov
12
asked Explaining chirality for spin 1/2 particle
Nov
1
awarded  Critic
Sep
22
comment Why doesn't gravity act as a measurement?
A related concept to your question is gravitational decoherence, arxiv.org/abs/gr-qc/0306084
Sep
7
comment Are Rabi oscillations a pure quantum process?
Hers it is: copilot.caltech.edu/classes/ee243/Rempe_collapse_revival.pdf
Sep
4
answered Are Rabi oscillations a pure quantum process?
Apr
21
accepted First order coherence function in terms of momentum distribution function
Apr
16
asked First order coherence function in terms of momentum distribution function
Apr
14
asked English translation of Helmholtz' paper: “On the Physical Significance of the Principle of Least Action”
Mar
24
awarded  Popular Question
Mar
20
awarded  Yearling
Mar
13
comment Hamiltonian of a simple graph
$\Sigma_z=S_1^z+S_2^z$ The first matrix you wrote for $\Sigma_z$ is consistent with the definitions for$S_1^z$ and $S_2^z$. What is the problem in $S_1^z |ZZ\rangle=-0.5|ZZ\rangle$ ? Isn't this expected?
Mar
10
answered Hamiltonian of a simple graph
Feb
12
comment Nuclear Magnetic Resonance (NMR) Conceptual Questions
Are you having difficulty trying to visualize the time evolution of the magnetization? Try to use this simulator: drcmr.dk/BlochSimulator
Jan
6
comment Simulating the evolution of a wavepacket through a crystal lattice
@hwlau I am not an expert in either of them. For sufficiently small systems, direct evolution with a simple 4th order Runge Kutta algorithm is sufficient. This amounts to using a truncated Taylor expansion of the time evolution operator. The Hamiltonian is represented as a sparse matrix.
Dec
31
comment Simulating the evolution of a wavepacket through a crystal lattice
Have you thought of using numerical algorithms, such as tDMRG, TEBD ?
Oct
26
awarded  Commentator
Oct
26
comment What is the spin rotation operator for spin > 1/2?
Of course I am asking about the analogous formula for the expansion of the exponential in terms of cosines and sines not about the spin matrix !