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  • 0 posts edited
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  • 33 votes cast
Apr
13
asked Creation operators that differ by a reciprocal lattice vector
Apr
4
asked Commutation of photonic crystal master equations
Mar
24
asked Analytical derivation of photonic bandstructure in photonic crystal
Mar
22
asked Image charges and image-image interactions
Mar
10
comment Why is response of system same frequency as driving force frequency
Ok so I think what you're saying is you plug in an arbitrary function as a fourier integral and if you work through only the frequency component the same as the driving force drops out as non-zero. But I'll work through it and see for myself.
Mar
10
comment Why is response of system same frequency as driving force frequency
Thank you for this insightful answer. Can you comment on the ansatz, as I think it is this assumption that I am having trouble justifying. Why should the solution oscillate at the same frequency as the driving force?
Mar
10
comment Why is response of system same frequency as driving force frequency
Ok how about a linear chain of identical masses connected by identical springs, where the first one is driven at a constant frequency. I believe one assumes that all members will oscillate at the same frequency as the driving and then with this assumption work out the amplitudes and phases of each member, but I'm asking why we can assume they all oscillate at the same frequency as the driving frequency.
Mar
10
asked Why is response of system same frequency as driving force frequency
Mar
8
accepted Confusion with poles of single particle green's function / propagator
Feb
16
revised Eigenvalues of Hamiltonian with on-diagonal coordinate
added 614 characters in body
Feb
16
comment Eigenvalues of Hamiltonian with on-diagonal coordinate
What do I mean... good question... well under the influence of a strain the graphene Hamiltonian above can be modified such that there is a 'gauge field' which introduces terms on the off-diagonal which are of the form $x$ or $y$. This leads to Landau levels etc. I'm wondering what happens when the coordinate dependent terms are of the diagonals.
Feb
16
asked Eigenvalues of Hamiltonian with on-diagonal coordinate
Jan
3
awarded  Popular Question
Jan
1
revised Confusion with poles of single particle green's function / propagator
added 996 characters in body; edited tags; edited title
Jan
1
asked Confusion with poles of single particle green's function / propagator
Nov
23
comment Is angular momentum conserved for a mass fixed to a horizontal guide
Good, just checking I haven't gone mad. I think the lecturer applied Noether's theorem to the case of origin at the crossing point to show the Lagrangian is not invariant. However, from further reading I believe Noether's theorem is not valid if the transformation breaks the constraints. So performing a rotation to check for angular momentum conservation is not valid as it breaks the horizontal and vertical constraints.
Nov
23
accepted Is angular momentum conserved for a mass fixed to a horizontal guide
Nov
23
comment Is angular momentum conserved for a mass fixed to a horizontal guide
This agrees with my thought process. Thank you for confirmation!
Nov
23
comment Is angular momentum conserved for a mass fixed to a horizontal guide
I agree. But, is angular momentum conserved about the origin at the crossing point of the guides?
Nov
23
comment Is angular momentum conserved for a mass fixed to a horizontal guide
@brucesmitherson please note i've edited first paragraph to make question more explicit