5,547 reputation
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bio website sjbyrnes.com
location Massachusetts
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visits member for 2 years, 10 months
seen 21 hours ago

Feb
23
answered Why viscosity is diffusive?
Feb
23
answered Continuum limit for solid mechanics
Feb
12
answered Is crystal momentum an operator?
Feb
12
answered Classical and quantum probabilities in density matrices
Feb
9
comment Are the recently observed Dirac monopoles separable?
In a true magnetic monopole, the Dirac string is completely unobservable, even in theory. The string is not a real thing, just a way of describing some of the mathematical manipulations. Is that the case here too?
Feb
8
comment Maxwell equations and symmetry
Don't forget about vectors versus pseudovectors, when you're doing the P transformation.
Feb
1
comment About partially polarized light and the degree of polariztion
#3 - No. For example, if you mix 1 watt of circularly polarized light with 1 watt of unpolarized light.
Jan
30
comment Do holes have wavefunctions?
Normally people bypass the whole discussion by making the single-particle approximation, i.e. not talking about Slater determinants in the first place, but instead treating each electron or hole as an independent particle. Many-particle-effects are taken into account semi-heuristically (if you need higher accuracy) by "exchange forces" and "pauli blocking" etc. etc. (You asked about Slater determinants, so I answered, but this whole topic is not the usual approach.)
Jan
30
comment Do holes have wavefunctions?
An electron-hole excitation is another way to say "move an electron from the valence band to the conduction band". So you would replace one of the valence-band wavefunctions with a conduction-band wavefunction in the Slater determinant.
Jan
29
answered Do holes have wavefunctions?
Jan
29
answered Maximising entropy when energy is shared between systems
Jan
29
comment Why does $E=\nabla\phi$ follow from $\nabla\times E=0$?
en.wikipedia.org/wiki/… - click "show" in the gray box to see a proof
Jan
15
answered If you “disobey” the constraints of the Kramers-Kronig relations, what happens? Do you get non-physical results?
Jan
15
revised Is coherent light required for interference in Young's double slit experiment?
more on temporal coherence
Jan
6
awarded  Custodian
Dec
29
comment Fermi level in equilibrium and non-equilibrium situations
Possible duplicate: physics.stackexchange.com/questions/68162/…
Dec
19
answered Understanding Wikipedia's “Semiconductor Band Structure” diagram where the bandgap appears to increase with increasing density of states
Dec
5
comment Lasers and Collimation
You need the correct definition, not just an unambiguous definition. For example, if you say "'neutron' is a term for any neutral particle", it's an unambiguous definition, but it's not the correct definition. :-P You can't call something a "plane wave" unless it has planar wavefronts (note the plural; one planar wavefront is not enough) AND (related to that) it has constant intensity in the lateral directions. The Naik quote is consistent with that. Again, you can look it up in any textbook or ask any expert what "plane wave" means.
Dec
5
comment Lasers and Collimation
"Plane wave" is a technical term with a standard definition that you can (and should) look up in any textbook. You'll see that the definition of "plane wave" is not what you think it is. (Sure, if you look around enough, you can find someone who has misused the term "plane wave". But I promise, the term "plane wave" is completely standard and unambiguous.) I'm glad you seemingly understand the physics of light propagation, but you do NOT know the terminology for talking about it, e.g. the standard definitions of "plane wave" and "collimated".
Dec
3
comment Lasers and Collimation
I hope you are aware that a Gaussian beam is not a plane wave anywhere, full stop. It is not a plane wave at the beam waist, it is not a plane wave anywhere else. Nor is it "collimated" at the beam waist, or anywhere else. I think you're confused about the definition of "plane wave", and "collimated".