Comic Discussion > QUESTIONABLE CONTENT
WCDT Strips 3456-3460 (10th to 14th April 2017)
Case:
--- Quote from: Storel on 11 Apr 2017, 14:16 ---You know, once I found out that a positron is just an anti-matter electron, I realized that Asimov's positronic brains didn't make any sense. Anything you can do with positrons, you can do with electrons much more easily since you don't have to worry about building your computer out of antimatter...
--- End quote ---
:-D [1]
Is it cold in here?:
This is a placeholder that will get merged with the current weekly comic thread, not to replace it, but just to change its thread title.
Thrudd:
--- Quote from: Storel on 11 Apr 2017, 14:16 ---
--- Quote from: gopher on 11 Apr 2017, 00:58 ---
--- Quote from: BenRG on 10 Apr 2017, 04:29 ---Basically, I think that we can say that Bubbles is somewhat neurotic.
--- End quote ---
More Positronic to me. #3Laws.
--- End quote ---
You know, once I found out that a positron is just an anti-matter electron, I realized that Asimov's positronic brains didn't make any sense. Anything you can do with positrons, you can do with electrons much more easily since you don't have to worry about building your computer out of antimatter...
--- End quote ---
I am not so sure of the correlation of the nomenclature.
It really was handwaving by a really good writer though.
In semiconductor theory, a conductor can be saturated with electrons, and the repulsion causes them to maintain a specific pattern.
A space can exist that has no electron, and it acts as if it is something real with a positive charge. It's called a hole.
There's a whole way of looking at semiconductors where the holes are considered to explain the action of the semiconductor and it refers to "hole current".
This is the 'positronic' system that Asimov was using and a lot of authors and researchers latter on ran with the idea.
Nothing to do with particle physics though the physicists may have absconded with the term for their own use, just like spin, flavor and orientation.
Perfectly Reasonable:
Go on --- Tell us about muons. Just like electrons, but punchier.
So why are the specials apologizing about meat? Last I looked, they were all about blood.
Clearly I need to get out more...
Case:
--- Quote from: Thrudd on 11 Apr 2017, 18:42 ---Nothing to do with particle physics though the physicists may have absconded with the term for their own use, just like spin, flavor and orientation.
--- End quote ---
Naw, that's just Asimow who is calling a hole a 'positron'. There's too many high-energy guys working in condensed matter theory to get away with abusing jargon like that. Wrt. e.g. sublattice 'spin' in Graphene, though, you may be have a point ...
:-D
--- Quote ---As a consequence, at low energies, even neglecting the true spin, the electrons can be described by an equation that is formally equivalent to the massless Dirac equation. Hence, the electrons and holes are called Dirac fermions. (Wiki: Graphene, Electronic properties, Dispersion)
--- End quote ---
P.S.: OK, it's actually (a k*p - approximation of a tight-binding calculation of Graphene close to the Dirac-points that conveniently resembles) a Dirac-equation in 2D, rather than a Dirac-equation in 3+1 D, but still ...
P.P.S.: Sorry for the geekery - that's actually (part of) my research interest.
(click to show/hide)
--- Quote from: Thrudd on 11 Apr 2017, 18:42 ---In semiconductor theory, a conductor can be saturated with electrons, and the repulsion causes them to maintain a specific pattern.
--- End quote ---
?
Methinks you rather mean (external) 'periodic potential' (single-particle term) instead of (two-particle) Coulomb-repulsion? Periodic potential => Bloch Wavefunctions (Yeah, Wannier-Schmanier ...) => quasi-continuous Bandstructure. Coulomb is a two-body term in the Hamiltonian: RPA (or rather the re-summation of the Dyson-Series/the self-energy according to Murray Gell-Mann and Keith Brueckner) works in most 'weakly screened' (semi-) metals with D>1, and allows you to account for Coulomb-repulsion by inserting an 'effective' electron-mass into the non-interacting theory. Hence: Electron Gas.
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