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Connor McCormick ☀️ pfp
Connor McCormick ☀️
@nor
Ok so I think electrons and photons are not actually particles. Look up phonons
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Greg Lang pfp
Greg Lang
@designheretic
Don’t electrons and protons carry physical momentum—whereas phonons do not? Correct me if I’m wrong, but I always took that distinction as the line between particles (protons, electrons and even photons weirdly) and quasiparticles (phonons—aka quantized sound waves) Genuinely curious—am I missing something?
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Connor McCormick ☀️ pfp
Connor McCormick ☀️
@nor
I think phonons carry momentum too
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FelipeFlores.⌐◨-◨ pfp
FelipeFlores.⌐◨-◨
@flancaster
They carry only "mathematical momentum" in the sense that, within equations of motion, they have a momentum quantity ħK (with K the wave-vector), but that momentum is not always conserved. Physical momentum, in other hand, is always globally conserved (if system is translation-invariant).
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EulerLagrange pfp
EulerLagrange
@eulerlagrange.eth
Momentum is always conserved. Phonons are a bit nutty, but it’s still conserved as long as you are careful about boundary conditions and any defects of the crystalline structure
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FelipeFlores.⌐◨-◨ pfp
FelipeFlores.⌐◨-◨
@flancaster
Check this, btw https://en.wikipedia.org/wiki/Umklapp_scattering
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Connor McCormick ☀️ pfp
Connor McCormick ☀️
@nor
What’s the conclusion here: conserved or not?
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EulerLagrange pfp
EulerLagrange
@eulerlagrange.eth
Conserved, but it’s a different type of momentum
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Greg Lang pfp
Greg Lang
@designheretic
So what then is the distinguishing attribute between quasi- and actual particles, to return to the original question?
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Connor McCormick ☀️ pfp
Connor McCormick ☀️
@nor
Quasiparticles are wave propagations in mediums of more fundamental particles, and these waves seem to exhibit similar properties as quantum particles
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Greg Lang pfp
Greg Lang
@designheretic
Ok, so at a fundamental level, quasiparticles are not unfairly characterized as useful fictions advanced for the sake of uncomplicating adjacent theoretical discussions—while particles themselves are the core subject of study—and so the fact that they share properties is their instrumental purpose in action, right?
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