Linked Questions

1
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2answers
88 views

What principle of quantum mechanics tells us that harmonic fluctuations of a field act like localized particles? [duplicate]

"Quasiparticles" are ubiquitous in condensed matter physics, e.g. magnons and phonons, and more generally all particles in quantum field theory are considered the elementary harmonic ...
227
votes
20answers
37k views

What exactly is a photon?

Consider the question, "What is a photon?". The answers say, "an elementary particle" and not much else. They don't actually answer the question. Moreover, the question is flagged as a duplicate of, "...
19
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3answers
3k views

What is the meaning of the size of a particle in QFT?

I have often seen people refer to the size of a particle being at most a given value, or a particle being a point particle, in the context of quantum field theory. Examples are the Wikipedia entry on ...
3
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5answers
4k views

How does the Wave Particle Duality fit with Quantum Field Theory?

It's heard quite often that fundamental particles (photons, quarks, etc) act as both particles and waves. Now, I'm looking at it from a Quantum Field perspective. Is this localized energy ripple ...
2
votes
3answers
882 views

How are photons made?

I mean in manufacturing a bicycle we know how to "ensemble" a bicycle, what actions and "assembly of parts". So what steps are needed for make a photon? Also is there a limit on how many photons for ...
1
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4answers
525 views

How can fields interaction give rise to particles?

We say light a matter-wave, meaning along with its wave property it shows particle nature. But how can fields interaction (electric and magnetic) give rise to particles (photon)? I wish someone could ...
4
votes
4answers
518 views

What really is a particle?

In Classical Mechanics we consider particles as things whose internal structure for the purpose of studying some phenomenon might be neglected. In that setting we associate particles to points and ...
4
votes
1answer
448 views

Status of particles in interacting QFT

From my readings in QFT and answers such as this, I've read that the concept of particles and particle-number in interacting systems becomes ill-defined in QFT. Of course, in the real world, a number ...
1
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2answers
234 views

What carries the electrostatic and magnetostatic forces?

In the Standard Model of QM, all forces are mediated or carried by particles (for want of a better word) called bosons. The photon is an example of a force-carrying gauge boson, and mediates the ...
3
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2answers
182 views

What are the two elements of the electron field?

I'm not a physicist, I don't know if this will make a lot of sense, so bear with me. I'm just reading about how particles like the photon, electron, graviton, etc are each associated with their own ...
1
vote
2answers
118 views

How are scalar fields = particles?

Two such particles I'm thinking of are the inflaton & the Higgs. They are both scalar fields, but they're also both particles with well-defined masses. How is it that scalar fields correspond to ...
2
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1answer
134 views

How to write localised wave function of a particular shape in Quantum Field theory?

We know how to write localised wave function for Quantum Mechanics . Say for a free particle of mass $m$ in non-relativistic Quantum Mechanics , we can have a Gaussian wave packet, $$ \Psi(x, 0 ) = ...
5
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0answers
121 views

Why do we say that elementary particles are pointlike? [duplicate]

When people discuss quantum field theory in a popular context, they say that fundamental particles, such as quarks and electrons, are pointlike, with zero size. However, I don't think this is what ...
0
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0answers
48 views

Limit on speed of expansion of the bounded support interval of a position wave function in relativistic quantum mechanics

If the support of a quantum mechanical position wave function is a bounded interval, and that interval is expanding or contracting, then I think it cannot change in any direction faster than $c$. To ...