Linked Questions

2 votes
1 answer

What is a particle in QFT framework? [duplicate]

I've heard that in QFT a particle is a local excitation of a quantized field, but I can't understand how can I imagine this. For example in the second quantization of the Klein-Gordon field we get an ...
nabla_quadro's user avatar
1 vote
2 answers

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 ...
Kai's user avatar
  • 3,640
-1 votes
0 answers

What is a particle according to quantum field theory? [duplicate]

I don't know what to say but... I just want a brief discussion about quantum field theory and how can you describe a particle according to this theory...
Aleph's user avatar
  • 1
240 votes
22 answers

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, "...
John Duffield's user avatar
57 votes
6 answers

Haag's theorem and practical QFT computations

There exists this famous Haag's theorem which basically states that the interaction picture in QFT cannot exist. Yet, everyone uses it to calculate almost everything in QFT and it works beautifully. ...
Rafael's user avatar
  • 2,691
19 votes
2 answers

Bound states in QED

I am a beginner in QED and QFT. What is known (or expected to be) about bound states in QED? As far as I understand, in non-relativistic QM electron and positron can form a bound state. Should it be ...
MKO's user avatar
  • 2,002
22 votes
3 answers

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 ...
doetoe's user avatar
  • 9,174
6 votes
5 answers

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 ...
user avatar
2 votes
3 answers

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 ...
tyoc213's user avatar
  • 179
4 votes
1 answer

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 ...
Dragonsheep's user avatar
1 vote
4 answers

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 ...
Lamichhane88's user avatar
4 votes
4 answers

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 ...
Gold's user avatar
  • 34.7k
1 vote
2 answers

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 ...
Guy Inchbald's user avatar
  • 7,269
1 vote
2 answers

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 ...
Allure's user avatar
  • 19.4k
3 votes
2 answers

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 ...
Felipe Reigosa's user avatar

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