Linked Questions

0 votes
1 answer
114 views

Fields or Particles [duplicate]

What is more fundamental, particles or fields? I keep reading what appears to be conflicting answers on this, but I am sure it is just a limitation of my understanding. I have heard some physicists ...
Quantum1's user avatar
243 votes
22 answers
42k 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, "...
John Duffield's user avatar
56 votes
9 answers
8k views

Is a "third quantization" possible?

Classical mechanics: $t\mapsto \vec x(t)$, the world is described by particle trajectories $\vec x(t)$ or $x^\mu(\lambda)$, i.e. the Hilbert vector is the particle coordinate function $\vec x$ (or $x^\...
Tobias Kienzler's user avatar
38 votes
5 answers
8k views

How are forces "mediated"?

I hope this is the right word to use. To me, these forces seem kind of fanciful (except for General Relativity and Gravity, which have a geometric interpretation). For example, how do two charged ...
Justin L.'s user avatar
  • 5,990
24 votes
5 answers
6k views

Why are particles in Quantum Mechanics indistinguishable?

I'm currently reading about tensor products in Quantum Mechanics and composite systems and I've read that in Quantum Mechanics particles are indistinguishable while in Classical Mechanics that's not ...
Gold's user avatar
  • 36.4k
28 votes
3 answers
3k views

Do standard model particles actually exist or merely usefully describe behaviors of a medium?

I've read about how sound propagation can be modeled as phonon particles moving and interacting. I understand that this is a useful mathematical construct to describe the behavior of longitudinal ...
William Grobman's user avatar
24 votes
4 answers
8k views

Why is the partition function divided by $(h^{3N} N!)$?

When computing partition functions for classical systems with $N$ particles with a given Hamiltonian $H$ I've seen some places writing it as $$Z = \dfrac{1}{h^{3N} N!}\int e^{-\beta H(p,q)}dpdq$$ ...
Gold's user avatar
  • 36.4k
33 votes
3 answers
5k views

What is the physical interpretation of second quantization?

One way that second quantization is motivated in an introductory text (QFT, Schwartz) is: The general solution to a Lorentz-invariant field equation is an integral over plane waves (Fourier ...
yjc's user avatar
  • 753
16 votes
6 answers
2k views

Can elementary particles be explained adequately by a wave-only model?

I have been watching quantum mechanics documentaries and reading a layman's book called "The Quantum Universe". I believe I understand why the double slit experiments exclude a particle only model. ...
mfergus9's user avatar
  • 161
14 votes
4 answers
2k views

Why can't two different quantum states evolve into the same final state?

Is it true that two different states cannot evolve into the same final state? Can they achieve this state at different times? If yes, what is the proof?
Doubting Thomas's user avatar
30 votes
4 answers
5k views

What is the meaning of a state in QFT?

I guess this may be more of a mathematical than a physics question, but it comes down to physical interpretations, so I'm posting it here. In classical Quantum Mechanics, we can define a state $\left|...
FrancisFlute's user avatar
  • 1,106
12 votes
2 answers
7k views

How did Planck derive his formula $E=hf$?

Some time ago I asked my quantum physics lecturer the question: How did Planck derive his formula, the Planck–Einstein relation $$E=hf$$ with constant of proportionality $h$, the Planck constant. I ...
user46147's user avatar
  • 3,034
9 votes
5 answers
5k views

What is Size of Photon?

Is there any size of photon if so what is it? And also which particle had smallest size / radius / volume considering all of the matter.
Parth Maske's user avatar
17 votes
1 answer
10k views

First quantization vs second quantization

What is the difference between first quantization and second quantization and where does the name second quantization come from?
Gert's user avatar
  • 297
11 votes
3 answers
1k views

Can electrons be non-fundamental in higher dimensions?

I was wondering, is it necessary that all elementary particles remain elementary in higher dimensions too, or can there be a higher curled dimension (like those in string theory) where an electron, ...
Syed Ilyas's user avatar

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