Linked Questions

0 votes
3 answers
515 views

Exchange particles-real or just mathetical constructs? [duplicate]

Are the intermediate vector bosons real (like the electrons) or just mathetical constructs?i have got a theory to unify the 4 forces, but it does not tell anything about exchange particles in case of ...
farizrahman4u's user avatar
42 votes
2 answers
21k views

Why on-shell vs. off-shell matters?

The definitions between on- and off-shell are given in Wikipedia. Why is it so important in QFT to distinguish these two notions?
FraSchelle's user avatar
  • 10.5k
63 votes
4 answers
6k views

How exact is the analogy between statistical mechanics and quantum field theory?

Famously, the path integral of quantum field theory is related to the partition function of statistical mechanics via a Wick rotation and there is therefore a formal analogy between the two. I have a ...
user26866's user avatar
  • 3,442
34 votes
4 answers
4k views

"Slightly off-shell"?

I'm not new to QFT, yet there are some matters which are quite puzzling to me. I often come across the statement that real particles (the ones we actually measure in experiments, not virtual ones) are ...
Frederic Brünner's user avatar
22 votes
2 answers
4k views

Virtual particles and physical laws

Recently, I was reading about Hawking Radiation in A Brief History of Time. It says that at no point can all the fields be zero and so there's nothing like empty space(quantum fluctuation etc.). Now, ...
Yashbhatt's user avatar
  • 1,794
21 votes
2 answers
14k views

Virtual photons, what makes them virtual?

The wikipedia page "Force Carrier" says: The electromagnetic force can be described by the exchange of virtual photons. The virtual photon thing baffles me a little. I get that virtual particles ...
Lucas's user avatar
  • 471
14 votes
3 answers
1k views

Does radio use virtual photons?

In radio communication each accelerated electron in the transmitter antenna interacts with an electron in the receiver antenna by exchanging a photon. Is that photon always a virtual photon as ...
John Eastmond's user avatar
6 votes
3 answers
2k views

Creation of particle anti-particle pairs

I was reading some QFT notes and there is one point that I don't understand, they are justifying why we need QFT saying that the number of particles is not preserved once we consider special ...
inquisitor's user avatar
7 votes
2 answers
2k views

How do we distinguish between virtual particle exchange and particle decay?

The difference between virtual particles and unstable particles is discussed at length in this question (namely, virtual particles correspond to internal lines in Feynman diagrams and are not ...
James's user avatar
  • 2,841
4 votes
3 answers
4k views

Does the Breit Wigner formula apply to intermediate virtual particles?

Breit Wigner Formula describes the cross section for interactions that proceed dominantly via a intermediate particle (O*) A+B → O* → C + D: $$σ = \frac{2\Pi}{k^{2}}\frac{Γ_{i}Γ_{f}}{(E-E_{o})^{2} + (...
Paul's user avatar
  • 41
4 votes
1 answer
1k views

The nature of time, according to quantum field theory

I will try my best to ask the question that best fits something I have been pondering on for a few days. Are virtual particles really constantly popping in and out of existence? Or are they ...
Nostrum's user avatar
  • 141
14 votes
1 answer
458 views

Why aren't all particles virtual? [duplicate]

It is my understanding that virtual particles are those that are internal to a particular interaction. They do not fulfill the requirements of a freely-travelling particle (ie a plane wave) and as ...
superluserdo's user avatar
3 votes
3 answers
1k views

Decay of matter

I was watching Stephen Hawking's documentary and in there he explained how he realized why black holes eventually disintegrate: There are ripples in space, an antiparticle and a particle get ...
OutFall's user avatar
  • 121
2 votes
2 answers
356 views

Suppression of $W$ boson propagator by its mass

In my experimental particle physics introductory class it was often said that quantum electrodynamics (QED) is very predictive for sufficiently small center of mass energys since the $W^\pm$-...
AlmostClueless's user avatar
3 votes
2 answers
402 views

Is $E^2-P^2=m^2$ true only for free particles?

I'm studying Friedman and Susskind's Special Relativity and Classical Field Theory and follow them in using $c=1$. They derive the above relation by first using Lagrangian of a free particle $\mathcal ...
Atom's user avatar
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