Linked Questions

0
votes
3answers
326 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 ...
51
votes
4answers
4k 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 ...
25
votes
2answers
11k 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?
30
votes
4answers
2k 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 ...
18
votes
2answers
3k 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, ...
18
votes
2answers
12k 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 ...
13
votes
3answers
837 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 ...
5
votes
3answers
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 ...
4
votes
3answers
3k 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} + (...
6
votes
2answers
1k 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 ...
5
votes
1answer
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 ...
13
votes
1answer
251 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 ...
3
votes
3answers
281 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 ...
3
votes
1answer
114 views

how to explain the diagram of declaring finding a new particle?

When experimenters declare finding a new particle, they often present a diagram similar as below It's Z boson invariant mass distribution in the electron channel. I need some explanations to help ...
4
votes
2answers
273 views

On-shellness of photons

In principle, we could describe all physics without EM fields (or photons), as they are mainly a useful tool to describe "action at distance" (which does not mean instantaneous) between charged ...

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