# What is responsible for force in the standard model?

1. Feb 23, 2015

### ftr

It is touted that modern physics has discovered what is actually responsible for force which are particles. Yet, the force responsible for EM is "virtual" particles and then you have the "W" particle in Electroweak. So it seems the issue is not all that clear. I know how the math works, but I am just wondering about the aesthetics and the exactness of the statements made at least in the media.

2. Feb 23, 2015

### mathman

Your question is vague. What is not clear?

3. Feb 23, 2015

### ftr

let me rephrase. Are all the force carriers in the SM of similar nature or not? My understanding is that virtual particles(responsible for EM) are not the same as real particles(responsible for EW). And yet when you even read Scientific American they brush this under the carpet and generally say ...the "particles" responsible for the force ......

4. Feb 23, 2015

### sk1105

Virtual particles are just a device used to model what happens during physical processes. As well as for EM interactions, they are commonly used to model sound waves travelling through solids: the sound is of course a pressure wave, but sometimes it makes the calculations easier if we re-imagine it not as a wave but as a stream of particles called phonons. These phonons don't actually exist, but pretending that they do for modelling purposes does not change the physics. Real particles, on the other hand, are, well, real!

5. Feb 23, 2015

### ftr

Thanks for the reply. Hence my question. More specifically, having two mechanisms for force carriers, is that correct?

6. Feb 23, 2015

### Staff: Mentor

Most weak processes (in particular, all decays of known particles apart from the top quark) do not involve real W or Z bosons, simply because the energy is not large enough.
There is no fundamental difference between electromagnetism and the weak force in that aspect. Actually, both can be combined to the electroweak interaction.

7. Feb 23, 2015

### bahamagreen

When one says "Virtual particles are just a device used to model what happens during physical processes.", is this modeling of something like apparent fictitious forces due to the quantum dynamical geometry?

8. Feb 23, 2015

### ftr

So, are you saying that virtual particles can get real and they are not actually mathematical! or what?

P.S. Nevermind, I guess I am not the only one who is confused. My question has been elaborated on here

http://physics.stackexchange.com/questions/4349/are-w-z-bosons-virtual-or-not

Last edited: Feb 23, 2015
9. Feb 23, 2015

### bhobba

They are mathematical artefacts of the perturbation formalism used. It's related to this thing called a Dyson series and Feynman Diagrams that's a pictorial representation of the Dyson Series:
http://en.wikipedia.org/wiki/Dyson_series
http://en.wikipedia.org/wiki/Feynman_diagram

Certain lines in those diagrams are called virtual particles. They are not in any sense real - simply what has been chosen to call them - they could have been called Jaberwocy lines - it wouldn't make any difference.

Perturbation theory is not the only method available to do Quantum Field Theory and when they are used virtual particles do not appear - they are simply an artefact of that way of doing the math.

When physicists speak about virtual particles explaining something like the force between particles they mean its the explanation when you use perturbation theory.

Thanks
Bill

10. Feb 23, 2015

### ftr

Thanks Bill. While the formalism is ok but it just feels conceptually uncomfortable. I will sleep on it and chew on it in the morning.