When Virtual Becomes Real

TrickyDicky

This could be confusing for newcomers, the fact that the gauge bosons come in real and virtual versions, for instance the W boson is defined in the wikipedia as the particle that as well as the Z boson mediaes the weak force, so the doubt arises as to wether is referring to the virtual W or the real boson W and when it describes its basic properties it states that "in practice it can be considered to be a virtual particle". So I would like to ask the experts which are the force mediators the virtual gauge bosons or the "real" ones because often it's not very clearly defined. In case the mediators are virtual bosons, what is the role of the real particles? In the case of the photons it's obvious they are the EM radiation , but what about the W and Z particles? ( I believe the gluon hasn't been found yet)
Also I read the mean-life of the W and Z bosons it's around 10E-25 seconds so I guess they can't be directly detected , and were discovered by indirect means, can someone explain in lay terms how? Thanks

tiny-tim

Hi TrickyDicky!
Wikipedia is not reliable on this topic (see post 13 above). Stop reading it!
I think wikipedia means that in practice we can't produce real W and Z … hmm … that's not really true either.
Always virtual.
Real W and Z buzz around colliding with things just as real photons do … this has nothing to do with the maths of virtual particles "mediating" an interaction.

TrickyDicky

Thanks, that was my idea but I wanted to check.

jtbell

So do other particles, e.g. electrons and positrons. See for example the first-order Feynman diagram for Delbrück scattering.

Huttate

I chuckle at the "Wikipedia is not reliable" post followed immediately by a post referencing Wikipedia as a proof.

Why do not those of you criticising Wikipedia get on there and correct it so that us who rely [too heavily?] on it do not come away misinformed?

oraclelive

Since there's a discussion going on real and virtual particle. What then is a real particle having understood that a virtual particle prompts the uncertainty of its energy and momentum in Heisenberg uncertainty principle?

ExecNight

I pose the question;

What's the difference between the operating system installed on your notebook and installed on a virtual machine =)

I guess the point is, the virtual system acts like its on a seperate physical system, but its actually not. Just using the resources of another physical system, its not becoming a real notebook all of a sudden.

Hehe analogies :P

3m0k177y

virtual particles can materialize, its even been observed and tested. but not all virtual particles do so.
what im saying is this; a virtual particle is what has a probability of being there, meaning that it is possible for it to be there. since everything in the universe is in a way random, we cant assume that a true vacuum without any particles whatsoever is possible, there is a possibility that particles are in the vacuum.
there is also the possibility that ALL particles got out of the vacuum in the first place, but unless we have a head count on all particles all throughout the experiment, there cant be any certainty of a true vacuum.
since we cant have a head count on all the particles, we cant truly observe their positions, their probability of being in any finite place is 0, they are still in superposition. even though they were just taken out of the vacuum, some of the particles that have superposition in the vacuum are observed in there, they have materialized in the vacuum.
but, before they materialized in the vacuum, they were virtual because they werent observed. using this reasoning, one can theorize that virtual particles can materialize where they stand and become real.
if you think the example i gave has no scientific evidence to back it up, it does, it was tested, it was proven.
you cant say that virtual particles are JUST a tool for calculating.

StevieTNZ

Just simply don't rely on it. People can change the errors, but others can change those changes, so it could end up in a cycle.

StevieTNZ

Reading this: http://www.scientificamerican.com/ar...-particles-rea
and looking at the responses to the OP.

Different.

lugita15

This is an interpretational question. Perturbation series in quantum field theory consist of terms which can very conveniently be represented as Feynman diagrams, and these Feynman diagrams can very naturally be interpreted as depicting the exchange of virtual particles. It's a matter of philosophical preference whether there terms in the perturbation series are actually discussing the exchange of real objects, or whether the fact that perturbation series can be interpreted using virtual particles is a mathematical coincidences. People who believe in virtual particles point out how intuitive they make phenomena in QFT. Others, however, believe that virtual particles are not real because they only seem to show up when you're doing perturbative calculations, not other kinds of calculations. They also say that virtual particles shouldn't be believed in because they're undetectible, since they just go from one particle to another particle; however, in that sense you could say that ALL particles are undetectable in transit, not just "virtual ones".

salvestrom

You're the first person to actually state this that I've come across. All other responses are very much "it's just maths".

A seemingly midway view that I've come across explained that virtual particles are general disturbances in a field that have properties similar to known particles and are treated as such to do the calculation, but at no point should they be thought of as the actual corresponding particle.

It does seem strange that the standard model parades around the 'real' bosons when they apparently only ever exist in collidors and have nothing to do with force mediation.

juanrga

No virtual particles are not real particles. Moreover, there is a school of thought believing that some 'real' particles as photons are in reality fictitious.