Source of Virtual Particles in Space?

[tom.stoer]

yes, and that such activity violates conservation of energy! Even the quote I posted from Lisa Randall [Harvard] says that...and I have repeatedly read such things...and repeatedly not understood whether such can be 'correct'...

Naty1, I think we do not agree on all aspects regarding virtual particles, and especially not on all aspects regarding their interpretation. But I think we all DO agree that statements like "virtual particles violate energy conservation" are WRONG. This is due to the fact that it's not a wrong interpretation, but that is in contradiction to exact math.

We can discuss about the interpretation or reality of "-1 car" in the calculation "1 car = 2 cars - 1 car", and perhaps we don't agree. But we DO agree that this equation does NOT violate car-conservation.

So again, I am sorry to say that, statements like non-conservation of energy due to virtual particles are rubbish.

 

[strangerep]

[...]

Even when there is not enough energy for pair creation, multiparticle states appear, for example, as intermediate states in second-order perturbation theory. We can think of such states as existing only for a very short time, according to the uncertainty principle ΔΕΔt=h. As we go to higher orders in perturbation theory, arbitrarily many such "virtual" particles can be created.

(JK423's emboldening).

A lecturer in a QED course I attended 15yrs ago tended to say similar things. Sad.

Probably the final paragraph in that section (bottom of p14 and over to 15) is all the motivation that is really needed:

QFT provides a natural way to handle not only multiparticle states, but also transitions between states of different particle number. It solves the causality problem by introducing antiparticles, then goes on to explain the relation between spin and statistics. But most important, it provides the tools necessary to calculate innumerable scattering cross sections, particle lifetimes, and other observable quantities. The experimental confirmation of these predictions, often to an unprecedented level of accuracy, is our real reason for studying QFT.

Thus, P&S is perhaps best regarded as a learn-to-calculate book.

 

[strangerep]

Maybe a better question is what is a particle?

... umm,... you'd better search back through several years of previous threads before opening that can of worms again.

Alternatively, search the contents page of Arnold's FAQ for the word "particle". There's more than enough reading there to occupy several rainy days.

 

[A. Neumaier]

Of course, have a look at Peskin & Schroeder, page 13, 3rd paragraph,

Even when there is not enough energy for pair creation, multiparticle states appear, for example, as intermediate states in second-order perturbation theory. We can think of such states as existing only for a very short time, according to the uncertainty principle ΔΕΔt=h. As we go to higher orders in perturbation theory, arbitrarily many such "virtual" particles can be created.

They are careful to say ''We can think of such states as'', implying that it is just a convenient visualization, not a physical fact.

 

[Naty1]

I've tried to connect to Arnold Neumaier's FAQ here...

http://arnold-neumaier.at/physfaq/topics/unstable.html


but keeping getting a message:

Forbidden

You don't have permission to access /~neum/physfaq/physics-faq.html on this server.

Any suggestions on how to access this information will be appreciated!

 

[Naty1]

Even when there is not enough energy for pair creation, multiparticle states appear, for example, as intermediate states in second-order perturbation theory. We can think of such states as existing only for a very short time, according to the uncertainty principle ΔΕΔt=h. As we go to higher orders in perturbation theory, arbitrarily many such "virtual" particles can be created...

I'm not familiar with the creation of 'multiparticle states'...can anyone recommend
an online source where I can learn more about this?
Thanks.

 

[A. Neumaier]

I've tried to connect to Arnold Neumaier's FAQ here...

http://arnold-neumaier.at/physfaq/topics/unstable.htmlbut keeping getting a message:
Any suggestions on how to access this information will be appreciated!

There appears to be a problem with our web server. Just try again at a later time. (Web support is already in the weekend; so this might get fixed only on Monday.)

 

[xlsdx]

is this not an expected outcome from the probabilistic nature of quantum mechanics? if any particle's wave-function gives it the chance to exist anywhere in the universe, multiplied by the number of particles in the universe, surely it fits that some portion of the particles in the universe would spontaneously appear/disappear from random locations?