what the term "virtual particles" referred to


by actionintegral
Tags: referred, term, virtual particles
Careful
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#19
Nov29-06, 11:33 PM
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Quote Quote by Ratzinger View Post
Right.

I'm just saying this for the last time, especially for those who compute one Feynmann diagramm to many. There is someting called conservative force field. So forget your Peskin and Schroeder, we talking first year physics course.
The holy church might want to learn that Maxwell's theory interacting with currents goes beyond conservative forces (see the Lorentz Dirac equation).

Quote Quote by Ratzinger View Post
How do two unaccelerated charges (a concervative force field that is, no external forces acting on these charges) communicate? They can't produce photons, pions, whatever constantly out of nothing.
Perhaps you have ever thought that these radiative losses are very very small, the coupling constant in front of the dissipation term in the lorentz Dirac equation equals (2 \mu q^2 )/(3 c^3) which is roughly around
10^{-54} in SI units. Moreover, the Lorentz Dirac equation comes from conservation of total energy momentum (and angular momentum if one includes magnetic dipole degrees of freedom). In the classical theory, there are no vacuum fluctuations, so that invalidates your argument below

Quote Quote by Ratzinger View Post
There has to be messengers that violate conservation of energy but obey time-energy uncertainty. I call them virtual particles. Period.
Now, about the word virtual as Reilly explains it. Come on guys, do we call planets in the solar system virtual ???? There is no difference between those planets (regarding this aspect) and the nucleons building the deuteron, Einstein's theory is even predicting a dynamical mass for our earth coming from the gravitational field of the sun (in the same way as the nucleons are dressed by gluons I guess).
We call them virtual because they are useless to include in the state description for the scattering matrix where we ideally measure and prepare free particles.

Careful
Jheriko
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#20
Nov30-06, 07:25 AM
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Quote Quote by selfAdjoint View Post
And what is it that photon counters count?
Just because something is non-localised and probabilistic doesn't mean it can't interact with something else. A photon has a probability of being detected by a detector... that doesn't make it anyless real imo. It certainly doesn't introduce a circular argument, it just makes it more difficult to model the photon's interactions.
actionintegral
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#21
Nov30-06, 02:52 PM
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Quote Quote by reilly View Post
In ordinary QM, the tunneling particles are virtual when inside a high enough potential barrier -- they have the wrong energy-momentum relationship to be a free particle.
Regards,
Reilly Atkinson
This "feels" right to my tiny brain. I would like to learn how to prove this. Does it follow from the schroedinger equation?
Careful
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#22
Dec1-06, 03:13 AM
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Quote Quote by Jheriko View Post
Just because something is non-localised and probabilistic doesn't mean it can't interact with something else. A photon has a probability of being detected by a detector... that doesn't make it anyless real imo. It certainly doesn't introduce a circular argument, it just makes it more difficult to model the photon's interactions.
Or the photon just is something different than most of us imagine it to be.
selfAdjoint
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#23
Dec1-06, 10:15 AM
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Quote Quote by Careful View Post
Or the photon just is something different than most of us imagine it to be.

Yeah; back when I was even more ignorant than I am now I used to say that the photon is like a beautiful woman of a certain age. We don't know, and it's not important, what she looks like at home, it only matters what she looks like when she comes to visit us.
Careful
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#24
Dec1-06, 10:26 AM
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Quote Quote by selfAdjoint View Post
Yeah; back when I was even more ignorant than I am now I used to say that the photon is like a beautiful woman of a certain age. We don't know, and it's not important, what she looks like at home, it only matters what she looks like when she comes to visit us.
Haha, the thing is that we do not wish to remain that ignorant (at least not when you are a healthy man with some potential), we want to keep her during the night and inevitably will see her in the morning. The thing is : if she was good during her first night, we MUST learn to appreciate her at breakfast.
selfAdjoint
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#25
Dec1-06, 01:46 PM
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Quote Quote by Careful View Post
Haha, the thing is that we do not wish to remain that ignorant (at least not when you are a healthy man with some potential), we want to keep her during the night and inevitably will see her in the morning. The thing is : if she was good during her first night, we MUST learn to appreciate her at breakfast.

The experienced and loving heart finds no problem with this. The morning can and should be a time of affection, not clinical inspecdtion!
Careful
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#26
Dec2-06, 02:52 AM
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Quote Quote by selfAdjoint View Post
The experienced and loving heart finds no problem with this. The morning can and should be a time of affection, not clinical inspecdtion!
Exactly, and that is why you will appreciate the photon more when you find a natural, local (in the sense that there is no action at a distance) model which explains its appearances to macroscopic apparati. In this regard, the ideas spelled out by the group of people Zbyszek belongs to (with amongst others Bill Unruh), are very interesting.

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selfAdjoint
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#27
Dec2-06, 08:43 AM
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Quote Quote by Careful View Post
Exactly, and that is why you will appreciate the photon more when you find a natural, local (in the sense that there is no action at a distance) model which explains its appearances to macroscopic apparati. In this regard, the ideas spelled out by the group of people Zbyszek belongs to (with amongst others Bill Unruh), are very interesting.

Careful
I have no particular animus against action at a distance, recalling that Newton was right and Descartes was wrong in their day, and we are all, after all, in "a day", and not at the asymptotic end of time.

But if I was going out on a risky limb for the sake of local action, I'd go by way of Einstein's and Schroedinger's unsymmetrical theory: http://www.artsci.wustl.edu/~jashiff...hrodinger.html, which is better than the rap the quantum consensus gives it. Especially look for Hlavaty's book Geometry of Einstein's Unified FIeld Theory. He gives a derivation of a spinor bundle over spacetime arising from the geometry. Reading this as a young man I was somewhat inoculated against quantum mysticism and its syntactic inverse, classical reductionism. A plague on both their houses.
Careful
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#28
Dec2-06, 12:34 PM
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Quote Quote by selfAdjoint View Post
I have no particular animus against action at a distance, recalling that Newton was right and Descartes was wrong in their day, and we are all, after all, in "a day", and not at the asymptotic end of time.

But if I was going out on a risky limb for the sake of local action, I'd go by way of Einstein's and Schroedinger's unsymmetrical theory: http://www.artsci.wustl.edu/~jashiff...hrodinger.html, which is better than the rap the quantum consensus gives it.
You mean gravitation with an antisymmetric ``metric'' field, I guess. Might be interesting, but it is for sure better to start with understanding Maxwell theory properly (which is much ``easier'' to start with but still more than difficult enough).

Anyway, reading over this thread again, I noticed I should have said something about the Coulomb force. There is nothing which suggests that the latter needs to be of ``quantum mechanical origin'' and (therefore) neither needs to be associated to some time-energy uncertainty. Actually, the total ``mass'' of the (infinite) Coulomb field equals the rest mass of the particle assuming it has the classical radius R (at least when the particle is not accelerating and energy is measured in the local Lorentz frame associated to the particle); it seems clear to me that there is no such thing needed as constant particle production out of nothing. But it is certainly interesting to contemplate the inner workings of the Coulomb force.

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Ratzinger
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#29
Dec3-06, 06:59 AM
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I just noticed that I wrote in my previous 'Feynmann diagramm' which gives me five points on the crackpot list, I believe.

I have further realized that taking virtual particles too literal is also seen as crackpotterish by knowledgeable physicsts. But I like to point out that I was refering to conservative force fields and not those virtual particles coming from scattering. I admit that my billard ball thinking is pretty crappy, but still I like to know more about conservative force and its quantum treatment.


Anyway, reading over this thread again, I noticed I should have said something about the Coulomb force. There is nothing which suggests that the latter needs to be of ``quantum mechanical origin'' and (therefore) neither needs to be associated to some time-energy uncertainty. Actually, the total ``mass'' of the (infinite) Coulomb field equals the rest mass of the particle assuming it has the classical radius R (at least when the particle is not accelerating and energy is measured in the local Lorentz frame associated to the particle); it seems clear to me that there is no such thing needed as constant particle production out of nothing. But it is certainly interesting to contemplate the inner workings of the Coulomb force.

So there is none. That's intersting. Could you please expand on it?

By the way a great FAQ by a guy called Arnold Neumaier. Check S3, especially S3e in it.
Careful
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#30
Dec3-06, 07:40 AM
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Quote Quote by Ratzinger View Post
I just noticed that I wrote in my previous 'Feynmann diagramm' which gives me five points on the crackpot list, I believe.
Don't bother ...

Quote Quote by Ratzinger View Post
I have further realized that taking virtual particles too literal is also seen as crackpotterish by knowledgeable physicsts. But I like to point out that I was refering to conservative force fields and not those virtual particles coming from scattering. I admit that my billard ball thinking is pretty crappy, but still I like to know more about conservative force and its quantum treatment.
Well, I for sure believe off shell particles should be taken seriously, and finding the carriers of the Coulomb field is definetly a deep problem which is IMO not properly solved at all in QED. What I do consider as a problematic aspect is that people believe this problem has a priori something to do with the second quantized theory as it stands now.

Quote Quote by Ratzinger View Post
So there is none. That's intersting. Could you please expand on it?
I assume you want to know more about my motivations for banning vacuum fluctuations or about my comments on time/energy uncertainty ? For the latter, I have given my opinion in a thread on the ``beyond the standard model'' forum (basically there is no time operator). Concerning the vacuum fluctuations, let me say that a deeper study of the classical theory can bring new insights. A very useful paper is ``Classical electrodynamics of retarded fields and point particles'' by Teitelboim, Villarroel and Van Weert : Rivista del nuovo cimento vol 3, n° 9, 1980. Their aim was to write a review paper containing contemporary insights, hoping that it might serve people who try to solve this problem.

I quickly read a part of Arnold Neumaier : pretty much the standard story, if he would apply the scattering matrix approach to the universe, he would speak of virtual planets and by no means would he be able to say whether the universe contains black holes or not (pretty much the Hawking story), the only information he considers real are (special relativistic) free field states (so he works with states on some conformal past and future boundary). Of course this is as unphysical as one can only get, you can expect this kind of nonsense when people forget that a very useful approximation (in the laboratory) is not to be taken as a fundamental axiom. He makes a valid point though when he says that the virtual particle content depends upon the quantization method (which is a pretty obvious thing), but I disagree that it would lead to a strange picture of reality. It merely tells me that the quantization method cannot give a complete description of reality as it stands. But yeah, if you take the latter as ``forbidden territory'' then you are pretty much forced to state what this (clever) man says.

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reilly
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#31
Dec3-06, 03:27 PM
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Quote Quote by actionintegral View Post
This "feels" right to my tiny brain. I would like to learn how to prove this. Does it follow from the schroedinger equation?

Yes indeed. Follows from the standard solution.
Regards,
Reilly Atkinson


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