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A version of QED without ultraviolet divergences

A version of QED without ultraviolet divergences - Physics Forum

A version of QED without ultraviolet divergences - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


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  #61  
Old 08-11-2004, 08:06 PM
Eugene
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Default A version of QED without ultraviolet divergences



Eugene wrote:

I must correct myself again. They actually discuss the first
"direct process" in the paper, see eq. (3). However, according to them,
this requires participation of at least 5 low-energy photons,
which makes it also a high-order low-probability process. I trust them
when they say that they performed calculations for both
variants and found that the second one is more probable.
So, I finally think their claim in the paper is correct.

Eugene.


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  #62  
Old 08-11-2004, 08:20 PM
FrediFizzx
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Default A version of QED without ultraviolet divergences

"Eugene" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ]...
|
|
| Eugene wrote:
| >
| >
| > Eugene wrote:
| >
| >>
| >>
| >> greywolf42 wrote:
| >>
| >>> "Eugene" <[Only registered users see links. ]> wrote in message
| >>> news:[Only registered users see links. ]...
| >>>
| >>>>
| >>>> FrediFizzx wrote:
| >>>>
| >>>>
| >>>>> | > I hardly think they are artifacts since real particles are seen
to
| >>>>> | > get a momentum "kick" from invisible vacuum virtual particles in
| >>>>
| >>>>
| >>>>
| >>> actual
| >>>
| >>>>> | > experiments. So you are wrong about that.
| >>>>> |
| >>>>> | Could you give a reference to the experiment where such "kicks"
| >>>>> | are observed?
| >>>>>
| >>>>> [Only registered users see links. ]
| >>>>>
| >>>>> The electron (shown in red) from the electron beam is detected to
| >>>>> go off
| >>>>
| >>>>
| >>>>
| >>> at
| >>>
| >>>>> a different angle from the "kick" that it gets from the gamma photon
| >>>>
| >>>>
| >>>>
| >>> which
| >>>
| >>>>> is virtual.
| >>>>
| >>>>
| >>>>
| >>>> I looked at their article in Phys. Rev. Lett. 79 (1997), 1626.
| >>>> I like this nice experiment.
| >>>> In the abstract they say: "These results are the first laboratory
| >>>> evidence for inelastic light-by-light scattering involving only REAL
| >>>> photons".
| >>>
| >>>
| >>>
| >>>
| >>> While they *said* this is what they did, if you read the paper,
| >>> you'll find
| >>> that they didn't do any such thing:
| >>> [Only registered users see links. ]
| >>>
| >>>
| >>
| >> You are right that all they see is that they shoot a high energy
| >> electron at a laser beam and an electron-positron pair comes out.
| >> According to QED, this can be explained in two ways:
| >>
| >> First: direct process (electron + photon) -> (electron + pair)
| >>
| >> Second: two stage process: Compton scattering
| >> (electron + photon) -> (electron' + photon') followed
| >> by pair creation (photon' + photon'') -> (electron + positron)
| >>
| >> First direct process has QED description starting from the
| >> 3rd perturbation order. The second variant is a combination
| >> of two 2nd order processes.
| >
| >
| > Sorry, I must correct myself. In the second variant, the second
| > stage requires collision of one high energy photon with
| > at least four low-energy laser photons (as they say in the article).
| > This makes the perturbation
| > order of this process much higher that 2nd. This gives more
| > credence to the statement that the first direct process has
| > the most significant contribution to the rate of generation of
| > the electron-positron pairs. So, I tend to agree with you
| > that they haven't seen direct creation of the pair from
| > colliding photons.
| >
| > This, however, does not change anything in the discussion of
| > non-existence of virtual photons.
| >
| > Eugene.
|
| I must correct myself again. They actually discuss the first
| "direct process" in the paper, see eq. (3). However, according to them,
| this requires participation of at least 5 low-energy photons,
| which makes it also a high-order low-probability process. I trust them
| when they say that they performed calculations for both
| variants and found that the second one is more probable.
| So, I finally think their claim in the paper is correct.

Hehe; having some trouble with this? Yes, I think they got it right. Plus,
I do believe the other thing they detect is the original high energy
electron besides the e+e- pair. The detection of original electron and its
properties is how they figure a high energy *virtual* gamma was created.
There are many other articles written about this. You should read them all.

FrediFizzx

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  #63  
Old 08-11-2004, 09:01 PM
Eugene
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Default A version of QED without ultraviolet divergences



FrediFizzx wrote:


So, I would like to express my point as clearly as I can
(I am not going to flip-flop now).
We agreed that there are two processes in their experiment:

First: direct process

(electron + 5 photons) -> (electron + pair)

Second: two-stage process

(electron + photon) -> (electron + high-energy photon)
(high-energy photon + 4 photons) -> pair

All particles mentioned here are real.

In description of the first process, current QED theory introduces
a (high energy) virtual photon as an intermediate step. My point is
that this virtual photon is not observable and is not needed.
I can formulate a theory
which describes this scattering event in full agreement with data,
but which does not use the concept of virtual particles. In my
theory, the direct
process is described by a direct potential between real particles.
In terms of creation and annihilation operators, this potential
has 6 annihilation operators (1 for electron and 5 for photons)
and 2 creation operators (1 for electron and 1 for positron).
This potential not only allows you to calculate scattering amplitudes,
but also to calculate time dynamics of particles in the region of
interaction. The time dynamics is probably irrelevant for this
particular experiment, because there is no chance to observe time
evolution is such high energy processes. But the possibility
to obtain such time-dependent dynamics is an important feature
which confirms the consistency of my approach in contrast to QED.

I rest my case.

Eugene.

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  #64  
Old 08-12-2004, 04:50 AM
FrediFizzx
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Posts: n/a
Default A version of QED without ultraviolet divergences

"Eugene" <[Only registered users see links. ]> wrote:
|
|
| FrediFizzx wrote:
[snip since you buggered the quote attributes again]

| > Hehe; having some trouble with this? Yes, I think they got it right.
Plus,
| > I do believe the other thing they detect is the original high energy
| > electron besides the e+e- pair. The detection of original electron and
its
| > properties is how they figure a high energy *virtual* gamma was created.
| > There are many other articles written about this. You should read them
all.
| >
| > FrediFizzx
| >
|
| So, I would like to express my point as clearly as I can
| (I am not going to flip-flop now).
| We agreed that there are two processes in their experiment:
|
| First: direct process
|
| (electron + 5 photons) -> (electron + pair)
|
| Second: two-stage process
|
| (electron + photon) -> (electron + high-energy photon)
| (high-energy photon + 4 photons) -> pair
|
| All particles mentioned here are real.

No. All photons are virtual. You can't ever be in the "frame" of a photon.
Besides that, the high-energy photon is not detected or detectable directly
anywise.

| In description of the first process, current QED theory introduces
| a (high energy) virtual photon as an intermediate step. My point is
| that this virtual photon is not observable and is not needed.

No photon is directly observable. Once more; *You can't be in the "frame"
of a photon*!

| I can formulate a theory
| which describes this scattering event in full agreement with data,
| but which does not use the concept of virtual particles. In my
| theory, the direct
| process is described by a direct potential between real particles.
| In terms of creation and annihilation operators, this potential
| has 6 annihilation operators (1 for electron and 5 for photons)
| and 2 creation operators (1 for electron and 1 for positron).
| This potential not only allows you to calculate scattering amplitudes,
| but also to calculate time dynamics of particles in the region of
| interaction. The time dynamics is probably irrelevant for this
| particular experiment, because there is no chance to observe time
| evolution is such high energy processes. But the possibility
| to obtain such time-dependent dynamics is an important feature
| which confirms the consistency of my approach in contrast to QED.

I have no problem with this for certain calculations but you have no
fundamental explanation for how a quantum object can have a potential that
extends so far out into space. Basically you are making the particles huge.
And we know that is not the case. Plus I can't buy into the instantaneous
action of a coulomb field at a distance. Are you saying that if I jiggle an
electron over here it will instantaneously jiggle one over there in perfect
unison? I don't think so unless they are somehow bound together.

FrediFizzx

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  #65  
Old 08-12-2004, 06:59 AM
Eugene
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Default A version of QED without ultraviolet divergences



FrediFizzx wrote:

I do not understand you at all. Why do we need to go to the "frame" of
a photon in order to observe it? Simple photographic plate is not
enough? In fig. 1. of their paper they show the path of these high
energy photons by a broken line. I am pretty sure they have a good
shielding in place to protect themselves from this gamma radiation.
There is nothing "virtual" about these photons. They are real things
and can do real damage.



That's exactly what I am saying.


Only experiment can solve our dispute. That's what bothers me most:
Experimentalists spend billions of dollars studying some obscure
particles, and nobody was able to perform a simple definitive experiment
with one charge over here and one charge over there. This is probably
the most fundamental question in physics, and I think the answer is
not so difficult to obtain.

Eugene.


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  #66  
Old 08-12-2004, 08:00 PM
greywolf42
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Default A version of QED without ultraviolet divergences

"Eugene" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ]...

{snip higher levels}


Indeed, that is the experiment.


Which is all very well, but the point is that the experiment did not collide
(real) photons on (real) photons.

{snip QED explanation from Eugene post 1}


True.


It doesn't matter what theory says is probably happening. What matters is
that the experiment does not collide photons on photons. Electrons collide
with photons. And pair production from photon/electron collisions is old
hat. (And no proof of QED.)

The physical experiment does not change with interpretations of theory.
You've nicely demonstrated the fallacy of the converse approach in your
three posts.

--
greywolf42
ubi dubium ibi libertas
{remove planet for e-mail}


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