Gregory L. Hansen:

And this is one reason that I think that virtual particles are a source of
all evil. It's not because there's really anything wrong with the
concept, when it's understood. But because it leads to such staggering
misunderstandings, even among the studied. When they read that particles
pop into existence for a brief time, people naturally think of particles
popping into existence for a brief time. And then they think of all kinds
of things that particles do, like transfer energy and momentum, and run
into other particles. E.g. why don't electrons in a LINAC scatter from
those vacuum particles?

Simple. Dig up a copy of bjorken & drell, vol I and look up, disconected
graph (or diagram, I don't remember which). The reason will be obvious.
On the other hand, it's very easy to see how specific diagrams contribute
to observable effects. For example, the diagram,

\ is the first order correction to the magnetic moment.
.\ It is easily interpreted that way, too. The virtual
.. \ photon which connects to the ingoing and outgoing
. /~~~~ electron lines carries momentum. That modifies the
/ momentum at the vertex in the middle. A charge which
/ scatters from the electron then sees the modified
momentum present at the middle vertex which connects
the exchanged photon.

Being concerned about whether or not virtual photons are
just mathematical artifacts is like being concerned about
whether or not a multipole expansion of a charge distribution
is an artifact, which I have yet to see ever arouse the
angst or hand wringing. I attribute such conundrums to the fact
that experiments haven't been producing enough new discoveries
to keep theorists occupied.

Quantum field theory is a theory of fields. It has a particle
interpretation, but the fundamental entity is the field. Virtual
particles are the expression of the field in momentum eigenstates. When
momentum is transferred from the field to an electron, we say a virtual
photon was exchanged. The virtual photons are the interactions that the
field could be involved in, they're not an accounting of the interactions
that have been completed.

How about a short excursion here. What do you think happens if
you quantize the field in a curved spacetime? Specifically,
will all of the observers agree on which particles are ``real''
and which are virtual?

Bilge ha escrito:
i.e., the uncertainty relations permitting the short term violation
of conservation of energy.

This is a common misconception.

This means that there exists a substance
that penetrates everywhere, effects real things, but cannot be
directly observed. This looks very much like long forgotten aether.

Only to you.

This is not correct. Similar claims were done by people so smart like
Einstein, Dirac or Feynmann or Wheeler between others.

As history showed us, physics is doing much better if such
unobservable "substances" like aether or virtual photons are removed
from the theory and the theory is formulated in terms of directly
observable things, like real physical photons, electrons, etc.

Please explain precisely how to observe a real electron. Every
signal which is observed from a detector is observed through the
forces produced by virtual interactions, i.e., the motion of an
indicator on a meter, the chemical reactions in ones retina
which propagate via more chemical reactions through the visual
cortex, etc. I could claim the exact opposite with greater
veracity. Give me a single example of any observation in which
the final step in the observation involves any of the free
particles you call real.

It is well known that fields are -by definition- unobservables, and
that one only measure particles and motion of particles. Have you read
chapter 3 of Weinberg manual? There Weinberg clearly states that one
measures in particle physics experiments are particles. One NEWER
measures fields.

In fact your above discussion proves that you do not know even that a
field is!!!! Even if one does the hyphotesis of the field exists and
even if one does hypothesis one is measuring via meters, chemical
reactions, etc. One is NOT measuring the field.

You appears to mix the concept of *FIELD* with the concept of *strengh
of the FIELD* at one point.

That is, even if could prove that we are measuring the *strengh of the
FIELD* at one point x in an instant t, that is VERY different from
proving that the FIELD exist. If you want prove that field exist, you
would measure the *strengh of the FIELD* not only in the point where
the test particle is sited. You may also measure the *strengh of the
FIELD* in the rest of points of the universe (even beyond observable
universe) and remember that you cannot use tests particles (because if
you use test particles you are measuring really forces newer fields).
Can do that guy? Can you prove that fields exist?

Juan R.

Center for CANONICAL |SCIENCE)

In article ,
Bilge wrote:
Gregory L. Hansen:

And this is one reason that I think that virtual particles are a source of
all evil. It's not because there's really anything wrong with the
concept, when it's understood. But because it leads to such staggering
misunderstandings, even among the studied. When they read that particles
pop into existence for a brief time, people naturally think of particles
popping into existence for a brief time. And then they think of all kinds
of things that particles do, like transfer energy and momentum, and run
into other particles. E.g. why don't electrons in a LINAC scatter from
those vacuum particles?

Simple. Dig up a copy of bjorken & drell, vol I and look up, disconected
graph (or diagram, I don't remember which). The reason will be obvious.
On the other hand, it's very easy to see how specific diagrams contribute
to observable effects. For example, the diagram,

I'm talking about laymen and physics students, and you're pulling out
Bjorken & Drell? Come on, Bilge...

Anecdote: During a meeting to discuss homework problems, a fellow student
asked the professor how the exchange of virtual photons can create an
attractive force. The professor said something about uncertainty in where
the photon was created. The student said "That makes sense. Wait, no it
doesn't!"

And he was right, it doesn't make sense. They both had in mind a picture
of billiard balls knocking into each other, and they were a graduate
student and a professor of physics.



\ is the first order correction to the magnetic moment.
.\ It is easily interpreted that way, too. The virtual
. \ photon which connects to the ingoing and outgoing
. /~~~~ electron lines carries momentum. That modifies the
/ momentum at the vertex in the middle. A charge which
/ scatters from the electron then sees the modified
momentum present at the middle vertex which connects
the exchanged photon.

Being concerned about whether or not virtual photons are
just mathematical artifacts is like being concerned about
whether or not a multipole expansion of a charge distribution
is an artifact, which I have yet to see ever arouse the
angst or hand wringing. I attribute such conundrums to the fact
that experiments haven't been producing enough new discoveries
to keep theorists occupied.

And nobody is puzzled about the field creating an attractive force until
the exchange of particles is introduced. Better, I think, to make it
clear that the virtual particle does what the field does because it's a
representation of the field. I wouldn't call them a mere mathematical
artifact because momentum transfers are usually the observable
consequence of the field, and virtual particles are a lot like a listing
of the things the field could do to a particle. Especially at first
order.


Quantum field theory is a theory of fields. It has a particle
interpretation, but the fundamental entity is the field. Virtual
particles are the expression of the field in momentum eigenstates. When
momentum is transferred from the field to an electron, we say a virtual
photon was exchanged. The virtual photons are the interactions that the
field could be involved in, they're not an accounting of the interactions
that have been completed.

How about a short excursion here. What do you think happens if
you quantize the field in a curved spacetime? Specifically,
will all of the observers agree on which particles are ``real''
and which are virtual?

I have to admit I'm sort of taking Wald's word for this. I haven't gone
far into QFT on curved manifolds. But Wald was quite insistent.

--
"And don't skimp on the mayonnaise!"

Gregory L. Hansen ha escrito:

In article .com,
Juan R. wrote:

Gregory L. Hansen ha escrito:
Quantum field theory is a theory of fields. It has a particle
interpretation, but the fundamental entity is the field. Virtual
particles are the expression of the field in momentum eigenstates. When
momentum is transferred from the field to an electron, we say a virtual
photon was exchanged. The virtual photons are the interactions that the
field could be involved in, they're not an accounting of the interactions
that have been completed.

Precisely Weinberg begins from particles and then obtains the fields.
Weinberg does not claim that the field was fundamental as many
textbooks incorrectly does. However, the field approach is not posible
in bounded states and this is the reason that quantum field theory is
defined only for isolated particles (S-matrix).

Not possible in bounded states? I'm suspicious of that claim! When you
churn the Lagrangian through the Euler-Lagrange equations you get an
equation of motion like the Dirac equation with electromagnetic
interaction. There's nothing inherently S-matrix about it until you
specialize to high energies.

Where is there a complete bound-state theory in Weinberg manual for
example?

R-QFT clearly states that only possible observables are those derived
from S-matrix, which is only valid for independent particles (remember
the cluster decomposition principle). In rigor R-QFT only deal with
free fields.

In the

e + e = 2 photon

scattering. R-QFT only can study the wavefunction of the electrons or
the photons when are not interacting. That is when the wavefunction
factorizes |12 = |1|2.

In an atom or molecule you can claim that electrons are infinitely
separated and |12 is NOT |1|2. All test of QED are for nonboundend
states for example scattering two two electrons in acellerator physics
(which is an ONE-body problem), hidrogen atoms or hidrogenic ions
He^(++). In fact, recent test of two electrons in bound states has been
a failure.

Yes one can obtain a Dirac equation for a single particle. What is the
corresponding equation for two particles. It cannot be derived from
field theory and equations proposed in literature /ad hoc/, for example
two-body covariant are not rigorous and not complete.

Bethe-Salpeter and others are incorrect. At one hand, one claims that
two body state is a 16 component wavefunction. At the other hand in the
interaction regime one uses propagators derived from formals series of
QED which clearly state that there is not two body wavefunction for the
two electrons.

Why you think that R-QFT states that only scattering states are
observables?

Still today, nobody has found the correct, consistent, and complete
relativistic equation for N-bodies (perhaps our center has already done
but are cheking details).


Juan R.

Center for CANONICAL |SCIENCE)

Gregory L. Hansen ha escrito:

In article om,
Juan R. wrote:

Gregory L. Hansen ha escrito:

What effect does the 00 component of the metric have on a test particle?
How does that compare with the effect of a Newtonian gravitational
potential? In the weak field limit, how large, and how important, are the
other components of the metric compared with the 00 component?

That was addressed both here and in sci.physics.research.

And I trust that you'd demonstrated an acceleration proportional to the
mass of the source, and inversely proportional to the square of the
distance.

And proved that ct collapses as dimension (which is the correct
physics) but that parameter tau reduces to Newtonian time (which is a
parameter NEWER a dimension). And also proved as covariant derivatives
reduce to Newtonian ones (Carlip, the 'great relativisit' was unable to
prove this), etc.

But still that is not exactly Newtonian gravity. In fact, the
functional dependence (x, t) is just wrong, because GR is a field
theory and cannot deal with nonlocal AAAD contributions. Moreover i
proved that the curvature of spacetime is ZERO, doing the curvature
interpretation of GR just wrong. If A is cause of B elimination of A
may eliminate the effect B. This is a basic principle of science that
relativists just ignore!

If you eliminate curvature and still there is gravity then curvature is
NOT the cause of gravity.

Moreover, there is no posibility for fixing the gauge of the potential
obtained inside GR. Either one use incorrect -experimentally false
boundaries as in Ehlërs approach- or either one is forced to use
**aditional** equations does not derived from field equations of GR.
Therefore one continues to not derive NG from GR.

Moreover i exactly computed in sci.physics was the nonrelativistic
limit of trayectory from the GR geodesic equation. But trajectory
where? I just computed the nonrelativistic limit of trajectory on a
relativistic spacetime.

If i had computed the nonrelativistic limit of spacetime i had obtained
(1 -1 -1 -1) which is Minkoskian spacetime and if i had computed then
the trajectory on THAT spacetime i would obtain a = 0. This indicates
the breaktrought of the curvature interpretation.

What sense has the computation of a nonrelativistic trajectory on a
relativistic spacetime? One may be coherent.

Moreover, all of discussion on sci. was for one body system. The
equation of motion for one test body. One can prove that the two body
equation of motion cannot be obtained. This difficulty is common to all
relativistic theories: Maxwell EM, R-QFT, RQM, SR, and GR.


Juan R.

Center for CANONICAL |SCIENCE)

Bilge wrote:
How about a short excursion here. What do you think happens if
you quantize the field in a curved spacetime? Specifically,
will all of the observers agree on which particles are ``real''
and which are virtual?

You don't need to introduce the complexity of curved spacetime to make
this point. Just introduce an accelerated observer in Minkowski
spacetime. Hint: look up Unruh radiation.


Tom Roberts

Bilge ha escrito:
How about a short excursion here. What do you think happens if
you quantize the field in a curved spacetime? Specifically,
will all of the observers agree on which particles are ``real''
and which are virtual?

Since as proven by Cartan extension the Rieman curvature geometrization
of GR is a approximation (GR cannot deal with spin for example), one
can regeometrize GR on the so called torsion gravity (there spacetime
is just flat).

Also in quantum FTG (the theory worked by Feynman or Weimberg between
others) spacetime is just flat.

For a formulation of particles on curved spacetime you can see
Hoyle/Narlikar theory using Synge parallel propagators

Try again on your irrational defense of fields :-)

Juan R.

Center for CANONICAL |SCIENCE)

Eugene Stefanovich:


Gregory L. Hansen wrote:

Quantum field theory is a theory of fields. It has a particle
interpretation, but the fundamental entity is the field. Virtual
particles are the expression of the field in momentum eigenstates. When
momentum is transferred from the field to an electron, we say a virtual
photon was exchanged. The virtual photons are the interactions that the
field could be involved in, they're not an accounting of the interactions
that have been completed.

The electrostatic field created by your Van de Graaf has virtual photons
because that's the way a field is represented in quantum field theory.

Then you change one unobservable entity (virtual particles) for another
unobservable entity (quantum fields). I think I have a better idea.

Most people would disgree that a theory based on instantaneous
action at a distance is a better idea, since the instantaneous
part conflicts with observations.

One can formulate quantum field theory, e.g., QED, without using fields
as basic concepts. This sounds rather controversial, but it can be done.

Sure. You can rename anything and then claim you've eliminated the
concept. That doesn't make it so. It does, however, make it easier
to make the mistake of treating what is supposed to be unobservable
in field theory as observable.

QED can be formulated entirely in terms of observable (not "bare", not
"virtual", but "real", "physical", or "dressed") particles - photons and
electrons and their interactions. Quantum fields are needed only as
temporary formal crutches for writing down the interparticle
interactions and proving that they are relativistically invariant.

The approach I am talking about is completely equivalent to the old
renormalized QED as far as the S-matrix is concerned. In contrast
to the old theory, it has a

You need to distinguish between any formal results you might
have obtained and your quirky interpretation which gives physical
status to things which are unobservable. To illustrate the difference,
let's just apply your _interpretation_ of instantaneous propagation
and watch the equivalence vanish.

Consider a longlived, metastable state. Such a state could be
due to the ground and first excited states being connected by
a forbidden transition. Now, one could arrange to populate a
large number of such states such that the emitted radiation
has a fairly constant intensity. Now, at some distance away,
you set up some apparatus capable of producing a strong electric
field which may be turned on and then turned off very quickly
after being turned on. Since such an electric field will
result in level mixing in the atoms (or nuclei, or whatever),
the transition rate will change due to the pulse of the electric
field. That will change the intensity and spectral characteristics
of the emitted radiation.

According to you, an observer located at the apparatus should
observe the change in intensity in half the time that a more sane
view would allow, since according to you, the electric field
propagates everywhere instantaneously, so that the only delay
observed by the observer in question is the transit of the light,
one way.

Thhe rest of the boring nay-sayers would require the time for the
electric field to propagate to the metastable states to be included.
Since the propagation speed is no greater than c, twice the time
should be required.

well-defined finite Hamiltonian that allows one to go beyond scattering
events and consider the time evolution of interacting systems.

Unfortunately, what you consider to be some sort of observable
time evolution constitutes a violation of the uncertainty principle,
yet you arent willing to go out on a limb and state that.

In this approach, the interaction between charged particles is
instantaneous (rather than retarded), but I am not aware of any
experiment that unambiguosly demonstrates the (usually presumed)
retarded character of interaction between electrons.

I'm not sure you are aware of how to even do one, since the only
things you've these so-called observations might tell anyone are
things which are clearly ruled out by quantum mechanics. For example,
I believe one of your examples was the evolution of the individual
spins of two particles throught a collision. That contradicts the
fact that the coupling of the spins results in the individual spins
not being good quantum numbers.

Juan R.:

Gregory L. Hansen ha escrito:
Quantum field theory is a theory of fields. It has a particle
interpretation, but the fundamental entity is the field. Virtual
particles are the expression of the field in momentum eigenstates. When
momentum is transferred from the field to an electron, we say a virtual
photon was exchanged. The virtual photons are the interactions that the
field could be involved in, they're not an accounting of the interactions
that have been completed.

Precisely Weinberg begins from particles and then obtains the fields.
Weinberg does not claim that the field was fundamental as many
textbooks incorrectly does. However, the field approach is not posible
in bounded states and this is the reason that quantum field theory is
defined only for isolated particles (S-matrix).


Hurry and claim your $1,000,000.00 from the clay mathematics institute.
What you've just claimed is that you know qcd cannot give a bound state
and hence the proton cannot be explained by qcd. One of the millenium
challenge problems involves proving such a result for a yang-mills field,
so you should receive a healthy funding boost by supplying your results.

In article ,
Bilge wrote:
Eugene Stefanovich:


Gregory L. Hansen wrote:

Quantum field theory is a theory of fields. It has a particle
interpretation, but the fundamental entity is the field. Virtual
particles are the expression of the field in momentum eigenstates. When
momentum is transferred from the field to an electron, we say a virtual
photon was exchanged. The virtual photons are the interactions that the
field could be involved in, they're not an accounting of the interactions
that have been completed.

The electrostatic field created by your Van de Graaf has virtual photons
because that's the way a field is represented in quantum field theory.

Then you change one unobservable entity (virtual particles) for another
unobservable entity (quantum fields). I think I have a better idea.

Most people would disgree that a theory based on instantaneous
action at a distance is a better idea, since the instantaneous
part conflicts with observations.

What's-his-name, author of a Dover book on classical field theory written
with the purpose of being extensible to quantum field theories, wrote
about a delayed action at a distance theory. I had trouble understanding
how a theory could be both action at a distance and delayed. Just
wondering if you know anything about that and have comments on it.


--
"The result of this experiment was inconclusive, so we had to use
statistics." (Overheard at international physics conference)