Field is more fundamental than particles

[exponent137]

A lot of times I read that "Field is more fundamental than particles". This comes from QED. I read some explanations, but I do not understand precisely, what aspect of particles is mentioned.
If we say that elementary particles are black holes (let us assume that BH exists smaller than the Planck mass), how the above rule disturbes existence of such a black holes-particles?

 

[Vanadium 50]

Elementary particles are not black holes, so it's pointless to speculate as if they were.

 

[exponent137]

I did not use a right word. Maybe we can say that they are gravitational objects, as said Hadley (4 geons arXiv...) or Duff (Gravitational constant does not exist, so $\mu$ of particles are so important. arXiv..). But name black hole is easier to comprehend, although it does not mean directly macroscopic black hole.

But, what means that fields are more important than particles from this aspect?

Or a different question: if Higgs boson will be discovered, how it will reduce particle-gravitational theories?

 

[A. Neumaier]

A lot of times I read that "Field is more fundamental than particles". This comes from QED. I read some explanations, but I do not understand precisely, what aspect of particles is mentioned.

In quantum field theory, the field aspect and the particle aspect are complementary to each other (in a precise sense related to what is called ''second quantization'').

Experimentally, depending on the experimental situation, we ''see'' one or the other.

But one can understand the particle concept as a limit of the field concept (in the limit of geometric optics), but there is no way to regard the field concept as a limit of the particle concept.

Moreover, in all realistic quantum field theories, a pure particle view cannot even formally capture all aspects of the fields. Dynamical symmetry breaking, for example, is an intrinsic field phenomenon.

Finally, even in atomic physics and quantum chemistry, electrons are usually delocalized - a feature naturally explained in terms of fields but very counterintuitive in terms of particles.

For all these reasons, the field aspect must be considered to be more fundamental.

 

[kote]

^ That was a surprisingly good (and concise) explanation.

I especially like the last one about "delocalized" particles. The false dichotomy between locality and realism and the endless arguments that have resulted haven't been helpful at all considering that the essence of the particle concept is really in both: local realism.

 

[kote]

I like this one too...

Several recent arguments purport to show that there can be no relativistic, quantum-mechanical theory of localizable particles and, thus, that relativity and quantum mechanics can be reconciled only in the context of quantum field theory. We point out some loopholes in the existing arguments, and we provide two no-go theorems to close these loopholes. However, even with these loopholes closed, it does not yet follow that relativity plus quantum mechanics exclusively requires a field ontology, since relativistic quantum field theory itself might permit an ontology of localizable particles supervenient on the fundamental fields. Thus, we provide another no-go theorem to rule out this possibility.

http://arxiv.org/abs/quant-ph/0103041
http://www.jstor.org/pss/10.1086/338939

 

[A. Neumaier]

I like this one too...

http://arxiv.org/abs/quant-ph/0103041
http://www.jstor.org/pss/10.1086/338939

How do these results square with successful covariant multiparticle theories like those discussed by Keister and Polyzou?

http://www.imamu.edu.sa/Scientific_selections/abstracts/Physics/Relativistic Hamiltonian Dynamics in Nuclear and Particle Physics.pdf

 

[kote]

I left out the last sentence of the abstract:

Finally, we allay potential worries about this conclusion by arguing that relativistic quantum field theory can nevertheless explain the possibility of "particle detections," as well as the pragmatic utility of "particle talk."

It seems like this works with the concept of "macroscopic locality" talked about by Keister and Polyzou. But I didn't read through the entire thing, so maybe I've missed something.

What Halvorson is interested in is the ontological possibility of microscopically local particles, and that's what he argues against.

 

[A. Neumaier]

What Halvorson is interested in is the ontological possibility of microscopically local particles, and that's what he argues against.

It is strange that people who discuss the (im)possibility of realistic theories always seem to be bound to a particle view.

Do you know of serious work on realistic theories of fields rather than particles?
Bell inequalities no longer apply in this case!

 

[kote]

It is strange that people who discuss the (im)possibility of realistic theories always seem to be bound to a particle view.

Do you know of serious work on realistic theories of fields rather than particles?
Bell inequalities no longer apply in this case!

No, but to a philosopher of science the question of whether or not any realistic theories are possible lies outside of physics. All we can do is look at individual theories and see if they are possible, valid, and consistent with experiments, their math, and certain ontological concepts. I am not aware of no-go theorems against the possibility of realistic fields, and I don't have any particular reason to believe that there should be any of these no-go theorems.

The real bite is that fundamental reality cannot be described by local interactions between 3d/4d objects (particles). Since we've already discovered that, and that's the naive reality that we seemed to want, I'm pretty indifferent to whether or not you want to call fields or delocalized particles or whatever else "real." I tend to side with Bohr's thoughts in "Atomic Theory and the Description of Nature" on the ontological results of it all.

 

[A. Neumaier]

No, but to a philosopher of science the question of whether or not any realistic theories are possible lies outside of physics.

But I believe that it can even be substantiated mathematically, if the answer is positive.

If the universe were classical, hardly anybody would doubt the realistic view. In QM, doubts persist only because people think of reality only in terms of particles rather than fields.

The real bite is that fundamental reality cannot be described by local interactions between 3d/4d objects (particles).

Isn't all that is needed approximately local interactions? We cannot even test exact locality...

I tend to side with Bohr's thoughts in "Atomic Theory and the Description of Nature" on the ontological results of it all.

But doesn't Bohr assume a classical world in which the interpretation is done?

We now know that there is no such world, since everything is quantum from the smallest to the largest...

 

[kote]

But I believe that it can even be substantiated mathematically, if the answer is positive.

The best you can do with any given theory that claims to be realistic is show that it is logically consistent and consistent with known experiments that have been performed. You can never prove that there isn't some underlying microscopic probabilistic reality leading you to experimental results that seem deterministic within your measurement error. You can never prove that there aren't really more extraneous dimensions or degrees of freedom than what you've used to construct your theory. Physical theories can only be falsified, never proven.

If the universe were classical, hardly anybody would doubt the realistic view. In QM, doubts persist only because people think of reality only in terms of particles rather than fields.

All QM did was shed light on the epistemological issues that already existed. We can never know whether or not a theory truly represents reality or just approximates experimental results. Moving from a particle concept to a field concept doesn't fix these foundational issues.

Isn't all that is needed approximately local interactions? We cannot even test exact locality...

Sure, if all that you are looking for is a formula for predicting the results of experiments. If you're looking for what's actually out there, it's not enough.

But doesn't Bohr assume a classical world in which the interpretation is done?

We now know that there is no such world, since everything is quantum from the smallest to the largest...

The world Bohr was interested in was the 3 dimensional world that he experienced, filled with 3 dimensional things like tables and chairs. The fact that we can't visualize the mechanisms that produce this world of our experience doesn't mean that it is any less real... but that's another topic, and one that is primarily based on aesthetics .

 

[A. Neumaier]

The best you can do with any given theory that claims to be realistic is show that it is logically consistent and consistent with known experiments that have been performed. You can never prove that there isn't some underlying microscopic probabilistic reality leading you to experimental results that seem deterministic within your measurement error. You can never prove that there aren't really more extraneous dimensions or degrees of freedom than what you've used to construct your theory. Physical theories can only be falsified, never proven.

Yes, but this is consistent with may claim that [kote:] ''the question of whether or not any realistic theories are possible'' [AN:] ''can even be substantiated mathematically, if the answer is positive''.

All QM did was shed light on the epistemological issues that already existed.

That's a severe understatement. Of course, QM shed light on this, but the issues were resolved satisfactorily if QM were not interpreted in the weird way it is interpreted today. Special relativity and general relativity also shed light on the epistemological issues that already existed. But a consensus was soon found - they didn't cause such heated an ongoing, unresolved dispute.

We can never know whether or not a theory truly represents reality or just approximates experimental results. Moving from a particle concept to a field concept doesn't fix these foundational issues.

But this is a truism and wouldn't cause foundational troubles if other things were settled. This can be seen from the situation in the foundation of math. Nobody finds it a serious problem that we can never know whether or not set theory is consistent, though it merits occasional philosophical investigations.

Sure, if all that you are looking for is a formula for predicting the results of experiments. If you're looking for what's actually out there, it's not enough.

There is no way to find out what is ''actually'' there - it is even questionable whether one can make sense of what this should mean. Thus it is enough to have convincing and intelligible models of what's actually out there.

The world Bohr was interested in was the 3 dimensional world that he experienced, filled with 3 dimensional things like tables and chairs. The fact that we can't visualize the mechanisms that produce this world of our experience doesn't mean that it is any less real...

But we now know that this world of things like tables and chairs is accurately described by quantum mechanics at all levels except perhaps the very smallest and very largest.

 

[DarMM]

Do you know of serious work on realistic theories of fields rather than particles?
Bell inequalities no longer apply in this case!

Not in 4D, but in 3D and 2D you can prove the existence of the fields and from them build the local C*-algebra and from the algebra you can prove Bell's inequalities. In fact states in QFT violate the classical bound by the maximum amount $$\sqrt{2}$$.
For the 4D case, since fields haven't been constructed you can't do this, but if you accept that the fields exist, then the C*-algebra exists and the same applies.

No mention of particles occurs in these constructions.

 

[A. Neumaier]

Not in 4D, but in 3D and 2D you can prove the existence of the fields and from them build the local C*-algebra and from the algebra you can prove Bell's inequalities. In fact states in QFT violate the classical bound by the maximum amount $$\sqrt{2}$$.
For the 4D case, since fields haven't been constructed you can't do this, but if you accept that the fields exist, then the C*-algebra exists and the same applies.

No mention of particles occurs in these constructions.

This is not what I was aiming at - indeed, I was a bit inaccurate in what I intended to say.

Of course, Bell inequality violations can be proved once you have nontrivial tensor product states - they are independent of the particle picture. But the proof of the Bell inequalities requires an underlying hidden variable theory of classical _particles_!

Given a classical hidden variable field theory, one cannot prove the Bell inequalities, as far as I know! Thus their violation in a quantum theory say nothing at all.

 

[kote]

There is no way to find out what is ''actually'' there - it is even questionable whether one can make sense of what this should mean. Thus it is enough to have convincing and intelligible models of what's actually out there.

This is exactly why I'm relatively indifferent to whether or not fields are called real or not. It reduces to a question of aesthetics and language. We're arguing over what to call the situation, we're not arguing over what the situation actually is.

The fact that there has been a lot of confusion over and misinterpretation of QM is not evidence for its ontological implications. QM helped to demonstrate a lot of philosophical issues, but much of the logical meat was already present in relativity and even earlier. Bohr even based many of his philosophical conclusions directly on relativity, for example, without need for QM. From ATDN - http://books.google.com/books?id=-BQ7AAAAIAAJ&lpg=PA116&ots=cFKisJAByp&dq=Atomic%20Theory%20and%20the%20Description%20of%20Nature%20%22with%20respect%20to%20our%20emancipation%20from%20the%20demand%20for%20visualization%22&pg=PA116#v=onepage&q&f=false

I am glad to have the opportunity of emphasizing the great significance of Einstein's theory of relativity in the recent development of physics with respect to our emancipation from the demand for visualization. ...the theory of relativity reminds us of the subjective character of all physical phenomena...

This is similar to how QFT is finally helping to get rid of the particle concept as fundamental, even though this is already a logical consequence of standard QM. The confusion is more a social result than a consequence of the physics - maybe physicists hadn't taken enough philosophy courses :tongue:.

 

[A. Neumaier]

The fact that there has been a lot of confusion over and misinterpretation of QM is not evidence for its ontological implications. The confusion is more a social result than a consequence of the physics - maybe physicists hadn't taken enough philosophy courses :tongue:.

But how do you explain that there is no such confusion in general relativity but in quantum mechanics a lot of it remains to this day? It can't be a matter of philosophy courses, since these would affect both discipline equally.

 

[kote]

But how do you explain that there is no such confusion in general relativity but in quantum mechanics a lot of it remains to this day? It can't be a matter of philosophy courses, since these would affect both discipline equally.

The philosophy thing was a joke, but I do think a lot of it is just people talking past each other and not recognizing the different assumptions that are being made. There hasn't been much rigor around the interpretational aspects of QM. Evidence for that is the "Copenhagen Interpretation" that was taught (and argued against) for years but that had very little to do with Bohr, Heisenberg, or anyone else's actual views.

The historical development of relativity and QM were very different and shed a lot of light on how consensus was reached more quickly in one than the other.

Einstein was more the sole owner of relativity, so he got to decide the interpretation. With QM, it was built up by a lot of people over a longer period of time, with little to no work done on interpretational issues until later on. Planck commented on his quantized black-body equation that “it could not be expected to possesses more than a formal significance.” Similarly, Bohr offered no explanation or interpretation for the behavior of his atomic model except to say that it seemed to fit experiments. There were 25 years between Planck quantizing light and Heisenberg finally formalizing QM. In that time, 6 different people would win Nobel prizes for work in quantum physics. Given this history, I don't find it surprising that there wasn't much consensus around interpretation.

 

[A. Neumaier]

The philosophy thing was a joke, but I do think a lot of it is just people talking past each other and not recognizing the different assumptions that are being made. There hasn't been much rigor around the interpretational aspects of QM. Evidence for that is the "Copenhagen Interpretation" that was taught (and argued against) for years but that had very little to do with Bohr, Heisenberg, or anyone else's actual views.

The historical development of relativity and QM were very different and shed a lot of light on how consensus was reached more quickly in one than the other.

Einstein was also more of the sole owner of relativity, so he got to decide the interpretation. With QM, it was a built up by a lot of people over a longer period of time, with little to no work done on interpretational issues until later on. Planck commented on his quantized black-body equation that “it could not be expected to possesses more than a formal significance.” Similarly, Bohr offered no explanation or interpretation for the behavior of his atomic model except to say that it seemed to fit experiments. There were 25 years between Planck quantizing light and Heisenberg finally formalizing QM. In that time, 6 different people would win Nobel prizes for work in quantum physics. Given this history, I don't find it surprising that there hasn't been much consensus around interpretation.

But this confusion was all before Heisenberg 1925, who started the actual revolution. Why do you think things didn't quickly settle afterwards?

Within 20 years of Heisenberg's discovery of the basic equations of motion, the major problems in quantum mechanics were solved, including a fully working scheme for atomic and molecular physics and QED.

 

[kote]

But this confusion was all before Heisenberg 1925, who started the actual revolution. Why do you think things didn't quickly settle afterwards?

Within 20 years of Heisenberg's discovery of the basic equations of motion, the major problems in quantum mechanics were solved, including a fully working scheme for atomic and molecular physics and QED.

By that time opinions had already been formed. As a result, Heisenberg's formulation was not well accepted as far as its ontological implications. This is one of the reasons that Schrodinger developed his equation a year later, and it's one of the reasons Schrodinger's equation essentially replaced matrix mechanics. Heisenberg, try as he might, was certainly not accepted as the philosophical thought leader of QM. QM never had its Einstein.

 

[DarMM]

This is not what I was aiming at - indeed, I was a bit inaccurate in what I intended to say.

Of course, Bell inequality violations can be proved once you have nontrivial tensor product states - they are independent of the particle picture. But the proof of the Bell inequalities requires an underlying hidden variable theory of classical _particles_!

Given a classical hidden variable field theory, one cannot prove the Bell inequalities, as far as I know! Thus their violation in a quantum theory say nothing at all.

Actually any theory with an observable algebra which is Abelian (which would include classical field theories) possesses Bell's inequalities:

S.J. Summers and R. Werner, Bell’s inequalities and quantum field theory, I, General setting,
Journal of Mathematical Physics, 28, 2440–2447

Perhaps I'm missing something though.

 

[A. Neumaier]

Actually any theory with an observable algebra which is Abelian (which would include classical field theories) possesses Bell's inequalities:

S.J. Summers and R. Werner, Bell’s inequalities and quantum field theory, I, General setting,
Journal of Mathematical Physics, 28, 2440–2447

Perhaps I'm missing something though.

But the states are different, so the Bell inequalities violated in current experiments are not those for which the abelian theory applies.

See http://arnold-neumaier.at/ms/lightslides.pdf

 

[DarMM]

But the states are different, so the Bell inequalities violated in current experiments are not those for which the abelian theory applies.

I have read your reference, but I don't really understand. Could you explain in a little more detail why the Abelian theory wouldn't apply, I'm probably missing something obvious.

 

[A. Neumaier]

I have read your reference, but I don't really understand. Could you explain in a little more detail why the Abelian theory wouldn't apply, I'm probably missing something obvious.

Well, in the slides, the same Bell violation experiment is interpreted twice: Once in terms of a quantum particle picture, and once in terms of the classical Maxwell equation. The observed Bell inequality violations for the former are completely consistent with the latter.

I don't know exactly why the theorem you mentioned doesn't apply, but since the slides contain a very explicit example, you'd be able to figure out what happens.

 

[DarMM]

I don't know exactly why the theorem you mentioned doesn't apply, but since the slides contain a very explicit example, you'd be able to figure out what happens.

Oh, that's fine. I thought there might have been some explicit reason. I'll have a closer look and try to figure out the relation between the theorem and your example.

 

[exponent137]

How it is with this explanation:
Photons are product of electromagnetic field. This field is more fundamental, than photons.
Photons are version of excitations of harmonic oscilator. So EM field is like harmonic oscilator. So [a,a+]
Similarly it is with rest particles, they need field. So {a,a+}

If I am wrong what is this field, which is more basic than photons. And what is field which is more basic than rest particles?

p.s.
Nikolic wrote article
http://arxiv.org/PS_cache/quant-ph/pdf/0609/0609163v2.pdf
Now I am not interested in Bohm interpretation, but Nikolic writes cleary.
Are possible some comments on the basis on its article.

Regards e^137

 

[exponent137]

I please for visualization of field:
At the first quantization I imagine double-slit experiment, let us say with electrons. When we measure paths of electrons through slits, we obtain two gaussian curves on screen. When we do not measure electron paths, we obtain sinusoidal curve on screen.
At the first example we measure particles, at the second example we measure fields, are not we?
But, what is extension of this field in the experiment to the second quantization?

 

[A. Neumaier]

Well, in the slides, the same Bell violation experiment is interpreted twice: Once in terms of a quantum particle picture, and once in terms of the classical Maxwell equation. The observed Bell inequality violations for the former are completely consistent with the latter.

I don't know exactly why the theorem you mentioned doesn't apply, but since the slides contain a very explicit example, you'd be able to figure out what happens.

Oh, that's fine. I thought there might have been some explicit reason. I'll have a closer look and try to figure out the relation between the theorem and your example.

Any news on this?

 

[A. Neumaier]

I please for visualization of field:
At the first quantization I imagine double-slit experiment, let us say with electrons. When we measure paths of electrons through slits, we obtain two gaussian curves on screen. When we do not measure electron paths, we obtain sinusoidal curve on screen.
At the first example we measure particles, at the second example we measure fields, are not we?
But, what is extension of this field in the experiment to the second quantization?

In both cases, we measure the quantum fields. Even electron paths and detector click are measurements of the field.

Only the particle picture is weird when applied outside the validity of a semiclassical approximation.