Particle vs Wave Interpretations of QM

[Matterwave]

everything is made of energy

One issue with this statement is that energy is not an invariant. Different reference frames will give a different accounting of energy.

 

[selfsimilar]

To all above
Ordinarily yes we look at energy as a property and an accounting system more or less. But at the highest level in QFT eventually particles are created with creation operator pumping energy in a space time point. which although it does not indicate what it is it just says raised by so and so energy. So to me this time we are talking complete different language. Although, early on when relativity was in early stages even Einstein came up with the "relativistic mass" term which included the energy due to momentum pc. note we are talking about the energy that creates invariant mass that later was accepted. All I am saying is what QFT is saying, you can correct me if I am wrong.

 

[PeterDonis]

at the highest level in QFT eventually particles are created with creation operator pumping energy in a space time point. which although it does not indicate what it is it just says raised by so and so energy.

A creation operator does not represent an actual physical process. (It's not even an observable since it has no eigenstates.) It's a mathematical device to construct states containing particles from the vacuum state.

 

[Matterwave]

But at the highest level in QFT

What do you mean by "highest level"? QFT and GR both form our fundamental understanding of physics.

particles are created with creation operator pumping energy in a space time point.

Creation operators are a mathematical construct we use to do free field theory. We know how to manipulate the algebra of quantum harmonic oscillators so we took that mathematical machinery and use it in QFT.

I don't know what you mean by "pumping energy in a space time point".

note we are talking about the energy that creates invariant mass that later was accepted.

We just call this the rest mass. It would be wrong / confusing to call it "energy".

All I am saying is what QFT is saying, you can correct me if I am wrong.

No, what you wrote is not what QFT is saying.

 

[weirdoguy]

pumping energy in a space time point

Again, energy is one of many of particles properties! As others have said, it does not work the way you think, but even if it did, those operators would "pump" also other quantities besides energy. I really don't like how pop-sci sources elevate energy to some superior quantity. The "holy trinity" of qunatities that arise from considerations about invariance of lagrangian under time translation, space translation rotaion is energy, momentum, and angular momentum. Latter two are equally important.

 

[jeffn1]

A fundamental "particle" is an excitation in its quantum field. An excitation in a quantum field is energy. I don't think you can blame "pop sci" (although I think you can potentially blame "pop sci" for elevating the role of consciousness in quantum theory).

99% of baryon mass is the result of kinetic energy trapped inside the particle by the strong nuclear force, described by Quantum Chromodynamics (QCD).

 

[PeterDonis]

An excitation in a quantum field is energy.

No, an excitation in a quantum field has energy.

99% of baryon mass is the result of kinetic energy trapped inside the particle by the strong nuclear force

Sure, energy and mass are equivalent. That doesn't mean a quantum field excitation "is" energy, any more than it "is" mass. Energy/mass is a property of quantum fields.

 

[weirdoguy]

An excitation in a quantum field is energy.

Sigh... Why on earth, after so many posts about what energy is, you decide to write this nonsense? Why did you ignore everything we said about that? Can you find any textbook that says what you said? Why not?

I don't think you can blame "pop sci"

Then what can I blame? You won't findy what you wrote in any textbook on the subject. If not laymen literature, then you are just making stuff up. And that is against PF rules.


EDIT. Sorry for beating this dead horse, I didn't see @PeterDonis response.

 

[Roberto Pavani]

after so many posts about what energy is

is probably a Pandora's box better left closed. Physics is very good at defining how energy is calculated and what role it plays in a theory, but much less so at answering the ontological question of what energy is.

 

[Morbert]

is probably a Pandora's box better left closed. Physics is very good at defining how energy is calculated and what role it plays in a theory, but much less so at answering the ontological question of what energy is.

Disabusing people of notions like everything is made of energy is well within the wheelhouse of physicists.

 

[Matterwave]

is probably a Pandora's box better left closed. Physics is very good at defining how energy is calculated and what role it plays in a theory, but much less so at answering the ontological question of what energy is.

I don't view it that way.

Energy as a concept is quite well defined and precise within each physical theory. Indeed that definition involves mathematics, but that does not suggest the theory only tells you how to calculate. For the theory does give labels to the mathematical objects and e.g. tells you that energy and velocity are not the same concepts.

As others have pointed out repeatedly, within our physical theories, energy is a property of "the stuff there is". What really is "the stuff there is" is a difficult ontological problem but that's not a problem with energy.

 

[apostolosdt]

I am curious whether undergrad physics students take courses on the philosophy of science. For example, does your syllabus include reading the seminal book, The Structure of Scientific Revolutions by Thomas Kuhn. Physics is sort of the cutting edge for these type of issues. Of course, Newton to Einstein was a classic example of a Kuhnian "paradigm shift". I might tend to argue that particle oriented quantum mechanics to field-based quantum field theory represents a similar shift. Thoughts?

In my undergrad studies in Greece, I did attend a course on epistemology; it wasn't a requirement towards the degree and I took it out of curiosity. I had to read Kuhn myself, though, as the lecturer tried his best to infuse his own political ideas in the class, rather than concentrate on the subject itself. I also attended some lectures given by the Philology Dept. on Lakatos' ideas.

As for your argument about the "paradigm shift," one good checking point---due to Kuhn, of course---is an accompanying shift in textbooks material. Have you noticed anything; You should presumably go back into textbooks of early '50s.

 

[apostolosdt]

Yes, its definitely a Kuhnian shift as it introduces something that implies a new ontology or metaphysics that didn't exist before. I think another poster Bhobba said something like you cannot get non-relativistic quantum mechanics out of relativistic quantum field theory, only a relativistic field theory. This would be a another good argument that this is a Kuhnian shift as it shows that you cannot recover quantum mechanics from field theory without some extra implied ontology or metaphysics that wasn't originally there.

There is nothing "ontological or metaphysical" in QFT. It is doing physics at very small regions of space [quantum mechanics] in which energies involved are extremely large [relativity]. The real question however is why one shouldn't consider expanding, so to speak, the concepts and methodology of Schrödinger's onto relativistic particles; in other words, why not simply quantize particles under extreme velocities nearing speed of light?

All good graduate texts deal with such questions and show the various non-physical situations we are driven into (for instance, Shankar's Principles of QM, 2nd ed.; see end of chapter 20). There are also more involved questions that require QFT in order to be answered, like that of causality, demanding that outside the light-cone propagation amplitudes should vanish.

And all these in the realm of physics as a science---not under some metaphysical umbrella.

 

[iste]

There is nothing "ontological or metaphysical" in QFT. It is doing physics at very small regions of space [quantum mechanics] in which energies involved are extremely large [relativity]. The real question however is why one shouldn't consider expanding, so to speak, the concepts and methodology of Schrödinger's onto relativistic particles; in other words, why not simply quantize particles under extreme velocities nearing speed of light?

All good graduate texts deal with such questions and show the various non-physical situations we are driven into (for instance, Shankar's Principles of QM, 2nd ed.; see end of chapter 20). There are also more involved questions that require QFT in order to be answered, like that of causality, demanding that outside the light-cone propagation amplitudes should vanish.

And all these in the realm of physics as a science---not under some metaphysical umbrella.

I'm not making a claim that there's something metaphysical or ontological about QFT; I am saying it implies a metaphysics or ontologies regarding the universe that are radically different than before its conception.

 

[apostolosdt]

I'm not making a claim that there's something metaphysical or ontological about QFT; I am saying it implies a metaphysics or ontologies regarding the universe that are radically different than before its conception.

I'm just worried that the term is being heavily overused for anything not scientifically conceivable. And I assume you are aware of the term's origin, but please use with caution!

 

[apostolosdt]

[...] QFT does not remove the need for quantum interpretations [...].

I should agree but not because QFT doesn't remove any need for interpretation; only because QFT has never established any interpretation of its 'quantum' sector.

 

[bhobba]

QFT has never established any interpretation of its 'quantum' sector.

Perhaps thats because QFT does not reduce to ordinary QM:
https://arxiv.org/abs/1712.06605

Thanks
Bill

 

[apostolosdt]

Perhaps thats because QFT does not reduce to ordinary QM:
https://arxiv.org/abs/1712.06605

Thanks
Bill

Thanks for bringing it to my attention. I may attempt to delve into its arguments some time, if nothing else just to honour the author.

 

[jeffn1]

I can't help thinking, from a big picture conceptual perspective, that the shift from QFT clearly represents a paradigm shift. It shifts the perspective from the behavior of individualized particles to universal quantum fields, with particles constituting excitations of the underlying field. I can't help thinking that the quantum field permeating all space and time (as far are we know) is relevant to the biggest mysteries of quantum theory, namely nonlocal quantum entanglement.

 

[iste]

I'm just worried that the term is being heavily overused for anything not scientifically conceivable. And I assume you are aware of the term's origin, but please use with caution!

When I say ontologies and metaphysics I basically just mean any claims about what "stuff" exists and the nature of that "stuff". And even if qft still needs underlying interpretation, it still implies different kinds of "stuff".