I The thermal interpretation of quantum physics

[A. Neumaier]

So in essence particles are fields of nothing but numbers sometimes localised and others extended greatly, correct.

No.

In general, fields are just themselves, not composed of other stuff. The temperature field in a room is not composed of anything but describes how warm it is in different places. Similar for other fields, e.g. the water level of the moving surface of a lake, or the salt concentration in the lake. They are not composed of water but describe properties of the lake.

Electron fields and other fundamental stuff are not much different in principle, only in their quantum properties.

Partcles are moving localized aspects of fields, described by bloblike or beamlike currents. The paths they travel are often more real than the particles themselves. Think of rain pouring down or of moving water wavelets, but don't take the imagery too seriously!

 

[ftr]

Particles are moving localized aspects of fields

And Fields are aspects of what?

 

[DarMM]

And Fields are aspects of what?

They're just fields as such, same as they are in classical field theory, just the structure of their properties is different.

 

[ftr]

They're just fields as such, same as they are in classical field theory, just the structure of their properties is different.

In classical field theory temperature field is an aspect of energy of the particles. The post said that particles are aspect of fields while everybody knows that fields must be aspect of particles.

 

[DarMM]

In classical field theory temperature field is an aspect of vibration energy of the particles. The post said that particles are aspect of fields while everybody knows that fields must be aspect of particles.

In QFT in general, not specifically the Thermal Interpretation, the fields aren't generally "aspects of particles". There are several states that don't really admit a particle interpretation, particles only emerge at asymptotic times, the particle content is observer dependent (i.e. Unruh effect). I don't see how the fields are aspects of particles.

 

[A. Neumaier]

And Fields are aspects of what?

They are aspects of what we can observe.

 

[A. Neumaier]

In classical field theory temperature field is an aspect of energy of the particles.

No. This holds only for ideal gases, but not for the temperature of liquid water, say, as it figures in the Navier-Stokes equations.

everybody knows that fields must be aspect of particles.

Everybody who looks deeper knows that the fundamental theory of Nature is quantum field theory, and not quantum particle theory. Particles are described in terms of fields.

 

[ftr]

I don't see how the fields are aspects of particles.

Ever since I was born in QM theory world I was taught that particles and fields are dual description, and since we say here is a particle and not here is a field I presume that fields are aspects of particles.

 

[DarMM]

Ever since I was born in QM theory world I was taught that particles and fields are dual description

I don't see how that could be possible in general interacting field theories which have states without a particle decomposition.

 

[A. Neumaier]

we say here is a particle and not here is a field I presume that fields are aspects of particles.

Informally, we say here is a particle (mainly because of tradition), but looking at the math involved in their relativistic description one finds that the particle picture is purely figurative, while everything is expressed in terms of fields.

 

[ftr]

I don't see how that could be possible in general interacting field theories which have states without a particle decomposition.

Informally, we say here is a particle (mainly because of tradition), but looking at the math involved in their relativistic description one finds that the particle picture is purely figurative, while everything is expressed in terms of fields.

First I hear that fields are fiction(i.e. mathematical), now I hear that particles are fiction.
then this post

They are aspects of what we can observe

The interpretation was suppose to make things clear, was it?
edit: ok I admit this has made me to think a lot harder.

 

[A. Neumaier]

First I hear that fields are fiction(i.e. mathematical), now I hear that particles are fiction.

In some sense, only Nature is real, and all talk about it is already fiction. In any case, particles are more superficial fiction than quantum fields. Nobody ever has seen a particle. We just imagine it as a tiny cannon ball or a tiny wavelet, or whatever...

The interpretation was suppose to make things clear, was it?

The thermal interpretation is supposed to resolve the issues with the traditional interpretations, primarily the measurement problem.

Clarity will rule only 5-10 years after a single interpretation is accepted by the majority, and textbooks are rewritten accordingly. Thus you need to be patient.

The only shortcut is to learn to understand things from the ground, starting with the math, rather than from what you hear people say.

 

[julcab12]

First I hear that fields are fiction(i.e. mathematical), now I hear that particles are fiction.
then this postThe interpretation was suppose to make things clear, was it?

Fields are real and particles blurry bundles of real in approximation. The usual convention is coined behavior, depending on how you view it. For loopy guys- are interactive, transformative via timelike slices-- Thermal Time (Still Blurry Though). In terms of field--mathematical abstraction are often so closely related to "real" stuff that they're confused with each other. A vector is not real, a force is. But we're so used to vector forces, we swap them carelessly. We can do so only because we know forces behave (with an extremely fine approximation) as vectors, but vectors are not real. Vector fields are not real, for the same reasons vectors are not real; the electrical field is real and you could feel it if you had the right organs. Hilbert spaces are not real, superposition is.

 

[ftr]

Fields are real

Although "real" is hard to define, but typically in physics we mean that something that has certain property that can be measured directly or indirectly. I don't know of any experiment that has measured electron field and typically the fields are expressed using imaginary numbers.

 

[A. Neumaier]

I don't know of any experiment that has measured electron field

Then you can learn something new!

Atomic force microscopy displays the surface of the electron cloud around a nucleus, not a number of tiny electron particles surrounding the nucleus. See ''Does an atom mostly consist of empty space?'' from my theoretical physics FAQ.

 

[ftr]

Then you can learn something new!

That is what attracts me to science, I get very bored when I sail an open sea. What is the unit of measurement.

P.S. I don't see a single sentence that says "electron field" in your first reference.

 

[DarMM]

I forgot to ask this. Is the Thermal Interpretation contextual?

If I have a set of nine devices for a four level system that represent one of the nine orthogonal bases in Cabello's proof of Kochen-Specker. And "let us say" that to keep determinism we end up with a contextual assignment whereby projector $P_5$ is assigned a value of $1$ (i.e. is the result that will occur) when measured as part of operator $A$, but assigned a value of $0$ when measured as part of operator $B$. This determination $\nu(P_5,A) = 1$ implicitly includes the full dynamics of the environment, since it is just a statement of the value that will obtain.

How does this contextuality arise in the thermal interpretation? I assume it is that given a fixed environmental state $\rho_E$ the metastable states on devices implementing $A$ and $B$ are different enough that under influence from the environment one will decay onto the $P_5$ component of the slow manifold and the other will not.

 

[A. Neumaier]

That is what attracts me to science, I get very bored when I sail an open sea. What is the unit of measurement.

P.S. I don't see a single sentence that says "electron field" in your first reference.

It talks about forces. Forces are vector fields (generalizing the gravitational forces familiar to anyone). The detailed force measured depends on the instrument, but they are all calculated from the interaction with the electron field (plus the Coulomb fields of the nuclei).

 

[A. Neumaier]

I forgot to ask this. Is the Thermal Interpretation contextual?

Of course, since quantum mechanics is. The stochastic influences depend on the environment, which is the context. No two environments are identical. (But conventional contextuality discussions are not applicable since they assume sharp outcomes, while the thermal interpretation is about explaining when sharp outcomes should be expected.)

Note that the thermal interpretation gives no details, only the conceptual intuition needed to turn each specific problem into a precise problem of statistical mechanics. To find out how the slow manifold looks like is for each case a separate statistical mechanics problem.

In Part III, I discussed two particular measurement situations treated by AB&N and B&P, respectively. The techniques generalize, but have not yet been applied to generic measurement situations which would allow to treat not only particular cases but fairly general settings.

Thus there is still a lot of research potential in the application of the thermal interpretation.

 

[DarMM]

Of course, since quantum mechanics is.

I think this is a difference of phrasing. Quantum Mechanics (in the typical view) retains nonconextuality by sacrificing determinism, i.e. there are sets of projectors to which one cannot assign elements of ${0,1}$ noncontextually. Either you give up determinism, i.e. assign real values elements of $[0,1]$, or you accept the contextuality.
Although some call any violation of either contextuality.

Regardless the explanation is as I expected. Have you read:
Heywood, P., & Redhead, M. L. G. (1983). Nonlocality and the Kochen-Specker paradox. Foundations of Physics, 13(5), 481–499

It contrasts the different forms of locality implied by different methods of having contextuality, i.e. ontological vs environmental contextuality.

 

[A. Neumaier]

Have you read:
Heywood, P., & Redhead, M. L. G. (1983). Nonlocality and the Kochen-Specker paradox. Foundations of Physics, 13(5), 481–499

I had studied the Kochen-Specker theorem in detail, but didn't read all of the surrounding literature.

I lost interest in quantum-logic related results (though I read the book Quantum logic by Karl Svozil and more) long ago, when I realized that quantum logic is a very poor logic in which not even implication is sensibly defined. Thus one can make only the most primitive logical arguments. The fact is that all predictive power in quantum physics comes from applying classical logic to get results about q-expectations, and nothing but confusion comes from considering quantum logic.

 

[A. Neumaier]

Three reviews (Part I, Part II, Part III) of my three papers are now on PhysicsOverflow, together with some comments by me.

 

[Mentz114]

[..]

I discussed two particular measurement situations treated by AB&N and B&P, respectively. The techniques generalize, but have not yet been applied to generic measurement situations which would allow to treat not only particular cases but fairly general settings.

Thus there is still a lot of research potential in the application of the thermal interpretation.

I have to say it looks incredibly hard. I doubt if a general theory is possible.
I looked at buying a copy of the B&P book but the earliest delivery date for a new one is June !
I'm not sure if Breuer et al (2015) is cited in the Thermal papers but it gives a foretaste and is available on arXiv.

Non-Markovian dynamics in open quantum systems
Heinz-Peter Breuer, Elsi-Mari Laine, Jyrki Piilo, Bassano Vacchini

arXiv:1505.01385v1 [quant-ph] 6 May 2015

I like very much the re-synthesis of QT in the Thermal interpretation. Dropping particles gets rid of a lot of Platonic nonsense. Nice move.

 

[A. Neumaier]

I looked at buying a copy of the B&P book but the earliest delivery date for a new one is June !
I'm not sure if Breuer et al (2015) is cited in the Thermal papers but it gives a foretaste and is available on arXiv.

H. P. Breuer & F. Petruccione,
Stochastic dynamics of open quantum systems: Derivation of the
differential Chapman-Kolmogorov equation,
Physical Review E51, 4041-4054 (1995).

is freely online and related to what I discuss. But it works with pure states rather than with the mixed states required for the thermal interpretation.

 

[A. Neumaier]

I looked at buying a copy of the B&P book

You may wish to look at bookfinder! (But your shipping country and hence the prices may be different.)
I wonder why used copies may be more expensive than new ones by a large factor...

 

[A. Neumaier]

I assume it is that given a fixed environmental state $\rho_E$ the metastable states on devices implementing $A$ and $B$ are different enough that under influence from the environment one will decay onto the $P_5$ component of the slow manifold and the other will not.

The state of the universe probably never factors even approximately into an environmental state and a system state. Exact factorization is just an assumption made (in addition to other highly idealized assumptions such as that this environmental state is a harmonic heat bath) in many discussions of the measurement problem, to be able to do something at all.

 

[vanhees71]

I don't think that's true. It's neither true that the weirdness is resolved by the minimal interpretation, nor is it true that it has anything to do with prejudice by "common sense". The minimalist interpretation is pretty much what Bell was criticizing in his essay. To quote from it:

Here are some words which, however legitimate and necessary in application, have no place in a formulation with any pretension to physical precision: system, apparatus, environment, microscopic, macroscopic, reversible, irreversible, observable, information, measurement.

Well, Bell's merit for me lies not so much in his philosophical ideas but to the contrary in bringing philosophical unsharp considerations, particularly from the EPR article and the even weirder reply by Bohr to it into a sharp scientifically intervestigable quantitative realm. By deriving his famous inequalities with their clear contratidction to the probabilistic prediction of QT he has set the "macroscopic prejudices" by EPR to the test. The better and better Bell tests with all kinds of quantum systems, particularly quantum optics (photons), decides forQT with an astonishing significance. Although Bell seems not to have liked this, that's an empirical fact about nature.

Now, a physical theory has to describe all phenomena, and among the very persistent phenomena is the classical behavior of macroscopic systems. It's not enough for QT to describe the microscopic constituents (nowadays quarks, leptons, some gauge fields, and the Higgs field) but also the emergent classical behavior of matter (from the hot and dense elementary-matter gas of the early universe to the rather cold matter surrounding us in everyday life), and that's why all the words, Bell doesn't like are of substantial importance for physics. If you want to understand macroscopic matter from first principles you have to use many-body methods, make use of the separation of the "micro vs. macro scales". The key to understand many-body statistical physics is indeed the notion of information a la Shanon, Jaynes, and von Neumann.

To make sense of what's observed, particularly when dealing with the microscopic constituents there's no other way to also think about the measurement devices, which are to explained by the same many-body physics as anything else. Even the very definition of the microscopic constituents in a physical, i.e., operational sense, hinges on this understanding of what's observed. E.g., a photon (or more generally any state of "electromagnetic fields") manifest themselves finally still by their interaction with macroscopic matter. Einstein's perception of the em. field as particle-like photons is self-contradictory, while modern quantum optics naturally explains it by the observable manifestations of the interaction between the electromagnetic field with the matter fields describing the detectors, i.e., the photoelectric effect.

 

[vanhees71]

Just to understand. Take a particle reaction like $\pi^{+} \rightarrow \mu^{+} + \nu_{\mu}$. In the thermal interpretation I assume what is happening here is that locally devices probe $\pi^{+}, \mu^{+}, \nu_{\mu}$ fields (of course these are not fundamental fields, but let's ignore that for now). Via interaction with the fields each of the devices' slow modes are placed into a bistable state and environmental noise triggers these to decay into the detection/non-detection states?

That's an excellent example for my case against Bell's unrealistic attempt to forbid fundamental notions of physics as an empirical science in #177 since the mentioned weak-decay process involves a "muon neutrino".

Now what is a neutrino within the fundamental models we have to describe them? That's a more complicated question than one might think, because it relates to the only really estabilshed fact about physics beyond the standard model, namely that there is what's called "neutrino mixing".

In the usual pragamatic interpretation of the meaning of the pion-decay we deal with particles. Now particles within relativistic quantum field theory are only well defined in the sense of asymptotitic free states, where a Fock-space description makes sense and one thus can define (generalized) mass-momentum-spin eigenstates of occupation number 1, i.e., a "single-particle Fock state".

Now the mass-eigenstates of the neutrino fields cannot be prepared since neutrinos are produced via the weak interaction (like the above considered pion decay), and the corresponding weak current couples to flavor not mass eigenstates. The flavor eigenstates however cannot be interpreted as one-particle Fock states, because they have indetermined mass.

What we detect as "neutrinos" are indeed not "neutrinos as particles" but the reaction of the neutrino with the detector material. Indeed, the long-baseline experiments prove neutrino-mixing, and it may well be that the "muon neutrino" from the pion decay is detected as an "electron neutrino" due to the "neutrino oscillations". Seen from this perspective, in the QFT formalism neutrinos make only sense as "internal lines in Feynman diagrams", i.e., one has to consider both the creation process (here the pion decay) as well as the detection process (not mentioned above) to have a consistent interpretation of "what's measured".

 

[stevendaryl]

Now, a physical theory has to describe all phenomena, and among the very persistent phenomena is the classical behavior of macroscopic systems. It's not enough for QT to describe the microscopic constituents (nowadays quarks, leptons, some gauge fields, and the Higgs field) but also the emergent classical behavior of matter (from the hot and dense elementary-matter gas of the early universe to the rather cold matter surrounding us in everyday life), and that's why all the words, Bell doesn't like are of substantial importance for physics.

I think you misunderstand Bell if you think that he doesn't like measurements and observations and so forth. What he's saying is that a fundamental theory should not be expressed in terms of those concepts, because they are very subjective and fuzzy. Fuzziness is often hiding contradictions.

So the minimal interpretation, with its distinction between measurements and other interactions is a subjective, fuzzy interpretation. Measurements are certainly important to our discovering facts about the world, but physics is supposed to describe the world in a way that doesn't require there to be anyone or anything performing measurements. For example, presumably enough hydrogen will collapse into a star and produce energy by nuclear fusion even if nobody is around to look at it (as was the case for the first few billion years after the Big Bang).

Because it is described in terms of "measurement", the minimal interpretation doesn't seem very minimal at all, to me. It's sweeping a huge amount of complexity under the rug using that term. For example, we could define a measurement of a property is an interaction that triggers an amplification process resulting in an irreversible change, where different initial values of the property result in macroscopically distinguishable end states. I think that covers the usual cases that we would consider "measurement". But it's enormously complicated and fuzzy. Irreversibility, like macrosopic, is a fuzzy large-numbers concept. There is no actual irreversibility, only for all practical purposes (FAPP) reversibility. (I don't know whether Bell coined that acronym, but he uses it.) There is no actual macroscopic/microscopic distinction, we only call something "macroscopic" when it becomes too complex to analyze all the parts in complete detail. So the minimal interpretation is, in my mind, built on sand. Measurement is a fuzzy concept that is ultimately subjective. If your physics depends on measurement as a fundamental concept, then your physics is fundamentally subjective.

 

[MathematicalPhysicist]

If your physics depends on measurement as a fundamental concept, then your physics is fundamentally subjective.

What's bad with subjective physics, if there's no objective reality?