A Do bosons contradict basic probability laws?

[Philip Koeck]

I don't know which "classical paths" you are referring to. As in the operator formalism also in the path-integral formalism many-body systems are most efficiently described by the field-theoretical formalism, i.e., path integrals integrating over field configurations.

I mean:
Would one see the clusters flying in straight lines between collisions as in classical mechanics?
Remember that we are filming the clusters in 3D, so we are carrying out position measurements at regular time points. Doesn't the wave function collapse whenever we measure the position?

 

[vanhees71]

This is explained rather by the famous paper by Mott on why we see straight-line tracks of $\alpha$ particles when looking at a lump of $\alpha$-radiating matter in a cloud chamber. It's the interaction between the particles and the detector (in that case consisting of the vapour molecules). There's no collapse needed at all!

N. Mott, The Wave Mechanics of alpha-Ray Tracks, Proceedings of the Royal Society of London. Series A 126 (1929) 79.

https://doi.org/10.1098/rspa.1929.0205

What has this to do with indistinguishable particles though?

 

[Philip Koeck]

This is explained rather by the famous paper by Mott on why we see straight-line tracks of $\alpha$ particles when looking at a lump of $\alpha$-radiating matter in a cloud chamber. It's the interaction between the particles and the detector (in that case consisting of the vapour molecules). There's no collapse needed at all!

N. Mott, The Wave Mechanics of alpha-Ray Tracks, Proceedings of the Royal Society of London. Series A 126 (1929) 79.

https://doi.org/10.1098/rspa.1929.0205

What has this to do with indistinguishable particles though?

Thanks for the link to Mott's paper. I have to have a closer look at it.

I thought measurements in general made the wave function collapse. Is that not an accepted interpretation of the measurement process?

If every particle or cluster in a chamber appears to be moving in a straight line wouldn't that make the particles/clusters distinguishable?
If I saw some almost continuous lines in a video recording or a cloud chamber I would draw the conclusion that all the position measurements along such a line are measurements of the same particle and, essentially, I've labelled the particles by observing them.

 

[PeroK]

Thanks for the link to Mott's paper. I have to have a closer look at it.

I thought measurements in general made the wave function collapse. Is that not an accepted interpretation of the measurement process?

If every particle or cluster in a chamber appears to be moving in a straight line wouldn't that make the particles/clusters distinguishable?
If I saw some almost continuous lines in a video recording or a cloud chamber I would draw the conclusion that all the position measurements along such a line are measurements of the same particle and, essentially, I've labelled the particles by observing them.

Each particle in a bubble chamber is essentially an isolated system. The particles do not interact with each other and are clearly not in thermal equilibrium.

Also, these lines are not continuous. At the atomic level they are formed by a sequence of discrete collisions. They only look continuous at a macroscopic scale.

 

[vanhees71]

The collapse is part of some flavors of the socalled Copenhagen interpretation of quantum mechanics. I personally think it's superfluous and misleading, contradicting fundamental principles of relativistic quantum field theory (microcausality). I follow the minimal statistical interpretation of QT, which is the essence of the theory needed to do science. Everything else is philosophy and thus a matter of opinion rather than part of physics as a natural science.

 

[Philip Koeck]

Each particle in a bubble chamber is essentially an isolated system. The particles do not interact with each other and are clearly not in thermal equilibrium.

Also, these lines are not continuous. At the atomic level they are formed by a sequence of discrete collisions. They only look continuous at a macroscopic scale.

Let's think of the gas of clusters which is monitored by 3D-video.
Even if there are no long range forces between the clusters they would still collide and form a system that tries to achieve thermal equilibrium, just like an ideal gas. The question is whether this equilibrium will be that of distinguishable or indistinguishable particles.

I realize that the lines won't be continuous even in a video, but they would suggest a straight classical path, from which I would conclude that it's always the same particle on a given path.

 

[PeroK]

Let's think of the gas of clusters which is monitored by 3D-video.

And if you had a 3D video of a hydrogen atom then you'd see precisely where the electron was at all times and could plot its classical orbit round the nucleus.

You can't just pretend that there is no such thing as QM. That if you have a 3D video camera that QM will just "go away".

 

[vanhees71]

Well, such a 3D cam itself cannot exist because of QT. One should also be aware that classical statistical physics is incomplete. Boltzmann and Gibbs had a lot of problems with particularly the distinguishability of classical particles (Gibbs's paradox, how to gauge phase-space cells, etc.), all of which are solved with many-body QT of indistinguishable particles, and that the distributions are rather Bose-Einstein and Fermi-Dirac distributions than Maxwell-Boltzmann distributions is an empirical fact, explaining a lot of other problems related to a classical statistical model.

 

[PeterDonis]

Let's think of the gas of clusters which is monitored by 3D-video.

Let's close this thread since it is now degenerating into personal speculation.