Particles in dBB Interpretation

[Feeble Wonk]

I was recently reading a PF thread that was questioning the meaning of zero dimensional fundamental "point" particles and virtual particles, and it raised a question in my mind.

It's been my impression from previous discussions that most physicists don't really think of fundamental particles as infinitesimally tiny pieces of material "stuff" moving through time and space in a continuous manner. But then I thought of the dBB interpretation adherents, and I became more uncertain about that.

How does dBB view the the physical nature of fundamental particles?

 

[atyy]

Particles in dBB are point particles. They are also "point particles" in the standard interpretation of quantum mechanics, in the sense that when one measures a position, one gets a point in space. The difference between dBB and the standard interpretation is that particles in DBB have trajectories, but not in the standard interpretation.

 

[Feeble Wonk]

So, dBB does not posit any greater "materiality" to the fundamental particles and their pilot waves than other interpretations? Sorry if the question seems silly. I'm even less well versed in dBB than I am regarding the other schools of thought.

 

[atyy]

dBB does posit greater materiality, because it posits trajectories for the particles.

 

[jtbell]

So, dBB does not posit any greater "materiality" to the fundamental particles and their pilot waves than other interpretations?

I suppose that depends on your definition of "materiality."

 

[Feeble Wonk]

dBB does posit greater materiality, because it posits trajectories for the particles.

I've seen many references to dBB trajectories, but I'm confused as to what they really mean. I haven't been able to find a WIKI type of summary about that concept, and it doesn't appear to be included in their discussion of dBB theory. Can anyone offer a layman level explanation that is low on mathematics and high on conceptual description?

 

[Feeble Wonk]

I'm assuming that there is much more to the concept than the basic trajectory of any other projectile.

 

[atyy]

No, it's the simple common sense concept of trajectory.

dBB is just complete common sense and nothing mysterious about quantum mechanics at all.

 

[Feeble Wonk]

No, it's the simple common sense concept of trajectory.

dBB is just complete common sense and nothing mysterious about quantum mechanics at all.

So, if the particle has a precise location at all times, how does the uncertainty principle still hold?

 

[atyy]

So, if the particle has a precise location at all times, how does the uncertainty principle still hold?

In dBB, all the uncertainty is placed in the initial conditions. Also, the trajectories don't obey Newton's laws.

 

[stevendaryl]

In dBB, all the uncertainty is placed in the initial conditions. Also, the trajectories don't obey Newton's laws.

It occurs to me that the interpretation of the uncertainty principle must be different for dBB. In dBB, particles have definite (although unknown) positions and velocities at all times.

 

[atyy]

It occurs to me that the interpretation of the uncertainty principle must be different for dBB. In dBB, particles have definite (although unknown) positions and velocities at all times.

It's a bit different, but the usual "impossible to have simultaneous position and momentum" is essentially correct. Of course it is, because it is a Copenhagen myth and all Copenhagen myths including collapse of the wave function are true There are possibly some exceptions to the no simultaneous position and momentum myth, but the exceptions are not made use of by dBB. The usual simultaneous position and momentum which are impossible to have are canonically conjugate position and momentum, as defined by the quantum non-commutation relation. dBB particles have simultaneous position and velocity, but the velocity does not form the quantum canonically conjugate momentum.

It is "obvious" in quantum mechanics that position and momentum cannot be simultaneously measured, because the setup for each measurement is different. In fact, a momentum measurement can be conceived as a different position measurement. For example, in the double slit experiment, a measurement of position at a large distance from the slit is essentially a measurement of momentum at the slit, because the large distance limit is the "Fraunhofer" limit, which is essentially a Fourier transform. dBB just makes use of the idea that all our measurements are position measurements.

 

[Demystifier]

Can anyone offer a layman level explanation that is low on mathematics and high on conceptual description?

Oliver Passon is a good start:
http://lanl.arxiv.org/find/quant-ph/1/au:+Passon_O/0/1/0/all/0/1

 

[Feeble Wonk]

Oliver Passon is a good start:
http://lanl.arxiv.org/find/quant-ph/1/au:+Passon_O/0/1/0/all/0/1

I'm reading through the Passon papers you suggested. Thank you. Very interesting. They appear to be a good summary of dBB and the related concepts.

I am getting the impression, though, that there is a significant difference between dBB and most of the other QT interpretations with regard to how they view the nature of the fundamental particles. Many of the other interpretations appear, to me anyway, to view particles as field fluctuations, statistical tools, informational representations or some other type of abstract conceptualization. It seems to me that dBB implies a more concrete existence of subatomic particles that are really "out there". Am I mistaken in that impression?

 

[Demystifier]

You understood it correctly.