- #1

- 8,614

- 4,647

Peter Donis said:Whatever is keeping us from making deterministic predictions about

the results of quantum experiments, it isn't chaos due to nonlinear

dynamics of the quantum state.

A. Neumaier said:However, it is chaos in the (classical) part of the quantum state that

is accessible to measurement devices.

A. Neumaier said:What we directly observe in a measurement device are only macroscopic (what I called ''classical'') observables, namely the expectation values of certain smeared field operators. These form a vast minority of all conceivable observables in the conventional QM sense. For example, hydromechanics is derived in this way from quantum field theory. it is well-known that hydromechanics is highly chaotic in spite of the underlying linearity of the Schroedinger equation defining (nonrelativistic) quantum field theory from which hydromechanics is derived. Thus linearity in a very vast Hilbert space is not incompatible with chaos in a much smaller accessible manifold of measurable observables.

stevendaryl said:I really don't think that chaos in the macroscopic world can explain the indeterminism of QM. In Bell's impossibility proof, he didn't make any assumptions about [...]

A. Neumaier said:Bell doesn't take into account that a macroscopic measurement is actually done by recording field expectation values. Instead he argues with the traditional simplified quantum mechanical idealization of the measurement process. The latter is known to be only an approximation to the quantum field theory situations needed to be able to treat the detector in a classical way. Getting a contradiction from reasoning with approximations only shows that at some point the approximations break down.

stevendaryl said:Well, that is certainly far from being an accepted resolution. I don't see how anything in his argument depends on that.

It is the resolution given by my thermal interpretation, and this resolution is valid (independent of the thermal interpretation) even without being accepted.

Bell assumes that measurement outcomes follow strictly and with infinite precision Born's rule for a von Neumann measurement. But the latter is known to be an idealization.

Last edited: