# Recent content by Morbert

1. ### A How do entanglement experiments benefit from QFT (over QM)?

A Boolean logic is an event algebra that follows from a sample space of elementary event propositions. If you construct a Boolean logic around a sample space appropriate for the $S_x$ measurement you made, you cannot include propositions like $S_z = \uparrow$, as you cannot construct a...
2. ### A How do entanglement experiments benefit from QFT (over QM)?

I don't think it was a simplified version of this. But let my try to address possible ambiguities. If we have a Hilbert space of the X apparatus $\mathcal{H}_X$, Y apparatus $\mathcal{H}_Y$, the microscopic system $\mathcal{H}_s$, and a coin $\mathcal{H}_c$, and if we model the...
3. ### A How do entanglement experiments benefit from QFT (over QM)?

If the selection of a subexperiment can be modelled by some appropriate variable like the outcomes of a coin flip that perfectly correlates with the subexperiment, there would be a common sample space, yes. E.g. The outcomes (heads, A),(heads,B),(tails,C),(tails,D). If you can carry out the...
4. ### A How do entanglement experiments benefit from QFT (over QM)?

In classical physics, different samples spaces can be related to one another by coarsening or refining, and there is a single sample space that is a common refinement of all others. In quantum physics, there isn't a common refinement.
5. ### A How do entanglement experiments benefit from QFT (over QM)?

Is the protean nature of ensembles in QM a weakness in the minimalist ensemble interpretation? My understanding so far: The theory of a given system is the double $(H,\rho)$, the dynamics and the preparation. I.e. All physical content is contained in these terms. The triple...
6. ### I Ontology of spin measurement

Ah ok, I missed the earlier context of the discussion.
7. ### I Ontology of spin measurement

Bohmian Mechanics is the main subject of the book. The quotes are from chapter 11.5: "A Universal Bohmian Theory". Specifically, the wavefunction is described as nomological in response to the objection that the wavefunction in BM doesn't experience any back-action from the existing configuration.
8. ### I Ontology of spin measurement

Hmm, I'm not sure that's necessarily the case. BM can frame the wavefunction as nomological rather than ontological. I.e. Instead of being a thing that exists, it is a representation of the behaviour of things that exist. From "Quantum Physics Without Quantum Philosophy" by Goldstein et al "It...
9. ### A Wigner's Friend and Incompatibility

Sorry, I forgot to respond to this even though I said I would. I got some interesting (and hopefully correct) results. For simplicity, I'll represent Wigner's friend, his device, and his lab all with $F$, and Wigner's own lab including himself with $W$. I'll also ignore the coin toss (which...
10. ### A Wigner's Friend and Incompatibility

Ok so it sounds like it ultimately boils down to a matter of interpretation regarding the nature of collapse. Anyway: The histories formalism iiuc would imply direct analogue between the FR experiment and the WF experiment. In the WF experiment we have an isolated system that evolves into...
11. ### A Wigner's Friend and Incompatibility

Hmm, I guess the issue is Wigner predicts his measurement outcome with certainty, which would not be the case if he used a collapsed state or a mixture. Richard Healey argues that Wigner can use the pure state for setting credence about his own measurement, and a mixed state to set credence...
12. ### A Wigner's Friend and Incompatibility

Sorry, by macroscopic subspaces I mean the very large subspaces associated with pointer properties. But this just raises a similar question about pointer properties. Both Wigner and his friends use different pointer properties, each suitable for their own measurement purposes. Wigner's friend...
13. ### A Wigner's Friend and Incompatibility

Interesting. In the conventional WF thought experiment, it's usually supposed that Wigner is able to model his friend's lab with unitary evolution, right up to the point of measurement. If he should not do that, can he still know beforehand, with certainty, the result of his measurement outcome...
14. ### A Wigner's Friend and Incompatibility

To expand a bit on my last messages, and to lay out my understanding of events: Let's say Wigner prepares eveything in the state $\rho = [\psi_0,D_\mathrm{ready},F_\mathrm{ready},L_\mathrm{ready}]\otimes\frac{1}{2}([\mathrm{heads}]+[\mathrm{tails}])$ (Where I have included an additional...
15. ### A Wigner's Friend and Incompatibility

Actually my previous answer might be completely wrong and your intuition correct. If Wigner's friend wants to compute a prediction that Wigner definitely records $1$, he needs a record of his entire lab including himself, which should be incompatible with his record of his own measurement. I...