
Ruth Kastner replied to the topic Quantum theory is incompatible with relativity: A proof beyond Bell's theorem in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
Dear Aurelien, RTI does not require any preferred foliation; it does not require any future boundary condition. It is not a hidden variable approach nor does it rely on a notion that measurement outcomes are ‘already there’ in the future–i.e. it is not a block world ontology. I understand that the original TI may have seemed to imply that, but…[Read more]

Ruth Kastner replied to the topic Quantum theory is incompatible with relativity: A proof beyond Bell's theorem in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
Thanks Shan. In RTI the quantum state Psi> is fully ontic. But the advanced state <Psi is also fully ontic, so RTI is a different animal from the usual ‘quantum interpretation.’ This is why it is not subject to the dilemma you pose. It has real ontic collapse, but the collapse is not with respect to just a forwardpropagating quantum state. In…[Read more]

Ruth Kastner replied to the topic Quantum theory is incompatible with relativity: A proof beyond Bell's theorem in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
Thanks Aurelien, I am indeed aware of the Sutherland model and you are correct that it is covariant, except perhaps for the final boundary condition which has to be defined in a particular frame (but it’s a matter of debate as to whether that ‘really’ fixes a preferred frame). Other than the final B.C., the model preserves full Lorentz covariance.…[Read more]

Ruth Kastner replied to the topic Quantum theory is incompatible with relativity: A proof beyond Bell's theorem in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
I’m afraid this is not the correct conclusion. While RTI is certainly not the usual ad hoc collapse theory, it certainly is a nonunitary objective reduction theory (see below). So it cannot be subject to your argument concerning unitaryonly theories. There is real dynamical reduction in TI–it just does not take the form that you’ve assumed…[Read more]

Ruth Kastner replied to the topic Quantum theory is incompatible with relativity: A proof beyond Bell's theorem in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
But the existence of the observed correlation does not compel the idea that there is some sort of collapse signal that ‘travels faster than light.’ You might be supposing that such a ‘collapse signal’ is needed to enforce the correlation, but that is not the case in TI, where the correlation is enforced through the combination of the quantum state…[Read more]

Ruth Kastner replied to the topic Quantum theory is incompatible with relativity: A proof beyond Bell's theorem in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
Thanks Shan for this question. If the measurement events are spacelike separated, then according to relativity, there is no invariant time order for the two events. That is, it’s not possible to consider them simultaneous in any invariant sense–that would pick out a preferred frame, and relativity doesn’t allow that. For an observer heading…[Read more]

Ruth Kastner replied to the topic Quantum theory is incompatible with relativity: A proof beyond Bell's theorem in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
Yes, I think the definition of ‘collapse’–what collapse means physically–does matter for the issue of concern to you. In this latest post you seem to be talking about a single quantum, not an entangled state, right? Bell’s inequality concerns correlations between entangled particles.
In any case, for this singleparticle measurement, the…[Read more] 
Ruth Kastner replied to the topic Quantum theory is incompatible with relativity: A proof beyond Bell's theorem in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
Again, collapse in TI for any detected quantum is associated with both emission and absorption of that quantum–two events for each detected quantum, not one. This is an important difference bewteen TI and other collapse theories, which view collapse as singling out a particular time index. That is not the case in TI. In TI, collapse establishes…[Read more]

Ruth Kastner replied to the topic Microscopic account of a measurement process in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
Jonathan, I have to differ with your initial claim that “Every interpretation of quantum mechanics posits, as axioms, a set of rigid idealizations about measurement.” This not the case, since the transactional interpretation does not do so. Measurement is neither idealized nor an axiom in TI (nor in RTI, the relativistic version.) In TI,…[Read more]

Ruth Kastner replied to the topic Quantum theory is incompatible with relativity: A proof beyond Bell's theorem in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
Hi Shan:
I’ve started looking at this interesting paper, but I do have to note that there is an exception to the general observation that ‘Collapse theories single out a preferred frame’. The Transactional Interpretation is a collapse theory, but it does not single out a preferred frame. This is made explicit in its relativistic development, RTI,…[Read more] 
Ruth Kastner started the topic UnitaryOnly Quantum Theory Cannot Consistently Describe the Use of Itself in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
There has been much discussion about the FR paradox, but to my knowledge, it has not yet been considered that the paradox is a consequence of the traditional assumption that quantum theory ‘really’ has only unitary dynamics; i.e., that there is no ‘objective reduction’ or physical nonunitarity in QM. Here it is argued that it is the unitaryonly…[Read more]

Quantum Speculations started the topic Closing the superdeterminism loophole in Bell's theorem in the forum 2019 International Workshop: Beyond Bell's theorem 5 years, 2 months ago
http://philsciarchive.pitt.edu/16203/
It is well known that there is a freedomofchoice loophole or superdeterminism loophole in Bell’s theorem. Since no experiment can completely rule out the possibility of superdeterminism, it seems that a local hidden variable theory consistent with relativity can never be excluded. In this paper, we…[Read more]

Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 11 months ago
Thanks Richard, let me address your comment that:
… if there were no true magnitude claims then an application of the Born rule would have nothing to which to assign probabilities!
The above statement/position depends on the notion of ‘magnitude claim’. That’s a linguistic entity, and I think we earlier agreed that QM doesn’t demand or depend…[Read more]

Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 11 months ago
Mark: of course, I’ve contended and continue to contend that the disease infecting conventional approaches to QM is that nobody can define ‘measurement’. This leaves adherents of these traditional approaches to simply help themselves to measurement results. In particular, I would have to respectfully differ with Richard’s comment:
The argument…

Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 11 months ago
Thanks very much Richard.
Of course, in the transactional picture, once photons are detected/actualized (as is necessary to yield a current), collapse has occurred, and conserved quantities (such as angular momentum, spin, etc) have been transferred. (Photons are the mediator of em processes such as the creation of electron current; for details,…[Read more] 
Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 11 months ago
Thanks very much, Richard.
Regarding the interpretation of probability, it seems that this is still an open question. I don’t think the Born probability is restricted to being about semantic objects such as claims. It can be directly about a system’s actualized properties (at least it certainly can in TI).
But in any case: I recognize that…[Read more] 
Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 11 months ago
Richard, do I understand correctly that in your proposed approach, measurement outcomes have no relation to values of observables for the system? My question arises from your statement:
In particular, it makes no assumption concerning the actual spin values of the measured particles, either before or after the spin measurements. It assumes only…

Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 11 months ago
Thanks, Richard for this clarification.
Of course, I think your analysis can also perfectly well apply to an ontic role for the quantum state.
Under an epistemic view of the quantum state, then it seems to me that if one posits that measurements really do have definite outcomes, then an implicit hidden variable view must be lurking in the…[Read more] 
Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 11 months ago
This is an interesting situation: assessments of the bearing and validity of the FR proof greatly depend on what quantum theory itself is taken to be. For example, Editor has referred to two different forms of QT:
(1) QT with collapse postulate — call it “QTCP”
(2) QT without collapse postulate — call it “QTNCP”
…and has noted, based on…[Read more] 
Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 11 months ago
I would just comment here that Brukner’s formulation of the measurement problem presupposes an epistemic interpretation of the quantum state relative to a particular observer. So his analysis and conclusions do not apply to cases in which the quantum state ontologically refers. In particular, he concludes that facts are necessarily…[Read more]
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