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R. E. Kastner

Publications and source records attributed to R. E. Kastner.

At least 55 records · Page 3Linked to original sources
arXiv2015

Antimatter in the Direct-Action Theory of Fields

One of Feynman's greatest contributions to physics was the interpretation of negative energies as antimatter in quantum field theory. A key component of this interpretation is the Feynman propagator, which seeks to describe the behavior of antimatter at the virtual particle level. Ironically, it turns out that one can dispense with the Feynman propagator in a direct-action theory of fields, while still retaining the interpretation of negative energy solutions as antiparticles.

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arXiv2015

Haag's Theorem as a Reason to Reconsider Direct-Action Theories

It is argued that the severe consequences of Haag's inconsistency theorem for relativistic quantum field theories can be successfully evaded in the direct-action approach. Some recent favorable comments of John Wheeler, often mistakenly presumed to have abandoned his own (and Feynman's) direct-action theory, together with the remarkable immunity of direct-action quantum electrodynamics to Haag's theorem, suggest that it may well be a good time to rehabilitate direct action theories. It is also noted that, as extra dividends, direct-action QED is immune to the self-energy problem of standard gauge field QED, and can also provide a solution to the problem of gauge arbitrariness.

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arXiv2014

The Emergence of Spacetime: Transactions and Causal Sets

This paper discusses how the transactional interpretation of quantum mechanics can provide for a natural account of the emergence of spacetime events from a quantum substratum. In this account, spacetime is not a substantive manifold that becomes occupied with events; rather, spacetime itself exists only in virtue of specific actualized events. This implies that spacetime is discrete rather than continuous, and that properties attributed to spacetime based on the notion of a continuum are idealizations that do not apply to the real physical world. It is further noted that the transactional picture of the emergence of spacetime can provide the quantum dynamics that underlie the causal set approach as proposed by Sorkin and others.

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arXiv2014

Maudlin's Challenge Refuted: A Reply to Lewis

Lewis has recently argued that Maudlin's contingent absorber experiment remains a significant problem for the Transactional Interpretation (TI). He argues that the only straightforward way to resolve the challenge is by describing the absorbers as offer waves, and asserts that this is a previously unnoticed aspect of the challenge for TI. This argument is refuted in two basic ways: (i) it is noted that the Maudlin experiment cannot be meaningfully recast with absorbers described by quantum states; instead the author replaces it with an ordinary which-way experiment; and (ii) the extant rebuttals to the Maudlin challenge in its original form are not in fact subject to the alleged flaws that Lewis ascribes to them. This paper further seeks to clarify the issues raised in Lewis' presentation concerning the distinction between quantum systems and macroscopic objects in TI. It is noted that the latest, possibilist version of TI (PTI) has no ambiguity concerning macroscopic absorbers. In particular, macroscopic objects are not subject to indeterminate trajectories, since they are continually undergoing collapse. It is concluded that the Maudlin challenge poses no significant problem for the transactional interpretation.

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arXiv2013

Measurement: still a problem in standard quantum theory

It is argued that recent claims by A. Hobson that standard quantum theory has no measurement problem cannot be sustained. Moreover, it is pointed out that taking the reduced density operator of a component system as an epistemic (ignorance-based) mixture has long been known to be untenable based on direct proof.

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arXiv2012

On Delayed Choice and Contingent Absorber Experiments

It is pointed out that a slight variation on the Wheeler Delayed Choice Experiment presents the same challenge to orthodox quantum mechanics as Maudlin-type contingent absorber experiments present to the Transactional Interpretation (TI). Therefore, the latter cannot be used as a basis for refutation of TI.

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arXiv2011

de Broglie waves as the "Bridge of Becoming" between quantum theory and relativity

It is hypothesized that de Broglie's 'matter waves' provide a dynamical basis for Minkowski spacetime in an antisubstantivalist or relational account. The relativity of simultaneity is seen as an effect of the de Broglie oscillation together with a basic relativity postulate, while the dispersion relation from finite rest mass gives rise to the differentiation of spatial and temporal axes. Thus spacetime is seen as not fundamental, but rather as emergent from the quantum level. A result by Solov'ev which demonstrates that time is not an applicable concept at the quantum level is adduced in support of this claim. Finally, it is noted that de Broglie waves can be seen as the "bridge of becoming" discussed by Elitzur and Dolev (2005).

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arXiv2011

Better than "flashes": Transactions

I discuss Gisin's result showing that sets of quantum-correlated spacelike events cannot be described by a covariant probability distribution over hidden variables, and his conclusion that Tumulka's "rGRWf" (relativistic GRW "flash ontology" model) is an appropriate model to resolve the apparent conflict between quantum theory and relativity. The contrasts and similarities between the Transactional Interpretation's (TI) handling of a specific measurement result and that of GRW approaches are clarified. I argue that TI resolves the apparent conflict between quantum theory and relativity described by Gisin in a harmonious manner, without the necessity of modifying the theory.

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arXiv2011

Quantum Nonlocality: Not Eliminated by the Heisenberg Picture

It is argued that the Heisenberg picture of standard quantum mechanics does not save Einstein locality as claimed in Deutsch and Hayden (2000). In particular, the EPR-type correlations that DH obtain by comparing two qubits in a local manner are shown to exist before that comparison. In view of this result, the local comparison argument would appear to ineffective in supporting their locality claim.

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arXiv2010

The Quantum Liar Experiment in Cramer's Transactional Interpretation

Cramer's Transactional Interpretation (TI) is applied to the "Quantum Liar Experiment" (QLE). It is shown how some apparently paradoxical features can be explained naturally, albeit nonlocally (since TI is an explicitly nonlocal interpretation, at least from the vantage point of ordinary spacetime). At the same time, it is proposed that in order to preserve the elegance and economy of the interpretation, it may be necessary to consider offer and confirmation waves as propagating in a "higher space" of possibilities.

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arXiv2010

The Hardy Experiment in the Transactional Interpretation

The Hardy experiment is analyzed from the standpoint of the Transactional Interpretation (TI) in its possibilist variant, PTI. It is argued that PTI provides a natural and illuminating account of the associated phenomena, resolving the apparent paradox which arises from the mistaken notion that components of the state vector labeled by spacetime regions imply the actual presence of a corpuscle in that region.

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arXiv2010

Why Everettians Should Appreciate the Transactional Interpretation

The attractive feature of the Everett approach is its admirable spirit of approaching the quantum puzzle with a Zen-like "beginner's mind" in order to try to envision what the pure formalism might be saying about quantum reality, even if that journey leads to a strange place. It is argued that the transactional interpretation of quantum mechanics (TI), appropriately interpreted, shares the same motivation and achieves much more, with far fewer conceptual perplexities, by taking into account heretofore overlooked features of the quantum formalism itself (i.e. advanced states). In particular, TI does not need to talk about brain states, consciousness, or observers (rational or otherwise). In its possibilist variant ("PTI"), it shares the realist virtues of treating state vector branches as genuine dynamical entities, without having to explain how or why all of their associated outcomes actually happen (they don't), how to account for a plenitude of counterpart observers in some coherent notion of trans-temporal identity of the bifurcating observers (observers don't bifurcate in TI), nor how the certainty of all outcomes could be consistent with any coherent theory of probability, let alone the Born probability (the Born probability emerges naturally in TI). In short, TI is precisely the one-world interpretation Kent is looking for in his (2010).

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arXiv2010

Comment on "Comment on 'On Visibility in the Afshar Two-Slit Experiment' "

Tabish Qureshi (2010) has recently objected to an aspect of my discussion of a thought experiment by Srikanth (2001). I believe his objection is based on a misunderstanding about my presentation, but I accept responsibility for not being more clear. Here I attempt to clear up any confusion and to point out that one can indeed obtain interference in this experiment based on taking care to correctly characterize the detection process. I also emphasize that Qureshi and I are in full agreement concerning the assertion that when interference is present, there is no genuine 'which slit' information, and that in this case, the measurement necessary to preserve interference precludes determination of an actual slit of origin for the photon.

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arXiv2009

On Visibility in the Afshar Two-Slit Experiment

A modified version of Young's experiment by Shahriar Afshar indirectly reveals the presence of a fully articulated interference pattern prior to the post-selection of a particle in a "which-slit" basis. While this experiment does not constitute a violation of Bohr's Complementarity Principle as claimed by Afshar, both he and many of his critics incorrectly assume that a commonly used relationship between visibility parameter V and "which-way" parameter K has crucial relevance to his experiment. It is argued here that this relationship does not apply to this experimental situation and that it is wrong to make any use of it in support of claims for or against the bearing of this experiment on Complementarity.

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arXiv2005

Why the Afshar Experiment Does Not Refute Complementarity

A modified version of Young's experiment by Shahriar Afshar demonstrates that, prior to what appears to be a ``which-way'' measurement, an interference pattern exists. Afshar has claimed that this result constitutes a violation of the Principle of Complementarity. This paper discusses the implications of this experiment and considers how Cramer's Transactional Interpretation easily accomodates the result. It is also shown that the Afshar experiment is analogous in key respects to a spin one-half particle prepared as ``spin up along $\bf x$'', subjected to a nondestructive confirmation of that preparation, and post-selected in a specific state of spin along $\bf z$. The terminology ``which-way'' or ``which-slit'' is critiqued; it is argued that this usage by both Afshar and his critics is misleading and has contributed to confusion surrounding the interpretation of the experiment. Nevertheless, it is concluded that Bohr would have had no more problem accounting for the Afshar result than he would in accounting for the aforementioned pre- and post-selection spin experiment, in which the particle's preparation state is confirmed by a nondestructive measurement prior to post-selection. In addition, some new inferences about the interpretation of delayed choice experiments are drawn from the analysis.

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arXiv2004

Shutters, Boxes, But No Paradoxes: Time Symmetry Puzzles in Quantum Theory

The ``N-Box Experiment'' is a much-discussed thought experiment in quantum mechanics. It is claimed by some authors that a single particle prepared in a superposition of N+1 box locations and which is subject to a final ``post-selection'' measurement corresponding to a different superposition can be said to have occupied ``with certainty'' N boxes during the intervening time. However, others have argued that under closer inspection, this surprising claim fails to hold. Aharonov and Vaidman have continued their advocacy of the claim in question by proposing a variation on the N-box experiment, in which the boxes are replaced by shutters and the pre- and post-selected particle is entangled with a photon. These authors argue that the resulting ``N-shutter experiment'' strengthens their original claim regarding the N-box experiment. It is argued in this paper that the apparently surprising features of this variation are no more robust than those of the N-box experiment and that it is not accurate to say that the particle is ``with certainty'' in all N shutters at any given time.

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arXiv2003

Weak Values and Consistent Histories in Quantum Theory

A relation is obtained between weak values of quantum observables and the consistency criterion for histories of quantum events. It is shown that ``strange'' weak values for projection operators (such as values less than zero) always correspond to inconsistent families of histories. It is argued that using the ABL rule to obtain probabilities for counterfactual measurements corresponding to those strange weak values gives inconsistent results. This problem is shown to be remedied by using the conditional weight, or pseudo-probability, obtained from the multiple-time application of Luders' Rule. It is argued that an assumption of reverse causality (a form of time symmetry) implies that weak values obtain, in a restricted sense, at the time of the weak measurement as well as at the time of post-selection. Finally, it is argued that weak values are more appropriately characterised as multiple-time amplitudes than expectation values, and as such can have little to say about counterfactual questions.

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