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Cambridge University Press eBooks

The Relativistic Transactional Interpretation

Ruth E. Kastner

Published Apr 22, 2022• 0 citations
Publisher

Abstract

In this chapter, the fully relativistic form of the transactional interpretation is presented in terms of the Davies quantum direct-action theory (QDAT). Aspects of the QDAT are clarified and reinterpreted. Specifically, the coupling constant (charge) is identified as the basic amplitude for the generation of offers and confirmations, which herald the onset of non-unitarity constituting the measurement interaction. Thus, the QDAT has both unitary and non-unitary processes, the former being force-type interactions mediated by virtual photons and the latter being radiative processes in which energy is transferred via real photons. The nature of the so-called light-tight box condition for the quantum level is clarified, and it is noted that no particular cosmological structure is required for this to be fulfilled. It is argued that RTI has advantages over another relativistic collapse-type theory, rGRWf.

DOI
10.1017/9781108907538.006

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•Jan 1, 2014•9 citations
In this chapter, the fully relativistic form of the transactional interpretation is presented in terms of the Davies quantum direct-action theory (QDAT). Aspects of the QDAT are clarified and reinterpreted. Specifically, the coupling constant (charge) is identified as the basic amplitude for the generation of offers and confirmations, which herald the onset of non-unitarity constituting the measurement interaction. Thus, the QDAT has both unitary and non-unitary processes, the former being force-type interactions mediated by virtual photons and the latter being radiative processes in which energy is transferred via real photons. The nature of the so-called light-tight box condition for the quantum level is clarified, and it is noted that no particular cosmological structure is required for this to be fulfilled. It is argued that RTI has advantages over another relativistic collapse-type theory, rGRWf.
This paper presents key aspects of the quantum relativistic direct-action theory that underlies the Relativistic Transactional Interpretation. It notes some crucial ways in which traditional interpretations of the direct-action theory have impeded progress in developing its quantum counterpart. Specifically, (1) the so-called 'light tight box' condition is re-examined and it is shown that the quantum version of this condition is much less restrictive than has long been assumed; and (2) the notion of a 'real photon' is disambiguated and revised to take into account that real (on-shell) photons are indeed both emitted and absorbed and therefore have finite lifetimes. Also discussed is the manner in which real, physical non-unitarity naturally arises in the quantum direct-action theory of fields, such that the measurement transition can be clearly defined from within the theory, without reference to external observers and without any need to modify quantum theory itself. It is shown that field quantization arises from the non-unitary interaction.
The Transactional Interpretation has been subject at various times to a challenge based on a type of thought experiment first proposed by Maudlin. It has been argued by several authors that such experiments do not in fact constitute a significant problem for the transactional picture. The purpose of this work is to point out that, when the relativistic level of the interpretation is considered, Maudlin-type challenges cannot even be mounted, since the putative 'slow-moving offer wave,' taken as subject to contingent confirmation, does not exist. This is a consequence of the Davies relativistic quantum-mechanical version of the direct-action theory together with the asymmetry between fermionic field sources and bosonic fields. The Maudlin challenge therefore evaporates completely when the relativistic level of the theory is taken into account.
In view of a resurgence of concern about the measurement problem, it is pointed out that the Relativistic Transactional Interpretation (RTI) remedies issues previously considered as drawbacks or refutations of the original TI. Specifically, once one takes into account relativistic processes that are not representable at the non-relativistic level (such as particle creation and annihilation, and virtual propagation), absorption is quantitatively defined in unambiguous physical terms. In addition, specifics of the relativistic transactional model demonstrate that the Maudlin `contingent absorber' challenge to the original TI cannot even be mounted: basic features of established relativistic field theories (in particular, the asymmetry between field sources and the bosonic fields, and the fact that slow-moving bound states, such as atoms, are not offer waves) dictate that the `slow-moving offer wave' required for the challenge scenario cannot exist. It is concluded that issues previously considered obstacles for TI are no longer legitimately viewed as such, and that reconsideration of the transactional picture is warranted in connection with solving the measurement problem.
In this chapter, the relativistic transactional interpretation (RTI) is shown to completely nullify the Maudlin objection (a type of contingent absorber experiment) to the original, nonrelativistic TI. RTI is applied to some prominent quantum “paradoxes” such as the quantum eraser and the Frauchiger–Renner paradox and shown to resolve these. In addition, RTI derives standard decoherence results while also providing an account of concrete measurement outcomes that is missing in standard (unitary-only) decoherence theory.