In a nutshell, the measurement problem (MP) is this: given an interaction among quantum systems (such as an unstable atom, atoms comprising a Geiger Counter, atoms comprising a vial of gas, a cat, a friend of Wigner, etc.), which of those interactions constitutes ‘measurement,’ and why? During the past several decades, worries about the MP largely abated due to a popular sense that environmental decoherence took care of defining measurement in a unitary-only picture (even though there were numerous criticisms of that approach—e.g., Dugić and Jeknić-Dugić, 2012; Fields, 2010; Kastner, 2014c). However, there remains a marked lack of consensus, and recently there has been a resurgence of concern around this issue. Griffiths goes so far as to remark that:
“…the failure of quantum physicists to solve the measurement problem(s) is not only an intellectual embarrassment…but also a serious impediment to ongoing research in areas such as quantum information, where understanding microscopic quantum properties and how they depend on time is central to the enterprise.” (Griffiths, 2017)
However, perhaps the situation is not so dire. The present author would like to issue a gentle reminder that in fact there is a strong contender for solving the measurement problem in the Relativistic Transactional Interpretation (e.g., Kastner, 2012); which must be carefully distinguished from the original TI of Cramer (1986). Making that distinction clear is a major objective of the present work. First, however, it is well known that about a decade after Cramer’s original proposal, Maudlin (1996; 2nd ed. 2002) raised what appeared at the time to be a fatal objection to TI, and at that point a consensus developed that TI was not viable. What went largely unnoticed after Maudlin’s apparent disposal of TI were several publications demonstrating that the Maudlin objection was not in fact fatal (e.g., Marchildon, 2006; Kastner, 2006; Kastner 2012, Chapter 5). More importantly, however, is that the Maudlin objection is itself completely nonviable once the relativistic level of the transactional picture (RTI) is taken into account (Kastner 2017a).In view of the ongoing concern about the MP, this more recent nullification of the Maudlin objection is briefly reviewed herein, as well as the RTI solution to the measurement problem, including quantitative criteria for the processes of emission and absorption (Kastner 2012, Section 6.3.4). The latter were taken as primitive in the original Cramer account, apparently leading many researchers to discount it. The RTI development, which remedies these lacunae in the original TI, does not seem to have penetrated the community, since a recent review by L. Marchildon of Cramer’s latest book (Cramer 2016) completely omits it. Based only on the older version of TI presented in Cramer’s book, Marchildon expresses his worry that
“In an important sense, TI is not better defined than the the Copenhagen interpretation…in Cramer’s view, transactions play the part of collapse. True, they are somewhat immune to questions like “When does the collapse occur?,” but they require emitters and absorbers. These should be macroscopic (classical) objects if transactions are truly irreversible. The classical-quantum distinction or apparatus definition therefore plagues Cramer’s view just as it does Bohr’s or von Neumann’s.” (Marchildon 2017
)In fact, however, this is no longer the case. Emission and absorption are now quantitatively defined at the microscopic level, and the microscopic/macroscopic transition is quantitatively defined (although fundamentally indeterministic).1 So the issue leading to Marchildon’s assessment that TI fares no better than the Copenhagen Interpretation is precisely what has been resolved in the relativistic extension of TI (RTI). Since this is a serious misunderstanding of the present status of the transactional interpretation, I shall deal with that first (following a brief review of basic principles of TI), and shall subsequently review the nullification of the Maudlin challenge.
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