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.
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.
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 book is an attempt to build a consistent relativistic quantum theory of interacting particles. In the first part of the book "Quantum electrodynamics" we follow rather traditional approach to particle physics. Our discussion proceeds systematically from the principle of relativity and postulates of quantum measurements to the renormalization in quantum electrodynamics. In the second part of the book "Quantum theory of particles" this traditional approach is reexamined. We find that formulas of special relativity should be modified to take into account particle interactions. We also suggest reinterpreting quantum field theory in the language of physical "dressed" particles. This formulation eliminates the need for renormalization and opens up a new way for studying dynamical and bound state properties of quantum interacting systems. The developed theory is applied to realistic physical objects and processes including the energy spectrum of the hydrogen atom, the decay law of moving unstable particles, and the electric field of relativistic electron beams. These results force us to take a fresh look at some core issues of modern particle theories, in particular, the Minkowski space-time unification, the role of quantum fields and renormalization as well as the alleged impossibility of action-at-a-distance. A new perspective on these issues is suggested. It can help to solve the old problem of theoretical physics -- a consistent unification of relativity and quantum mechanics.
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.
We consider the manner in which the spacetime manifold emerges from a quantum substratum through the transactional process, in which spacetime events and their connections are established. In this account, there is no background spacetime as is generally assumed in physical theorizing. Instead, the usual notion of a background spacetime is replaced by the quantum substratum, comprising quantum systems with nonvanishing rest mass. Rest mass corresponds to internal periodicities that function as internal clocks defining proper times, and in turn, inertial frames that are not themselves aspects of the spacetime manifold, but are pre-spacetime reference structures. Specific processes in the quantum substratum serve to distinguish absolute from relative motion.
What does it mean to say that an event is physically possible?One might say, in the spirit of everyday usage, that an event is physically possible if its occurrence is consistent with the laws of physics.But which laws of physics, starting from when?Here things get tricky.In a Laplacian universe governed by the fully-deterministic laws of classical electrodynamics and mechanics, exactly one future is consistent with any complete and precise specification of initial conditions.Given an incomplete, imprecise specification -the best that human observers can achieve, even in principle -many futures may appear to be physically possible, but only one of them actually is.In this kind of universe, our intuitive notion that many different outcomes of an experiment, for example, are physically possible is just an ignorancedriven delusion.Philosopher of physics Ruth Kastner's new book, The Transactional Interpretation of Quantum Mechanics, subtitled The Reality of Possibility, takes on this question of the meaning of physical possibility in the theoretical context defined by relativistic quantum field theory.Lest this seem daunting, be assured that this is a philosophical book; aside from Chapters 5 and 6 dealing with technical objections, it emphasizes ontological questions and employs the physics -all of which is clearly presented for the non-expert -as a way to raise them.The ontological questions that it raises, not just 'what is possibility?' but also 'what is actuality?' and 'what are space and time?' underlie not just physics but any theory of action.The Transactional Interpretation of Quantum Mechanics is, therefore, not just about the interpretation of quantum mechanics; it is about how 'nature makes its choice' in any circumstance, and how 'the actual arises from the potential' (205) as a result.After briefly introducing quantum theory and its various interpretations in Chapter 1, Kastner addresses, in Chapter 2, the essential preliminary question of what is to count as an acceptable scientific explanation.The divide between realists and instrumentalists about quantum theory -or between 'ontic ' and 'non-ontic' approaches