Volume 6, Issue 2, pages 24-39
Ruth E. Kastner earned her M.S. in Physics and Ph.D. in Philosophy (History and Philosophy of Science) and the University of Maryland, College Park (1999). She has taught a variety of philosophy and physics courses throughout the Baltimore-Washington corridor, and currently is a member of the Foundations of Physics group at UMCP. She is also an Affiliate of the physics department at the SUNY Albany campus. She specializes in time-symmetry and the Transactional Interpretation (TI) of quantum mechanics, and in particular has extended the original TI of John Cramer to the relativistic domain. Her interests and publications include topics in thermodynamics and statistical mechanics, quantum ontology, counterfactuals, spacetime emergence, and free will. She is the author of two books: The Transactional Interpretation of Quantum Mechanics: The Reality of Possibility (Cambridge, 2012) and Understanding Our Unseen Reality: Solving Quantum Riddles (Imperial College Press, 2015). She is also an Editor of the collected volume Quantum Structural Studies (World Scientific, 2016).
This paper presents an analysis of decoherence resulting from the physically real non-unitarity, or ‘objective reduction,’ that occurs in the Transactional Interpretation (TI). Two distinct aspects of the decoherence process are identified and disambiguated; specifically, (i) the resolution of the basic measurement interaction with respect to the observable under study, and (ii) the effect on the measured system of repetition of the measurement interaction. It is shown that the measurement interaction as described in TI leads naturally to the same quantitative expression for the decoherence functional as in the standard unitary-only account. However, unlike in the unitary-only approach, under TI, the reduced density operator for the measured system can legitimately be interpreted as representing the occurrence of an actual measurement result.