Volume 4, Issue 3, pages 210-222
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).
The Transactional Interpretation offers a solution to the measurement problem by identifying specific physical conditions precipitating the non-unitary `measurement transition’ of von Neumann. Specifically, the transition occurs as a result of absorber response (a process lacking in the standard approach to the theory). The purpose of this Letter is to make clear that, despite recent claims to the contrary, the concepts of `absorber’ and `absorber response,’ as well as the process of absorption, are physically and quantitatively well-defined in the transactional picture. In addition, the Born Rule is explicitly derived for radiative processes.