(Apologies for cross posting) Hi All,
The next Foundations of Physics seminar (http://bit.ly/SydFop) is next week, Wednesday the 15th of September at 11:30am in the philosophy common room, Main Quad. Our speaker will be Ken Wharton presenting a talk entitled "Towards a physical interpretation of the Feynman path integral". Classical action principles and their quantum counterparts (e.g. the Feynman path integral) are tremendously useful mathematical tools with essentially no physical interpretation. The common claim that these tools are equivalent to dynamical equations is incorrect; no common interpretation can be shared by these two frameworks. (Furthermore, dynamical quantum theory has no accepted interpretation to fall back upon.) Action principles require two consecutive boundary conditions on any subsystem; one obvious physical interpretation is that these are imposed by consecutive external physical measurements. But this raises two immediate obstacles: 1) Least-action principles fail if the boundary conditions are not imposed in coordinate space, which seems to rule out measurements of quantities such as velocity; 2) Taken literally, the mathematics implies a retrocausal influence of the second measurement on unconstrained past parameters. Far from being serious roadbloacks, these "obstacles" actually point the way towards a novel and exciting interpretation of quantum theory, unavailable to a purely dynamical framework. (This seminar is the technical companion to last month's philosophy seminar.) Hope to see you all on Wednesday, Pete --- Peter Evans Centre for Time University of Sydney
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