34,023 research outputs found
Time reversal in classical electromagnetism
Richard Feynman has claimed that anti-particles are nothing but particles `propagating backwards in time'; that time reversing a particle state always turns it into the corresponding anti-particle state. According to standard quantum eld theory textbooks this is not so: time reversal does not turn particles into anti-particles. Feynman's view is interesting because, in particular, it suggests a nonstandard, and possibly illuminating, interpretation of the CPT theorem. In this paper, we explore a classical analog of Feynman's view, in the context of the recent debate between David Albert and David Malament over time reversal in classical electromagnetism
Philosophical problems of space-time theories
I present a discussion of some open issues in the philosophy of space-time
theories. Emphasis is put on the ontological nature of space and time, the
relation between determinism and predictability, the origin of irreversible
processes in an expanding Universe, and the compatibility of relativity and
quantum mechanics. In particular, I argue for a Parmenidean view of time and
change, I make clear the difference between ontological determinism and
predictability, propose that the origin of the asymmetry observed in physical
processes is related to the existence of cosmological horizons, and present a
non-local concept of causality that can accommodate both special relativity and
quantum entanglement.Comment: 20 pages, small changes to match the version published by Cambridge
University Pres
Bayesian Probabilities and the Histories Algebra
We attempt a justification of a generalisation of the consistent histories
programme using a notion of probability that is valid for all complete sets of
history propositions. This consists of introducing Cox's axioms of probability
theory and showing that our candidate notion of probability obeys them. We also
give a generalisation of Bayes' theorem and comment upon how Bayesianism should
be useful for the quantum gravity/cosmology programmes.Comment: 10 pages, accepted by Int. J. Theo. Phys. Feb 200
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