A coordinate-free formulation is established for (semi) classical particle-field interactions. The exterior language of spacetime chains and De-Rham currents enables the description to include extended strings and membranes besides point particles. Treating physical fields in terms of sections of particular bundles, a unified account of interactions is presented in terms of an intrinsic action principle on a bundle of jets over spacetime. The theory is illustrated by considering the specific model of point particles with intrinsic spin covariantly coupled to theU(1) (...) andSL(2, C) connections describing the electromagnetic and gravitational fields, respectively. The notion of dual spin is examined in this context and coupled equations for this particle-field system are explicitly derived in a local chart. Attention is drawn to the global implications of the theory. (shrink)

The Battle of Drepana in 249 b.c. marks the most significant defeat of Roman naval forces at the hands of their Carthaginian opponents during the First Punic War. Attempting to take the Punic fleet in the harbour of Drepana by surprise, the consul P. Claudius Pulcher sailed with his ships from Lilybaeum about midnight, and reached Drepana at dawn. Yet, owing to swift and level-headed counter-measures taken by the Punic commander, Adherbal, the unfolding fight – partly in the harbour, mostly (...) off the shore – turned into a fiasco for the Romans. The consul got away; he returned to Rome, where the Senate instructed him to appoint a dictator. How soon he returned, and by what route, is the question. (shrink)

least this was his later view. He had begun with the more obvious but more naive view that need was the key to the process and that removal of the need ...

Quantum theory does not only predict probabilities, but also relative phases for any experiment, that involves measurements of an ensemble of systems at different moments of time. We argue, that any operational formulation of quantum theory needs an algebra of observables and an object that incorporates the information about relative phases and probabilities. The latter is the (de)coherence functional, introduced by the consistent histories approach to quantum theory. The acceptance of relative phases as a primitive ingredient of any quantum theory, (...) liberates us from the need to use a Hilbert space and non-commutative observables. It is shown, that quantum phenomena are adequately described by a theory of relative phases and non-additive probabilities on the classical phase space. The only difference lies on the type of observables that correspond to sharp measurements. This class of theories does not suffer from the consequences of Bell's theorem (it is not a theory of Kolmogorov probabilities) and Kochen–Specker's theorem (it has distributive “logic”). We discuss its predictability properties, the meaning of the classical limit and attempt to see if it can be experimentally distinguished from standard quantum theory. Our construction is operational and statistical, in the spirit of Copenhagen, but makes plausible the existence of a realist, geometric theory for individual quantum systems. (shrink)

Note de présentation du Dictionnaire de Spiritualité, ascétique et mystique, doctrine et histoire dont les premiers volumes ont été édités en 1937 et qui s'achève avec les tables publiées en 1995.