Explaining Leibniz-equivalence as difference of non-inertial appearances: dis-solution of the Hole Argument and physical individuation of point-events

摘要

"The last remnant of physical objectivity of space-time" is disclosed in thecase of a continuous family of spatially non-compact models of generalrelativity (GR). The {\it physical individuation} of point-events is furnishedby the intrinsic degrees of freedom of the gravitational field, (viz, the {\itDirac observables}) that represent - as it were - the {\it ontic} part of themetric field. The physical role of the {\it epistemic} part (viz. the {\itgauge} variables) is likewise clarified as emboding the unavoidablenon-inertial aspects of GR. At the end the philosophical import of the {\itHole Argument} is substantially weakened and in fact the Argument itselfdis-solved, while a specific four-dimensional {\it holistic and structuralist}view of space-time, (called {\it point-structuralism}), emerges, includingelements common to the tradition of both {\it substantivalism} and {\itrelationism}. The observables of our models undergo real {\it temporal change}:this gives new evidence to the fact that statements like the {\it frozen-time}character of evolution, as other ontological claims about GR, are {\it modeldependent}. \medskip Forthcoming in Studies in History and Philosophy of ModernPhysics