0 M ay 2 00 2 Space - Time , General Covariance , Dirac - Bergmann Observables and Non - Inertial Frames
نویسنده
چکیده
Both particle physics and all the approaches to gravity make use of variational principles employing singular Lagrangians [1]. As a consequence the Euler-Lagrange equations cannot be put in normal form, some of them may be non independent equations (due to the contracted Bianchi identities) and a subset of the original configuration variables are left completely or partially indetermined. Moreover, even with reasonable boundary conditions at spatial infinity , the fact that often Euler-Lagrange equations, like in the case of Einstein’s equations, are not a hyperbolic system of partial differential equations implies a very difficult and nearly untractable initial value problem in configuration space. This state of affairs is a source of an endless number of problems at the ontological level for philosophers of science. Instead in physics we accept the fact that the historical development of particle theory and of general relativity has selected certain variational principles and certain configuration variables as the most convenient to englobe useful properties like locality, manifest Lorentz covariance, minimal couplings (the gauge principle), general co-
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تاریخ انتشار 2002