Global versus Local -- Mach's Principle versus the Equivalence Principle

摘要

The equivalence principle is the conceptual basis for general relativity. Incontrast Mach's principle, although said to have been influential on Einsteinin his formulation of general relativity, has not been shown to be central tothe structure of general relativity. In this essay we suggest that the quantumeffects of Hawking and Unruh radiation are a manifestation of a {\it thermal}Mach's principle, where the local thermodynamic properties of the system aredetermined by the non-local structure of the quantum fields which determine thevacuum of a given spacetime. By comparing Hawking and Unruh temperatures forthe same local acceleration we find a violation of the Einstein elevatorversion of the equivalence principle, which vanishes in the limit that thehorizon is approached.