Padmanabhan, T.2012-03-012012-03-011990-05-21http://hdl.handle.net/11007/49In the upper and lower quadrants of flat spacetime, (±T>‖X‖) it is possible to introduce a system of coordinates in which the metric is explicitly time dependent. The conventional interpretation of quantum field theory, based on a Fock basis, cannot be implemented in a natural fashion in such coordinates. This difficulty suggests that quantum theory is covariant only for a subset of the coordinate transformations which are allowed in the classical theory.enPhysical interpretationQuantum field theoryNoninertial cooridnate SystemsArticle