Effects of rotation and gravity on superconductors

The internal electric fields, which are induced by rotation and the earth's gravitational field, produce in turn inhomogeneous changes in the transition temperatures of superconductors. We show that such changes are within the power of observation in the case of rotation. This effect of inhomogeneity, traditionally neglected in the theory of rotating superconductors, provides a basic distinction between rotation which is a real quantity and the vector potential (of a homogeneous magnetic field) which is defined only within an arbitrary choice of a gauge.