  Neither BCS theory nor London theory contain any charge asymmetry. However it
is an experimental fact that a rotating superconductor always exhibits a
magnetic field parallel, never antiparallel, to its angular velocity. This and
several other experimental observations point to a special role of charge
asymmetry in superconductivity, which is the foundation of the theory of hole
superconductivity. The theory describes heavy dressed {\it positive} hole
carriers in the normal state that undress by pairing and become light undressed
{\it negative} electron carriers in the superconducting state.
Superconductivity is driven by kinetic energy lowering rather than by
electron-phonon coupling as in BCS. In quantum mechanics, kinetic energy
lowering is associated with $expansion$ of the electronic wave function, and
hence we predict: (1) Superconductors expel $negative$ charge from their
interior which consequently becomes $positively$ charged; (2) Macroscopic
electrostatic fields exist in the interior of superconductors always, and in
certain cases also outside near the surface; (3) Macroscopic spin currents
exist in the superconducting state; (4) Superconductors are 'rigid' with
respect to their response to applied longitudinal electric fields. These
predictions apply to all superconductors and are testable but are as yet
untested. The theory predicts highest $T_c$'s for materials for which normal
state transport occurs through $(positive)$ holes in $negatively$ charged
anions.
