  We extend the transformation-optics paradigm to a complex spatial coordinate
domain, in order to deal with electromagnetic metamaterials characterized by
balanced loss and gain, giving special emphasis to parity-time (PT) symmetric
metamaterials. We apply this general theory to complex-source-point radiation
and anisotropic transmission resonances, illustrating the capability and
potentials of our approach in terms of systematic design, analytical modeling
and physical insights into complex-coordinate wave-objects and resonant states.

Optics