Squeezing of open boundaries by Maxwell-consistent real coordinate transformation

To simulate open boundaries within finite computation domain, real-function coordinate transformation in the framework of generally covariant formulation of Maxwell equations is proposed. The mapping--realized with arctangent function here--has a transparent geometric meaning of pure squeezing of space, is admissible by classical electrodynamics, does not introduce artificially lossy layers (or `lossy coordinates') to absorb outgoing radiation nor leads to non-Maxwellian fields. At the same time, like for anisotropic perfectly matched layers, no modification (except for transformation of material tensors) is needed to existing nearest-neighbor computation schemes, which makes it well suited for parallel computing implementation.