reflectionless การใช้

One caveat with perfectly matched layers is that they are only reflectionless for the " exact ", continuous wave equation.
The solitons of the Novikov Veselov equation at positive energy are transparent potentials, similarly to the one-dimensional case ( in which solitons are reflectionless potentials ).
As a consequence, the PML approach is no longer valid ( no longer reflectionless at infinite resolution ) in the case of periodic media ( e . g . photonic crystals or phononic crystals ) or even simply a waveguide that enters the boundary at an oblique angle.
In general, any absorber, whether PML or not, is reflectionless in the limit where it turns on sufficiently gradually ( and the absorbing layer becomes thicker ), but in a discretized system the benefit of PML is to reduce the finite-thickness " transition " reflection by many orders of magnitude compared to a simple isotropic absorption coefficient.