  A general conformal mapping is proposed to design omnidirectional broadband
wave absorbers by transformation method. When applied to electromagnetic (EM)
and acoustic waves, the existing material parameters of the EM and acoustic
omnidirectional absorbers, which are previously obtained by Hamiltonian optics
and geometry acoustics, can be recovered. In addition, magnetic and
mass-density-controlled omnidirectional absorbers for EM and acoustic waves can
also be designed, respectively. We then apply the conformal mapping to design
an omnidirectional elastic wave absorber, the corresponding material
realization of such elastic absorber is also proposed and validated by
numerical simulation.
