Two-channel resonance scattering of waves and particles by point and planar defects

The shattering of a wave (quasiparticle) with a dispersion curve consisting of two quadratic branches by a planar defect is discussed. The analog of s uch a process is the scattering of a similar wave (quasiparticle) in a one- dimensional system by a point defect. It is shown that even when the defect is passive, i.e., has no internal degrees of freedom, scattering may becom e resonant. The physical explanation of this effect is that a wave with a l ower-lying spectrum scattered by the defect is in resonance with a localize d (bound) state emerging because of the interaction between the defect and a wave with a higher-lying spectrum. (C) 1999 American Institute of Physics . [S1063-7761(99)02501-9].