Many-body wave scattering problems in the case of small scatterers
  Formulas are derived for solutions of many-body wave scattering problems by small particles in the case of acoustically soft, hard, and impedance particles embedded in an inhomogeneous medium. The case of transmission (interface) boundary conditions is also studied in detail. The limiting case is considered, when the size $a$ of small particles tends to zero while their number tends to infinity at a suitable rate. Equations for the limiting effective (self-consistent) field in the medium are derived. The theory is based on a study of integral equations and asymptotics of their solutions as $a\to 0$. The case of wave scattering by many small particles embedded in an inhomogeneous medium is also studied. 
A. G. Ramm
math-ph cond-mat.mtrl-sci math.AP math.MP physics.class-ph