3  Integral Equation Formulations of the Eigenvalue Problems

In this section the homogeneous boundary condition is enforced on the integral equation formulations in order to obtain the integral equations for the Helmholtz eigenvalue problem. The ensuing indirect integral equation reformulation of the Helmholtz eigenvalue problem with the general boundary condition (2) is
a(p) { Lk m}S (p)+ b(p) æ
è
{ Mkt m}S (p)+ c(p) m(p) ö
ø
= 0      (p Î S)
which arises through the substitution of (5) and (6) into (2) where s has been replaced by m in (5)-(6).
The indirect formulations for the Dirichlet and Neumann eigenproblems are as follows:
Dirichlet
    { Lk m}S (p) = 0      (p Î S) ,
Neumann
      { Mkt m}S (p)+ c(p) m(p) = 0      (p Î S) .
The direct formulation for the Dirichlet and Neumann eigenproblems are as follows:
Dirichlet
     { Lk m}S (p) = 0 ,    (p Î S)
Neumann
       { Mk m}S (p) + c(p) m(p) = 0 ,    (p Î S)
where j has been replaced by m in (7)-(8).