Nyström type methods for Fredholm integral equations with weak singularities (Q977403)

Nyström type methods are constructed and justified for a class of Fredholm integral equations of the second kind \[ u(x)=\int_0^1[a(x,y)|x-y|^{-v}+b(x,y)] u(y)dy=f(x), \;\;0\leq x\leq 1, \] where \(0<v<1,\) functions \(a(x,y)\) and \(b(x,y)\) may have boundary singularities with respect to \(y:\) \[ a(x,y),b(x,y)\in C^m([0,1]\times (0,1)), m\in N_0, \] \[ \left|\left(\frac{\partial}{\partial x} \right)^k \left( \frac{\partial}{\partial y} \right)^l a(x,y) \right|\leq cy^{-\lambda_0-l}(1-y)^{-\lambda_1-l} \] \[ \left|\left(\frac{\partial}{\partial x} \right)^k \left( \frac{\partial}{\partial y} \right)^l b(x,y)\right|\leq c y ^{-\mu_0-l}(1-y)^{-\mu_1-l} \] where \((x,y)\in [0,1]\times (0,1),\;\;k,l\in N_0,\;\;k+l\leq m,\) \(\lambda_0,\lambda_1,\mu_0,\mu_1\in R,\) \(\mu_0,\mu_1<1,\) \(N_0={0}\cup N,\) \(N={1,2,\dots}, R\in (-\infty,\infty)\). The proposed approach is based on a suitable smoothing change of variables and product integration techniques. Global convergence estimates are derived and a collection of numerical results is given.