In the present paper we consider discrete versions of the modified projection methods for solving a Urysohn integral equation with a kernel of the type of Green's function. For r ≥ 0, a space of piecewise polynomials of degree ≤ r with respect to an uniform partition is chosen to be the approximating space. We define a discrete orthogonal projection onto this space and replace the Urysohn integral operator by a Nyström approximation. The order of convergence which we obtain for the discrete version indicates the choice of numerical quadrature which preserves the orders of convergence in the continuous modified projection methods. Numerical results are given for a specific example.

In the present paper we consider discrete versions of the modified projection methods for solving a Urysohn integral equation with a kernel of the type of Green’s function. For r ≥ 0, a space of piecewise polynomials of degree ≤ r with respect to an uniform partition is chosen to be the approximating space. We define a discrete orthogonal projection onto this space and replace the Urysohn integral operator by a Nyström approximation. The order of convergence which we obtain for the discrete version indicates the choice of numerical quadrature which preserves the orders of convergence in the continuous modified projection methods. Numerical results are given for a specific example.

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Consider a linear operator equation x − Kx = f , where f is given and K is a Fredholm integral operator with a Green's function type kernel defined on C[0, 1]. For r ≥ 1, we employ the interpolatory projection at 2r + 1 collocation points (not necessarily Gauss points) onto a space of piecewise polynomials of degree ≤ 2r with respect to a uniform partition of [0, 1]. Previous researchers have established that the iteration in case of the collocation method improves the order of convergence by projection methods and its variants in the case of smooth kernel with piecewise polynomials of even degree only. In this article, we demonstrate the improvement in order of convergence by modified collocation method when the kernel is of Green's function type.

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