Boundary value problems for systems of difference equations associated with systems of second-order ordinary differential equations

we study difference equations which arise as discrete approximations to two-point boundary value problems for systems of second-order ordinary differential equations. We formulate conditions which guarantee a priori bounds on first differences of solutions to the discretized problem, We establish existence results for solutions to the discretized boundary value problems subject to nonlinear boundary conditions. We apply our results to show that solutions to the discrete problem converge to solutions of the continuous problem in an aggregate sense. @ 2002 Elsevier Science Ltd. All rights reserved. Keywords-Discrete Nagumo conditions, Boundary value problem, Systems of difference equations, Brouwer degree, Second-order systems of ordinary differential equations.