A superconsistent Chebyshev collocation method for second-order differential operators

A standard way to approximate the model problem -u = f, with u(+/-1) = 0, is to collocate the differential equation at the zeros of T-n': x(i), i = 1,..., n - 1, having denoted by T,, the nth Chebyshev polynomial. We introduce an alternative set of collocation nodes z(i), i = 1,..., n - 1, which will provide better numerical performances. The approximated solution is still computed at the nodes {x(i)}, but the equation is required to be satisfied at the new nodes {z(i)}, which are determined by asking an extra degree of consistency in the discretization of the differential operator.