A high-order compact finite difference scheme for a fully nonlinear
parabolic differential equation is analyzed. The equation arises in the
modeling of option prices in financial markets with transaction costs.
It is shown that the finite difference solution converges locally
uniformly to the unique viscosity solution of the continuous equation.
The proof is based on a careful study of the discretization matrices and on
an abstract convergence result due to Barles and Souganides.