Orthogonal polynomials and semi-iterative methods for the Drazin-inverse solution of singular linear systems

Summary.

In this work we present a novel class of semi-iterative methods for the Drazin-inverse solution of singular linear systems, whether consistent or inconsistent. The matrices of these systems are allowed to have arbitrary index and arbitrary spectra in the complex plane. The methods we develop are based on orthogonal polynomials and can all be implemented by 4-term recursion relations independently of the index. We give all the computational details of the associated algorithms. We also give a complete convergence analysis for all methods.