Gradient method for nondensely defined closed unbounded linear operators

Sung J. Lee, M. Zuhair Nashed
1983 Proceedings of the American Mathematical Society  
The paper establishes the convergence of the steepest descent method for least-squares solutions of operator equations in Hubert spaces for any (nondensely defined, unbounded) closed linear operator with closed range. This is done by using a graph topology, an explicit graph topology adjoint, and existing theory of steepest descent for bounded linear operators.
doi:10.1090/s0002-9939-1983-0699408-9 fatcat:6ibk3lxdobh2rnvisgiwp5gxgy