| Quasi-Newton methods have been widely studied for well-posed problems. This thesis provides more insight to the regularization properties of quasi-Newton methods; that is, the behavior of quasi-Newton methods on ill-posed problems. The four quasi-Newton methods considered are conjugate gradient least squares (CGLS), Barzilai-Borwein (BB), residual norm steepest descent (RNSD) and Landweber (LW). These regularization properties are studied in two ways. The first is by analyzing the so-called "filter factors" of the four names quasi-Newton methods. The second was is by observing the behavior of the residual on CGLS and RNSD. |
