Preface: numerical and applied linear algebra

This special issue of Advances in Computational Mathematics is devoted to Numerical and Applied Linear Algebra, which is an important area of mathematics and a fundamental part of engineering and computational science problems. One of the main tools of this area is matrices, properties of which are studied and computations of them are performed, with different methods, in a variety of applications. The special issue contains 12 papers reflecting some specialized themes on numerical and applied linear algebra and at the same time gives an idea of the broadness of this area, which has grown spectacularly in the last decades. The work entitled “Structured linear algebra problems in adaptive optics imaging”, by Johnathan M. Bardsley, Sarah Knepper, and James Nagyy, discusses an adaptive optics image problem to remove the effects of the phase error. For solving the Kronecker product structured, rank-deficient least-squares problem on the Fried geometry, two types of regularization are considered: a truncated singular value decomposition type and a Tikhonov type. The paper “On the numerical solution of large-scale sparse discrete-time Riccati equations”, by Peter Benner and Heike Faßbender, deals with the numerical solution of discrete algebraic Riccati equations. Since the systems considered are large-scale, the solution process for the computation of a