Jörg Liesen

The mathematical theory of Krylov subspace methods with a focus on solving systems of linear algebraic equations is given a detailed treatment in this principles-based book. Starting from the idea of projections, Krylov subspace methods are characterised by their orthogonality and minimisation properties. Projections onto highly nonlinear Krylov subspaces can be linked with the underlying problem of moments, and therefore Krylov subspace methods can be viewed as matching moments model

The mathematical theory of Krylov subspace methods with a focus on solving systems of linear algebraic equations is given a detailed treatment in this principles-based book. Starting from the idea of projections, Krylov subspace methods are characterised by their orthogonality and minimisation properties. Projections onto highly nonlinear Krylov subspaces can be linked with the underlying problem of moments, and therefore Krylov subspace methods can be viewed as matching moments model reduction. This allows enlightening reformulations of questions from matrix computations into the language of orthogonal polynomials, Gauss-Christoffel quadrature, continued fractions, and, more generally, of Vorobyev's method of moments. Using the concept of cyclic invariant subspaces, conditions are studied that allow the generation of orthogonal Krylov subspace bases via short recurrences. The results motivate the important practical distinction between Hermitian and non-Hermitian problems. Finally, the book thoroughly addresses the computational cost while using Krylov subspace methods. The investigation includes effects of finite precision arithmetic and focuses on the method of conjugate gradients (CG) and generalised minimal residuals (GMRES) as major examples. There is an emphasis on the way algebraic computations must always be considered in the context of solving real-world problems, where the mathematical modelling, discretisation and computation cannot be separated from each other. The book also underlines the importance of the historical context and demonstrates that knowledge of early developments can play an important role in understanding and resolving very recent computational problems. Many extensive historical notes are included as an inherent part of the text as well as the formulation of some omitted issues and challenges which need to be addressed in future work. This book is applicable to a wide variety of graduate courses on Krylov subspace methods and related subjects, as well as benefiting those interested in the history of mathematics.

This self-contained textbook, now in a thoroughly revised and expanded second edition, takes a matrix-oriented approach to Linear Algebra. It presents a complete theory, including all details and proofs, culminating in the Jordan canonical form and its derivation. Throughout, the book emphasizes the practical applicability of results. It therefore also covers special topics in Applied Linear Algebra, such as matrix functions, the singular value decomposition, the Kronecker product, and linear matrix equations. New to this edition are topics such as the Frobenius canonical form and a more detailed treatment of infinite-dimensional vector spaces, along with many additional exercises. The book’s matrix-oriented approach enhances intuition and simplifies abstract concepts, making them easier to understand and to apply in real-world scenarios. Key applications are illustrated through detailed examples. Additionally, several "MATLAB Minutes" allow students to explore concepts and results through computational experiments, supported by a brief introduction to MATLAB fundamentals. Together with over 380 exercises, this encourages active engagement with the material.

Dieses Lehrbuch über die Lineare Algebra deckt den gesamten Stoff der zweisemestrigen Grundvorlesung ab. Seine anschauliche und konsequent matrizenorientierte Herangehensweise ermöglicht Studierenden ein intuitives Verständnis der abstrakten Objekte. Die im Buch präsentierten vielfältigen Anwendungen und Beispiele motivieren Studierende zur intensiven Auseinandersetzung mit der Linearen Algebra als leistungsfähiges mathematisches Werkzeug. In vielen „MATLAB-Minuten“ können sich Studierende wichtige Sätze und Konzepte am Rechner erarbeiten. Alle notwendigen Vorkenntnisse werden in einer MATLAB-Kurzeinführung erläutert. Das Buch enthält zudem über 350 Übungsaufgaben, die das Erlernen des Stoffes unterstützen. Interessierte Studierende finden darüber hinaus historische Notizen zur Entwicklung des Gebiets. Für diese vierte Auflage wurde das Buch durchgesehen und ergänzt. Zu den Ergänzungen gehören insbesondere die genauere Betrachtung von Projektionen, die Herleitung der Frobenius-Normalform von Endomorphismen sowie der Beweis eines wichtigen Satzes über Matrixfunktionen basierend auf der Lösung des Hermite-Interpolationsproblems. Hinzugekommen sind außerdem mehr als 20 neue Aufgaben sowie Begriffe wie der Bidualraum, derogatorische Matrizen, Invariantenteiler und Isometrien. Der übersichtliche Aufbau und das bewährte Konzept des Lehrbuchs wurden beibehalten.

This self-contained textbook takes a matrix-oriented approach to linear algebra and presents a complete theory, including all details and proofs, culminating in the Jordan canonical form and its proof. Throughout the development, the applicability of the results is highlighted. Additionally, the book presents special topics from applied linear algebra including matrix functions, the singular value decomposition, the Kronecker product and linear matrix equations.The matrix-oriented approach to linear algebra leads to a better intuition and a deeper understanding of the abstract concepts, and therefore simplifies their use in real world applications. Some of these applications are presented in detailed examples. In several ‘MATLAB-Minutes’ students can comprehend the concepts and results using computational experiments. Necessary basics for the use of MATLAB are presented in a short introduction. Students can also actively work with the material and practice their mathematical skills in more than 300 exercises.