A consistent and near complete survey of the important progress made in the field over the last few years, with the main emphasis on the rigidity method and its applications. Among others, this monograph presents the most successful existence theorems known and construction methods for Galois extensions as well as solutions for embedding problems combined with a collection of the existing Galois realizations.

A consistent and near complete survey of the important progress made in the field over the last few years, with the main emphasis on the rigidity method and its applications. Among others, this monograph presents the most successful existence theorems known and construction methods for Galois extensions as well as solutions for embedding problems combined with a collection of the existing Galois realizations.

This book contains 22 lectures presented at the final conference of the Ger man research program (Schwerpunktprogramm) Algorithmic Number The ory and Algebra 1991-1997, sponsored by the Deutsche Forschungsgemein schaft. The purpose of this research program and of the meeting was to bring together developers of computer algebra software and researchers using com putational methods to gain insight into experimental problems and theoret ical questions in algebra and number theory. The book gives an overview on algorithmic methods and on results ob tained during this period. This includes survey articles on the main research projects within the program: * algorithmic number theory emphasizing class field theory, constructive Galois theory, computational aspects of modular forms and of Drinfeld modules * computational algebraic geometry including real quantifier elimination and real algebraic geometry, and invariant theory of finite groups * computational aspects of presentations and representations of groups, especially finite groups of Lie type and their Heeke algebras, and of the isomorphism problem in group theory. Some of the articles illustrate the current state of computer algebra sys tems and program packages developed with support by the research pro gram, such as KANT and LiDIA for algebraic number theory, SINGULAR, RED LOG and INVAR for commutative algebra and invariant theory respec tively, and GAP, SYSYPHOS and CHEVIE for group theory and representation theory.

The field of magnetic ultrathin films continues to be an exciting and rapidly expanding one, as demonstrated by recent advances in giant magnetoresistance (GMR), exchange-coupled structures, and magnetic anisotropies. New GMR materials, such as Mn perovskites, have been developed, and new effects, such as exchange coupling through semiconducting interlayers, non-Heisenberg-type coupling, perpendicular GMR, and hot electron spin-valve effects, have been discovered. This book from MRS offers an international perspective on the expanding activity, and features developments in both fundamental and applied areas. Topics include: novel magnetic nanostructures and applications; growth, structure and interfaces; interlayer coupling; magnetic anisotropy; ultrathin films, magnetic domains; giant magnetoresistance; colossal magnetoresistance; spectroscopies, magneto-optical properties and granular nanostructures.