This volume contains 39 of the papers presented at the Sixth European Multigrid Conference, held in Gent, Belgium, September 27-30, 1999. The topics treated at the conference cover all aspects of Multigrid Methods: theory, analysis, computer implementation, applications in the fields of physics, chemistry, fluid mechanics, structural mechanics and magnetism.

This volume contains a selection from the papers presented at the Fourth European Multigrid Conference, held in Amsterdam, July 6-9,1993. There were 78 registered participants from 14 different countries, and 56 presentations were given. The preceding conferences in this series were held in Cologne (1981, 1985) and in Bonn (1990). Also at the other side of the Atlantic special multigrid conferences are held regularly, at intervals of two years, always in Copper Mountain, Colorado, US. The Sixth Copper Mountain Conference on Multigrid Methods took place in April, 1993. Circumstances prevented us from putting a larger time interval between the Copper and Amsterdam meetings. The next European meeting is planned in 1996, a year later than the next Copper Meeting. When the first multigrid conference was held in 1981 there was no doubt about the usefulness of a conference dedicated specially to multigrid, because multigrid was a new and relatively unexplored subject, still in a pioneering stage, and pursued by specialists. The past twenty years have shown a rapid growth in theoretical understanding, useful applications and widespread acceptance of multi grid in the applied disciplines. Hence, one might ask whether there is still a need today for conferences specially dedicated to multigrid. The general consensus is that the answer is affirmative. New issues have arisen that are best addressed or need also be addressed from a special multigrid point of view.

A thoughtful consideration of the current level of development of multigrid methods, this volume is a carefully edited collection of papers that addresses its topic on several levels. The first three chapters orient the reader who is familiar with standard numerical techniques to multigrid methods, first by discussing multigrid in the context of standard techniques, second by detailing the mechanics of use of the method, and third by applying the basic method to some current problems in fluid dynamics. The fourth chapter provides a unified development, complete with theory, of algebraic multigrid (AMG), which is a linear equation solver based on multigrid principles. The last chapter is an ambitious development of a very general theory of multigrid methods for variationally posed problems. Included as an appendix is the latest edition of the Multigrid Bibliography, an attempted compilation of all existing research publications on multigrid.

These proceedings contain a selection of papers presented at the Third European Conference on Multigrid Methods which was held in Bonn on October 1-4, 1990. Following conferences in 1981 and 1985, a platform for the presentation of new Multigrid results was provided for a third time. Multigrid methods no longer have problems being accepted by numerical analysts and users of numerical methods; on the contrary, they have been further developed in such a successful way that they have penetrated a variety of new fields of application. The high number of 154 participants from 18 countries and 76 presented papers show the need to continue the series of the European Multigrid Conferences. The papers of this volume give a survey on the current Multigrid situation; in particular, they correspond to those fields where new developments can be observed. For example, se veral papers study the appropriate treatment of time dependent problems. Improvements can also be noticed in the Multigrid approach for semiconductor equations. The field of parallel Multigrid variants, having been started at the second European Multigrid Conference, is now at the centre of interest.

Multigrid methods are among the most efficient iterative methods for the solution of linear systems which arise in many large scale scientific calculations. Every researcher working with the numerical solution of partial differential equations should at least be familiar with this powerful technique. This invaluable book presents results concerning the rates of convergence of multigrid iterations.

rd This book presents a collection of selected contributions presented at the 3 International Workshop on Scientific Computing in Electrical Engineering, SCEE-2000, which took place in Warnemiinde, Germany, from August 20 to 23, 2000. Nearly hundred scientists and engineers from thirteen countries gathered in Warnemiinde to participate in the conference. Rostock Univer sity, the oldest university in Northern Europe founded in 1419, hosted the conference. This workshop followed two earlier workshops held 1997 at the Darmstadt University of Technology and 1998 at Weierstrass Institute for Applied Anal ysis and Stochastics in Berlin under the auspices ofthe German Mathematical Society. These workshops aimed at bringing together two scientific communi ties: applied mathematicians and electrical engineers who do research in the field of scientific computing in electrical engineering. This, of course, is a wide field, which is why it was decided to concentrate on selected major topics. The workshop in Darmstadt, which was organized by Michael Giinther from the Mathematics Department and Ursula van Rienen from the Department of Electrical Engineering and Information Technology,brought together more than hundred scientists interested in numerical methods for the simulation of circuits and electromagnetic fields. This was a great success. Voices coming from the participants suggested that it was time to bring these communities together in order to get to know each other, to discuss mutual interests and to start cooperative work. A collection of selected contributions appeared in 'Surveys on Mathematics for Industry', Vol.8, No. 3-4 and Vol.9, No.2, 1999.

This proceedings volume covers the broad interdisciplinary spectrum of scientific computing and presents recent advances in theory, development of methods, and applications in practice.

The focus of this book is concerned with the modeling and precise numerical simulation of mechatronic sensors and actuators. These sensors, actuators, and sensor - actuator systems are based on the mutual interaction of the me chanical field with a magnetic, an electrostatic or an electromagnetic field. In many cases the transducer is immersed in an acoustic fluid and the solid-fluid coupling has to be taken into account. Examples are: piezoelectric stack ac tuators for common-rail injection systems, micromachined electrostatic gyro sensors used in stabilizing systems of automobiles or ultrasonic imaging sys tems for medical diagnostics. The modeling of mechatronic sensors and actuators leads to so-called mul tifield problems, which are described by a system of nonlinear partial dif ferential equations. Such systems can not be solved analytically and, thus a numerical calculation scheme has to be applied. The schemes discussed in this book are based on the finite element (FE) method, which is capable of efficiently solving the partial differential equations. The complexity of the simulation of multifield problems consists in the simultaneous computation of the involved single fields as well as in the coupling terms, which intro duce additional nonlinearities. Examples are: moving conductive (electrically charged) body within a magnetic (an electric) field, electromagnetic and/or electrostatic forces.

It was about 1985 when both of the authors started their work using multigrid methods for process simulation problems. This happened in dependent from each other, with a completely different background and different intentions in mind. At this time, some important monographs appeared or have been in preparation. There are the three "classical" ones, from our point of view: the so-called "1984 Guide" [12J by Brandt, the "Multi-Grid Methods and Applications" [49J by Hackbusch and the so-called "Fundamentals" [132J by Stiiben and Trottenberg. Stiiben and Trottenberg in [132J state a "delayed acceptance, resent ments" with respect to multigrid algorithms. They complain: "Nevertheless, even today's situation is still unsatisfactory in several respects. If this is true for the development of standard methods, it applies all the more to the area of really difficult, complex applications." In spite of all the above mentioned publications and without ignoring important theoretical and practical improvements of multigrid, this situa tion has not yet changed dramatically. This statement is made under the condition that a numerical principle like multigrid is "accepted", if there exist "professional" programs for research and production purposes. "Professional" in this context stands for "solving complex technical prob lems in an industrial environment by a large community of users". Such a use demands not only for fast solution methods but also requires a high robustness with respect to the physical parameters of the problem.