Iteration theory has its roots in the operation of substituting functions into itself. This has led to questions like that of the behaviour of functions by repeating this substitution and when the number of iterations tends to infinity. The terms 'orbit' and 'chaos' appropriately describe this behaviour. Dynamical systems and the theory of functional equations play important roles in this field.

The journal aequationes mathematicae publishes papers in pure and applied mathematics and, in particular, articles on functional equations, combinatorics and dynamical systems. Its 50th volume appears in 1995. To mark this occasion, we are publishing in book form a repre sentative collection of outstanding survey papers assembled for our anniversary issue of aequationes mathematicae. The articles by Quackenbush, Targonski and Moszner discuss composition of functions from different points of view: universal algebra, dynamical systems (iteration) and functional equa tions. The Ono-Robbins-Wahl and the Vince papers, on number theory and tiles, respectively, are thematically linked by lattices. Combinatorics, in turn, links the Vince paper with that of Tutte, whose subject is chromatic sums, its tools differential and functional equations. The Paganoni-Ratz and the Forti papers deal with conditional functional equations and with the related topic of stability. Applications to the social and behavioral sciences, in particular to aggregation (and some theory) are presented in the paper by J. Aczel. The aim of the collection is to survey selected fields of current interest. We trust that it will be useful and informative for researchers, teachers, graduate and advanced undergraduate stu dents of mathematics, and for those interested in applications in related fields. lanDs Aczel Aequationes Mathematicae 50 (1995) 1 0001-9054/95/020001-01 $1.50 + 0.20/0 University of Waterloo © 1995 Birkhiiuser Verlag, Basel Editorial Volume 50 of Aequationes Mathematicae This is the fiftieth volume of aequationes mathematicae. Not only our modesty but also lack of space keeps us from self-congratulation.

This is the first collective study of a foundational text in modern philosophy and logic, Gottlob Frege's Basic Laws of Arithmetic. Twenty-two Frege scholars discuss a wide range of philosophical and logical topics arising from Basic Laws of Arithmetic, and demonstrate the technical and philosophical richness of this great work.

Aimed at both students and researchers in philosophy, mathematics and the history of science, this edited volume, authored by leading scholars, highlights foremost developments in both the philosophy and history of modern mathematics.

Chaotic behavior arises in a variety of control settings. In some cases, it is beneficial to remove this behavior; in others, introducing or taking advantage of the existing chaotic components can be useful for example in cryptography. Chaos in Automatic Control surveys the latest methods for inserting, taking advantage of, or removing chaos in a variety of applications. This book supplies the theoretical and pedagogical basis of chaos in control systems along with new concepts and recent developments in the field. Presented in three parts, the book examines open-loop analysis, closed-loop control, and applications of chaos in control systems. The first section builds a background in the mathematics of ordinary differential and difference equations on which the remainder of the book is based. It includes an introductory chapter by Christian Mira, a pioneer in chaos research. The next section explores solutions to problems arising in observation and control of closed-loop chaotic control systems. These include model-independent control methods, strategies such as H-infinity and sliding modes, polytopic observers, normal forms using homogeneous transformations, and observability normal forms. The final section explores applications in wireless transmission, optics, power electronics, and cryptography. Chaos in Automatic Control distills the latest thinking in chaos while relating it to the most recent developments and applications in control. It serves as a platform for developing more robust, autonomous, intelligent, and adaptive systems.

This book is essentially devoted to complex properties (Phase plane structure and bifurcations) of two-dimensional noninvertible maps, i.e. maps having either a non-unique inverse, or no real inverse, according to the plane point. They constitute models of sets of discrete dynamical systems encountered in Engineering (Control, Signal Processing, Electronics), Physics, Economics, Life Sciences. Compared to the studies made in the one-dimensional case, the two-dimensional situation remained a long time in an underdeveloped state. It is only since these last years that the interest for this research has increased. Therefore the book purpose is to give a global presentation of a matter, available till now only in a partial form. Fundamental notions and tools (such as “critical manifolds”), as the most part of results, are accompanied by many examples and figures.