# Problems in mechanics open the door to the orderly world of chaos

August 22, 2016The word "chaos" has two meanings that are almost exact opposites. In general usage, it means "wild unpredictable confusion". In physics and mathematics it often refers to the behavior of systems for which the tools of traditional mathematics fail and one is forced to think in a rigorous new semi-quantitative way.

The first person to realize this was the French mathematician Henri Poincaré. In the late 19th century he was challenged to prove that the solar system is stable, but instead raised the possibility that it might not be! If one ignores the gravitational attraction between the planets one is left with a solvable problem that appears in all undergraduate mechanics texts. Including these small perturbations leads to a problem that can be described with partial differential equations, but these equations have no proper solutions except possibly in terms of infinite series. These equations can be solved numerically of course, but the results show an odd combination of order and unpredictability. Poincaré went on to lay the foundation for the study of such systems. He identified criteria that make a system inescapably chaotic and showed how a kind of order can emerge from the chaos. In this century, the Russian mathematician Kolomogrov developed what has come to be called the KAM theorem; one of the crowning works of modern mathematics. He showed that there is an odd fractal-like landscape of infinite series solutions in otherwise unsolvable problems.

Lectures in Nonlinear Mechanics and Chaos Theory begins by reviewing the tools of traditional classical mechanics--the Hamiltonian formulation, abstract transformation theory, and perturbation theory--and shows how they ultimately fail. It then moves on to the landmarks of chaos theory, the Poincaré-Hopf or "hairy ball" theorem, followed by the Poincaré-Birkoff theorem for rational winding numbers, and finally, the KAM theorem. These are discussed in terms of rigorous mathematics and illustrated with numerous examples of computer-drawn solutions. It finishes with a discussion of the relevance of the KAM theorem and measure theory to the ergodic hypothesis.

This book is based on a one-quarter course in graduate mechanics that has been given in the Physics Department of Oregon State University. It is intended to be used as a textbook to review conventional mechanics and introduce students to more recent developments in chaos theory.

This book retails for US$35 / £29 (paperback) and US$70 / £58 (hardback), and is also available on Amazon, Barnes and Noble, and other major online booksellers. To know more about the book or to purchase a copy, visit http://www.worldscientific.com/worldscibooks/10.1142/10070

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**About the Author**

Albert W Stetz is Professor Emeritus in the Physics Department of Oregon State University, USA, with a career in nuclear and elementary particle physics. He currently teaches courses for non-majors in topics such as quantum mechanics, cosmology, and the physics and philosophy of time.

**About World Scientific Publishing Co.**

World Scientific Publishing is a leading independent publisher of books and journals for the scholarly, research, professional and educational communities. The company publishes about 600 books annually and about 130 journals in various fields. World Scientific collaborates with prestigious organizations like the Nobel Foundation, US National Academies Press, as well as its subsidiary, the Imperial College Press, amongst others, to bring high quality academic and professional content to researchers and academics worldwide. To find out more about World Scientific, please visit http://www.worldscientific.com. For more information, contact Amanda Yun at heyun@wspc.com

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