This title is part of UC Press's Voices Revived program, which commemorates University of California Press’s mission to seek out and cultivate the brightest minds and give them voice, reach, and impact. Drawing on a backlist dating to 1893, Voices Revived makes high-quality, peer-reviewed scholarship accessible once again using print-on-demand technology. This title was originally published in 1992.

The history of quantum theory is a maze of conceptual problems. In this lucid and learned book, Olivier Darrigol tracks the role of formal analogies between classical and quantum theory, from Planck's first introduction of the quantum of action to Dirac's formulation of quantum mechanics. In so doing, Darrigol illuminates not only the history of quantum theory but also the role of analogies in scientific thinking and theory change. The most remarkable result of such analogical argument in quantum theory was Bohr's correspondence principle which, in Darrigol's words, "performed the acrobatic task of bridging two mutually contradictory theories (classical electrodynamics and atomic theory), without diminishing the contrast between them". By analyzing the origins, development, and applications of this principle, From c-Numbers to q-Numbers explains the remarkable fruitfulness of the research done under Bohr's guidance between 1916 and 1925 and shows why Heisenberg claimed that quantum mechanics was born as "a quantitative formulation of the correspondence principle". With a physicist's sure hand, Darrigol examines the formal and the epistemological aspects of the analogy between classical and quantum mechanics. Unlike previous works, which have tended to focus on qualitative, global arguments, he follows the lines of mathematical reasoning and symbolizing, and by doing so he is able to show the motivations of early quantum theorists more precisely - and provocatively - than ever before. For instance, Darrigol demonstrates that a universal principle of elementary chaos underlay Planck's analogies, and that Bohr's correspondence principle was related to his elaboration of a minimal-quantumtheoretical language. Most striking, Darrigol reveals how Dirac's personal conception of the relations among algebra, geometry, use of the analogy between c-numbers and and physics conditioned his highly creative q-numbers. Original, erudite, and witty, From c-Numbers to q-Numbers sets a new standard for the philosophically perceptive and mathematically precise history of quantum mechanics. For years to come it will influence historical and philosophical discussions of twentieth-century physics.

Main features: i) A different approach for teaching Quantum Mechanics encompassing old quantum mechanics, matrix mechanics and wave mechanics in a historical perspective which helps to consolidate most important concepts of Quantum Mechanics; ii) Original information from the most important papers of Quantum Mechanics; iii) Derivation of all important equations of Quantum Mechanics, for example, Heisenberg’s uncertainty principle, de Broglie’s wave-particle duality, Schrödinger’s wave equation, etc., showing their interrelations through Dirac’s equations and other applications of matrix and wave mechanics; iv) Comprehensive mathematical support for the understanding of Quantum Mechanics; derivation of all equations make reading easier; v) The illustrations of the book cover examples, exercises and do-it-yourself activities; vi) Fundamentals of Fortran and numerical calculation along with the source codes for numerical solutions of several mathematical and quantum problems. All source codes are in the author’s site: (https://www.fortrancodes.com/); vii) Chapters devoted to linear algebra and differential equations applied to quantum mechanics and their numerical solutions; viii) Complete solution for the one-electron and two-electron problems using Schrödinger’s time independent equation along with their source codes.

This book serves as an introduction to number theory at the undergraduate level, emphasizing geometric aspects of the subject. The geometric approach is exploited to explore in some depth the classical topic of quadratic forms with integer coefficients, a central topic of the book. Quadratic forms of this type in two variables have a very rich theory, developed mostly by Euler, Lagrange, Legendre, and Gauss during the period 1750–1800. In this book their approach is modernized by using the splendid visualization tool introduced by John Conway in the 1990s called the topograph of a quadratic form. Besides the intrinsic interest of quadratic forms, this theory has also served as a stepping stone for many later developments in algebra and number theory. The book is accessible to students with a basic knowledge of linear algebra and arithmetic modulo $n$. Some exposure to mathematical proofs will also be helpful. The early chapters focus on examples rather than general theorems, but theorems and their proofs play a larger role as the book progresses.

An illustrated exploration of mathematics and its history, beginning with a study of numbers and their symbols, and continuing with a broad survey that includes consideration of algebra, geometry, hyperbolic functions, fractals, and many other mathematical functions.