viii Preface
computational examples and exercises. The applications in Chapter 6 are given
special emphasis.
When taught as a one-semester graduate course, we assume students have some
knowledge of complex numbers and so Chapter 1 is given just a brief review. Chap-
ters 2, 3, and 4 are covered completely, parts of Chapters 5 and 6 are covered, along
with Chapter 7. If time allows, Chapters 8 and 9 are summarized at the end of the
course. In the homework, the emphasis is on the theoretical exercises.
We have tried to present this material in a fashion which is both rigorous
and concise, with simple, straightforward explanations. We feel that the modern
tendency to expand textbooks with ever more material, excessively verbose ex-
planations, and more and more bells and whistles, simply gets in the way of the
student’s understanding of the material.
The exercises differ widely in level of abstraction and level of difficulty. They
vary from the simple to the quite difficult and from the computational to the the-
oretical. There are exercises that ask students to prove something or to construct
an example with certain properties. There are exercises that ask students to apply
theoretical material to help do a computation or to solve a practical problem. Each
section contains a number of examples designed to illustrate the material of the
section and to teach students how to approach the exercises for that section.
This text, in its various incarnations, has been used by the author and his
colleagues for several years at the University of Utah. Each use has led to improve-
ments, additions, and corrections.
The text begins, in Chapter 1, with a discussion of the fact that the real number
system is insufficient for some purposes (solving polynomial equations). The system
of complex numbers is developed in an attempt to remedy this problem. We then
study basic arithmetic of complex numbers, convergence of sequences and series of
complex numbers, power series, the exponential function, polar form for complex
numbers and the complex logarithm.
The core material of a complex variables course is the material covered here
in Chapters 2 and 3. Analytic functions are introduced in Chapter 2 as functions
which have a complex derivative. This leads to a discussion of the Cauchy-Riemann
equations and harmonic functions. We then introduce contour integrals and the
index function (winding number) for closed paths. We prove the Cauchy-integral
theorem for triangles and then for convex sets. We believe that this approach leads
to the simplest and quickest rigorous proof of a form of Cauchy’s theorem that can
be used to prove the existence of power series expansions for analytic functions.
The proof that analytic functions have power series expansions occurs early in
Chapter 3. This is followed by a wide range of powerful applications with simple
proofs Morera’s Theorem, Liouville’s Theorem, the Fundamental Theorem of
Algebra, the characterization of zeroes and singularities of analytic functions, the
Maximum Modulus Principle, and Schwarz’s Lemma.
Chapter 4 begins with a proof of the general form of Cauchy’s Theorem and
Cauchy’s Formula. These theorems involve functions which are analytic on a general
open set. The integration takes place around a cycle (a generalization of a closed
path) which is required to have index zero about any point not in the set. We
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