These notes are based on lectures given at the University of Virginia
over the past twenty years. They may be viewed as a course in function
theory for nonspecialists. Chapters 1-6 give the function-theoretic
background to Hardy Classes and Operator Theory, Oxford Mathematical
Monographs, Oxford University Press, New York, 1985. These chapters were
written first, and they were origi- nally intended to be a part of that
book. Half-plane function theory continues to be useful for applications
and is a focal point in our account (Chapters 5 and 6). The theory of
Hardy and Nevanlinna classes is derived from proper- ties of harmonic
majorants of subharmonic functions (Chapters 3 and 4). A selfcontained
treatment of harmonic and subharmonic functions is included (Chapters 1
and 2). Chapters 7-9 present concepts from the theory of univalent
functions and Loewner families leading to proofs of the Bieberbach,
Robertson, and Milin conjectures. Their purpose is to make the work of
de Branges accessible to students of operator theory. These chapters are
by the second author. There is a high degree of independence in the
chapters, allowing the material to be used in a variety of ways. For
example, Chapters 5-6 can be studied alone by readers familiar with
function theory on the unit disk. Chapters 7-9 have been used as the
basis for a one-semester topics course.