Given a mathematical structure, one of the basic associated mathematical
objects is its automorphism group. The object of this book is to give a
biased account of automorphism groups of differential geometric struc-
tures. All geometric structures are not created equal; some are
creations of ods while others are products of lesser human minds.
Amongst the former, Riemannian and complex structures stand out for
their beauty and wealth. A major portion of this book is therefore
devoted to these two structures. Chapter I describes a general theory of
automorphisms of geometric structures with emphasis on the question of
when the automorphism group can be given a Lie group structure. Basic
theorems in this regard are presented in §§ 3, 4 and 5. The concept of
G-structure or that of pseudo-group structure enables us to treat most
of the interesting geo- metric structures in a unified manner. In § 8,
we sketch the relationship between the two concepts. Chapter I is so
arranged that the reader who is primarily interested in Riemannian,
complex, conformal and projective structures can skip §§ 5, 6, 7 and 8.
This chapter is partly based on lec- tures I gave in Tokyo and Berkeley
in 1965.