After the pioneering work of Schur, little progress was made for half a century on projective representations, despite considerable activity on the related topic of linear representations. However, in the last twenty years, important new advances have spurred further research. This book develops both the early theory of Schur and then describes the key advances that the subject has seen since then. In particular, the theory of Q-functions and skew Q-functions is extensively covered which is central to the development of the subject.

The author surveys the known results in these fields and indicates directions for further research and wider application of the methods of Lie sphere geometry. Further key features of Lie Sphere Geometry 2/ Provides the reader with all the necessary background to reach the frontiers of research in this area; Fills a gap in the literature; no other thorough examination of Lie sphere geometry and its applications to submanifold theory; Complete treatment of the cyclides of Dupin, including 11 computer-generated illustrations; Rigorous exposition driven by motivation and ample examples.