This series of pages started out as an accompaniment to a series of seminars given at NTNU, and subsequently at Sheffield University, entitled:
This was intended to be accessible to anyone with knowledge of basic finite dimensional differential topology. Thus there was a reasonable amount of background material to be explained before the subject of Dirac operators was broached. This could be divided into three broad areas: differential topology of loop spaces, spinors in arbitrary dimension, and the Atiyah-Singer index theorem (in finite dimensions).
The latter two of these topics are already superbly covered by books accessible to any differential topologist, perhaps with a little functional analysis. The book LM89 is an excellent introduction to both topics in finite dimensions whilst PR94 deals with spinors in arbitrary dimension. A group-centric viewpoint is presented in PS86, which is required reading for anyone seriously thinking about loop spaces.
The main reference for the first topic is KM97 in which is developed a theory of analysis in infinite dimensions in arbitrary topological vector spaces. However, this means that whilst being an excellent book, its subject matter is perhaps too broad and too deep for someone who just wants to know about the differential topology of loop spaces.
This led to the writing of arXiv:math.DG/0510097 with the intention was to provide a more gentle introduction than KM97 but still including the required detail to understand the differential topology of the space of smooth loops. It subsequently grew beyond that remit as more topics were added.
That article is now in the process of being imported in to the nLab. In the transfer, its scope is being extended to more general mapping spaces as many of the basic structure of loop spaces holds in this more general setting.