In November 2004, M. Yor and R. Mansuy jointly gave six lectures at
Columbia University, New York. These notes follow the contents of that
course, covering expansion of filtration formulae; BDG inequalities up
to any random time; martingales that vanish on the zero set of Brownian
motion; the Azéma-Emery martingales and chaos representation; the
filtration of truncated Brownian motion; attempts to characterize the
Brownian filtration.
The book accordingly sets out to acquaint its readers with the theory
and main examples of enlargements of filtrations, of either the initial
or the progressive kind. It is accessible to researchers and graduate
students working in stochastic calculus and excursion theory, and more
broadly to mathematicians acquainted with the basics of Brownian motion.