  In this paper, we introduce a numeraire-free and original probability based
framework for financial markets. We reformulate or characterize fair markets,
the optional decomposition theorem, superhedging, attainable claims and
complete markets in terms of martingale deflators, present a recent result of
Kramkov and Schachermayer (1999, 2001) on portfolio optimization and give a
review of utility-based approach to contingent claim pricing in incomplete
markets.
