Solution
= Solution
A predictable strategy $H$ is <self-financing portfolio>[self-financing] when its wealth $X=H\cdot P$ satisfies
$$
dX_t=H_t\cdot dP_t.
$$
It is admissible when its wealth obeys the stipulated lower bound, here taken to be nonnegative. A strictly positive Itô process $Y$ is a <martingale deflator> when every deflated asset price $YP^i$ is a <local martingale>.