ABSTRACT
The question of the best possible L2-approximation of stochastic integrals by integrals over simple integrands is strongly motivated by Stochastic Finance if one wishes to replace continuously adjusted portfolios by discretely adjusted ones. So corresponding approximation rates for deterministic time nets are studied in [11], [6], [4], and [10], whereas random time nets are treated in [7]. For the European Call Option in the Black-Scholes model it is shown in [5] that replacing the L2-estimates by much more restrictive BMQf-estimates, where S = (St)te[o,T\ is the price process, one obtains the same optimal approximation rate if the discretely adjusted portfolios are based on deterministic time nets.
