Optimality of VWAP Execution Strategies under General Shaped Market   Impact Functions
  In this short note, we study an optimization problem of expected implementation shortfall (IS) cost under general shaped market impact functions. In particular, we find that an optimal strategy is a VWAP (volume weighted average price) execution strategy when the market model is a Black-Scholes type with stochastic clock and market trading volume is large. 
Takashi Kato
q-fin.TR