Before revision:  We compute in particular the finite memory corrections to the square root impact law, as well as the impact decay and the permanent impact of a meta-order  .
After revision:  We compute in particular the finite memory corrections to the square root impact law, as well as the impact decay and the permanent impact of a meta-order . The latter is found to be linear in the traded volume and independent of the trading rate, as dictated by no-arbitrage arguments .