**intended as a comment but not enough points to comment yet
Order execution optimization: how to execute changes to your portfolio without suffering (too much) from implementation shortfall. Work of Almgren and Chris set a modern foundation of this space, and on top of that work of Jim Gatheral for closed form solution. In addition, consider if you're executing an order for market neutral portfolio but market is trending one way, if you only submit passive orders, one way will be filled faster than the other direction which leads to breach of neutral. I learned this idea from my professors' work which also offer a solution to this problem, check Optimal Microstructure Trading with a Long-Term Utility Function!