I have started exploring portfolio optimization results that pop out when I don’t constrain the weights to sum to 1. For instance, in a dollar-neutral portfolio, the weights sum to 0. Also, some dollar neutral portfolios are more “extreme” than others, as measured by the sum of the absolute values of the weights.
So how do I know if my broker will let me implement strategies like these? What are the accounting keywords that I have to understand to be able to answer this without resorting to the trial and error approach? I am looking for help converting some of this accounting language into mathematical language. Is the only that is necessary to consider my margin requirements?
For equities, the primary consideration appears to be Reg T. The end-of-day margin requirement is 50% for both long and short positions.