I've been calling this ratio "acceleration" in my head, so I'll do the same in this post. The question is, is this relationship used anywhere and if so, how? My thought process is as follows.
Risk is typically quantified through standard deviation. But how good of a proxy for risk is SD really? Upside deviation is not risk, it's the definition of reward!
So "acceleration" might quantify upside variance per unit of downside variance. I can imagine a momentum strategy using an "acceleration-weighted" allocation scheme. Like riding a rising wave.
This could also be some obscure Greek that I'm not aware of, or have a completely different use. Just wondering. Thanks.