Mathematics is a language that doesn't fit into ASCII and commonly uses one-character variable names. If you are implementing a documented mathematical algorithm (i.e. one with a description in a paper or book) then sticking to the notation of the paper (i.e. using one character variable names) makes sense to me.
I find math far easier to read when the authors use proper names for variables. But I understand that it isn't the idiomatic style and agree that it can be useful to match the paper when re-implementing an algorithm.