I'm looking for a math symbol to represent the concatenation of two vectors: if x = (x1, x2) and y = (y1, y2) then x ? y = (x1, x2, y1, y2).
I'm not very much at home in vector calculus, so I don't know if there's a standard symbol for this. If not, then I remember from formal language theory that there's a round caret-like symbol for concatenating two strings, which would be fine for my purposes. I can't find it, though; the sources I've found online all recommend using juxtaposition for concatenation, but I'm afraid this would be mistaken for the dot product.
amssymb are both available.