Most for the grid fill was fairly easy, helped by the 11-letter across clues for positioning. However, I can't make sense of the down solution that finishes in the bottom left cell. The word play and the checked letters give me an answer, but it seems to have nothing to do with the definition in the clue.
Meanwhile, I have 6 letters of the theme word. I thought it was going to refer to an eminent mathematician, but not so sure now - and how would that relate to the title of the puzzle?
Not sure either about joining up the letters- the O's look promising but can't see what else.