I write science for my job and fiction for fun. The mental processes are not that different between a murder mystery and a theoretical physics paper. In both cases, you've got a tangle of pieces floating in abstract space, be they preconditions for a theorem or clues to whodunit, and you have to instantiate them somehow, picking a linear order of text to lock down the loose assemblage. You're trying to cast a shadow of this damn strange thing made of parts that stick together or split apart depending on how you turn the whole.