In this talk, we will discuss dormant opers, which are certain flat bundles on an algebraic curve in positive characteristic related to linear differential equations having a full set of solutions. The moduli theory of such objects (in special cases) has been studied in the context of p-adic Teichmüller theory, and has many different aspects, including the connections with the intersection theory of Quot schemes and the combinatorics of colored graphs, as well as rational polytopes. One goal of my research is to solve the counting problem of dormant opers while deepening our understanding of these connections. As an approach to that problem in the case of prime-power characteristic, I have recently been thinking about a kind of arithmetic lifting of dormant opers, which I call “canonical diagonal lifting”. I would like to talk about that topic, starting with some basics on flat bundles.