An example of the terminology that surrounds discounting that confuses me can be found in "Investment and Hysteresis" by Dixit:
Let future revenues be discounted at a positive rate $\rho > 0 \ldots$ Then, given a current level $R$ of revenues, the expected present value of the discounted future streams of revenues is $R / \rho$.
Hence, the net present value of the investment is quantified as $R/\rho - K$, where $K$ is the sunk cost.
What I would like to understand is what this formulation has to do with exponential discounting; in particular, where is the sum over the time periods (alluded to in the phrase "future revenue streams", but also made clear in the context of the paper)? Is this some kind of economist shorthand?
This matters because, as far as I can see, he uses the exact expression above for the NPV in the key derivation in the paper, which suggests to me that I've misunderstood his concept of "discounting".
(This notation is not unique to this paper: I've encountered this in several places; cf. Allcott and Greenstone "Is there an Energy Efficiency Gap".)