The only assumption made here is ambition, and it is explicitly stated. An ambitious civilization will figure out a use for whatever amount of harvestable ener

The only assumption made here is ambition, and it is explicitly stated. An ambitious civilization will figure out a use for whatever amount of harvestable energy is available. Computation, if nothing else. The paper is about upper bounds; whether any civilization can (or wants to) actually reach anywhere near them is another question for another paper.