="Warren Smith" <warren.wds@gmail.com> ...there are no magic alien mass-removal techniques... ...That is why this is "math fun,"... ...sci-fi writers should fuggedaboudit...
Warren, methinks you may be autocurmudgeoning overmuch. As you mentioned originally, Niven's Nifty Neutronium comes gift-wrapped in a "stasis field". Of course stasis fields present even more substantial conundrums, and not just for the physicist, but for the novelist too--Niven noted they were just too damn handy and got tired of having to come up with fictional excuses for why they couldn't be used to solve various plot problems. Niven's canon also includes candidate alien mass-removal techniques: simply use Puppeteer stepping disc technology to teleport it elsewhere...