The sphere spectrum
BID, Lisboa 2017 		  1. Extensions of number systems
2. Negative numbers
3. Briefly on sheep 		4. A trade deficit
5. Out in space
6. Ulla and Henriette live in RP∞ 		7. Negative sets
8. The sphere spectrum
9. Brave New World

A trade deficit

But, what about the negative numbers?

Mad sheep Ull i får Can we talk about minus the set {Ulla, Henriette, Vignette}?

that is, is there a "set" X such that the union of X and {Ulla, Henriette, Vignette} is the empty set (don't fool yourself into believing that X="the wolf": the union of UHV and the wolf is a (nonempty) wolf).

Out in space
Bjørn Ian Dundas
2017-07-21 14:40:56 UTC