21 Oct
2009
21 Oct
'09
2:19 p.m.
Rich wrote: << . . . separability test seems to work if we allow spheres as separators (instead of just allowing planes).
Yes -- the family F = {all spheres and planes in R^3} is large enough to separate any two circles in R^3 that don't link. By the way, F has a natural topology homeomorphic to a punctured P^4 (4-dimensional projective space minus a point). --Dan _____________________________________________________________________ "It don't mean a thing if it ain't got that certain je ne sais quoi." --Peter Schickele