NMSU • BLAST-2009

**Something Old, Something New, Something Borrowed, ...**

F.E.J. Linton • Wesleyan Univ. Math/CS Emeritus

F.E.J. Linton • Wesleyan Univ. Math/CS Emeritus

These are the slides for a short presentation at the 2009 NMSU
BLAST Conference about a peculiar topological space that Peter
Johnstone, Bob Paré and I used some 30 years ago to solve a
topoidal problem.

"Short"? — Meant to occupy 15-20 minutes, tops.

"Peculiar"? — it has a discrete, dense, open subset, whose (closed)
complement is a discrete subspace as well, yet ...

"Topoidal problem"? — ... the whole space admits a double cover
with **no** continuous global section.

Seemed like the sort of mix of areas BLAST participants would appreciate. And the pictures may be a pleasant diversion, too :-) .