Makkai workship Birthday offering
Billed to the organisers as “a short talk ... offering
a peculiar
topological space that Peter Johnstone and I used some 30 years ago
to solve a topoidal
problem.”
The space? — Heath’s V-space, a retopologised real
upper half-plane.
The double cover? — Concocted by emulating one construction of
the connected double cover of the circle. [>>]