Something Old, Something New, Something Borrowed, ...
F.E.J. Linton • Wesleyan Univ. Math/CS Emeritus
F.E.J. Linton • Wesleyan Univ. Math/CS Emeritus
Take two copies of the upper half-plane, topologized by ...
taking as basic open neighborhoods of points on either x-axis
the symmetric “broken open Vs”, with fingers of equal length,
but with left finger in the same half-plane as the point on the x-axis,
and right finger in the other half-plane (omitting the corresponding point on
that other x-axis).