28 Jan
2003
28 Jan
'03
9:44 a.m.
Alex Simpson <als@inf.ed.ac.uk> writes:
The map e : 2^N --> [0,1] defined by
e x = x_0/2 + x_1/4 + x_2/8 + ...
is epi in the effective topos, but it is not regular epi.
This is clearly wrong. Every epi is regular, in a topos.
My original statement was correct. In the effective topos, the map from binary representations to Cauchy (= Dedekind) reals is not epi.
I stand corrected. I am confusing the effective topos with assemblies (or modest sets) over the first Kleene algebra. Andrej