28 Jan
2003
28 Jan
'03
12:50 p.m.
Andrej Bauer 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. Alex Simpson Alex Simpson, LFCS, Division of Informatics, Univ. of Edinburgh Email: Alex.Simpson@ed.ac.uk Tel: +44 (0)131 650 5113 Web: http://www.dcs.ed.ac.uk/home/als Fax: +44 (0)131 667 7209