Categories in Algebra, Geometry and Mathematical Physics
Conference in honour of Ross Street's sixtieth birthday
July 11-16 2005, Macquarie University, Sydney
Mon, 11 July: 14:45 - 15:25
Bi-Heyting toposes and essential covers
Johnstone, Peter (Cambridge University)
Recent work of Francis Borceux and Dominique Bourn has highlighted the
importance of (Grothendieck) toposes in which subobject lattices are
co-Heyting algebras as well as Heyting algebras. Clearly, if a topos admits
an essential surjection from a Boolean topos, then it has this property.
We investigate the extent to which the converse holds.