2 papers
math.CT2014
Notes on commutation of limits and colimits
Marie Bjerrum, Peter Johnstone, Tom Leinster +1
We show that there are infinitely many distinct closed classes of colimits (in the sense of the Galois connection induced by commutation of limits and colimits in Set) which are in…
math.CT2008
De Morgan's law and the theory of fields
Olivia Caramello, Peter Johnstone
We show that the classifying topos for the theory of fields does not satisfy De Morgan's law, and we identify its largest dense De Morgan subtopos as the classifying topos for the…