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CATEGORIES:Category Theory Seminar
SUMMARY:Trees for subtoposes of the effective topos - Sori
Lee\, DPMMS
DTSTART;TZID=Europe/London:20111025T141500
DTEND;TZID=Europe/London:20111025T151500
UID:TALK33951AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/33951
DESCRIPTION:For making concrete calculations about subtoposes
of the effective topos\, it is crucial to have a t
angible representation of the corresponding local
operators. We introduce tree-like structures calle
d `sights'\, in order to further understand a repr
esentation due to A.M. Pitts (which arises from th
e topos-theoretic construction of the least local
operator making a given subobject of a topos dense
) and to define another useful representation. We
apply these methods to establish some new examples
of subtoposes\, and to compare them to known ones
. We also remark that a realizability-like semanti
cs can be formulated for the arithmetic of subtopo
ses in terms of sights.
LOCATION:MR5\, Centre for Mathematical Sciences
CONTACT:Julia Goedecke
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