Jaap van Oosten (Utrecht, Netherlands), Local Operators in the Effective Topos


  • Feb. 16, 2012, 14:00 - 15:00


Local operators in the effective topos correspond to so-called "subtoposes" of this topos, and associated notions of realizability. The collection of local operators forms a Heyting algebra into which the upper-semilattice of Turing degrees embeds; in that respect it is similar to (the dual of) the Medvedev lattice. The talk aims to introduce the audience to this structure and to some techniques for doing calculations in it.

It is based on joint work by Sori Lee and the speaker.