Seminar series
Date
Wed, 04 Mar 2015
16:00
16:00
Location
C2
Speaker
Martin Escardo
Organisation
Birmingham
Voevodsky asked what the topology of the universe is in a
continuous interpretation of type theory, such as Johnstone's
topological topos. We can actually give a model-independent answer: it
is indiscrete. I will briefly introduce "intensional Martin-Loef type
theory" (MLTT) and formulate and prove this in type theory (as opposed
to as a meta-theorem about type theory). As an application or corollary,
I will also deduce an analogue of Rice's Theorem for the universe: the
universe (the large type of all small types) has no non-trivial
extensional, decidable properties. Topologically this is the fact that
it doesn't have any clopens other than the trivial ones.