Zulip Chat Archive
Stream: maths
Topic: Is every complete lattice compact?
Kenny Lau (Aug 23 2018 at 20:25):
Is every complete lattice compact? Here the topology is generated by sets of the form {x | a < x < b}
Kenny Lau (Aug 23 2018 at 20:33):
correction: the topology is generated by sets of the form {x | a < x < b} and {x | a < x} and {x | x < b}
Kevin Buzzard (Aug 23 2018 at 21:03):
I don't really understand the question but are the real numbers a counterexample?
Kenny Lau (Aug 23 2018 at 21:04):
it isn't a complete lattice
Johannes Hölzl (Aug 24 2018 at 07:14):
at least complete linear orders on a second countable topology form a complete lattice
compact (UNIV :: 'a::{complete_linorder,linorder_topology,second_countable_topology} set)
Johannes Hölzl (Aug 24 2018 at 07:15):
In Isabelle the proof goes over:
lemma compact_complete_linorder: fixes X :: "nat ⇒ 'a::{complete_linorder,linorder_topology}" shows "∃l r. strict_mono r ∧ (X ∘ r) ⇢ l"
Johannes Hölzl (Aug 24 2018 at 07:16):
strict_mono
means strictly increasing
Last updated: Dec 20 2023 at 11:08 UTC