Zulip Chat Archive
Stream: general
Topic: limit of a series of sets
Simon Hudon (Apr 06 2018 at 05:03):
I have an infinite series of sets that each include their successor and such that each is non-empty. How do I prove that the intersection of all sets is also non-empty?
variables (s : stream (set α)) (h₀ : ∀ i, s i ≠ ∅) (h₁ : ∀ i, s (i+1) ⊆ s i) example : (⋂ i, s i) ≠ ∅ := ...
Mario Carneiro (Apr 06 2018 at 05:46):
it's false? For example take s n := {m : nat // n <= m}
Kenny Lau (Apr 06 2018 at 05:47):
right, it’s false
Kenny Lau (Apr 06 2018 at 05:47):
i was thinking for 5 minutes whether it is true or false
Kenny Lau (Apr 06 2018 at 05:47):
take (0,1/n)
Simon Hudon (Apr 06 2018 at 11:34):
Damn it! You guys are right! I was hoping to generalize a theorem. I guess I'll have to keep thinking about restrictions
Chris Hughes (Apr 06 2018 at 13:37):
(deleted)
Last updated: Dec 20 2023 at 11:08 UTC