Search:
RSS
Authors

Recent Posts
(small) categories
Archives
Blogroll
Meta
Author Archives: Z Norwood
AC, part III: Choice in context
Wow, it’s been a long time since my last post. Sorry about that. I intend (though I’ll make no promises) to post a bit more regularly now. This final post in my ac series was advertised to be a post … Continue reading
Posted in AC, Logic, Set theory
6 Comments
Analysis exercise
Consider the following assertion: For any function from to the countable subsets of , there are real numbers and such that and . Can you prove it? Can you disprove it? If you can’t prove or disprove it, does your … Continue reading
Difficult undergrad proofs
Dear all: The other day I was reflecting on what material we covered in our undergrad courses, and I wondered what the most difficult proof we encountered in courses there was. Of course, we should keep in mind that every … Continue reading
Basic AC, part 2: Choice in Algebra
The outline I (apparently) wrote on the previous post in this series says this post should talk about the Axiom of Choice in algebra, particularly how it affects vector spaces and groups. Before I talk about vector spaces and groups, … Continue reading
Posted in AC, Linear Algebra, Logic
11 Comments
Two neat things
Today I stumbled across two lovely bits of math(s) I’d like to share. The first is a fun topological proof that there are infinitely many prime numbers. The second is a proof that the set of prime numbers is bounded… … Continue reading
ZN’s website
If you find yourself with absolutely nothing to do, check out my Churchill college website. There is currently almost nothing on it, but the notable thing that is there is a link to my ed Part III Commutative Algebra notes, … Continue reading
Wellordering the reals: a response
This is a reply to Jay’s comment. First, I should mention that in the absence of AC, the real numbers may not be wellorderable at all. In the Solovay model of ZF in which every set of reals is Lebesguemeasurable, … Continue reading