Yet another academic paper that dives into the rabbit hole of Zermelo’s "Axiom of Choice" 🐇🎩, as if it was the Da Vinci Code of set theory. 😴🔍 100 years and counting, and we're still trying to decipher what the heck the problem was—spoiler alert, it's probably just a bunch of mathematicians arguing over who gets the last slice of infinity pie. 🍰♾️
https://research.mietek.io/mi.MartinLof2006.html #AxiomOfChoice #SetTheory #InfinityPie #MathHumor #AcademicPapers #HackerNews #ngated
P. Martin-Löf (2006) 100 years of Zermelo’s axiom of choice: What was the problem with it? — Machine Intuitionist

A brain dump from Matrix Dreams: A better-defined series of sets

I’ve been pondering the weird collection of sets I cooked up in this post. In this post, I’d like to take a crack at defining the sets.

I’m going to bow to my ego and call these the MattSets. MattSet Prime is the set of all integers found in all the other MattSets.

MattSet0 is the set of all powers of two. As such, it is an even set. All members of MattSet0 are even.

There are two types of MattSets – even and not even (odd) sets. Each set is generated from the set before it.

MattSet1 is the first odd set. It is the set of all the numbers when multiplied by three that the numbers in the previous set is one more than. Another way to say this is – make an intermediary set of all members of MattSet0 (MattSetn-1 in general form) that are one more than a multiple of three. Take all the members of this intermediary set and apply the function (x-1)/3. This will give you MattSet1 which is an odd set.

MattSet2 is two be an even set. MattSet2 is the set of all integers that are twice a member of MattSet1 (MattSetn-1 in general form).

Each subsequent set is generated in the same way such that MattSets with even indexes are even numbers and MattSets with odd indexes are odd.

As far as I have, so far, tested each odd MattSet has half the number of members as the preceding even MattSet.

In theory: As n approaches infinity, the size of the MattSetn approaches 0. At least I think that it does.

The question I am looking to answer is does MattSet Prime contain all the positive integers? If I can’t prove that one way or the other, is there anything interesting about these sets that can be proved?

A better-defined series of sets, 8th October 2024, by Matt

Note: I’m not sure I was all that clear the first time, but only integer values can be members of these sets.

You could add some other series of (empty) sets for completion. MattSetnx. A member of the MattSetnx is an even number not found in MattSet0 that is twice the value of a MattSet0 member. MattSetn+1x. Would be all the even numbers not in the preceding sets that are twice the value of one of the previous nx sets. In theory, all MattSetnx sets are empty, as twice a power of two is another power of two.

Prove me wrong.

Syndicated to:

#maths #MatrixDreams #MattSet #setTheory #syndicated #MyVeryBestContent

Hey #SetTheory #lazyweb, if I have a set A and its proper subset B, what is the name that describes the elements in A that are not in B?

I _think_ it's 'symmetric difference', but that to me implies that B could be something other than a proper subset. Is there a more exact name?

0 can only be
- AOC dabbler
#settheory #logic
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F
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Readings shared April 13, 2025

The readings shared in Bluesky on 13 April 2025 are Completeness of decreasing diagrams for the least uncountable cardinality (in Isabelle/HOL). ~ Ievgen Ivanov. #ITP #IsabelleHOL #Math #SetTheory Ef

Vestigium
Completeness of decreasing diagrams for the least uncountable cardinality (in Isabelle/HOL). ~ Ievgen Ivanov. https://www.isa-afp.org/entries/Completeness_Decreasing_Diagrams_for_N1.html #ITP #IsabelleHOL #Math #SetTheory
Completeness of Decreasing Diagrams for the Least Uncountable Cardinality

Completeness of Decreasing Diagrams for the Least Uncountable Cardinality in the Archive of Formal Proofs

Readings shared April 11, 2025

The readings shared in Bluesky on 11 April 2025 are Code generation via meta-programming in dependently typed proof assistants. ~ Mathis Bouverot-Dupuis, Yannick Forster. #ITP #Agda #Rocq #LeanProver

Vestigium
A comparative review of ZFC, NBG, and MK axiom systems: Theoretical foundations and formalization in Coq. ~ Si Chen, Wensheng Yu. https://www.preprints.org/manuscript/202504.0684/v1 #ITP #Coq #Rocq #Math #SetTheory
The set of all sets that are not big enough to trigger Russell's Paradox.


Okay that sounds like a joke, but I have a clear memory of my algebra professor in undergrad saying "If you have a large category, you can always shrink it to a small category that includes all the objects you care about."

Unless you're a foundations creature, in which case the objects you care about might include sets or categories which are big enough to cause trouble.

#SetTheory #CategoryTheory #Math
Readings shared February 23, 2025

The readings shared in Bluesky on 23 March 2025 are A review on mechanical proving and formalization of mathematical theorems. ~ Si Chen, Wensheng Yu, Guowei Dou, Qimeng Zhang. #ITP #Coq #IsabelleHOL

Vestigium