set-theory

Urs Schreiber
3d ago

mathematical logic deduction system, natural deduction, sequent calculus, lambda-calculus, judgment type theory, simple type theory, dependent type theory collection, object, type, term, set, element equality, judgmental equality, typal equality universe, size issues higher-order logic This page is to record the reference: William Lawvere, Robert Rosebrugh: Sets for Mathematics Cambridge Universi…

Previously: Ordinal numbers and basic set theory Ordinals as nim-heaps Nim always ends, even with infinite ordinals Infinite Nim as a coin-moving game Coin-moving games without the coins Previously we saw how to interpret the difficult-seeming ordinal as a particular ordering of the set of finite sequences of numbers, revealing what seemed like a scary monster as gentle and straightforward. Now w…

$\newcommand\of{\subseteq}\newcommand\N{\mathbb{N}}\newcommand\R{\mathbb{R}}\def\<#1>{\left\langle#1\right\rangle}\newcommand\Z{\mathbb{Z}}\newcommand\Q{\mathbb{Q}}\newcommand\ltomega{{{<}\omega}}\newcommand\unaryminus{-}\newcommand\intersect{\cap}\newcommand\union{\cup}\renewcommand\emptyset{\varnothing}$Let us explore the vast and densely populated expanses of the lattice of all sets of natural…

Previously: Ordinal numbers and basic set theory Ordinals as nim-heaps Nim always ends, even with infinite ordinals Infinite Nim as a coin-moving game In the previous article we saw how to interpret Nim heaps of up to beans as coins on a quarter-infinite array: The coin here represents a heap of beans. The heap can be reduced to any smaller number of beans. In the coin version of the game, this…

Urs Schreiber
7/23/2026

transfinite arithmetic, cardinal arithmetic, ordinal arithmetic prime field, p-adic integer, p-adic rational number, p-adic complex number arithmetic geometry, function field analogy The cardinal numbers (or just cardinals) constitute a generalisation of natural numbers to numbers of possibly infinite magnitudes. Specifically, cardinal numbers generalise the concept of ‘the number of …’. In parti…

This post is going to be about what infinite ordinal numbers are, and about is in particular. I had a brainwave a while back (18 months now, wow, I have definitely not been blogging enough) and suddenly understood much better than I did before. I have several related ideas here and I am going to try to write one blog post about each of them, instead of one gigantic blog post about all of them t…

Kelvin Dafiaghor
7/9/2026

Here I discuss definition of set, subset, proper subset, de Morgan’s law, Associative law, Cartesian product with theory and solve two maths problem. set theory with problem. problems with set theory. set theory problems and solutions. set theory sample problems. what is the problem with set theory. set theory problems and solutions pdf. group theory [&#8230;]

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