Axioms of set theory | Wellfoundedness
In mathematics, the axiom of regularity (also known as the axiom of foundation) is an axiom of Zermelo–Fraenkel set theory that states that every non-empty set A contains an element that is disjoint from A. In first-order logic, the axiom reads: The axiom of regularity together with the axiom of pairing implies that no set is an element of itself, and that there is no infinite sequence (an) such that ai+1 is an element of ai for all i. With the axiom of dependent choice (which is a weakened form of the axiom of choice), this result can be reversed: if there are no such infinite sequences, then the axiom of regularity is true. Hence, in this context the axiom of regularity is equivalent to the sentence that there are no downward infinite membership chains. The axiom was introduced by ; it was adopted in a formulation closer to the one found in contemporary textbooks by . Virtually all results in the branches of mathematics based on set theory hold even in the absence of regularity; see chapter 3 of . However, regularity makes some properties of ordinals easier to prove; and it not only allows induction to be done on well-ordered sets but also on proper classes that are well-founded relational structures such as the lexicographical ordering on Given the other axioms of Zermelo–Fraenkel set theory, the axiom of regularity is equivalent to the axiom of induction. The axiom of induction tends to be used in place of the axiom of regularity in intuitionistic theories (ones that do not accept the law of the excluded middle), where the two axioms are not equivalent. In addition to omitting the axiom of regularity, non-standard set theories have indeed postulated the existence of sets that are elements of themselves. (Wikipedia).
Axiom of Regularity (Foundation) vs. Induction
Previous video on regularity: https://youtu.be/AqjctCRGxhw Errata: In 56:27 I say Regularity, but I meant to say Replacement. Text and links: https://gist.github.com/Nikolaj-K/bc9f67d685bcc7d1300372cfabceed9b
From playlist Logic
What's so wrong with the Axiom of Choice ?
One of the Zermelo- Fraenkel axioms, called axiom of choice, is remarkably controversial. It links to linear algebra and several paradoxes- find out what is so strange about it ! (00:22) - Math objects as sets (00:54) - What axioms we use ? (01:30) - Understanding axiom of choice (03:2
From playlist Something you did not know...
The perfect number of axioms | Axiomatic Set Theory, Section 1.1
In this video we introduce 6 of the axioms of ZFC set theory. My Twitter: https://twitter.com/KristapsBalodi3 Intro: (0:00) The Axiom of Existence: (2:39) The Axiom of Extensionality: (4:20) The Axiom Schema of Comprehension: (6:15) The Axiom of Pair (12:16) The Axiom of Union (15:15) T
From playlist Axiomatic Set Theory
A stable arithmetic regularity lemma in finite (...) - C. Terry - Workshop 1 - CEB T1 2018
Caroline Terry (Maryland) / 01.02.2018 A stable arithmetic regularity lemma in finite-dimensional vector spaces over fields of prime order In this talk we present a stable version of the arithmetic regularity lemma for vector spaces over fields of prime order. The arithmetic regularity l
From playlist 2018 - T1 - Model Theory, Combinatorics and Valued fields
N and Order | Axiomatic Set Theory, Section 3.2
We prove the natural ordering on the natural numbers is a total order. Transitivity (0:00) Asymmetry (6:02) All elements are comparable (8:45)
From playlist Axiomatic Set Theory
Orders and Ordered Sets | Axiomatic Set Theory, Section 2.3
We discuss order relations on sets, and isomorphisms of ordered sets. My Twitter: https://twitter.com/KristapsBalodi3
From playlist Axiomatic Set Theory
The Simplest Math No One Can Agree on- A Paradox of Choice
To build our mathematics we need a starting point, rules to dictate what we can do and assumed basic truths to serve as a foundation as we seek understanding of higher level problems. But what happens when we can't agree on what we should start with?
From playlist Summer of Math Exposition Youtube Videos
Verónica Becher: Independence of normal words
Abstract : Recall that normality is a elementary form of randomness: an infinite word is normal to a given alphabet if all blocks of symbols of the same length occur in the word with the same asymptotic frequency. We consider a notion of independence on pairs of infinite words formalising
From playlist Logic and Foundations
Set Theory (Part 2): ZFC Axioms
Please feel free to leave comments/questions on the video and practice problems below! In this video, I introduce some common axioms in set theory using the Zermelo-Fraenkel w/ choice (ZFC) system. Five out of nine ZFC axioms are covered and the remaining four will be introduced in their
From playlist Set Theory by Mathoma
RA1.3. Peano Axioms and Induction
Real Analysis: We consider the Peano Axioms, which are used to define the natural numbers. Special attention is given to Mathematical Induction and the Well-Ordering Principle for N. (Included is an example of how to show a triple equivalence.)
From playlist Real Analysis
Regularity and non-standard models of arithmetic #PaCE1
Follow-up video: https://youtu.be/7HKnOOvssvs Discussed text, including all links: https://gist.github.com/Nikolaj-K/101c2712dc832dec4991bf568869abc8 Curt's call: https://youtu.be/V93GQaDtv8w Timestamps: 00:00:00 Introduction 00:02:55 Wittgenstein and predicates (optional) 00:11:12 Skolems
From playlist Logic
SEPARATION BUT MATHEMATICALLY: What Types of Mathematical Topologies are there? | Nathan Dalaklis
The title of this video is a bit convoluted. What do you mean by "Separation but Mathematically"? Well, in this video I'll be giving a (very diluted) answer to the question "What types of mathematical topologies are there?" by introducing the separation axioms in topology. The separation
From playlist The New CHALKboard
Topology Without Tears - Video 2c - Infinite Set Theory
This is the final part, part (c), of Video 2 in a series of videos supplementing the online book "Topology Without Tears" which is available at no cost at www.topologywithouttears.net
From playlist Topology Without Tears
Computation Ep25, Stacks and CFGs (Apr 5, 2022)
This is a recording of a live class for Math 3342, Theory of Computation, an undergraduate course for math and computer science majors at Fairfield University, Spring 2022. The course is about finite automata, Turing machines, and related topics. Homework and handouts at the class websi
From playlist Math 3342 (Theory of Computation) Spring 2022
Axiom of Choice and Regularity each imply LEM
I recommend you go through all parts, but thee AC-LEM proof starts at 55:30. If you skip stuff, still watch the section at 8:22, because I talk in terms of those semantics later. The Regularity-LEM proof at 1:50:55 requires definitions from the earlier AC-LEM proof. Timestamps: 0:00 Intro
From playlist Summer of Math Exposition 2 videos
Linear Algebra 4.1 Real Vector Spaces
My notes are available at http://asherbroberts.com/ (so you can write along with me). Elementary Linear Algebra: Applications Version 12th Edition by Howard Anton, Chris Rorres, and Anton Kaul
From playlist Linear Algebra
Simplify a rational expression by using properties of exponents
👉 Learn how to simplify expressions using the quotient rule of exponents. The quotient rule of exponents states that the quotient of powers with a common base is equivalent to the power with the common base and an exponent which is the difference of the exponents of the term in the numerat
From playlist Simplify Using the Rules of Exponents | Quotient Rule
Assaf Rinot: Chain conditions, unbounded colorings and the C-sequence spectrum
Recording during the meeting "15th International Luminy Workshop in Set Theory" the September 23, 2019 at the Centre International de Rencontres Mathématiques (Marseille, France) Filmmaker: Guillaume Hennenfent Find this video and other talks given by worldwide mathematicians on CIRM's A
From playlist Logic and Foundations