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jHan
United States
Приєднався 10 січ 2021
Mathematics can sometimes be frustrating and unintuitive. This channel seeks to explain and express mathematical concepts and ideas in a beautiful, intuitive way. Animations are made with 3Blue1Brown's animation engine Manim: github.com/3b1b/manim
How to Construct Infinite Sets
What are the natural numbers? The integers? The rationals? The reals? While we may have an intuitive understanding of these numbers and sets, it is not so easy to actually construct these sets formally. To do so, we must use some axioms of set theory, and using only these assumptions, formally describe what these infinite sets should look like. We will develop various tools in set theory, like ordered pairs, relations, ordering, and equivalence classes, to begin with only zero, and from nothing, build all of the real numbers.
0:00 Introduction
1:46 Set Theory and Basic Notions
8:13 Axiom of Infinity and the Naturals
13:09 The Integers
23:19 The Rationals
26:00 The Reals
36:38 Conclusion
Additional Resources:
Wikipedia article on the Construction of the naturals: en.wikipedia.org/w/index.php?title=Natural_number#Set-theoretic_definition
Wikipedia article on the Construction of the Reals: en.wikipedia.org/wiki/Construction_of_the_real_numbers
Wikipedia article on ZFC: en.wikipedia.org/wiki/Zermelo-Fraenkel_set_theory
Axiom of Choice video: ua-cam.com/video/szfsGJ_PGQ0/v-deo.html
Cardinality of the Continuum video: ua-cam.com/video/iaUwNuaSLUk/v-deo.html
Music:
c418.bandcamp.com/album/dief
Imaginary Interlude by C418
c418.bandcamp.com/album/circle
minimal by C418
love by C418
patriciataxxon.bandcamp.com/album/crocus
Crocus 2 by Patricia Taxxon
Far the Days Come by Letter Box
------------------------------------------------------------------------------------------------
Animations were made by Manim, an open-source python-based animation program by 3Blue1Brown.
github.com/3b1b/manim
This video was submitted to 3Blue1Brown's SoMEπ (Summer of Math Exposition Community Edition).
some.3b1b.co/
0:00 Introduction
1:46 Set Theory and Basic Notions
8:13 Axiom of Infinity and the Naturals
13:09 The Integers
23:19 The Rationals
26:00 The Reals
36:38 Conclusion
Additional Resources:
Wikipedia article on the Construction of the naturals: en.wikipedia.org/w/index.php?title=Natural_number#Set-theoretic_definition
Wikipedia article on the Construction of the Reals: en.wikipedia.org/wiki/Construction_of_the_real_numbers
Wikipedia article on ZFC: en.wikipedia.org/wiki/Zermelo-Fraenkel_set_theory
Axiom of Choice video: ua-cam.com/video/szfsGJ_PGQ0/v-deo.html
Cardinality of the Continuum video: ua-cam.com/video/iaUwNuaSLUk/v-deo.html
Music:
c418.bandcamp.com/album/dief
Imaginary Interlude by C418
c418.bandcamp.com/album/circle
minimal by C418
love by C418
patriciataxxon.bandcamp.com/album/crocus
Crocus 2 by Patricia Taxxon
Far the Days Come by Letter Box
------------------------------------------------------------------------------------------------
Animations were made by Manim, an open-source python-based animation program by 3Blue1Brown.
github.com/3b1b/manim
This video was submitted to 3Blue1Brown's SoMEπ (Summer of Math Exposition Community Edition).
some.3b1b.co/
Переглядів: 4 701
Відео
The Axiom of Choice
Переглядів 95 тис.4 місяці тому
Mathematics is based on a foundation of axioms, or assumptions. One of the most important and widely-used set of axioms is called Zermelo-Fraenkel set theory with the Axiom of Choice, or ZFC. These axioms define what a set is, which are fundamental objects in mathematics. And the Axiom of Choice is arguably one of the most important and interesting axioms of ZFC. But what does it really say? An...
Genius Mathematicians Lost Too Soon
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Some mathematicians changed the field of mathematics at a young age, only to die too early. Let us look at the lives of some of these young, brilliant minds who left too soon. Evariste Galois was a French mathematician who laid the foundations of abstract algebra and Galois theory, proving the quintic's insolubility. Srinivasa Ramanujan was an Indian mathematician who, upon his genius being dis...
But what is a Vector Space?
Переглядів 3,5 тис.Рік тому
Vectors are fundamental tools in mathematics and sciences. Yet different fields like mathematics, physics, and engineering seem to define vectors differently. It is mathematics, unsurprisingly, that formally defines a vector. We will go through this process of formalization, using the foundational tools of abstract algebra to define and construct a vector space. Additional Resources: Wikipedia ...
Why Logarithms Appear in This Integral
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Before the days of Calculus, one Pierre de Fermat wanted to find the area under the function f(x)=x^n. This problem we now call "integration" was then called "quadrature" or "squaring". Fermat was able to square every function f(x)=x^n for any rational n except for one case: n=-1 (that is, the hyperbola). It turns out that this unique nature of the hyperbola was tied to logarithms and Euler's n...
How to Find the Biggest Primes
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How do people find big primes? These primes have millions of digits, and may take years of collective effort and computing power to be found. Unsurprisingly, mathematicians have figured out various ways to more efficiently and accurately find these big primes. In the process, the unique and interesting properties of various primes have also been found. Great Internet Mersenne Prime Search: www....
Cardinality of the Continuum
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What is infinity? Can there be different sizes of infinity? Surprisingly, the answer is yes. In fact, there are many different ways to make bigger infinite sets. In this video, a few different sets of infinities will be explored, including their surprising differences and even more surprising similarities. 0:00 - Euclid's Proof of Infinite Primes 1:55 - Bigger Infinities? 2:27 - Set Theory and ...
The Cardinality of an Interval
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Cantor's Diagonal Argument proves that there are an uncountable number of real numbers. But what about any interval of real numbers? Are those sets uncountable as well, no matter how small the interval?
Can the power of two irrationals be rational?
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Are there two irrational numbers, let’s say x and y, such that x to the y is rational? The answer to this question brings us through a fascinating journey about transcendental numbers and the Gelfond-Schneider theorem. Additional Resources: Where I found this theorem: math.stackexchange.com/questions/728223/simple-beautiful-math-proof/728276 Music: www.purple-planet.com Animations were made by ...
Why do trig functions appear in Euler's formula?
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Why do trig functions appear in Euler’s formula? This was the question I had when I first saw Euler’s formula. This connection between trigonometry and exponents seems so unexpected, especially along with complex numbers. To answer this question, we must journey into the intricate and beautiful mathematical relationship between trig functions, e, and complex numbers. We will look at two differe...
I wonder the cardinality of the complex numbers set (that set is also not ordinable like the real numbers set).
how can an axiom follow from something?
Very good explanations! You might have spelled out what "two to the power of aleph one" was; that had my audience slightly confused. My only complaint is the music, especially in the middle: dreary and unpleasantly atonal, including a weird "chchcht" noise that with my headphones on gave me the feeling something was being sprayed up the middle of my nose...
Clark James Williams Kenneth Robinson Anthony
How didn't I know about this channel earlier? The world needs to know about the channel.
Maybe it's just me, but I find the music very distracting. 10/10 for all the rest.
Fantastic video
Love the video! I do have one small criticism wholly unrelated to the mathematics: the background music is too loud to the point that it gets a bit overwhelming when wearing headphones. Everything else was pretty much perfect.
beautifully explained
0.011111...and 0.1 is actually the same number in binary, its like 0.999...=1, since the difference should be small enough to be 0, hence the same number🙃
Basic and unforgiveable mistakes? Set theory defines numerals as numbers, otherwise there are no sets or combinations. A set is a heiroglyph or picture of objects that look like mathematical symbols. The properties of the members within the heiroglyph are not transferred onto the set or heiroglyph. The stand-alone iconic form of a number is, and is called, a numeral. A numeral is void of a mathematical container, application or calculus, and a collection of them must be significant for it to be called a set or collection, for example a set of cutlery is significant because it is a tool. Numbers are not transferable between applications, and are themselves void, and not countable, existing only in their calculus. The introduction of infinity into set talking points is an attempt to place the first non-number into a count, usually placed at "the end" because it has no stop - numbers are created through a stop. The largest number is the last stop in the count, such as 6, or 13. Mathematicians will disagree. Mathematicians do not like philosophers.
Don’t try to comment about something you have no understanding in, you clearly haven’t taken any serious math courses
mileswmathis.com/nash.pdf
r u contributing to the advancement of PROPAGANDA? A lil dramatic. How many have been lost to history? TODAY a MATH & SCIENCE genius is CENSORED & completely ignored by the fraud that is mainstream math & science. Miles W Mathis.
Great job brother ❤
A am a mathematican my name its banmien 15 years a am creat new math name math its a black mathematics and very good theory
This channel will have a bright future
Really good animation!
Weirdly enough, this doesn’t sound like an axiom at all (even though it is called one). Kinda like Euclid’s 5th postulate.
I mean this video is phrased quite weird, but roughly the axiom states you can choose an element from any non-empty set, which does sound like a statement basic and assumed enough to be an axiom.
You cannot prove it using only ZF axioms, at least when it comes to infinite sets. That's why we state it as an additional axiom, although some argue that we shouldn't
@@methatis3013 What's the argument against the use of this axiom?
@HappinessReborn some of its implications and equivalences are quite weird, like the banach-tarski paradox or the well ordering principle (that I still don't believe)
thank you so much 🤩🤩🤩. much better than class
Excellent video !!!! Perfect explanations. Nice !!
11:51 That should be A(m,1) = A(m,0)^+ = m^+
The questions are giving me Vsauce vibes I love it
As someone who is familiar with programming and have mild experience with Agda, this was delightful to watch! It seems like everything up to your definition of the integers is fairly standard in Agda, but the way you defined the integers isn’t. (It seems more directly related to how they are defined in cubical Agda, or at least 1Lab.)
7:31 the (k+1) should entirely be the power of 2. But the result is still correct. Nice work.
Thankfully he used 2 as the base lol
This is amazing.
Every time you cut from the animations in front of a dark background to yourself in front of a white wall, I felt like I was getting flash banged and that ruined the flow of the video. Please try to avoid such drastic changes in brightness in future videos!
24:48 I think at the end of the first row it should say [(ad+bc, bd)]E. Great video!
I think I also read somewhere that AC is equivalent to Lagrange’s Theorem from group theory; specifically, the generalization to infinite groups. For this one, it’s actually easy to show AC implies LT, but harder to show LT implies AC.
I'm glad I stumbled across this comment! I remember at the beginning of grad school, my abstract algebra professor made a side comment that you could get Lagrange's Theorem for infinite groups if you're careful, but then didn't mention it. And I never looked into how that would be formulated until now. Thanks for the reminder to look into it! And the stuff I've read agrees with what you've said about the equivalence of AC and LT (for infinite sets), including which direction is easier.
Really nice overview of the motivation for being rigorous! Can you recommend a book or article to read up details? Especially about the step to the real numbers.
The construction from this video takes a lot from Elements of Set Theory by Herbet B. Enderton and Set Theory: An Open Introduction by Tim Button. The latter book is free to download here st.openlogicproject.org/.
at 32:52 , when presenting the dedekind cut for a rational, it's defined as `q < r`; does that imply that r itself isn't in the set defining Q? I feel it should be <= intuitively. also, is it possible to two irrationals without a rational between them? that would imply that there's reals with identical representations though, so I guess not by definition? I guess I'm pretty confused on how irrationals are represented, but that's a kernel for reading great video, thanks!
We want a consistent definition to define all real numbers, and since a Dedekind cut must not have a greatest element, q<=r would unfortunately not work. It's also important to note that this presentation is only for the sake of intuition, since it is circular logic (we can't say pi is the set of all rationals less than pi). This is why the formal definition of a Dedekind cut is more abstract. To answer your second question, yes, the rationals are dense over the reals: math.stackexchange.com/questions/421580/is-there-a-rational-number-between-any-two-irrationals. This discussion here uses a property of reals called the Archimedean property, which is a consequence of our completeness axiom. Finally, note that this is only one way to define Dedekind cuts and real numbers. There are plenty of other constructions which satisfies the real number axioms.
I was literally searching for this yesterday and I found almost nothing. Thx mate.
@19:45 wouldn’t showing this is a transitive relation use subtraction? But that’s not an operation we have yet. We would have that (a,b)~(c,d)~(e,f) Then a+d=b+c c+f=d+e We want to show a+f=b+e So we can add the two equations to get a+d+c+f=b+c+d+e Then by canceling the d+c on both sides we get that a+f=b+e, hence (a,b)~(e,f). But the step of canceling the d+c term uses subtraction which we don’t have yet, so I’m unsure about that.
Similar question on showing transitive property for rationals. It’s obviously transitive using division, but again we are trying to define rationals, so the division operation is not yet defined to use it show this transitive property. That would be circular.
The two sides are (d+c)th succesor, and we have that if m+ = n+, that is if successors are equal, then m=n; so we just ise induction
@@raptor9514 Thanks What about for multiplication
It turns out that this "cancellation" property of the naturals can be directly proven just by our natural number construction. The ability to subtract is really just the existence of additive inverses for all elements of a set. So while additive inverses imply cancellation, cancellation does not necessarily imply additive inverses (and thus subtraction). For the sake of time, I unfortunately had to skip these minor steps but the general idea is that we can prove the cancellation property in N by induction, and using the fact that the natural numbers are what's called "transitive sets".
@@jHan thanks, I appreciate this clarification. I think I’ve seen this proof before, but I thought the video was saying that the transitive step is trivial, but I think there’s something to show there using the induction. Quite nice that transitive property of the naturals gives us the cancellation rule which shows the transitive relation here.
@16:20 we would need a negative in front for negative real number though.
Mate I love your channel, it's criminally underrated. It's clear you have a real passion for mathematics. I graduated with a bachelors in Mathematics 4 years ago and I missed topics like these, we did a bit of set theory but never into the nitty-gritty like this. Would you ever consider doing a video of other constructions of the natural numbers like Peano axioms? Either way, love your content!
great, to say there's nothing is to be god. in the beginning there is nothing, and then god create 0, there there is nothing and 0. and from that all math and universe created. hahaha
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jHan is awesome. And handsome. But "is zero a natural number?"? Man ... the answer to that is very simple: each person decides ... it is a matter of convention. If you want to consider zero a natural number, ok. If you don't consider zero a natural, that's also ok. THAT'S the answer. There is nothing more to it. I don't understand why people still ask such question ...
I liked this presentation, but I feel like the last 30 seconds suddenly brought up some controversial claims with no backing. "Set theory isn't a painstaking formalization for the sake of formalization" I feel like that was why Set Theory was created, though that's certainly not what modern Set theorists do. "The axioms, theorems, and tools of Set theory have applications in every branch of mathematics" I feel like, with the possible exception of the Axiom of Choice, the axioms intentionally don't have applications. They're just a foundation from which we can get things the rest of math needs, like the fundamental property of the ordered pair. And the theorems and tools of Set theory, like forcing and the results that come from it, have essentially no bearing on other fields of mathematics. To be clear, I enjoyed my graduate Set theory classes and I like formalization! I just don't see things the same way.
I subscribed literally today and you uploaded a new vid already awesome
very clear thank you so much 🤩
Babe wake up new jHan video just released
Beautifully explained, connecting all the dots reaching the eureka moment. Thank you so much. Have subscribed to your channel immediately 😁
Great video !
Thank you
You didn't really explain what sets are very well, no offense. For example, at 4:55 (a,b) != (b,a) "a,b are not the same if b,a are not the same". This is very difficult to understand from the perspective of someone who doesn't know set theory. a and b are the same by virtue of the fact that they're a and b, so how can you say they're not the same? it's like saying: (1, 0) != (0, 1), "1,0 are not the same if 0,1 are not the same". What? And then your second example, (a,b) = (a', b') if and only if a=a' and b=b'. That's like saying 1=3*1 and 2=3*2. What? This left me no where closer to understanding set theory.
You’re doing great! Keep up the good work!
But does that mean all lines are equal? Because we can define a one to one correspondence for any two lines . Or we shouldn't related something that is physical to something that is human made( i.e points) I mean we shouldn't say that just because two lengths have the same no. Of points that mean they have same length? Isn't it a paradox I am very confused. If I take the length as an infinite set of points and we can show that all lines have same no. Of points so that means all lengths should be equal?
Look at my quant!
My name is also pronounced J-Han and I also make math UA-cam videos so what a weird coincidence. This is a great video. You are an excellent educator!
First time for me that someone described it so simply and obviously.