Andrew McCrady
Andrew McCrady
  • Видео 290
  • Просмотров 375 781
The Primitive Element Situation is Crazy
The Primitive Element Theorem was a big advancement in field theory. But what does it even mean? I'll explain what a field is, some interesting math history for context, and how to use Sage to easily do some BRUTAL algebra.
Просмотров: 182

Видео

How You Should Think About Infinite Cartesian Products
Просмотров 652Месяц назад
I regularly teach a topology class online, and often it's the first time my students encounter infinite Cartesian products of sets. This video aims to help you understand what elements of such products look like. Thank you for supporting my channel!
Kepler's Second Law as Understood by a Mathematician
Просмотров 3525 месяцев назад
Kepler's 2nd Law is one of my favorite applications of calculus and vectors. I only took one physics class during my school career, so my physical intuition isn't always great. But this proof relies mostly on math, and showcases how mathematics is a language to describe all that's around us (some physics stuff, anyway). I found the proof that I cover here in Krantz's textbook "Differential Equa...
The Subgroup Tests in Under 3 Minutes! Fast Abstract Algebra Help
Просмотров 716 месяцев назад
How do you show a subset of a group is a subgroup? Do you have to check all the group axioms? We'll talk about two ways to test if a subset of a group is a subgroup, and demonstrate how to do the tests with two examples. Hopefully this makes you feel better prepared to solve these kinds of group theory problems!
A Precursor to Group Theory
Просмотров 5796 месяцев назад
Here's a fast but clear introduction to group theory, which makes up a substantial part of a typical abstract/modern algebra class. Before you get frustrated with a super abstract textbook, take 10ish minutes understand the key concepts of group theory with examples and simple explanations. Please like and subscribe to help grow the channel!
Partial Sum Formulas and Asymptotic Analysis
Просмотров 2067 месяцев назад
Finding a summation formula to add the first n natural numbers is easy. Finding a summation formula to add the first n reciprocals is impossible, literally. At least in terms of elementary functions. This video dives into asymptotic analysis to prove there's no "nice" formula for the harmonic numbers. It's a great application of freshman calculus, how long can you follow along? Thanks to a view...
Homotopy Classes, the Path Product, and Associativity
Просмотров 3118 месяцев назад
We give clear explanations visuals for the path product and homotopies of paths in a topological space. We focus on the fact that the path product is not necessarily associative, but that we can extend the path product to equivalence classes of homotopic paths, and show that the path product is associative on these homotopy classes. Along the way we show that a path is homotopic to any reparame...
Homotopy Intro
Просмотров 3919 месяцев назад
Homotopy between paths in a topological space can be tough to understand. This video aims to make it easy to understand! We'll intuitively define what a homotopy between paths is, use pictures and demonstrations to understand this idea, then use this to understand the rigorous definition of a homotopy, along with examples. This video is part of a growing playlist of mine dedicated to topology. ...
Paths and the Path Product
Просмотров 1959 месяцев назад
This topology video introduces paths in a topological space, and then the path product. This is the first video introducing some material needed to discuss the homotopy groups of a topological space. We carefully go over the definitions and animate some examples. The only prerequisite is knowing what a topological space is. I'm aiming to make this an easy introduction to algebraic topology.
ElGamal Encryption and Elliptic Curve Cryptography
Просмотров 2689 месяцев назад
This video explains and illustrates all aspects of ElGamal Encryption and Elliptic Curve Cryptography through the story of Alice and Bob. Will Alice's secret message make it to Bob? More information about elliptic curves and elliptic curve cryptography: www.ams.org/journals/mcom/1987-48-177/S0025-5718-1987-0866109-5/S0025-5718-1987-0866109-5.pdf ruclips.net/video/RtiVaALdqX0/видео.html wstein.o...
Why is the orbit of a planet in a plane?
Просмотров 1,1 тыс.11 месяцев назад
Ever wonder why a planet orbits a star in a plane? Here's a cool proof that uses a little calculus, physics, and vector algebra. Behold, the power of mathematics!
Visual Calculus: Fubini's Theorem for Iterated Double Integrals
Просмотров 622Год назад
Visual Calculus: Fubini's Theorem for Iterated Double Integrals
The Alexander Subbase Theorem: help understanding the definitions and the proof
Просмотров 727Год назад
The Alexander Subbase Theorem: help understanding the definitions and the proof
Understand The Baire Category Theorem: Dense Sets, Nowhere Dense Sets, & Infinity
Просмотров 3 тыс.Год назад
Understand The Baire Category Theorem: Dense Sets, Nowhere Dense Sets, & Infinity
Piecewise Continuous Linear Functions are Dense Among Continuous Functions
Просмотров 799Год назад
Piecewise Continuous Linear Functions are Dense Among Continuous Functions
The Axiom of Choice: History, Intuition, and Conflict
Просмотров 10 тыс.Год назад
The Axiom of Choice: History, Intuition, and Conflict
Cards, Marriage, and Python: an Introduction to Graph Theory
Просмотров 224Год назад
Cards, Marriage, and Python: an Introduction to Graph Theory
Can you solve these three tricky counting problems?
Просмотров 91Год назад
Can you solve these three tricky counting problems?
How many squares are on a chessboard? And more!
Просмотров 343Год назад
How many squares are on a chessboard? And more!
How many triangles are there in an n by n grid?
Просмотров 538Год назад
How many triangles are there in an n by n grid?
The Complex Logarithm: Multivalued Functions?!?
Просмотров 1,4 тыс.Год назад
The Complex Logarithm: Multivalued Functions?!?
How Harmonic Functions Relate to Holomorphic Functions
Просмотров 733Год назад
How Harmonic Functions Relate to Holomorphic Functions
The Polar Form of the C R Equations
Просмотров 176Год назад
The Polar Form of the C R Equations
Harmonic Functions: why they are cool!
Просмотров 409Год назад
Harmonic Functions: why they are cool!
The Complex Trig Functions
Просмотров 203Год назад
The Complex Trig Functions
The Complex Exponential
Просмотров 271Год назад
The Complex Exponential
The Cross Ratio
Просмотров 1,2 тыс.2 года назад
The Cross Ratio
The Extended Complex Plane (Riemann Sphere)
Просмотров 4,9 тыс.2 года назад
The Extended Complex Plane (Riemann Sphere)
The Stereographic Projection: Learn it FAST!
Просмотров 11 тыс.2 года назад
The Stereographic Projection: Learn it FAST!
Euclidean Space, Locally Euclidean Space, and Manifolds
Просмотров 1,2 тыс.2 года назад
Euclidean Space, Locally Euclidean Space, and Manifolds

Комментарии

  • @AsiccAP
    @AsiccAP 18 часов назад

    love this video! I do hope the video is a bit louder though

  • @moonmartex
    @moonmartex 18 часов назад

    Pretty dope theorem

  • @nafisfaisal5817
    @nafisfaisal5817 День назад

    Nicely explained

    • @DrMcCrady
      @DrMcCrady День назад

      Thank you for your comment!

  • @djsjsjjejebfbdj
    @djsjsjjejebfbdj 6 дней назад

    At the end, wouldn't 0 itself be in the intersection though? would love to be corrected

    • @DrMcCrady
      @DrMcCrady 6 дней назад

      Hello, yep you’re right, 0 is in all of them.

  • @michaelschwartz839
    @michaelschwartz839 7 дней назад

    my goat

    • @DrMcCrady
      @DrMcCrady 7 дней назад

      Hope it was helpful!

  • @SSaitElmas
    @SSaitElmas 10 дней назад

    Thanks a lot. Great video.

    • @DrMcCrady
      @DrMcCrady 10 дней назад

      Thank you for your comment!

  • @NaderHGhanbari
    @NaderHGhanbari 11 дней назад

    Amazing visualization. When I first studied topology, I thought of R^w (or R^N) as the set of all real-valued sequences and R^w1 (or R^R) as the set of all real-valued functions. Later I learned about how this concept is called an Exponential in a Cartesian Category. Studying category theory really helped me go back and re-learn abstract algebra, topology, etc. through a new lens.

    • @DrMcCrady
      @DrMcCrady 11 дней назад

      Thank you for your comment!

  • @dev-ii9bd
    @dev-ii9bd 13 дней назад

    Wonderful. Thanks

    • @DrMcCrady
      @DrMcCrady 13 дней назад

      Thank you for your comment!

  • @curtischee2532
    @curtischee2532 13 дней назад

    Great video. I spent so much time trying to understand this. Your video really helps. Will you make more videos?

    • @DrMcCrady
      @DrMcCrady 13 дней назад

      Glad it was helpful! I do plan to try to make more videos, it’s just been tough to make as many as I used to.

  • @srijakarmakar
    @srijakarmakar 17 дней назад

    It's really good! Thanks for sharing 😊

    • @DrMcCrady
      @DrMcCrady 17 дней назад

      Thank you for your kind words, I hope it was helpful!

  • @CartDart
    @CartDart 18 дней назад

    Ok I just have to say this before I watch the whole video the bagel and the Coco milk looks delicious 😋

  • @malikialgeriankabyleswag4200
    @malikialgeriankabyleswag4200 27 дней назад

    This is the box topology not the product topology according to my modules material..

    • @DrMcCrady
      @DrMcCrady 27 дней назад

      Yep they’re the same for a product of a finite number of spaces.

    • @malikialgeriankabyleswag4200
      @malikialgeriankabyleswag4200 26 дней назад

      @DrMcCrady You're right sorry spoke before reaching far enough into the chapter 😂 my bad

    • @DrMcCrady
      @DrMcCrady 26 дней назад

      No problem thanks for watching!

  • @themagictoaster2058
    @themagictoaster2058 28 дней назад

    Such a cool proof, and very helpful!

    • @DrMcCrady
      @DrMcCrady 28 дней назад

      Glad to hear it!

  • @MathPhysicsEngineering
    @MathPhysicsEngineering Месяц назад

    On 5:30 you have a mistake when you say x* => x_n for all n=>N. Consider a monotone decreasing sequence x_n=1+1/n. Then x*=limsup(x_n)=liminf(x_n)=lim x_n = 1. Howevere x_n > 1 = x* for all n. The conclusion you derive later is correct but for the wrong reason. You need to conser the sequence X_n=sup{ x_m | m=>n}. Then x*=inf(X_n). Then you can say that by definition of inf there exists N such that x*+eps> X_N and since for every n=>N we have that X_N is the upper bound of {x_n | n=>N } we conclude that x*+eps > x_n for all n>N.

    • @DrMcCrady
      @DrMcCrady Месяц назад

      Hey thanks, I must have gotten too wrapped up in my picture 😁

  • @rosskious7084
    @rosskious7084 Месяц назад

    Using the concept of open balls without using the numerical meaning to drive the definition of continuity in topological spaces: got it!

    • @DrMcCrady
      @DrMcCrady Месяц назад

      Yep that sounds good!

  • @thomasjefferson6225
    @thomasjefferson6225 Месяц назад

    Pretty good video. i never thought of it like this before

  • @thomasjefferson6225
    @thomasjefferson6225 Месяц назад

    I like the idea that if a set is connected the only disjoint sets from the topology that form X are the entire space and the empty set. Or in other words, the only two clopen sets that can form the topology is the space itself and the empty set. Otherwise its not connected. thanks viro. I used this graph idea recently on this set of { (x, y in R^2 | x > 0 and y = sin(1/x)}. its graph is {x, f(x)} which is homeomprhic to the real line, and is thus path connected. i love this stuff. you an also use this connected property to show if something isnt a homeomorphism. for eample R -> S1 isnt a homeomorphism since if we take a point away from the line R we have created two connected componets. However if we remove a point from S1, its still connected! BLEW MY MIND, way easier than proving a homeomorphism typically.

    • @DrMcCrady
      @DrMcCrady Месяц назад

      The latter example about R and S1 is great!

  • @bartolobenlordd.9299
    @bartolobenlordd.9299 Месяц назад

    I wonder how do you animate these things?

  • @tom-e1w
    @tom-e1w Месяц назад

    I just finished learning about co-vectors which are the set of linear functions from R^n and has size R^n. I wonder what the size of other restricted sets of functions like polynomial functions or continuous functions ect.

    • @DrMcCrady
      @DrMcCrady Месяц назад

      Hi Tom, that’s such cool stuff! Each of those sets has the same cardinality as R.

  • @gileadedetogni9054
    @gileadedetogni9054 Месяц назад

    I should have seen this video when I started studying topology on infinite cartesian products, it would have made much more sense to me. Great video, as always :)

    • @DrMcCrady
      @DrMcCrady Месяц назад

      Thank you for the compliment!

  • @AlokKumar-q7h3u
    @AlokKumar-q7h3u Месяц назад

    Hello sir, I just want to know that the prove you have shown is Constructive or Non Constructive.

    • @DrMcCrady
      @DrMcCrady Месяц назад

      Hello AlokKumar! I believe the proof is constructive. E is non empty and bounded above so the supremum u of E exists. Then for any v in E with v<u we know [a,v] has a delta-fine partition P1^dot. Then we enlarge this to P2^dot that is a delta fine partition of [a,u], and ultimately show u is b, so the P2^dot we constructed wins the game for us.

    • @AlokKumar-q7h3u
      @AlokKumar-q7h3u Месяц назад

      ​@@DrMcCradyThanks sir ,this doubt was really a great trouble for me.

  • @stormysky7774
    @stormysky7774 Месяц назад

    Thank you so much for taking the time to draw out the visuals as well. It's really difficult to visualize without a representation sometimes so all the graphs are a godsend.

    • @DrMcCrady
      @DrMcCrady Месяц назад

      Glad it was helpful!

  • @erawanpencil
    @erawanpencil Месяц назад

    Why are 1's in these formulas? i.e. I'm not clear why the formulas all involve either +1 or -1 in some fashion. Why 1 and not some other number? I'm picturing light shining through a transparent sphere, and I wouldn't have thought something as clearcut as a simple factor of 1 would be at play, I would have thought it'd be some complicated mess involving pi or something. Thanks I appreciate it

    • @DrMcCrady
      @DrMcCrady Месяц назад

      Sure, the 1s come from the radius of the unit sphere. Around 1:06, the vertical axis is has a length of 1 unit since it reaches from the center of the sphere (the origin) to the North Pole N (top of the sphere). Next, P’s coordinate with respect to this axis is z, so the length of the vertical blue segment is the difference 1-z. In other words, the total colored part of the vertical axis has length 1, the orange part has length z, so the blue part has length 1-z.

  • @BEEP640
    @BEEP640 2 месяца назад

    Thank you so much! This helped me understand directional derivatives a lot more with the visualizing.

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      Glad it was helpful!

  • @polattopcu6124
    @polattopcu6124 2 месяца назад

    You have no idea how helpful these videos on complex analysis are to me. Thank you for your efforts

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      I’m glad to hear they’re helpful! Best wishes for the rest of your semester.

  • @EfExXE
    @EfExXE 2 месяца назад

    Wonderful explanation

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      Thank you, I hope it was helpful!

  • @hepp00
    @hepp00 2 месяца назад

    An amazin explanation. Respect

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      Thank you! Glad it was helpful!

  • @shashvatshukla
    @shashvatshukla 2 месяца назад

    This video makes the world a better place

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      Hope it was helpful!

  • @nicolasbello1275
    @nicolasbello1275 2 месяца назад

    Incredible video

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      Thank you! Hoping it was helpful.

  • @raagstar4084
    @raagstar4084 2 месяца назад

    This really helped me understand, thankyou very much keep it up

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      Glad it was helpful!

  • @kostas_fanou5898
    @kostas_fanou5898 2 месяца назад

    Very helpful!! Thank you

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      Glad it was helpful!

  • @pukaman2000
    @pukaman2000 2 месяца назад

    You cannot find the first N just as you cannot find the last real number closes to the origin.

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      We are using the fact that the natural numbers are well ordered with respect to our typical inequalities. You cannot pick a real number closest to the origin because the real numbers are not well ordered with respect to our typical inequalities. Does that make sense?

  • @bantix9902
    @bantix9902 2 месяца назад

    This is so cool!!!! I love math

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      Math is pretty great!

  • @cynnolini2208
    @cynnolini2208 2 месяца назад

    I'm watching all the videos in this playlist without headphones and my mum went: "He has such a beautiful voice" lolol and I agree tbh. Jokes aside thank you for sharing these, life-saving. ❤

    • @DrMcCrady
      @DrMcCrady 2 месяца назад

      Thank you, I am glad they are helpful, and tell your mom thanks!

  • @gileadedetogni9054
    @gileadedetogni9054 3 месяца назад

    Great vid bro

    • @DrMcCrady
      @DrMcCrady 3 месяца назад

      Hey thank you!

  • @logandihel
    @logandihel 3 месяца назад

    Thanks! I just encountered the phrase "commuting diagram" for the first time and this video was a great sanity check!

    • @DrMcCrady
      @DrMcCrady 3 месяца назад

      Glad it was helpful!

  • @ESCMatteo
    @ESCMatteo 3 месяца назад

    Thank you! It was very helpful :D

    • @DrMcCrady
      @DrMcCrady 3 месяца назад

      Glad it was helpful!

    • @ESCMatteo
      @ESCMatteo 3 месяца назад

      @@DrMcCrady You’re great! And you present things concisely so thanks again :)

  • @6388-s2n
    @6388-s2n 4 месяца назад

    Great video, thanks

  • @dr.salwasalman6752
    @dr.salwasalman6752 4 месяца назад

    Thanks

    • @DrMcCrady
      @DrMcCrady 4 месяца назад

      Glad it was helpful!

  • @frederickgriffth4431
    @frederickgriffth4431 4 месяца назад

    You saved my life😢😢😢!Very clear and helpful! Thank you!

    • @DrMcCrady
      @DrMcCrady 4 месяца назад

      Glad it was helpful!

  • @jessicakhoza4784
    @jessicakhoza4784 4 месяца назад

    thank you

    • @DrMcCrady
      @DrMcCrady 4 месяца назад

      Hope it was helpful!

  • @futureiskey6049
    @futureiskey6049 5 месяцев назад

    This is great

    • @DrMcCrady
      @DrMcCrady 5 месяцев назад

      Thank you, hope it was helpful!

  • @Timmy-zl1gu
    @Timmy-zl1gu 5 месяцев назад

    😀

  • @ismiregalichkochdasjetztso3232
    @ismiregalichkochdasjetztso3232 5 месяцев назад

    I think this deserves a sequel that explains intuitionistic logic.

  • @aryankushwaha7028
    @aryankushwaha7028 5 месяцев назад

    Really amazing ,can you teach complex number, like this

    • @DrMcCrady
      @DrMcCrady 5 месяцев назад

      Glad you liked it! I have a playlist of some lectures about complex variables, check it out.

  • @matheus3905
    @matheus3905 5 месяцев назад

    Your lectures are helping me tremendously in my Analysis course!

    • @DrMcCrady
      @DrMcCrady 5 месяцев назад

      Glad to hear it!

  • @Bethos1247-Arne
    @Bethos1247-Arne 5 месяцев назад

    Georg Cantor was German. Also if you use German names, could you pronounce them German?

    • @DrMcCrady
      @DrMcCrady 5 месяцев назад

      Es tut mir leid. Er wurde in St. Petersburg, zog aber im Alter von 10 Jahren nach Deutschland, also verstehe ich, dass es passender ist, ihn als Deutsch zu betrachten, mein Fehler.

  • @Necrozene
    @Necrozene 6 месяцев назад

    The Banach-Tarski construction produces sets without measure, so it is not a problem at all.

  • @Necrozene
    @Necrozene 6 месяцев назад

    Ever since I learned out it when I was 12, I was in love with it. It makes perfect sense, and no-one could adequately explain the problem.

    • @DrMcCrady
      @DrMcCrady 6 месяцев назад

      Wow 12 seems really young, impressive!

    • @Necrozene
      @Necrozene 6 месяцев назад

      @@DrMcCrady I had a great maths teacher, who had a beautiful poster. I was curious, and he took the time to explain it to me. Mr Doolan.

    • @Necrozene
      @Necrozene 6 месяцев назад

      @@DrMcCrady I'm watching a vid on Lie algebra right now! Love it!

    • @Necrozene
      @Necrozene 6 месяцев назад

      @@DrMcCrady Oh, and I thought the Banach-Tarski "paradox" was very cute. I saw no logical problem with that! We already knew that there were as many points in the segment [0;1] as the square [0;1]x[0;1] so there was no problem, just an amusing result! So, it's not continuous; that's OK!

    • @michaelmicek
      @michaelmicek 5 месяцев назад

      There is no well ordering for the reals. So yeah, I've hated it since I was introduced to it and think it's used to prove things that aren't "true" in essence.

  • @David-id6jw
    @David-id6jw 6 месяцев назад

    So it sounds like the Axiom of Choice isn't that you can pick an element from a set, it's that you can pick an element from a set and _know what it is._ For example, using the well-ordered principal, you can always find the smallest value in a set, so you can always choose the smallest element. Without the well-ordered principal, it's like trying to choose a sock when you can't tell which one is the left or right. That doesn't work with a bag of red marbles, because there's no order to them, so you can't pick the 'smallest'. If you could distinguish them by the number of atoms in each one, you could order them. If you had a bag of marbles of all different colors, you might order them by the wavelength of light that they reflect, and thus choose the one reflecting the shortest or longest wavelengths. But without some means of ordering (which requires additional information about the marbles other than "red"), whatever gets picked is arbitrary, not defined by a rule, and thus seems to fail the assertion because there is no function to get you the result. Or more accurately, a specific, repeatable result, because a function with a given input must always produce the same output. (This assumes that the different red marbles are in fact different entities, which is required by another comment describing how probability works.)