Real Analysis, Lecture 26: Ordinal Numbers and Transfinite Induction

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  • เผยแพร่เมื่อ 24 ม.ค. 2025

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  • @jimmydu444
    @jimmydu444 13 ปีที่แล้ว +47

    Thumbs up if you watched through all of the lectures!
    Thank you HMC and Professor Su!

    • @newkid9807
      @newkid9807 4 ปีที่แล้ว

      Wizard of Oz su... A good friend of mine described him perfectly, Win at all costs, the tragedy of Professor Su

    • @x0cx102
      @x0cx102 3 ปีที่แล้ว +4

      @@newkid9807 that makes absolutely no sense

    • @quantumgaming9180
      @quantumgaming9180 5 หลายเดือนก่อน

      @@x0cx102 indeed

  • @LaureanoLuna
    @LaureanoLuna 10 ปีที่แล้ว +19

    25:50 w+1 (omega plus one) is not the supremum of the set of all ordinals less than w+1, as he says. The set of all ordinals less than w+1 is w+1 itself and its supremum is its (great) union, which is just w, not w+1. Note that w+1 contains w while the union of w+1 does not contain w, since no member of w+1 contains w. Successor ordinals are never their own suprema, only limit ordinals are.

    • @LaureanoLuna
      @LaureanoLuna 10 ปีที่แล้ว +4

      Be careful: he makes the same mistake again at 34:11.

    • @BareClause
      @BareClause 6 ปีที่แล้ว +4

      Yes, in fact, an ordinal is a limit ordinal if and only if it is equal to its union and an ordinal is a successor ordinal if and only if it is equal to the successor of its union.

    • @markusklyver6277
      @markusklyver6277 ปีที่แล้ว

      I thought of this too. This property only holds for limit ordinals.

  • @jordanwoltjer2024
    @jordanwoltjer2024 9 หลายเดือนก่อน +4

    gonna miss you Professor Francis Su 😢

    • @jidrit999
      @jidrit999 4 หลายเดือนก่อน

      What happened

    • @jordanwoltjer2024
      @jordanwoltjer2024 4 หลายเดือนก่อน +2

      @@jidrit999 haha sorry, I just meant I had finished the last lecture and was sad to not have any more math content from him. To best of my knowledge he's still alive and well!

    • @jidrit999
      @jidrit999 4 หลายเดือนก่อน

      @@jordanwoltjer2024 ok you make me scare man

  • @jdbrown371
    @jdbrown371 5 ปีที่แล้ว +5

    40:00 Transfinite Induction

  • @joejoejoe3
    @joejoejoe3 ปีที่แล้ว

    this is a phenomenal lecture series! professor su is one of the best math lecturers i've ever seen, bravo!

  • @AdamMcLean
    @AdamMcLean 13 ปีที่แล้ว +3

    Professor Su is an excellent lecturer. He presents the sometimes dense material in a clear way. I hope he will issue some further lectures on related subjects. There is a lack of a good video course on complex analysis.

    • @beback_
      @beback_ 6 ปีที่แล้ว +1

      Presenting dense material to dense learners... :p

  • @DrThalesAlexandre
    @DrThalesAlexandre หลายเดือนก่อน

    Thank you for the lectures, Professor. It has been a pleasure!

  • @navidnoroozi8361
    @navidnoroozi8361 12 ปีที่แล้ว +4

    Prof. Su's lectures on Analysis I are really great. Hope that he will provide video lectures of Analysis II.

    • @newkid9807
      @newkid9807 4 ปีที่แล้ว +2

      Navid Noroozi his lectures on analysis 2 completely flopped, they were terrible...

    • @smalljbug
      @smalljbug 4 ปีที่แล้ว +1

      @@newkid9807 where did you find them?

    • @anasabdel2376
      @anasabdel2376 3 ปีที่แล้ว

      There is no link for analysis II please

  • @Liaomiao
    @Liaomiao 13 ปีที่แล้ว +1

    great set of lectures, hoping to see more lectures such as real analysis 2, complex analysis etc

  • @laurenbarghout4449
    @laurenbarghout4449 2 หลายเดือนก่อน

    Love watching this first thing in the morning with a cup of coffee. ~smiles

  • @kashnigahbaruda
    @kashnigahbaruda 13 ปีที่แล้ว +2

    Oh my god! Please give us analysis 2!
    (or anything with Professor F. Su!)

  • @biggerthaninfinity7604
    @biggerthaninfinity7604 3 ปีที่แล้ว

    50:00 Is there a set K in R^2 that intersects every line exactly twice?

  • @LaureanoLuna
    @LaureanoLuna 11 ปีที่แล้ว

    0:41:39 Frédéric Ouimet, one year ago: In defining inductive sets. it's not necessary to say that they must contain 0. It's enough to say that if everything less than n is in the set, then n is also in the set, for all n. Just as he defines. Since there is nothing less than 0 in the ordinals, everything less than 0 is in any set, hence 0 is in any inductive set so defined. Remember that any conditional with false antecedent is true; 'if m is less than 0, then m is in S' is true for any m and any S, because the antecedent is always false.

  • @brianbutler2481
    @brianbutler2481 8 ปีที่แล้ว

    Thanks so much Prof Su! I made it all the way through and I'm glad I did. The lectures were very high quality! Brian, HMC class of 1989

  • @2558rkr
    @2558rkr 11 ปีที่แล้ว +1

    prof. Fransic su thanks for all real analysis lectures,hopefully we will see u in real analysis-2

    • @jagwasenibanerjee1424
      @jagwasenibanerjee1424 4 ปีที่แล้ว

      Did you find any lectures on topics of analysis-2? From Prof Su or any other professors?

  • @biggerthaninfinity7604
    @biggerthaninfinity7604 3 ปีที่แล้ว

    18:50
    S(a) = { a U {a} } rather than S(a) = a U {a} ???
    Please, someone would help me. Thank you.

    • @biggerthaninfinity7604
      @biggerthaninfinity7604 3 ปีที่แล้ว

      [The Joy of Sets] - Keith Devlin, page 24
      n={0,1,2,...,n-1}
      So, n+1={0,1,2,...,n}=nU{n}.
      Page 23, As a result of our development of ordinals, we obtain, gratis, a neat definition of the natural numbers.
      Impressive!!! Now we define the integers, finally!!!

  • @NoNTr1v1aL
    @NoNTr1v1aL 3 ปีที่แล้ว +1

    Absolutely amazing video!

  • @chuchogl8160
    @chuchogl8160 9 ปีที่แล้ว +1

    Thanks Dr Francis, thanks to you I got an A in analysis 1. Waiting for the videos in Analysis 2.

    • @jagwasenibanerjee1424
      @jagwasenibanerjee1424 4 ปีที่แล้ว

      Did you find any lectures on topics of analysis-2? From Prof Su or any other professors?

  • @porterhowland8655
    @porterhowland8655 9 ปีที่แล้ว +2

    Really fun lectures! I'm hoping Professor Su also posts videos for Analysis II.

    • @jagwasenibanerjee1424
      @jagwasenibanerjee1424 4 ปีที่แล้ว

      Did you find any lectures on topics of analysis-2? From Prof Su or any other professors?

    • @porterhowland8655
      @porterhowland8655 4 ปีที่แล้ว

      Jagwaseni Banerjee I didn’t. I ended up just taking the second half of the course at university. For self study, I would recommend just going through Rudin on your own (and asking for help on math stack when you get stuck). The solutions for Rudin’s Principles of Mathematical Analysis are available online. Good luck!

    • @jagwasenibanerjee1424
      @jagwasenibanerjee1424 4 ปีที่แล้ว +1

      @@porterhowland8655 okay actually I have no mentor or guide or professor at this moment so I don't know if I am capable of learning from Rudin on my own. A little self doubt issues here..😅😅 I will try my best though. Thank for replying. Good luck to you too.😊

    • @porterhowland8655
      @porterhowland8655 4 ปีที่แล้ว

      Jagwaseni Banerjee good luck man! I can sympathize, because I’ve been in similar situations before: wanting to learn a subject, but don’t have anyone I can get help from when I’m stuck. Just try your best and see how far you get. ;)

    • @jagwasenibanerjee1424
      @jagwasenibanerjee1424 4 ปีที่แล้ว

      @@porterhowland8655 yes trying my best is all I can do. Thank you for your good wishes. Happy learning !😇

  • @Tetraglot
    @Tetraglot 11 ปีที่แล้ว +6

    Oh, it's an optional lecture… I was starting to get worried my real analysis class was skipping stuff xD

  • @jakejohnson6135
    @jakejohnson6135 12 ปีที่แล้ว

    On your proof by contradiction of strong induction: "if the least element n not in A is in N then there is an Sn that is in N that is also in A, therefore, n is in A." What if n is equal to 0, or whatever, such that it has no predecessor in N. Then there would be no Sn in A that comes before it.

  • @류성원-p9c
    @류성원-p9c 8 ปีที่แล้ว

    Great Lectures! Thank you so much Prof Su!

  • @markusklyver6277
    @markusklyver6277 ปีที่แล้ว

    I don't really understand the induction step of the transfinite induction example. Can someone explain how we verify that K_α satisfies the smiley conditions?

  • @jagwasenibanerjee1424
    @jagwasenibanerjee1424 4 ปีที่แล้ว

    Anyone have suggestions about any lectures on topics of analysis-2? Is there available lectures by Prof Su or any other professors?

  • @valtih1978
    @valtih1978 12 ปีที่แล้ว

    It is a great lecture. It is more instructive than all papers I have seen around but I still do not understand why w*w != w (owing to uncommunativity, like 2*w was exaplained) and how can you count the uncountable?

    • @robertwilsoniii2048
      @robertwilsoniii2048 7 ปีที่แล้ว

      Valentin Tihomirov It’s an ambiguous convention to adopt the meaning that w*w = w^2 which is no less ambiguous. But, the limit definition of w^2 is not ambiguous, and instead of choosing the x*w definition of multiplication it simply chooses the w*x convention. Thus w*w = w*x where x = w. I know it’s silly but that’s it.
      Notice, this means you have omega groups of omega. So, to visualize the set and it’s ordinal you have to visualize omega many sets of omega, or omega many sets of N, the natural numbers. This is a countable set.
      I’m not sure what the associated cardinal number for this set is but there is one.

  • @HotPepperLala
    @HotPepperLala 12 ปีที่แล้ว +2

    MORE ANALYSIS LECTURES PLEASE!!

    • @newkid9807
      @newkid9807 4 ปีที่แล้ว

      Hot Pepper Lala he is done when he says so!

  • @ricardosuarez2707
    @ricardosuarez2707 2 หลายเดือนก่อน

    Thank you so much

  • @xy-xe4zl
    @xy-xe4zl 4 ปีที่แล้ว +2

    thank you!and why there is no analysis II,i cant finish second half of baby rudin😂

    • @newkid9807
      @newkid9807 4 ปีที่แล้ว

      叶笑 because you’re an asshat

  • @aftermath4096
    @aftermath4096 12 ปีที่แล้ว

    yes he forgot to mention 1 (or 0) has to be in A for it to be inductive

  • @christophersedlak1147
    @christophersedlak1147 ปีที่แล้ว

    thanks

  • @daviangel
    @daviangel 13 ปีที่แล้ว

    OMG there is more!
    Doesn't it just become complex or functional analysis?

  • @youdontknowme398
    @youdontknowme398 4 ปีที่แล้ว

    Amazing video,Glad I've make it to the end

  • @rshrott
    @rshrott 12 ปีที่แล้ว

    Please tell me which textbook he teaches from.
    Thanks

  • @jaykazmi
    @jaykazmi 10 ปีที่แล้ว +7

    Prof Su. I think i'm not the first one to say but what the hell happened to Analysis 2 lectures?. dont get me wrong. You did a fine and noble job but this is plain co*& teasing:)! kidding... but seriously man, if you have them recorded, please upload them. Its been 4 years..And i hope the quality is much better ...Finger crossed. Thanks!

    • @brandomiranda6703
      @brandomiranda6703 6 ปีที่แล้ว

      did you find out if he released analysis 2?

    • @beback_
      @beback_ 6 ปีที่แล้ว

      I googled a bit for Advanced Analysis lectures and found this series:
      th-cam.com/video/-hErMp2FQ0o/w-d-xo.html
      Not yet sure how good they are.

  • @dopplerdog6817
    @dopplerdog6817 3 ปีที่แล้ว +1

    Ill miss cyclops smiley

  • @2558rkr
    @2558rkr 11 ปีที่แล้ว

    real analysis walter rudin

  • @lomertamahon1
    @lomertamahon1 11 ปีที่แล้ว +1

    This lecture died right about 28:00.

  • @-_Nuke_-
    @-_Nuke_- 7 ปีที่แล้ว +3

    +1 Vsauce brought me here :)

  • @matthewv5063
    @matthewv5063 11 ปีที่แล้ว

    ME! AND I HATE IT