2Fast2Finite: Breaking the natural speed limit of finite numbers

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ความคิดเห็น • 107

  • @SheafificationOfG
    @SheafificationOfG  4 หลายเดือนก่อน +12

    Thank you Brilliant for sponsoring!
    To try everything Brilliant has to offer-free-for a full 30 days, visit brilliant.org/GSheaf/ . You’ll also get 20% off an annual premium subscription!

    • @Fire_Axus
      @Fire_Axus 4 หลายเดือนก่อน

      you are a monster

  • @huhneat1076
    @huhneat1076 4 หลายเดือนก่อน +47

    This video is so wild. I can't tell at any moment if the 3B1B music is going to fade in, or if Kusuo is going to sneeze the video in half

  • @denizgoksu9868
    @denizgoksu9868 4 หลายเดือนก่อน +129

    Fast growing hierarchy my beloved

    • @Balequalm
      @Balequalm 3 หลายเดือนก่อน +1

      YİNE KARŞILAŞTIK!
      Sen matematik okuyor musun ya?

    • @yokoesque4288
      @yokoesque4288 หลายเดือนก่อน +1

      vay be deniz abem

  • @AdvayMengle
    @AdvayMengle 4 หลายเดือนก่อน +7

    Good to see transfinite induction repped on YT so well.

  • @Filup
    @Filup 4 หลายเดือนก่อน +43

    I am currently recovering from the flu and the Neir credits caught me so off guard that I almost died hacking my lungs up lmfao

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +12

      You almost experienced your own fast-credit ending! Glad you survived

  • @newwaveinfantry8362
    @newwaveinfantry8362 4 หลายเดือนก่อน +13

    That was a genius way to end the video!

  • @duncanw9901
    @duncanw9901 4 หลายเดือนก่อน +15

    Wainer's theorem on the indeterminacy of termination of some member of the fast-growing hierarchy floored me more than the main result did---might we expect a video on that one sometime?

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +9

      Just to clarify: all fast-growing functions (indexed by ordinals less than epsilon_0) provably terminate. The result is more that PA-provably terminating computable functions are necessarily bounded in growth by something in the fast-growing hierarchy (which implies the unprovability of Goodstein's theorem in PA).
      As for whether I'll make a video on it, we'll have to see! Ordinals have been getting a lot of my attention lately, and I want to diversify a bit to other topics I enjoy, but we'll see! In the meantime, you can always try giving Wainer's original paper a read: "A Classification of the Ordinal Recursive Functions" (though it's a 1970 paper, so it's not necessarily a walk in the park to parse).

    • @duncanw9901
      @duncanw9901 4 หลายเดือนก่อน

      @@SheafificationOfG I really should know to specify what something is provable relative to by now, lol. Yeah, thanks for the clarification and pointer, and no pressure! Great videos.

    • @duncanw9901
      @duncanw9901 4 หลายเดือนก่อน +1

      Oh I should also ask---first-order PA or (based and antifoundationalist-pilled) second-order PA? I would be much more surprised if it were the latter, as my intuition is basically that the latter entails everything "non-exotic and worth saying" about N.

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +3

      @@duncanw9901 PA as in first-order. Second-order is strong enough to define representations of ordinals!

  • @SultanLaxeby
    @SultanLaxeby 14 วันที่ผ่านมา

    This is actually a very good argument against mathematical finitism: there are interesting statements about finite objects which cannot be proved with finite methods!

  • @VaradMahashabde
    @VaradMahashabde 4 หลายเดือนก่อน +5

    The proof for the process ending in finite steps is relatively simple.
    Suppose the number in 42, in base 2 is 0b101010. Then make a tuple (1,0,1,0,1,0), with the numerical form being in base 2. Then the next entry is (1,0,1,0,0,2) = 101002 in base 3, then (1,0,1,0,0,1) in base 4, (1,0,1,0,0,0) in base 5, (1,0,1,0,1,0) in base 6, (1,0,0,6,6,6) in base 7, and so on.
    In this form, it is abundantly clear that the number is increasing in representation by increasing the base, but not in the actual face values. If we give a comparison relation to the tuples x= (x_m, ....,x_2,x_1,x_0), y= (y_n, ...,y_2,y_1,y_0), as x>y if m>n. If m=n, then x>y, if x_m > y_n. If x_n = y_n, then x>y if x_{m-1} > y_{m-1} and so on. Of course, x_m, y_N are non-zero.
    Using this comparison relation, we see that the entries keep decreasing.
    We know that x_0 is decremented at each step, so a finite number of steps. It will thus become 0 in a finite number of steps (precisely x_0 steps). Thus x_1 will be decremented in a finite number of steps and thus reaches 0 in a finite number of steps. Thus for any fixed i, x_i will be decremented in a finite number of steps, and reaches 0. Thus the largest x_n is set to 0 in a finite time. By induction, x_{n-1} is also set to 0 in a finite number of steps, and thus the entire tuple becomes (0,0,...,0,0) in finite time.
    Of course, inventing this machinery for the sake of this one proof fails to give any insight, the number of steps, etc, and the tuple construction is basically identical to a transfinite ordinal form. So the transfinite ordinal proof is prettier and more informative.

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +7

      This argument only addresses ordinary base b expansions, which is provable in PA. However, Goodstein sequences are based on *pure* (or hereditary) base b expansions, meaning that the exponents are recursively expanded in pure base b as well.
      For example, 42 = 2^5 + 2^3 + 2^1 would actually expand to 2^(2^2+1) + 2^(2+1) + 2^1, and the next step of the Goodstein sequence would be 3^(3^3 + 1) + 3^(3+1) + 3^1 - 1.
      In particular, you can't really represent these hereditary expansion shapes using mere tuples of numbers, and this structure significantly complicates the proof. This is the main reason for introducing ordinals in Goodstein's original proof!

    • @VaradMahashabde
      @VaradMahashabde 4 หลายเดือนก่อน +3

      @@SheafificationOfG oh right, forgot about the exponents
      Edit : so infinite ordinals effectively "compresses" the exponential indexing to not move, while the tuple system still uses finite numbers for indexing inside the ordinal, so can't capture the decreasing nature of the ordinals properly? Of course we could more tuples to index the position inside the main tuples, but that just removes the problem to exponents inside exponents, and infinite ordinals compress all of that.

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +7

      Exactly, the role of ordinals in the proof is to serve as a beautifully compact encoding of the tree-like "shape" of these nested exponentials, while also giving us exactly the kind of "ordering" we need to observe that these shapes descend to zero.

  • @notEphim
    @notEphim 4 หลายเดือนก่อน +59

    Now I hope one day you get ω-th subscriber, so your statement at the end is false

    • @viliml2763
      @viliml2763 4 หลายเดือนก่อน +11

      it would also be false if he had 0 subscribers

    • @computationaltrinitarianism
      @computationaltrinitarianism 4 หลายเดือนก่อน +16

      If he makes it to ε_0, and even base-k borrows will not make sense.

    • @finxy3500
      @finxy3500 4 หลายเดือนก่อน +8

      @@viliml2763 You forgot his desk fan

  • @carloselfrancos7205
    @carloselfrancos7205 4 หลายเดือนก่อน +2

    Well, I'm almost finished watching all of your videos. I can only say this: if you make more, I'll gladly watch it :)

  • @newwaveinfantry8362
    @newwaveinfantry8362 4 หลายเดือนก่อน +16

    I never thought I would see Psaiki K in a Googology video. 2024 is both amazing and terrible.

  • @StefanoTrevisani
    @StefanoTrevisani 4 หลายเดือนก่อน +2

    This was so enjoyable to watch. 😂 Finding the perfect spot between inflrmative and just trolling your viewers is not easy, chapeau!

  • @carloselfrancos7205
    @carloselfrancos7205 4 หลายเดือนก่อน +6

    Love this channel ! Very good work man

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +1

      Thanks fam!

    • @Fire_Axus
      @Fire_Axus 4 หลายเดือนก่อน +1

      your feelings are irrational

  • @Dedjkeorrn42
    @Dedjkeorrn42 4 หลายเดือนก่อน +1

    I appreciate the subtitles ❤

  • @Friek555
    @Friek555 3 หลายเดือนก่อน +2

    This single video has better memes than all of /r/mathmemes combined

  • @joeeeee8738
    @joeeeee8738 4 หลายเดือนก่อน +2

    I wonder what is the inflection point (since it grows and then comes back to 0). Or if there are multiple inflection points? As in a roller-coaster

  • @redpepper74
    @redpepper74 4 หลายเดือนก่อน +5

    “teal DW” really tickled my funny femur

  • @pyrogenic
    @pyrogenic 4 หลายเดือนก่อน +2

    This video was very interesting, but I'll admit that I might need to train for another thousand years to claim the understanding of the content as my own

  • @legendgames128
    @legendgames128 3 หลายเดือนก่อน +3

    "Well you probably looked it up on Wikipedia" So who did the calculation that even allowed Wikipedia to have that number?! /lighthearted

  • @legendgames128
    @legendgames128 3 หลายเดือนก่อน +1

    Also, for the sequence for 5, it looks like the 1s term for the first number in the term doubles and subtracts 1 every time it reaches the next chunk. So 1,3,7,... does this pattern hold?

  • @orterves
    @orterves 4 หลายเดือนก่อน +2

    1:41 I'll watch it after this one ok? TH-cam brought me here first is all

  • @pacificll8762
    @pacificll8762 4 หลายเดือนก่อน +5

    Merci pour cette vidéo géniale !

  • @glorialee-goldthorpe1007
    @glorialee-goldthorpe1007 4 หลายเดือนก่อน +3

    Awesome video ❤

  • @yk-il6dn
    @yk-il6dn 4 หลายเดือนก่อน +1

    Awesome video series! Was wondering what book you'd suggest to get further into the topics

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +2

      Thanks!
      I'm not sure about references pursuing this particular topic, but Jech's book on set theory is a good place to lay the necessary groundwork for anything else you look at, I think!
      (Alternatively, you can also look at the OG papers, like Kirby-Paris, Cichon, or Caicedo.)

    • @yk-il6dn
      @yk-il6dn 4 หลายเดือนก่อน

      @@SheafificationOfG Thanks for taking the time to give a detailed answer, I really appreciate it!

  • @Tumbolisu
    @Tumbolisu 5 วันที่ผ่านมา

    "ωonderful ωorld of ωrdinals" having inconsistent meaning for ω is such a crime

  • @maxmustermann5590
    @maxmustermann5590 4 หลายเดือนก่อน +2

    Please more on oridals and the fast growing hierachy. Also could you recommend a textbook om this topic for someone with engibeering math background?

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน

      I always recommend Jech's book on set theory. I don't remember if it talks about fast-growing hierarchies, but if you understand the fundamentals of the book, then you're already in a good place for learning other stuff on your own.

    • @icanfast
      @icanfast 3 หลายเดือนก่อน

      Please less on oridnals and the fast growing hierarchy.

  • @ccolombe
    @ccolombe 3 หลายเดือนก่อน

    The videos are so good

  • @DemonixTB
    @DemonixTB 3 หลายเดือนก่อน +2

    even though I already know about the Goodstein sequence, ordinal arithmetic, fundamental sequences, and the fast growing hierarchy
    this video feels impossible to follow.
    If this was a lecture, there would be some solace in knowing the teacher has to write all this notation down, giving me time to think, instead, you have so much of it appear and disappear so quickly and with so little attention given to it, (at points you literally say "it becomes this", and move on) it becomes nearly impossible to follow.

    • @avin9106
      @avin9106 2 หลายเดือนก่อน

      Just pause the video when necessary.

  • @joshuaidugboe214
    @joshuaidugboe214 4 หลายเดือนก่อน +2

    I know this is not related to the video but it just came to mind, is a set containing all combinations of the natural numbers larger than the set of real numbers?

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +4

      If by "set of all combinations" you mean "set of all subsets" (i.e., the power set), then the answer is no: the power set of the natural numbers is the *same size* as the set of real numbers.

    • @palamedez
      @palamedez 4 หลายเดือนก่อน +2

      The Power Set of the naturals P(ℕ) has the same cardinality as ℝ.
      You can for example take a map φ: ℝ -> P(ℕ) that maps a Real number to the Set of the decimal places of the number that have a 1.
      If you then take any M∈P(ℕ), you can just construct a real number by putting 1s at the decimal places given by the elements of M and 0s otherwise.
      So φ is surjective and therefore |ℝ|≥|P(ℕ)|
      You can show the converse statement by a simular Argument with the binary representation of a Real number.

  • @WoolyCow
    @WoolyCow 4 หลายเดือนก่อน +4

    bro i didnt understand any of this but it good yes video words thank you.

  • @Canadian_Teemo
    @Canadian_Teemo 4 หลายเดือนก่อน +1

    I see Saiki Kusuo no Psi Nan meme, I like

  • @cosmic4716
    @cosmic4716 4 หลายเดือนก่อน +3

    cool video!

  • @rtg_onefourtwoeightfiveseven
    @rtg_onefourtwoeightfiveseven 3 หลายเดือนก่อน

    6:37 Why does this not work for epsilon_0? Intuitively (naively), if you take {epsilon_0}_k = a k-high power tower of omega, it seems like epsilon_0 should be the limit of that as k goes to omega.

    • @SheafificationOfG
      @SheafificationOfG  3 หลายเดือนก่อน +2

      My definition doesn't account for epsilon_0, but what you suggest is the canonical way of making it work!

    • @rtg_onefourtwoeightfiveseven
      @rtg_onefourtwoeightfiveseven 3 หลายเดือนก่อน

      @@SheafificationOfG What stops the definition from accounting for epsilon_0 like it accounts for the ordinals below it?

    • @SheafificationOfG
      @SheafificationOfG  3 หลายเดือนก่อน +2

      @@rtg_onefourtwoeightfiveseven It's a deficiency of the definition I give: since epsilon_0 = omega^(epsilon_0)---which is then its Cantor normal form---my definition reduced to {epsilon_0}_k = omega^({epsilon_0}_k), which would just give {epsilon_0}_k = epsilon_0, at least as a minimal solution.
      For ordinals less than epsilon_0, we're guaranteed that the exponents in Cantor normal form are strictly smaller than the original ordinal, which makes the definition work.

    • @rtg_onefourtwoeightfiveseven
      @rtg_onefourtwoeightfiveseven 3 หลายเดือนก่อน

      @@SheafificationOfG Makes sense, thanks!

  • @natepolidoro4565
    @natepolidoro4565 26 วันที่ผ่านมา

    2:00 I have no idea what you mean by this. The shape? Is this video geared toward already having in-depth knowledge of ordinals and cardinals and such?

    • @SheafificationOfG
      @SheafificationOfG  26 วันที่ผ่านมา

      To be fair, this is a follow-up video (to "Solving a Finite Number Problem using Infinities")

  • @HazhMcMoor
    @HazhMcMoor 3 หลายเดือนก่อน

    All of these and we still haven't been able to prove Collatz conjecture. It'd be awesome if it's actually false but we need fastest growing hierarchy to prove that

  • @rafaelaraujo-wt6ek
    @rafaelaraujo-wt6ek 4 หลายเดือนก่อน +1

    Really cool!

  • @God-gi9iu
    @God-gi9iu 4 หลายเดือนก่อน +2

    So cool 👌

  • @michaelsheard4522
    @michaelsheard4522 4 หลายเดือนก่อน

    Excellent video! Minor correction: Stan Wainer is British; his last name is pronounced in the obvious English way, not German.

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน

      @michaelsheard4522 crap, thank you. I should've just looked him up before assuming haha

  • @LarsHHoog
    @LarsHHoog 4 หลายเดือนก่อน

    Would you consider to please remove the noise from the sound making it really hard to stay focused. Any kind of audio processing software with dignity has such functionality.

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +2

      Since the audio is actually a lot better than my earlier videos (can you imagine), I didn't actually notice the poor audio quality! I'll keep working on fixing the audio more as the videos roll out.

  • @monsterhunter8595
    @monsterhunter8595 4 หลายเดือนก่อน

    Nice!

  • @DanDart
    @DanDart 4 หลายเดือนก่อน

    Remember people: you can't address an ordinal number of things

  • @finxy3500
    @finxy3500 4 หลายเดือนก่อน +3

    If it's impossible to prove from first-order Peano axioms that every Goodstein sequence terminates, wouldn't that mean, by Gödel's completeness theorem, that there's a Model of the naturals in which they don't? What am I missing here?

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +2

      You're not missing anything! There are nonstandard models of the naturals where some numbers have infinite Goodstein sequences!

    • @finxy3500
      @finxy3500 4 หลายเดือนก่อน +1

      @@SheafificationOfG What axiom did we add to be able to prove Goodstein's theorem? The existence of infinite ordinals? That seems wrong to me, how would their existence change anything about the finite ordinals? I suppose you could just construct a model of the naturals in ZFC, prove this, and call it a day, but I am curious what axiom was implicitly used in this proof...

    • @japanada11
      @japanada11 4 หลายเดือนก่อน +2

      The implicit axiom used IS the axiom of infinity (existence of infinite ordinals). Even if the theorem says nothing about infinite ordinals, there is no proof without this axiom (or at least an axiom that's at least as strong).
      Basically, we live in one of two possible worlds:
      1) Peano+infinity is consistent. In this case Goodstein's theorem is true, but no Peano arithmetic proof exists.
      2) Peano+infinity is inconsistent. Then it's possible that there is a counterexample to Goodstein's theorem somewhere out there that we just haven't found yet.
      Unfortunately, by Gödel's second incompleteness theorem, we can never be 100% certain that we aren't in the second world.

    • @finxy3500
      @finxy3500 4 หลายเดือนก่อน

      @@japanada11 *true in the standard model that is.
      I currently think the critical part is transfinite induction. If you want to forgo the whole set theoretical framework I think just defining an element ω satisfying φ(ω) := ∀n((is_finite(n)) → ω > n), where is_finite is some predicate to which induction can be applied, and ∀ω' ≠ ω(φ(ω') → ω' > ω) and including transfinite induction as an axiom could work. (I assume TFI would need to be an axiom here, but I don't know)
      EDIT: upon further reflection I think ω needs to be outside of PA because it needs to be outside of reach of regular induction. So we'd need to define a sort of natural numbers using a predicate "ℕ∋" (think as this as a symbol only, not bound by the axioms of set theory) or you could call it is_finite where regular induction only applies when is_finite(n)

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน

      Good question!
      I'm not sure how you're representing "transfinite induction" in this language of PA + omega, but if it's capable of encoding all of the natural operations up to exponentiation with omega, then that should be enough.

  • @zuperdude7701
    @zuperdude7701 4 หลายเดือนก่อน +29

    Bro what are you talking about

    • @EntergeticalakaBot
      @EntergeticalakaBot 4 หลายเดือนก่อน +2

      You can’t handle this can you

    • @zuperdude7701
      @zuperdude7701 4 หลายเดือนก่อน +7

      @@EntergeticalakaBot im afraid not 😭. I tried to watch this casually but maybe in a few years

    • @EntergeticalakaBot
      @EntergeticalakaBot 4 หลายเดือนก่อน

      @@zuperdude7701 don’t worry i felt the same with another g++ video lol

    • @zeta3341
      @zeta3341 4 หลายเดือนก่อน +3

      ​@@zuperdude7701ngl I'm completely lost in the very first minute when a seemingly growing sequence goes to zero? Wat????

    • @its_lucky252
      @its_lucky252 4 หลายเดือนก่อน +1

      this isn't for middle schoolers lil bro

  • @joaocabralpv
    @joaocabralpv 3 หลายเดือนก่อน

    17:14 what if every one unsubscrives?

  • @shershahdrimighdelih
    @shershahdrimighdelih 2 หลายเดือนก่อน

    amazing ++++

  • @ModusTollendoTollens
    @ModusTollendoTollens 4 หลายเดือนก่อน

    GODstein . +10, like y a favoritos

  • @nzqarc
    @nzqarc 4 หลายเดือนก่อน

    And thats the weak Goodstein sequence.
    The stronger one actually reaches ε0 in FGH

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน +1

      This video actually covers the strong Goodstein sequences! The weak Goodstein sequence generated by 4 only has 21 terms.
      As shown in the theorem, the lengths of Goodstein sequences outgrow all functions in the fast-growing hierarchy indexed by ordinals less than epsilon_0. On the other hand, iirc, the weak Goodstein sequences grow at a rate comparable to f_omega.

    • @nzqarc
      @nzqarc 4 หลายเดือนก่อน

      @@SheafificationOfG That's a massive jump from the weak function to the strong one lmao

  • @barigamb
    @barigamb 4 หลายเดือนก่อน +1

    I understood like... maybe 40% of this... I'm gonna stick to number theory thank you very much this infinite ordinal stuff is confusing. Great video tho

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน

      The video relies a good bit on its prequel, so 40% ain't bad!

  • @BalthazarMaignan
    @BalthazarMaignan 4 หลายเดือนก่อน

    I didn't understand anything, but nice video nontheless

  • @ゾカリクゾ
    @ゾカリクゾ 4 หลายเดือนก่อน +2

    sir, this is a wendy's

  • @mashtonish
    @mashtonish หลายเดือนก่อน

    jfc, I thought "sheafification" (and your channel's about section) was something you made up as a joke to make fun of how teaching/learning mathematics is usually accompanied by frequent situations where you have a bit of confidence until you enter a class that starts using terms and definitions you're unfamiliar with as if you're supposed to know and understand them... And that you, the channel owner, felt comfortable making that joke because of all the math classes you've been through, taking note of the commonly hellish scenario... but... no. "Sheafification" is an actual thing... I've been bamboozled by the very situation I thought was intentional.

  • @sequentiacyclica
    @sequentiacyclica 4 หลายเดือนก่อน

    goodstin :)

  • @paulfoss5385
    @paulfoss5385 4 หลายเดือนก่อน

    Great video, I love seeing the content on your channel, but one thing I don't love is seeing pewdiepie's face because of his antisemitism, homophobia and toxic fanbase. But other than that I loved the video. I love nice proofs and interesting mathematical structures, but there's also a part of my brain that's tickled by "number get big", it's nice when both can be satisfied.

    • @SheafificationOfG
      @SheafificationOfG  4 หลายเดือนก่อน

      Yikes, I'm ngl I don't actually know the first thing about pewdiepie (I'm only aware of the meme), but I'll keep that in mind in the future, thanks for letting me know.
      Glad you liked the rest, though!

  • @lyricalcarpenter
    @lyricalcarpenter 4 หลายเดือนก่อน +2

    all of my code finishes in O(f_ω(n)) time ;-;