The Journey to 3264 - Numberphile

แชร์
ฝัง
  • เผยแพร่เมื่อ 1 เม.ย. 2023
  • Professor David Eisenbud talks about conics, and visits a few numbers along the way.
    More links & stuff in full description below ↓↓↓
    David Eisenbud Numberphile Playlist: bit.ly/Eisenbud_Videos
    David Eisenbud: math.berkeley.edu/people/facu...
    3264 and All That: A Second Course in Algebraic Geometry: amzn.to/3lQfyKR
    David Eisenbud author page on Amazon: amzn.to/3G2VJ9S
    Numberphile is supported by the Simons Laufer Mathematical Sciences Institute (formerly MSRI): bit.ly/MSRINumberphile
    We are also supported by Science Sandbox, a Simons Foundation initiative dedicated to engaging everyone with the process of science. www.simonsfoundation.org/outr...
    And support from The Akamai Foundation - dedicated to encouraging the next generation of technology innovators and equitable access to STEM education - www.akamai.com/company/corpor...
    NUMBERPHILE
    Website: www.numberphile.com/
    Numberphile on Facebook: / numberphile
    Numberphile tweets: / numberphile
    Subscribe: bit.ly/Numberphile_Sub
    Videos by Brady Haran
    Animation by Pete McPartlan
    Patreon: / numberphile
    Numberphile T-Shirts and Merch: teespring.com/stores/numberphile
    Brady's videos subreddit: / bradyharan
    Brady's latest videos across all channels: www.bradyharanblog.com/
    Sign up for (occasional) emails: eepurl.com/YdjL9
  • วิทยาศาสตร์และเทคโนโลยี

ความคิดเห็น • 225

  • @numberphile
    @numberphile  ปีที่แล้ว +31

    David Eisenbud Numberphile Playlist: bit.ly/Eisenbud_Videos
    David Eisenbud: math.berkeley.edu/people/faculty/david-eisenbud
    3264 and All That: A Second Course in Algebraic Geometry: amzn.to/3lQfyKR
    David Eisenbud author page on Amazon: amzn.to/3G2VJ9S

    • @Syncrotron9001
      @Syncrotron9001 ปีที่แล้ว

      When you make it above 9000 let me know

    • @jenspettersen7837
      @jenspettersen7837 ปีที่แล้ว +2

      Cool video! I am very excited about the recent einstein tiling discovery, I hope you'll manage to make a video about that!

    • @averagelizard2489
      @averagelizard2489 ปีที่แล้ว +1

      Can you please do SSCG(3) next?

  • @MrPictor
    @MrPictor ปีที่แล้ว +215

    Eisenbud's uncertainty principle: when drawing circles, the location of the pen cannot be known with any accuracy whatsoever.

  • @olivierbegassat851
    @olivierbegassat851 ปีที่แล้ว +248

    I love his D. Eisenbud's cadence and soft spoken-ness. It's always a pleasure when he's on Numberphile : )

    • @subnormality5854
      @subnormality5854 ปีที่แล้ว +8

      I miss the old days of the Eisenbud 17-gon

    • @wheatdaddy_9629
      @wheatdaddy_9629 ปีที่แล้ว +6

      Woah, phrasing, pal

    • @Sad_bumper_sticker.
      @Sad_bumper_sticker. ปีที่แล้ว +1

      Indeed, his way of speaking creates a truly unique cogni-feast ambience, I could listen to him teaching for hours without losing focus.

    • @codycast
      @codycast ปีที่แล้ว +1

      Some of you guys are strange.

    • @kostoffj
      @kostoffj ปีที่แล้ว +6

      Math ASMR

  • @kylegonewild
    @kylegonewild ปีที่แล้ว +141

    Parker Squares and Eisenbud Circles. Can't wait to see what approximate value gets created on Numberphile next.

  • @doodlegoat
    @doodlegoat ปีที่แล้ว +70

    Joke reference for those unfamiliar with English-language culture: "1066 And All That" is a parody of History teaching in British primary schools, published in 1930.

    • @NoNameAtAll2
      @NoNameAtAll2 ปีที่แล้ว

      can you give a timestamp as well?

    • @jorgechavesfilho
      @jorgechavesfilho ปีที่แล้ว +2

      This 1930 book inspired several other history books with similar titles and in the same sarcastic tone.

    • @DukeBG
      @DukeBG ปีที่แล้ว +2

      Oh, I was definitely not familiar with this fact! Is there something special about the year 1066 in that title?

    • @neilmasson3609
      @neilmasson3609 ปีที่แล้ว +7

      ​@@DukeBG That was the year that England was invaded by the Normans. It was supposed to be one of the only two dates taught in history which people actually remembered.
      I think that the other one was nineteen fourteen eighteen.

    • @NoNameAtAll2
      @NoNameAtAll2 ปีที่แล้ว +1

      @@DukeBG it's important for english history - french,english and norman leaders battled over who would rule brittain

  • @rif6876
    @rif6876 ปีที่แล้ว +21

    "The point at infinity" - greatly appreciate the rigor! always surprised that other mathematicians on numberphile dont state it that way.

  • @geekjokes8458
    @geekjokes8458 ปีที่แล้ว +19

    "if you may remember i did a video of the fundamental theorem of algebra", yes it was 8 years ago and one of my favourite numberphile videos ever

  • @hufflepuffjoh
    @hufflepuffjoh ปีที่แล้ว +86

    Oh my, it's been so long since we had an Eisenbud video! So great to see him back

    • @TippyHippy
      @TippyHippy ปีที่แล้ว +1

      l put my hamster in a sock and slammed it against the furniture.

  • @QuantumHistorian
    @QuantumHistorian ปีที่แล้ว +81

    Lovely topic! I can't help but feel that a little more explanation could be given to statements like _"A circle in the space of line,"_ not everyone watching numberphile is going to immediately see a parameter space as a geometric object.

    • @viliml2763
      @viliml2763 ปีที่แล้ว +14

      You mean "a line in the space of circles"? I thought that was a weird choice of phrase too but I guess that just means a one-parameter continuous family of circles

    • @QuantumHistorian
      @QuantumHistorian ปีที่แล้ว +3

      @@viliml2763 Yep, that's what I meant. And yes, that's exactly what it means. But to someone not used to abstracting things via geometry it's not obvious.

    • @lonestarr1490
      @lonestarr1490 ปีที่แล้ว +4

      @@QuantumHistorian And I think this non-obviousness is well placed in that context. It makes people stop and think, "wait. What _is_ a line really?"

    • @QuantumHistorian
      @QuantumHistorian ปีที่แล้ว +5

      @@lonestarr1490Yes, exactly, except that because the speaker *doesn't* stop and instead continues the stream of new ideas, the viewer doesn't have the time to stop and think unless they manually pause (or, if they do, they'll fall behind the rest of the video). That's precisely why the speaker should spend a little bit of time clarifying what he means by that in order to give the viewer time to digest that alternative way of thinking about things.

  • @penfelyn
    @penfelyn ปีที่แล้ว +13

    when you combine complex numbers with conics on Numberphile you get an iConic video

  • @patrickmckinley8739
    @patrickmckinley8739 ปีที่แล้ว +7

    11:50 What about the xy term? I don't understand why we're not dealing with a 6-dimensional space when conics are free to rotate.

  • @nokanol45
    @nokanol45 ปีที่แล้ว +82

    Off topic, but is a video about the singular aperiodic tiling (an "einstein") that was JUST discovered a few weeks ago in the pipelines? If so, I'm really looking forward to it!

    • @osmia
      @osmia ปีที่แล้ว +1

      +

    • @nosuchthing8
      @nosuchthing8 ปีที่แล้ว +8

      Here, here!
      And the trig functions that prove the Pythagorian theorem too.

    • @SaveSoilSaveSoil
      @SaveSoilSaveSoil ปีที่แล้ว

      I can't wait to see Prof. Kaplan on Numberphile!

    • @oz_jones
      @oz_jones ปีที่แล้ว +1

      @@nosuchthing8 *hear, hear

  • @redapplefour6223
    @redapplefour6223 ปีที่แล้ว +11

    i just happened to watch the video on matrix factorization a couple hours ago, i always misread the title as matrix multiplication and thought it wouldn't be particularly interesting since i already understand all that.. lovely to see another one with david eisenbud already! saw a video too, on projective geometry, which is related to this video's topic somewhat too! definitely one of the most odd sub box moments ive had like that before, most i can think of right now

  • @matthewsaulsbury3011
    @matthewsaulsbury3011 ปีที่แล้ว +13

    Wow! This is fascinating! As a photographer, I know the long side of an 8 MP picture has 3264 pixels, so that's somewhere else that number shows up! 😀👍🏼

  • @Donbros
    @Donbros 7 หลายเดือนก่อน +1

    I am actually impressed not by the video and theory but by how he drew those circles neatly

  • @pierreabbat6157
    @pierreabbat6157 ปีที่แล้ว +4

    7776 is called "weremeke" in Arammba, also "wärämäká" and "wermeke" in other Yam languages.

  • @wiserhinoceros
    @wiserhinoceros ปีที่แล้ว +5

    Loved this - such a clear explanation of ideas in Algebraic Geometry!

  • @subjectline
    @subjectline ปีที่แล้ว +6

    The 1066 and all that reference is very much in keeping with the Eisenbud style.

  • @RobotProctor
    @RobotProctor ปีที่แล้ว +112

    Collatz Conjecture Guy returns

    • @user-jc2lz6jb2e
      @user-jc2lz6jb2e ปีที่แล้ว +19

      "Collatz Conjecture guy" 🙄
      This is David fucking Eisenbud

    • @asheep7797
      @asheep7797 ปีที่แล้ว +4

      @@user-jc2lz6jb2e donald knuth goldbach?

    • @RobotProctor
      @RobotProctor ปีที่แล้ว +20

      @@user-jc2lz6jb2e it's supposed to be tongue and cheek; it's my ignorance not his.
      I bet he would get a kick out of the comment, not feel anger or anything. If I thought he would be upset by it I wouldn't have made the comment.

    • @emirates4321
      @emirates4321 ปีที่แล้ว

      ​@@user-jc2lz6jb2e nobody cares

    • @NotoriousSRG
      @NotoriousSRG ปีที่แล้ว +2

      Dang his mom really named him specifically

  • @sparkie4212
    @sparkie4212 ปีที่แล้ว +5

    Man, the Numberphile animations have come a long way...

  • @Parekhnish
    @Parekhnish ปีที่แล้ว +28

    8:53 should be (y - b), not (x - b)

    • @ravi12346
      @ravi12346 ปีที่แล้ว +1

      Also at 11:40, there should be an xy term as well. That *would* mean there are six parameters instead of five, but really we should think of all of these equations up to a multiplicative scalar (e.g. x^2 - y = 0 is the same conic as 2x^2 - 2y = 0), which drops us back down to five independent parameters.

    • @emilianol203
      @emilianol203 ปีที่แล้ว

      @@ravi12346 x^2-y=0 is the parabola y=x^2. But without the rectangular term xy u can't make a hyperbola

  • @iamthekittycat
    @iamthekittycat ปีที่แล้ว +7

    I once fell into a rabbithole of 3, 7, 9, 11, 13, and 37. I wasn’t disappointed.

    • @junerae
      @junerae ปีที่แล้ว +1

      intriguing, could you say more?

  • @zacadoole1
    @zacadoole1 ปีที่แล้ว +6

    Y’all should make a video on how those two students proved the Pythagorean theorem using trigonometry, everyone is talking about how cool it is but I haven’t been able to find anyone actually explaining the proof

  • @bhardwajsatyam
    @bhardwajsatyam ปีที่แล้ว +1

    At 15:32, "Sottile" turns to "Sotille" for a few frames!

  • @ryanswindell1936
    @ryanswindell1936 ปีที่แล้ว +3

    Equation of a circle at 8.56 should be (x-a)^2 + (y-b)^2 =r^2

  • @JA-cn6vu
    @JA-cn6vu ปีที่แล้ว +1

    15:57 "Circles are circles. You know what they are. They're round." Wow! There's my profundity for the night. My brain is full! 🤣

  • @Mikey_AK_12
    @Mikey_AK_12 ปีที่แล้ว +10

    This video was incredibly interesting, and I feel like the title and thumbnail don't do it justice - I could care less about a random integer sequence, but a story about quadratics and the fundamental theorem of algebra? That's definitely something I want to watch!

    • @xenmaifirebringer552
      @xenmaifirebringer552 ปีที่แล้ว

      Yeah, conic curves and anything with a graphical representation feel more appealing to me than random integers

  • @realcygnus
    @realcygnus ปีที่แล้ว +2

    I always enjoy an Eisenbud appearance.

  • @guessundheit6494
    @guessundheit6494 ปีที่แล้ว +3

    When will there be a video on the new mathematical proof by two US students, Calcea Johnson and Ne’Kiya Jackson? They proved the Indian sum of squares theory (x^2 + y^2 = z^2) using triogonmetry, the first people to do it. They're in high school.

  • @wyattstevens8574
    @wyattstevens8574 8 หลายเดือนก่อน

    15:13 I was in a program co-hosted by Dr. Sotille (Dr. "I can make all 3264 conics have real values for a, b, c, d, *and* e") a few years back. I still remember that half an hour into each session of the program, when middle-school and high school students would split up, he'd just yell "HEY!" to catch everyone's attention. Seriously- I can still imagine him doing that, which is the first thing I thought of after you mentioned him! (and after I realized he was it- that made me do a double-take!)

  • @derderrr7220
    @derderrr7220 ปีที่แล้ว

    equidecient spheroidal points - love it!

  • @christopherellis2663
    @christopherellis2663 ปีที่แล้ว

    Fascinating: like a route map through space in the microcosm and the microcosm

  •  ปีที่แล้ว +2

    I love this guy.

  • @KyleDB150
    @KyleDB150 ปีที่แล้ว +3

    He mentions at the end that the "theory of excess intersections" plays a role in physics, anyone know where that is?

  • @mtranchi
    @mtranchi ปีที่แล้ว +9

    Does that ironing board in his office have a story behind it?

    • @asheep7797
      @asheep7797 ปีที่แล้ว +13

      Yes, it was used for ironing.

    • @mtranchi
      @mtranchi ปีที่แล้ว +1

      @@asheep7797 Lol, standard slapstick humor. Kudos :)

    • @colinwood9717
      @colinwood9717 ปีที่แล้ว +1

      I couldn't stop staring at it!

  • @Gna-rn7zx
    @Gna-rn7zx ปีที่แล้ว +1

    Fascinating!

  • @topilinkala1594
    @topilinkala1594 ปีที่แล้ว +2

    All the books in highschool that had conics gave them as solution to ax^2 + by^2 + cxy + dx +ey + f = 0. That is six coefficients. The cross term xy was missing in this and my understanding is that it gives the tilt of the non symmetrical conics. Eg. you can alwas using just rotation of the axis change the co-ordinates so that the cross term disappears. But if you are talking about crossing points of conics I think you need to have it in there. Or can you actually write equations of two conics that have non-parallel axis in a co-ordinates where both equations do not have the cross term?

  • @TheIcy001
    @TheIcy001 ปีที่แล้ว +4

    Never clicked on a video so fast in my life! Saw the title and I just knew it would be David Eisenbud speaking, because of his book "3264 and All That"
    Side note, maybe a very small mistake: I computed the intersection of the hyperbola xy=1 and the degenerate conic xy=0 mentioned in 4:24 in projective space for fun, and I got 2 distinct points: [0:1:0] and [1:0:0]. So I don't think there's a tangency at infinity. Also there is a projective line at infinity, not a single point at infinity. Might have been a momentary confusion with the Riemann sphere which is usually used to compactify C^1, whereas the real projective plane is used to compactify R^2.

    • @issoroloap
      @issoroloap ปีที่แล้ว

      Hi! The point is that each of them is a double point (xy=0 and xy=z^2 gives xy=0 and z^2 =0, so the second equation gives twice the line at infinity). After all, as Eisenbud explained, you should expect 4 solutions in total, for the intersection of two conics. This is like a circle and an ellipse meeting at 4 points, or being tangent at 2 double points.

    • @TheIcy001
      @TheIcy001 ปีที่แล้ว

      @@issoroloap You’re right! I neglected the fact that there are 4 points of intersection of two conics counted with multiplicity. Furthermore I realized that I can see the tangency by the fact that the slope of the line joining the origin and the point on the curve (this is y/x) doesn’t change sign as you wrap around. However, I can still make the point that merely having slopes converge is not a sufficient geometric interpretation of tangency. That’s just saying they intersect at infinity.
      Maybe physical distance approaching 0 on the other hand is sufficient for tangency (for algebraic curves), but I haven’t worked that out yet

  • @OlivierMIEL
    @OlivierMIEL ปีที่แล้ว +9

    Why 5? Where did the xy term go?

    • @michaeltajfel
      @michaeltajfel ปีที่แล้ว +8

      Yes, the xy term should be included, but you can multiply all six constants by the same number, and you get the same conic. Thus there are really five constants to determine a conic.

    • @aceman0000099
      @aceman0000099 ปีที่แล้ว

      xy isn't a constant, so it can't be altered in the same way

    • @EebstertheGreat
      @EebstertheGreat ปีที่แล้ว

      @@michaeltajfel But what if the xy term has a coefficient of 0?

    • @ipudisciple
      @ipudisciple ปีที่แล้ว +1

      The right answer is that there are 6 parameters but only up to scaling. The equation is axx+byy+cxy+dx+ey+f=0, but replacing (a,b,c,d,e,f) by (ga,gb,gc,gd,ge,gf) has the same solution set, so we get 6-1=5 parameters. They simplified for presentation and you caught it.

    • @EebstertheGreat
      @EebstertheGreat ปีที่แล้ว

      @@ipudisciple That's still only true for nonzero g.

  • @CowboyRocksteady
    @CowboyRocksteady ปีที่แล้ว +2

    More eisenbud videos!!

  • @nickush7512
    @nickush7512 ปีที่แล้ว

    Facinating !! Thanks :)

  • @storytimewithunclekumaran5004
    @storytimewithunclekumaran5004 ปีที่แล้ว

    Great video.

  • @profdimateonline
    @profdimateonline ปีที่แล้ว

    Hi! Beautiful channel 👍

  • @nordicexile7378
    @nordicexile7378 ปีที่แล้ว +7

    Is there a reason that the general equation shown at 12:40 doesn't have an xy term? (ax^2 + by^2 + cx +dy + e) I have a vague memory that the xy term can be eliminated by rotating the coordinate plane, but it has been too long since I last looked at this stuff to remember for sure.

    • @landsgevaer
      @landsgevaer ปีที่แล้ว +6

      I think it is a mistake, or perhaps intentionally sweeping it under the rug, although the conclusion that there are 5 degrees of freedom in the parameters is still correct.
      Generally,
      ax²+bxy+cy²+dx+ey+f = 0
      seems to have six, but if we multiply the entire thing by a (nonzero) number we get a *different* equation for the *same* conic, so that is overcounting one degree of freedom.
      Your own argument that you could rotate away the xy seems correct, but I would object that you then would get a different (rotated!) conic.
      Maybe somebody else has a better justification for the choice in the video...

    • @diniaadil6154
      @diniaadil6154 ปีที่แล้ว

      xy can be rewritten as 1/4 * [(x+y)^2- (x-y)^2]

    • @landsgevaer
      @landsgevaer ปีที่แล้ว +2

      @@diniaadil6154 Yeah, so that is a transformation to variables v=x+y and w=x-y, but if you do that, the x² and y² terms are going to reintroduce v*w terms, so you haven't (generally) lost the product term...
      Unfortunately, I think it is a bit more tricky than that.

    • @stevenmellemans7215
      @stevenmellemans7215 ปีที่แล้ว +1

      I also spotted it and I have no clue other than it is a mistake.

    • @DukeBG
      @DukeBG ปีที่แล้ว

      It can be eliminated by rotation, yes. Not just v=x+y and w=x-y, but a more generic-looking matrix

  • @maxreenoch1661
    @maxreenoch1661 9 หลายเดือนก่อน

    8:56 is meant to have (y - b)^2 for anyone wondering

  • @scottrs
    @scottrs ปีที่แล้ว

    Sometimes I have no idea what you’re talking bout but when that happens I still know more.

  • @henrikmunch8609
    @henrikmunch8609 ปีที่แล้ว +1

    How come there is no x*y hyperbola term in the general conic equation at 11:48?

  • @physmanir0
    @physmanir0 ปีที่แล้ว +1

    At 9:00 the video reads (x-a)^2 + (x-b)^2 = r^2, I think this is typo - of its circle it should say (x-a)^2 + (y-b)^2 = r^2, no?

  • @jpgsawyer
    @jpgsawyer ปีที่แล้ว

    Very cool but here is an idea. Are there points in the plane that are not on a tangent to the n conics and is there a way to determine if you are on such a point?

  • @p23570
    @p23570 ปีที่แล้ว +2

    i'm a simple man, if i see numberphile posting a video of the bob ross of mathematicians, i watch the video and like it.

  • @KalenCarslaw
    @KalenCarslaw ปีที่แล้ว +1

    I need to go back and finish my Masters in Mathematics

  • @milmi__9582
    @milmi__9582 ปีที่แล้ว

    Great video

  • @SaveSoilSaveSoil
    @SaveSoilSaveSoil ปีที่แล้ว +2

    This professor speaks so melodiously that I wonder whether he has a joint appointment at the music department.

  • @GGoAwayy
    @GGoAwayy ปีที่แล้ว +1

    The conic stuff will always conjure up Cliff Stoll's bread in my mind.
    What's going on with that ironing board?

  • @SportFury1966
    @SportFury1966 ปีที่แล้ว +1

    A voice that is a cross between Tommy Chong and the Ren & Stimpy singer of Happy, Happy, Joy, Joy.
    'All the little creatures, maaaan.'

  • @moss0964
    @moss0964 ปีที่แล้ว

    "well i wanna tell you about some numbers"
    fantastic! i love numbers

  • @macronencer
    @macronencer ปีที่แล้ว +1

    8:52 It should be y-b, not x-b.

  • @animeking5068
    @animeking5068 ปีที่แล้ว

    Hey guys can you please update the viewcount of the 301 video

  • @adrianf.5847
    @adrianf.5847 8 หลายเดือนก่อน

    Somewhere at about 3:37 the equations become weird.
    I think the guy means that (1 + a^2)x^2 + 2abx + b^2 -1 = 0 has either two complex solutions or one complex solution of multiplicity two.

  • @fierydino9402
    @fierydino9402 ปีที่แล้ว +2

    Algebraic geometry looks very difficult. Is it really so? Or if I study step by step, can I smoothly follow the subject?

    • @moose9002
      @moose9002 11 หลายเดือนก่อน

      I think "step-by-step" is the key word here. Algebraic geometry requires fairly broad background to really get into, however, this background material is often best understood knowing how it used in algebraic geometry! Commutative algebra is certainly the biggest culprit in this regard. From my experience of learning the subject (which is admittedly not so much, but this is consistent with what more experienced people have told me) what really helps is the willingness to revisit things with the new perspectives you gained. I don't think there is any need to be intimidated, just read what you find interesting, and fill in the background as you need it. Eventually you'll learn a lot!

  • @Drachenbauer
    @Drachenbauer ปีที่แล้ว

    is a tilted cut through a cone really a perfect ellipse?
    I mean, at the higher end of the cut, the curvature of the cone´s surface narrower and at the lower end whider.

    • @razielhamalakh9813
      @razielhamalakh9813 ปีที่แล้ว +1

      You'd think, right? That's actually a common question. Turns out, because the cut approaches the wider part of the cone at a shallower angle, the section is in fact a perfectly symmetric ellipse. It is counterintuitive, I'll grant you.

  • @GilesForrester
    @GilesForrester 8 หลายเดือนก่อน

    ... that's the best use of an ironing board I've ever seen ...

  • @mofeyTEA
    @mofeyTEA 10 หลายเดือนก่อน

    why there is no xy term in quadratic formula?

  • @Doktor_Vem
    @Doktor_Vem ปีที่แล้ว +2

    I love this guys voice so much, but I do wish he'd articulate his words a little more d:

  • @howardg2010
    @howardg2010 ปีที่แล้ว +1

    Quadratic from Latin for 'square', not Greek for 'two', though.

  • @Marktewk
    @Marktewk ปีที่แล้ว

    Yes, but why the ironing board?

  • @theimmux3034
    @theimmux3034 ปีที่แล้ว

    please make a video on the recently discovered aperiodic hat tiling

  • @Nethershaw
    @Nethershaw ปีที่แล้ว

    Woof. Is there any way to visualize the complex solutions that makes any sense? It's difficult to imagine tangency between two curves in the real plane that involves the complex plane. Do you need a three-dimensional projection to show such a thing?

    • @GGoAwayy
      @GGoAwayy ปีที่แล้ว +2

      Turn the paper 90 degrees so you can't see the front or the back and are looking at it edge on... the circle and the line are overlapping in that dimension?

  • @shruggzdastr8-facedclown
    @shruggzdastr8-facedclown ปีที่แล้ว

    (@10:07): First, we had Parker Squares -- now, we have Eisenbud Circles!

  • @justarandomdood
    @justarandomdood ปีที่แล้ว

    19:00 bit of a typo/misspoken fact? (x-a)²+(y-b)² not (x-b)², right?

  • @SuperM789
    @SuperM789 ปีที่แล้ว

    at 1:44 the ellipse doesn't match with the formula below it. if x² is multiplied by 2, it should get skinnier, not flatten.

  • @johnchessant3012
    @johnchessant3012 ปีที่แล้ว +5

    I would love to know if there's a simple explanation for where the number 3,264 comes from? We know 2^3 = 8 and 6^5 = 7,776 but how do we get to 3,264?

    • @theflaggeddragon9472
      @theflaggeddragon9472 ปีที่แล้ว +7

      Intersection theory on moduli spaces. There's not a simple explanation

    • @soyokou.2810
      @soyokou.2810 ปีที่แล้ว +3

      ​@@theflaggeddragon9472 What is the expression of the number given by that theory?

    • @theflaggeddragon9472
      @theflaggeddragon9472 ปีที่แล้ว +17

      ​@@soyokou.2810 I am no expert in enumerative geometry (I barely know basic algebraic geometry), but after skimming the relevant section, here's what I can say.
      The space of plane conics (as Eisenbud indicated in the video) is 5-dimensional; in fact it is P^5 (projective 5-space). This means the parameters are unrestricted and have no nontrivial relations (no two equations ax^2 + by^2 + cx+dy + e with different coefficients are isomorphic. Given a plane conic C, it's _dual_ C^* is the set of tangent lines, a smooth conic in the dual projective plane (space of lines in projective plane). The difficulty in narrowing 6^5 = 7776 to 3264 comes down to casting out "degenerations" of conics (double lines and such, as Eisenbud mentioned). This is technical and requires working on a _compactified_ moduli space of conics. This is the closure of the space of usual conics C in P^5. In fact, we take pairs (C,C^*) in P^5 x (P^5)^* and take the closure in there. We call this space X.
      Fix five general place conics C_,i, i = 1,...,5. The space of tangent conics in X is a hypersurface of degree 6. As mentioned in the video, taking a naive intersection gives a count of 6^5. The issue is the degenerate intersections occurring on the boundary of X.
      Now there is an object called the "Chow ring" A(X) = direct sum A^i(X), essentially formal integral sums of subvarieties of X modulo an equivalence relation. The A^i(X) encodes varieties of codimension i in X. Algebra in this ring allows us to compute intersections and many other things in algebraic geometry.
      On the open subset of smooth conics U in X, the hypersurface Z of conics tangent to a given conic has degree 6 (mentioned in the video). Let a,b in A^1(X) be pullbacks to X in P^5 x (P^5)^* of hyperplane classes on P^5 x (P^5)^*, and c,d in A^4(X) be classes of curves that are pulled back from general lines in (P^5)x(P^5)^*. One cna show that A^1(X) is generated by a,b over the integers.
      Take an equivalence class [Z] containing the hypersurfaces we want to intersect. The degree of its 5th power tells us the number of intersections (this is the point of working with Chow rings). Hypersurfaces lie in A^1(X), and it's free part has rank 2, so you can write [Z] = pa + qb for some p,q in Q and x,y forming a basis for A^1(X) (tensor Q). From basic properties of degree, you can show that [Z] = 2a + 2b in fact. Hence deg[Z]^5 = 32 deg(a+b)^5. So its enough to calculate the degree of a^ib^(5-i) for each i = 0 ,..,5. By symmetry, enough to do for i = 0,1,2. The calculations with explanation are on page 307-308 of 3264 and all that.
      All in all, you get
      deg([Z]^5) = 2^5deg(a+b)^5 = 2^5(5C0 + 2(5C1) + 4(5C2) + 4(5C3) + 2(5C4) + 5C5) = 2^5 * 102 = 3264.
      Reply

    • @adamcetinkent
      @adamcetinkent ปีที่แล้ว +7

      ​@@theflaggeddragon9472 Blimey. That's what we get for asking questions! 😂

    • @viliml2763
      @viliml2763 ปีที่แล้ว

      ​@@theflaggeddragon9472 "no two equations ax^2 + by^2 + cx+dy + e with different coefficients are isomorphic"
      ax^2 + by^2 + cx+dy + e and k(ax^2 + by^2 + cx+dy + e) have different coefficients but are isomorphic
      the issue is forgetting the sixth, xy term

  • @Lattamonsteri
    @Lattamonsteri ปีที่แล้ว +1

    At what point does slicing a cone give me a parabola? :P There's a place where it it is an ellipse and then the other point when there's a clear parabola, but in between those two limits there's an area where the slice looks like an ellipse whose tip has been cut. Is there a name for that position where the slice starts resembling a proper parabola?

    • @embryonicsuperfemme
      @embryonicsuperfemme ปีที่แล้ว +1

      This would be easier to explain with a picture, but I'll try. He mentioned two degenerate conics: a single point x^2 = 0 and two lines (cut the cone in half). There is a third which is one line. If you take any point but the tip and draw a line to the tip you will have a line that runs along the side of the cone. You can imagine the cutting plane as just touching that line, like you were preparing to wrap the cone with it. Any plane parallel to that plane by pushing inwards will intersect with a parabola. Any deviation from this angle would either tip to ellipse or hyperbola.

    • @Lattamonsteri
      @Lattamonsteri ปีที่แล้ว

      @@embryonicsuperfemme i think i got it now, even without the picture :D thank you for your reply/explanation!

  • @leefisher6366
    @leefisher6366 ปีที่แล้ว

    10:17 - Funny, I always thought they were Parker Circles.

  • @marklewis383
    @marklewis383 ปีที่แล้ว

    Can someone further explain why a line tangent to a circle goes through two points?

    • @MeOnStuff
      @MeOnStuff ปีที่แล้ว +1

      It's not that it goes through two points (it only intersects the circle at a single point). It's that if you solve the underlying equations you get a repeated root. It's the same as, say, the equation x^2 = 0. This has one solution (x=0), but through the fundamental theorem of algebra we know every degree n polynomial has n roots: we can write it as a*(x-c_1)(x-c_2)...(x-c_n) = 0, where the c_i are complex numbers. So for x^2 = 0 this gives (x - 0)(x - 0) = 0. The c_i are, collectively, the roots, so in this example we have the roots 0 and 0 i.e. a repeated root at x = 0.
      The solutions are just the roots listed without repeats (without multiplicity, to use the maths term for it).
      Hope that helps.

  • @vincehomoki1612
    @vincehomoki1612 ปีที่แล้ว +1

    And another interesting thing about 3264:
    32=2^5
    64=2^6

  • @romainhaym747
    @romainhaym747 ปีที่แล้ว

    So…
    What’s the deal with the decorated ironing board???

  • @phizc
    @phizc ปีที่แล้ว

    I'm not a mathematician, and I really don't get this.. How will y=x² meet up again and be tangent at infinity? That would mean that the square root of y would be 0 at high enough values for y, wouldn't it? At least *sqrt(+inf)* = 0..?
    Thinking about it a bit more, thinking of the parabola as a conic section, if the cone has a bottom plane, they would indeed meet up again - as straight lines, so those would be tangent to the bottom plane, i.e. "infinity", though it would also "work" with a finite sized cone, it just have to be "closed". The way it's drawn at 4:46 would imply the cone has a convexly curved "bottom" though, with a "tangent transition" between the cone and the curve part. Otherwise there would be a "corner"..
    Anyway, I can't get the math to work with just y=x², but maybe it works with the ax² + by² + cx + dy + e formula..

  • @dzspdref
    @dzspdref ปีที่แล้ว

    8:55 Shouldn't that be (y-b)^2 ?

  • @josephang9927
    @josephang9927 ปีที่แล้ว +3

    It's kind of wild how abstract concepts can make a book and for a family 😊

  • @ravis1577
    @ravis1577 ปีที่แล้ว

    Translation to written words scroll is not helping full screen view. Pls do something

  • @PushyPawn
    @PushyPawn ปีที่แล้ว +1

    So many things went over my head that I now have a new haircut.

  • @deleted-something
    @deleted-something ปีที่แล้ว +1

    Interesting

  • @michaelfahie4228
    @michaelfahie4228 ปีที่แล้ว

    1:37 my brain came to a crashing halt when he showed that graph and said xy =1. The graph is incorrect and the equation is not a quadratic. I’m sure it’s a trivial error. Can someone tell me what the equation is supposed to be?

    • @michaelfahie4228
      @michaelfahie4228 ปีที่แล้ว

      I kept watching and realize that it’s the graph that was weird, not the equation

  • @wbfaulk
    @wbfaulk ปีที่แล้ว

    Professor Eisenbud's speech patterns remind me of Floyd the barber from _The Andy Griffith Show._

  • @alan2here
    @alan2here ปีที่แล้ว +1

    Does this include x^2 + y^2 = 0?

    • @willnewman9783
      @willnewman9783 ปีที่แล้ว

      Yes, but it should be thought of as being over the complex numbers, so it is more than just the origin.

  • @_ilsegugio_
    @_ilsegugio_ ปีที่แล้ว +4

    my grandson's grandson is gonna find this trivial

  • @disgruntledtoons
    @disgruntledtoons 5 หลายเดือนก่อน

    2^6 * 3 * 17. Seems like a pretty quick journey to me.

  • @soyokou.2810
    @soyokou.2810 ปีที่แล้ว

    Could this be the first video by numberphile on actual algebraic geometry?

    • @stephenbeck7222
      @stephenbeck7222 ปีที่แล้ว

      What do you define as algebraic geometry and what is just regular function graphings or like high school analytic geometry in the coordinate plane stuff? Eisenbud’s first numberphile video years ago was on the graph characteristics of odd functions.

    • @soyokou.2810
      @soyokou.2810 ปีที่แล้ว

      @@stephenbeck7222 Algebraic geometry is the geometric study of multivariable polynomials like the curves in this video. Classically, it uses lots of projective geometry like in this video, but modern algebraic geometry uses a lot of commutative algebra. Eisenbud is himself a famous algebraic geometer as the author of the book Commutative Algebra With a View Towards Algebraic Geometry.

  • @JavSusLar
    @JavSusLar ปีที่แล้ว

    11:39 why don't you invite to the party the term xy?

  • @doubledarefan
    @doubledarefan ปีที่แล้ว

    Slice a cone on the diagonal = Oval.
    Slice a cylinder on the diagonal = Ellipse.

  • @curtiswfranks
    @curtiswfranks ปีที่แล้ว

    Someone should formalize those shaving methods. There is no way that they worked so consistently without something going on there.

  • @alexandermitrofanov1327
    @alexandermitrofanov1327 ปีที่แล้ว

    Employer: shows me the graph of the salary growth
    Me: but it never reaches the value we agreed on
    Employer: oh it does, it does! but the point is imaginary

  • @lawrencecalablaster568
    @lawrencecalablaster568 ปีที่แล้ว

    How can he just say that two things which don’t intersect are intersecting, or that one point is two?

  • @ambassadorkees
    @ambassadorkees ปีที่แล้ว

    Cut through the top, and you get a triangle, or sharp corner, a special hyperbola

  • @wynoglia
    @wynoglia ปีที่แล้ว

    6:15 my brain: "boobies"
    Edit: 11:06 and the vid editor said "and I took that personally"

  • @alexandrepereira3902
    @alexandrepereira3902 ปีที่แล้ว

    Cool

  • @JavierSalcedoC
    @JavierSalcedoC ปีที่แล้ว +1

    32 x 102 and 32 x 243

  • @sumdumbmick
    @sumdumbmick ปีที่แล้ว

    it's not necessary for the slice to be parallel to the central axis to get a hyperbola. if it were it would mean that there's another type of conic section between the parabola and hyperbola. so it's curious that absolutely nobody postulates the existence of such a thing, and yet most people assert that a hyperbola arises when the cut is taken parallel to the axis of the cone.
    these are the actual conditions for getting the conic sections:
    circle - if the slice is perpendicular to the axis of the cone
    ellipse - if the slice is between perpendicular to the axis and parallel w/ the wall of the cone
    parabola - if the slice is parallel with the wall
    hyperbola - if the slice is between parallel with the wall and parallel with the axis
    you should learn to say things correctly, since it reduces the amount of gaslighting that students have to deal with to figure out wtf you're trying to communicate.

    • @sumdumbmick
      @sumdumbmick ปีที่แล้ว

      also, a proper 'cone' has six lobes. most of the ones you depict have 1, and only for the hyperbola do you finally show the classic 2.
      but if you use the correct number, 6, then your slices correctly illustrate all of the relationships which occur between conic sections. it's quite nice. and it also demonstrates very elegantly how thoroughly fubar modern philosophy of mathematics really is.

    • @sumdumbmick
      @sumdumbmick ปีที่แล้ว

      @3:54
      the 2 imaginary solutions here are on the hyperbola. they're imaginary here because the lobe of the cone that the hyperbola slices is on an axis perpendicular to the lobe sliced by the circle. why wouldn't you just mention that? or did you just not know about this?

    • @sumdumbmick
      @sumdumbmick ปีที่แล้ว

      this isn't controversial, either. it's literally how Special Relativity works.
      the curve of the relationship between t and t' is circular for vc. this is why tachyons would require energy inputs not to accelerate.

    • @sumdumbmick
      @sumdumbmick ปีที่แล้ว

      the other closure of the parabola occurs at the same exact spot as the vertex you have. it just looks like a mirrored copy of the parabola you drew.
      there is nothing happening at infinity. that's nonsense.
      for the hyperbola you showed, there is no contact between the y-axis and the hyperola at y = +inf. the hyperbola reaches a height of +inf when x is the successor to 0, which contrary to Peano, is not 1. but this successor is a value that we use all the time without understanding it, since it's absolutely required for evaluating limits.
      when you do something like:
      lim x->0+ 1/x = +inf
      you obviously can't evaluate at x=0, because division by 0 is undefinable. further, we know this function is discontinuous, since for x0 we get a positive branch that grows in magnitude as we approach 0. so, when we take this limit and say that it gives us positive infinity, what we did is we evaluated it at the successor to 0. which I will notate as L(0).
      now, you can trivially see that L(0), 0 and -L(0) are completely distinct values, because 1/L(0) = +inf, 1/0 is undefinable, and 1/-L(0) = -inf.
      your hyperbola reaches L(0), and when it does its height is the largest possible infinity that exists, but it does not reach 0. and thus it is simply nonsense to claim that it touches the vertical asymptote, x=0, at y = infinity.

    • @sumdumbmick
      @sumdumbmick ปีที่แล้ว

      it's hilarious to hear someone speak of rigor in mathematics when it's been known for 92 years that modern mathematics cannot possibly be rigorous.
      Incompleteness demonstrates that your assumptions about how mathematics works are wrong, and yet you just carry on acting as if that never happened... ok, but when that's the choice you make, you don't get to speak of rigor.

  • @adrianf.5847
    @adrianf.5847 8 หลายเดือนก่อน

    By the way: Gauß was awesome, but his "proof" of the fundamental theorem of algebra contained a gap. Only Jean-Robert Argand gave a complete proof. (Gauß did find the Tukey--Cooley algorithm 150 years before Tukey and Cooley. In general, some mathematicians are rightly considered great mathematicians, but their achievements are being confused in rather arbitrary fashion.)

    • @adrianf.5847
      @adrianf.5847 8 หลายเดือนก่อน

      Actually, the proof by Argand seems to use an incomplete infinite descent argument, which I believe would need some sort of Weierstrass theorem or ODE method to work. So I don't even know who first proved this theorem.