Ideals in Ring Theory (Abstract Algebra)

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  • เผยแพร่เมื่อ 4 พ.ย. 2024

ความคิดเห็น • 215

  • @Socratica
    @Socratica  3 ปีที่แล้ว +5

    Sign up to our email list to be notified when we release more Abstract Algebra content: snu.socratica.com/abstract-algebra

    • @Vivek-lu4eq
      @Vivek-lu4eq 4 หลายเดือนก่อน

      What is the name of background music that you used ? Please tell me !!!! 🤗🤗🤗

  • @JISHUDASSAMU
    @JISHUDASSAMU 4 ปีที่แล้ว +126

    Love the way she presents concepts.

    • @davethesid8960
      @davethesid8960 2 ปีที่แล้ว +3

      Well, definitely better than my teacher did.

    • @Dark_Souls_3
      @Dark_Souls_3 ปีที่แล้ว +1

      She’s just an actor, but I agree, the writing is amazing in these videos. Very good compared to other lectures I’ve been seeing!

  • @akashbiswas4666
    @akashbiswas4666 3 ปีที่แล้ว +59

    I want to thank Socratica .I'm from India🇮🇳 and by your abstract algebra video I completed my graduation which I failed last year so thank you so much❤❤❤❤😊😊😊

    • @Socratica
      @Socratica  3 ปีที่แล้ว +18

      Congratulations!! You should be very proud about your hard work. Thank you for telling us - it really inspires us to make more videos!! 💜🦉

    • @ABCXYZ-vg9gh
      @ABCXYZ-vg9gh 11 วันที่ผ่านมา

      Stop simping bro.

  • @TheDopplerEffect_
    @TheDopplerEffect_ 3 ปีที่แล้ว +10

    I don't usually comment on TH-cam videos, but damn this channel is the only thing helping me pass my third year abstract math class and I am so thankful that it exists. A sincere thank you from South Africa!!!

  • @junchichu8703
    @junchichu8703 4 ปีที่แล้ว +9

    OMG this 12 minutes video is like a sonata, I am completely into it. Such a pleasure in my mind to enjoy mathematics. Math is beautiful, thank you.

  • @larsmees4952
    @larsmees4952 4 ปีที่แล้ว +21

    I wish I discovered this channel at the beginning of the semester! Great explanations!!

    • @tiagonata1734
      @tiagonata1734 11 หลายเดือนก่อน

      Bro this is me for real

  • @terryendicott2939
    @terryendicott2939 4 ปีที่แล้ว +64

    The comments would be Ideal if they were devoid of puns. One could however Factor out the puns and see what is Left. Would that be Right? If so then it would be Double Sided, and puns in a Class of their own.

  • @JoSh-yu6jt
    @JoSh-yu6jt 4 ปีที่แล้ว +1

    This.Series.Is.Genius !!!!
    A big thanks to all the patreons. Such educational videos are a gift. 💯

  • @jiaxuanouyang2960
    @jiaxuanouyang2960 3 ปีที่แล้ว +3

    Professor didn't explain why an ideal is called ideal. Thanks a lot for clear and precise explanation!

    • @Socratica
      @Socratica  3 ปีที่แล้ว

      We're so glad we could help - thanks for letting us know!! 💜🦉

  • @ifyhu92
    @ifyhu92 6 หลายเดือนก่อน

    i just finished watching all abstract algebra videos they are amazing!!! Please keep going with the content this type of learning is sooo efficient and I actually learn something

  • @xFloppyDolphinn
    @xFloppyDolphinn 4 ปีที่แล้ว +3

    These keep popping up in my recommended. I don't understand much of it but it's still pretty interesting

  • @NotBary
    @NotBary 3 ปีที่แล้ว +16

    I just passed my abstract algebra final/class because of these videos, thanks a lot. Do you all plan on making any videos covering partial differential equations?

    • @Socratica
      @Socratica  3 ปีที่แล้ว +6

      This is so great to hear - thank you so much for sharing. It really does inspire us to make more videos when we hear they are helping!
      We'd love to continue our Calculus series and to also address PDEs. SO MUCH TO DO!! It's a good problem to have. 😄

  • @franciscovargas2600
    @franciscovargas2600 4 ปีที่แล้ว +3

    These videos are incredible, would be great to see a topology series !

    • @Grassmpl
      @Grassmpl 3 ปีที่แล้ว +1

      Nah they would just be homeomorphic to these videos.

  • @ggg148g
    @ggg148g 4 ปีที่แล้ว +2

    Amazing, wonderful, the clearest and most useful explanation ever. THANKS!!! Giving some money right now!!!

  • @iliyakantoma5413
    @iliyakantoma5413 4 ปีที่แล้ว +3

    Wow love it thank you for saving me.. I truly finds it difficult to understand this
    Abstract algebra before.

  • @samrichardson5971
    @samrichardson5971 4 ปีที่แล้ว +1

    I’m sure I’d have had to see the absorption property explained like this once upon a time but this was a really neat reminder of why an ideal has to satisfy it!

  • @elliotf-p9722
    @elliotf-p9722 3 ปีที่แล้ว

    These videos are joy personified

  • @HDQuote
    @HDQuote 4 ปีที่แล้ว +1

    ok, so to recap (correct me, if i am wrong):
    assume:
    (G,+,·) is a ring

  • @proggenius2024
    @proggenius2024 2 ปีที่แล้ว +1

    Socratica is by far my favorite YoutTube channel so far. Ironically, I have found this channel not a week ago, but couldn't believe the quality of delivery. Specially this lady who teachs Abstract Algebra is just incredible. Hail maths!

  • @tthtlc
    @tthtlc ปีที่แล้ว +1

    Thank you these are dream topics I have been yearning to learn since a teenager. Thanks.

    • @Socratica
      @Socratica  ปีที่แล้ว +1

      We're so glad you're learning with us! We love making these videos. And thank you for so kindly supporting our channel-it means we can keep making more! 💜🦉

  • @doodelay
    @doodelay 4 ปีที่แล้ว +5

    Hey socratica, I will literally watch Liliana teach any math and science overview from real analysis to topology to electromagnetism. I do not care. This channel has helped us immensely even without a whiteboard and I fear you're not taking advantage of our admiration

  • @raunitsingh676
    @raunitsingh676 3 ปีที่แล้ว

    One word for this video: PERFECT

  • @jeremyjakob9721
    @jeremyjakob9721 4 ปีที่แล้ว +9

    Awesome, but I hope some more videos are coming on prime ideals, maximal ideals, principal ideals and the isomorphism theorems.

  • @javiervega40
    @javiervega40 4 ปีที่แล้ว +1

    Your abstract algebra videos are amazing!!! Keep making videos!!!

  • @bhumikabaddhan1396
    @bhumikabaddhan1396 4 ปีที่แล้ว +2

    Omg I just understood everything...you made it easy ...Thank you!

  • @soulysouly7253
    @soulysouly7253 2 ปีที่แล้ว +1

    "There are many ways you can motivate the concept of an Ideal in abstract Algebra" Ma'am YOU're motivating me to learn that concept

  • @pyrotfboba
    @pyrotfboba 4 ปีที่แล้ว

    super happy to see these videos are being developed further!! hoping to see a video on the Sylow theorems and ring homomorphisms soon!

  • @giuliocasa1304
    @giuliocasa1304 2 ปีที่แล้ว

    Thank you! This is the best explanation of ring ideals I've found!

  • @PunmasterSTP
    @PunmasterSTP 3 ปีที่แล้ว

    Best math-pun-turned-into-sponsorship-message I've ever seen...

  • @tothepoint1815
    @tothepoint1815 3 ปีที่แล้ว +1

    Love the way she teaches.

  • @blessythomas7721
    @blessythomas7721 2 ปีที่แล้ว +2

    I finally got what ideals mean! Can't thank you enough!!😭💕

    • @Socratica
      @Socratica  2 ปีที่แล้ว +1

      This is so wonderful to hear! Thank you for telling us!! 💜🦉

  • @pankajjain4026
    @pankajjain4026 4 ปีที่แล้ว

    Just loved the way how you make concepts so easy and do relate the things ❤

  • @usmanaziz1679
    @usmanaziz1679 4 ปีที่แล้ว +4

    I was extremely waiting for your videos on the topic of Abstract Algebra please upload Daily videos

    • @gucker
      @gucker 4 ปีที่แล้ว

      Daily videos? Do you think making a video takes a couple of minutes?

    • @Socratica
      @Socratica  4 ปีที่แล้ว

      heehee thanks for that - if only! 💜🦉

    • @usmanaziz1679
      @usmanaziz1679 4 ปีที่แล้ว

      @@Socratica welcome @Socratica 😇

    • @usmanaziz1679
      @usmanaziz1679 4 ปีที่แล้ว

      @@gucker OK i know its too much difficult
      I'm sorry @Socratica

    • @Socratica
      @Socratica  4 ปีที่แล้ว +2

      We're so happy you're enjoying the videos!! But yes, it does take us a lot of work. More are coming! 💜🦉

  • @joetursi9573
    @joetursi9573 ปีที่แล้ว

    A wonderful explanation I've never seen in any text (Gallian included.)

  • @doodelay
    @doodelay 4 ปีที่แล้ว

    Hey socratic, I will literally watch Liliana teach any math and science overview from real analysis to topology to electromagnetism. I do not care. This channel has helped me immensely even without a whiteboard

  • @lukadeclerck4702
    @lukadeclerck4702 4 ปีที่แล้ว +1

    love your videos, just a tip: you could ask small questions to test the insight of the viewer and his understanding of what you said

  • @mohamedkhalid343
    @mohamedkhalid343 3 ปีที่แล้ว

    you are an ideal teacher

  • @robertkrohn9385
    @robertkrohn9385 4 ปีที่แล้ว

    These videos are incredible resources

  • @snoopywlk
    @snoopywlk 4 ปีที่แล้ว

    I love abstract algebra because of her ideal presentation.

    • @Grassmpl
      @Grassmpl 3 ปีที่แล้ว

      Yeah she's good at the generators and the relations.

  • @ahmadshahhimmat25
    @ahmadshahhimmat25 4 ปีที่แล้ว +9

    I request you to share some lectures according to Algebric topology.

    • @Grassmpl
      @Grassmpl 3 ปีที่แล้ว

      You can learn it yourself. That's a very fundamental group. Lol.

  • @live2laugh2
    @live2laugh2 3 ปีที่แล้ว

    Come here to find definition but got whole think clear really ❤️❤️❤️

  • @georgettebeulah4427
    @georgettebeulah4427 4 ปีที่แล้ว

    This make so much sense and meaning and really do understand what your saying and mean. Thank you for all the video

  • @Atul_Thakur97
    @Atul_Thakur97 4 ปีที่แล้ว +3

    i am early..but this video is very good... previous i had no interest in algebra..but due to you videos i like reading algebra

  • @unkown5528
    @unkown5528 3 ปีที่แล้ว

    Great videos, saviour for students in the pandemic

  • @Thats_A_Dummy_Name
    @Thats_A_Dummy_Name 4 ปีที่แล้ว

    You are awesome. I would love to see a similar video series on category theory concepts.

    • @Grassmpl
      @Grassmpl 3 ปีที่แล้ว

      The universal properties just get tensor and tensor.

  • @myworldfriends123
    @myworldfriends123 4 ปีที่แล้ว

    Your presentations are wonderful. I wish I had your videos when I was in college.

    • @Grassmpl
      @Grassmpl 3 ปีที่แล้ว

      You probably had to learn off of typewriter manuscripts.

    • @myworldfriends123
      @myworldfriends123 3 ปีที่แล้ว

      @@Grassmpl No, just chalk boards. :-)

  • @gogo-pj2lm
    @gogo-pj2lm 4 ปีที่แล้ว +1

    Months of waiting.... Finally!!!!

  • @Will-Ch
    @Will-Ch ปีที่แล้ว

    more videos please!!. thank you so much

  • @NorteSeVuelveElSur
    @NorteSeVuelveElSur 2 ปีที่แล้ว

    you snapped in this one 😍

  • @joetursi9573
    @joetursi9573 2 ปีที่แล้ว

    Wonderful presentation

  • @adsoyad2607
    @adsoyad2607 ปีที่แล้ว

    I've watched this video at least 8 times during the last 48 hours I'm losing it

  • @jessicacarneirohatta8195
    @jessicacarneirohatta8195 4 ปีที่แล้ว +5

    Liliana, sou sua fã! Diva em tudo que faz!

  • @bayupatten4777
    @bayupatten4777 7 หลายเดือนก่อน

    thanks a load this cleared up a lot for me

  • @tims2532
    @tims2532 4 ปีที่แล้ว

    Cant wait for this series to reach Galois theory!

  • @rbkstudios2923
    @rbkstudios2923 4 ปีที่แล้ว +3

    Hello
    I have great appreciation and reverence for your channel and it's prominence
    A need you to make a Video on
    1. Temperatures below absolute zero
    2. Gravitational waves property. If they travel at light speed, do they have other similar properties like reflection, refraction, diffraction, doppler shift polarization. What is their wavelength range?
    does special relativity apply to it?
    3. Collapsing an air bubble with sound underneath a liquid surface
    4. Square waves

  • @osebrainquestfoundation9631
    @osebrainquestfoundation9631 2 ปีที่แล้ว

    Great concept.

  • @dounia1988da
    @dounia1988da 3 ปีที่แล้ว

    Great job explaining

  • @ahmadshahhimmat25
    @ahmadshahhimmat25 4 ปีที่แล้ว

    I love your lectures

  • @iqrarali4631
    @iqrarali4631 3 ปีที่แล้ว

    Thank you so much for such a nice lectures. Would you plz upload short lectures on finite fields, Galois theory, elliptic curves, algebraic curves

  • @OCHOA0187
    @OCHOA0187 4 ปีที่แล้ว

    Hola hace poco vi uno de tus videos sobre las estrellas de neutrones, pero lo vi en un canal tuyo en español lo abandonaste hace 5 años cosa que no note hasta que me suscribi, quise ver mas de tus videos en este canal en español y me encontre con el video de un anuncio en el cual indicabas que volverias, creo animarte a que vuelvas en especial con los temas de astronomia y fisica, veo que aqui en tu canal de español no te ha ido muy bien que digamos pero he visto otros canales en español que les a ido muy bien y han crecido mucho hasta tener millones de suscriptores, te animo a que cumplas con lo dicho y vuelvas a tu canal en español saludos desde colombia.

  • @sauerkirschmarmelade._.807
    @sauerkirschmarmelade._.807 2 ปีที่แล้ว

    what the fuck 1 minute into the video and she already made me understand factor groups and normal subgroups

  • @theuberman7170
    @theuberman7170 4 ปีที่แล้ว +1

    This is still here!!!!??? I haven't been on this channel in 4 years!!!

  • @enpeacemusic192
    @enpeacemusic192 11 หลายเดือนก่อน

    The way I see it that an ideal is generated by an element you want to act as 0. Notice that the definition of an ideal is basically the definition of 0: 0 + 0 = 0 (I is a subgroup of the additive group) and 0 * r = 0 (xr is in I for all r in the ring and x in I)

  • @terryendicott2939
    @terryendicott2939 4 ปีที่แล้ว +2

    Serious comment. How deep are you going to go with ideals?
    You did a segment on modules some time ago. Please show the connection between modules and ideals.
    Let R be a ring with identity, 1, and let I be an ideal containing 1. What can be said about I?
    Are there proper ideals that may, as a set contain other ideals but are not contained in any proper ideals? That is, are there always maximal ideals?
    Let R be a commutative ring with identity. What do the quotient rings of maximal ideals look like?
    I could go on but I think that I am a bit far down the rabbit hole already.
    Thank for your work --- This is a great channel.

    • @tracyh5751
      @tracyh5751 4 ปีที่แล้ว +1

      And also, what happens if we try to mod out by a left ideal? A right ideal? What algebraic structure do we obtain? Socratica is doing such a great job with algebra. I took algebra years ago but I still love watching these videos presented so beautifully. :)

    • @terryendicott2939
      @terryendicott2939 4 ปีที่แล้ว

      @@tracyh5751 Let A be a ring with I a left ideal. Then A/I is left A-module.

    • @Grassmpl
      @Grassmpl 3 ปีที่แล้ว

      I think you know this stuff already. Ideals and quotient are also modules. Maximal ideal always exist due to Zorns Lemma.

  • @ياصاحبالعصروالزمانأغثني
    @ياصاحبالعصروالزمانأغثني 4 ปีที่แล้ว +2

    عاشت ايدك على هذا الشرح الاكثر من رائع💙

  • @Mau365PP
    @Mau365PP 4 ปีที่แล้ว +1

    Thank you Michael Harrison for the lectures.

  • @mariano5704
    @mariano5704 3 ปีที่แล้ว +1

    Thanks!

    • @Socratica
      @Socratica  3 ปีที่แล้ว

      Oh my goodness, thank you for your kind contribution, Socratica Friend! It really goes a long way helping us make more of these videos. 💜🦉

  • @AkamiChannel
    @AkamiChannel 2 ปีที่แล้ว

    Good stuff

  • @sujitmohanty1
    @sujitmohanty1 4 ปีที่แล้ว

    Fantastic expositor....

  • @gaboqv
    @gaboqv 4 ปีที่แล้ว

    it would be useful to add that ideals are in fact subrings if one keeps with the idea of a ring not needing an identity, I guess tough that rings with identity were more popular then too

  • @chounoki
    @chounoki 3 ปีที่แล้ว +3

    Wait, at 8:17, earlier you said that a ring does not require a multiplicative identity "1", but now you say that since ideal may not have a multiplicative identity "1" so ideal is not a subring. You contradict yourself.

    • @sharik2377
      @sharik2377 3 ปีที่แล้ว

      Yes! this made me so confused, every ideal is subring but the converse isn't true.

  • @joetursi9573
    @joetursi9573 3 ปีที่แล้ว

    Th other five partitions of Z are the can only be wriiten compactly ,as 1.z, 2.Z, 3.Z, 4.z and 5.z ie as normal subgroups by the definition of normal subgroups of Z she just gave.

  • @Ellanion
    @Ellanion 4 ปีที่แล้ว

    Many of your other videos are helpful because they are relevant to me and I gain a greater understanding. This video, I barely understand a single word, but it's somehow so very meditative to listen to.

  • @boradmay
    @boradmay 4 ปีที่แล้ว +2

    Wish my classes could be this simple and clear so I don't have to sit through 90 mins.

  • @akashbouddh6056
    @akashbouddh6056 4 ปีที่แล้ว

    Thank you very much ma'am 👍👍. We are like your teaching ideas.

  • @Mrpallekuling
    @Mrpallekuling ปีที่แล้ว

    Another example:
    The set 3Z formed by multiplying each integer by 3 forms an ideal.
    The quotient ring Z/3Z has three elements:
    0 + 3Z = {0, ±3, ±6, ±9,…}
    1 + 3Z = {…, −8, −5, −2, 1, 4, 7,…}
    2 + 3Z = {…, −7, −4, −1, 2, 5, 8,…}

  • @eerisken
    @eerisken 4 ปีที่แล้ว

    Hi Socratica, thanks for the videos. But Why don't you think to prepare a MOOC about Groups & Galois Theory on a site like Coursera, or Udemy?

  • @swastik2484
    @swastik2484 4 ปีที่แล้ว

    U teach very activel I IAM impressed

  • @craigwall9536
    @craigwall9536 4 ปีที่แล้ว +1

    Is there an order in which we should watch your videos in order to become familiar with these concepts? EDIT: Never mind. I found it.

  • @Mikey-mike
    @Mikey-mike 4 ปีที่แล้ว

    Well done.

  • @Leviathan-
    @Leviathan- 2 ปีที่แล้ว +1

    8:11 11:27 I think all ideals are the subrings even ideals are more than subrings because subrings contain their own element multiplication but ideal contain all multiplication of their element with any ring element. And it's not necessary for subring to contain the multiplicative identity 1 which is you telling that it is missing in an ideal then it is not subring example set of even number is the subring of the ring of the set of integer

  • @ishika01375
    @ishika01375 3 ปีที่แล้ว

    what an explanation! wow

  • @manuelortizrobles3944
    @manuelortizrobles3944 4 ปีที่แล้ว

    Qué penita verte por acá, de seguro vas a triunfar como no lo hiciste en socrática en español.....

  • @Nayanexx
    @Nayanexx 3 หลายเดือนก่อน

    She was an amazing actress in Brazil.

  • @latevilawson86
    @latevilawson86 3 ปีที่แล้ว

    Thanks for this video. I like your slide, please can indicate me the type of the beamer presentation are you using?

    • @Grassmpl
      @Grassmpl 3 ปีที่แล้ว

      This girl's skills are next level. The math and the visuals.

  • @charitylyngdoh8912
    @charitylyngdoh8912 4 ปีที่แล้ว

    Thank You Ma'am🙏

  • @mohanachuthvarma6478
    @mohanachuthvarma6478 4 ปีที่แล้ว

    best channel ever for learning can you please start Machine learning and data science please

  • @Viettrantuan
    @Viettrantuan 4 ปีที่แล้ว

    A very good expression. Could you tell me your software to make this video? Thanks so much!

  • @eletronica_do_airton
    @eletronica_do_airton 4 ปีที่แล้ว +7

    Seria bom se você fizesse uma versão em português também.

    • @hateranonimo1481
      @hateranonimo1481 4 ปีที่แล้ว +2

      Já existem Socrática português.

    • @andrerangel1029
      @andrerangel1029 4 ปีที่แล้ว

      Mas ela parou de colocar vídeos lá??? pq???

    • @mikelreis3153
      @mikelreis3153 4 ปีที่แล้ว +2

      @@andrerangel1029 ela é apenas uma apresentadora do canal, o dono é um cara, tem o canal em espanhol que parou faz uns 2 ou 3 anos de postar videos, faz 8 ou 6 anos que ela apresenta os 3 canais e talvez esteja esgotada e decidiram manter ela apresentando apenas esse canal, já que é o maior.

  • @majestic7768
    @majestic7768 4 ปีที่แล้ว

    A lot of subatomic geometry was involved in bringing this person into being.

  • @BrynSCat
    @BrynSCat 3 ปีที่แล้ว

    This may sound strange but is abstract algebra actually complete ?.If You treat a every number as already being 4d with 360 twist.(Hopf Vibration)Euler's identity is a realistic equation for a 1D number line. In Hopf Fib ration A Ring will always be a Field relative to another number ?.

  • @usmanaziz1679
    @usmanaziz1679 4 ปีที่แล้ว +11

    Please make a video on 1st , 2nd and 3rd isomorphic theorem with proof also explain Homomorphisim with your concept 😭😭😭

  • @TurrettiniPizza
    @TurrettiniPizza 4 ปีที่แล้ว +1

    thanks big sis

  • @zubairm7419
    @zubairm7419 4 ปีที่แล้ว +1

    Do you give your patreons an insight into your video production and editing process? Would love to become your patreon if you tell how you guys edit vids :)

    • @Socratica
      @Socratica  4 ปีที่แล้ว +1

      That's not something we've done before, but we have considered creating a new channel to share with everyone the lessons we've learned on making videos and running a TH-cam channel. Maybe we should do a poll to see how much interest there would be in this idea?

    • @zubairm7419
      @zubairm7419 4 ปีที่แล้ว

      @@Socratica , that'd be great. I really just want to know about your vid creation and editing process. :)

  • @haris525
    @haris525 4 ปีที่แล้ว

    Thank you! 🙏

  • @sharathkavinamoole325
    @sharathkavinamoole325 4 ปีที่แล้ว

    please provide full lecturing of abstract algebra.

  • @prashantanand6552
    @prashantanand6552 3 ปีที่แล้ว

    I got a bit confused. The video says that ideals are not a subring but the Gallian book says ideals are subring. Actually their definition starts from the statement that " A subring A of a ring R is called an ideal if....."

    • @Yougottacryforthis
      @Yougottacryforthis 2 ปีที่แล้ว

      The identity of multiplication isnt always necessary to be a sub-ring, that varies between professors. If you accept it doesn't require the identity then an ideal is for all intents and purposes the normal sub-ring.

  • @divyeshraj6306
    @divyeshraj6306 4 ปีที่แล้ว +1

    What is prime ideal??

  • @saurabhsingh-ow7ue
    @saurabhsingh-ow7ue 4 ปีที่แล้ว

    thank you madam..............

  • @yannisran7312
    @yannisran7312 3 ปีที่แล้ว

    8:00 I think you would want to say "addition" instead of "multiplication".

    • @MuffinsAPlenty
      @MuffinsAPlenty 3 ปีที่แล้ว

      No, she wants to say "multiplication". Saying that I is a normal subgroup already specifies that I is closed under addition. Subgroups have to be closed under the group operation, and rings are only groups with respect to addition, not multiplication. So by saying "subgroup", that automatically implies "closed under addition".
      But an ideal needs to be closed under more than just addition, it *also* needs to be closed under multiplication (well, it needs to be closed under multiplication in a very "strong" way).
      This is why she says "the ideal is a normal subgroup that's *_also_* closed under multiplication."