Galois Fields: Arithmetic on a Finite Set of Numbers
Audience:
Tags: field-theoryfinite-fields
Finite fields, or Galois fields are mathematical structures that behave in familiar ways under addition, subtraction, multiplication, and division, but have only a finite number of elements in them. In this video, I introduce how to construct Galois fields both for simple modular arithmetic and the more complex prime power fields.
Target audience: undergraduate math students and math enthusiasts who are familiar with modular arithmetic.
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Thanks, very nice video with beautiful animations of the clock and in general very clear explanations (though I would have needed a bit more video time to better understand how you calculate the numbers in higher-order Galois fields).
Here are some more technical remarks:
- I like how the background color is changing for different chapters (which would be great if you’d mark them in YouTube as chapters).
- In general I feel the piano music is too load and hectic (e.g. 0:46, 1:39, 7:49, 10:53). If you want to keep it at that level, you might want to tweak some EQ on it, such that your voice has room by ducking frequencies of your voice in the music. The music also comes in very load (0:46) or too abruptly stops at 10:55.
- 11:45 binary representation string slightly shifts left/right during the animation, which is a bit annoying.
- 4:32 em dashes would be better instead of two dashes
- (!!) 6:00 kerning of text weird in the sentence “Not standard notation” (i.e. look at the spacing of characters), also at 10:15
- 6:14 really nice explanation with the sudoku and then linking this to the property of groups
- 6:44 “if we convert this to base 10” <- this was not explicitly stated for the table when you showed it a few second before that which confused me a bit at first
- 7:25 an implication arrow (double-stroked) might be a better typographic choice here as it’s the more standard notation
- 3:24 Not sure what the point is of briefly displaying a Wikipedia page in the video.
- 8:18 “so it preserves the mod 3x3 structure” -> very nicely motivated and illustrated beforehand
- I think the last part of the video could use some better thought-out explanations to make it easier to follow step-by-step and not get lost in a load of bitstrings.
What immediately kept me engaged was the music!
I like the topic and style, but I think the video could be trimmed down a little bit.
I think the working through of Galois’ work was very well done. I didn’t feel particularly invested because the story element came later. The uses for these fields were glossed over in favor of their derivation.
Very nice video.
The use of a clock to visually explain modular arithmetic was a fantastic choice and greatly helped the video.
The topic was very interesting, well motivated as a natural extension to ‘clock counting’ and then nicely contextualized by applications in computer science at the end.
The calculation of GF(64) was done a little quickly for how involved it was, but very interesting nonetheless.
The music was often too loud or too fast paced and distracted from the arguments being made.
I think this does introduce Galois Theory fairly well to an undergraduate student.
We cover the basics of cyclic groups without explicitly saying it. We could introduce fields better. The relevance with polynomials was okay and founded as a working solution. We could explore what we can do with the space.
However I think that when we introduce the example with encryption, we see an example that gets a little too outside the scope of some of our interest in the modular arithmetic.
Overall a great video to share with students and introduce the value of Galois Theory.
Great and informative video. Perhaps it was worth to mention that the GF(p^n) is unique up to isomorphismms since you can pick different irreducible polynomials. Maybe mentioning conway polynomials would’ve been interesting. And more details on the cryptography applications would have been cool
Possible error in the red text at 10:16 “the division isn’t not that hard”
I think the audience for this video is a bit more advanced than what you were aiming for— hitting instead someone who already completed an Algebra I class, but one had to rush though or omit some field topics (unfortunately, this is the common situation in my experience). For that audience, the motivation seems pretty clear, all of the concepts are recalled in a sensible way, and I could see the bit-shifting discussion at the end being a cool takeaway. That said, I worry that there’s too much preamble, making it harder to appreciate the bits at the end which might be new to them.
For the stated audience, the jump up to polynomials is genuinely hard. You handled it decently, but in way that feels too slick to grab onto. I wish I had a good suggestion, but the medium pulls against you whenever you need to introduce a new concept for later use, since there’s not enough time to let it sink in— and this time the pull was too strong.
Unfortunately, the thing I will remember most from this video is the distracting background music. I think I see what you were trying to do with it, using the phrasing to mirror the arc of your script, with the frenetic parts emphasizing the turning points. I just think that it was a bit too loud, the silences were not managed well (why music at 9:00 but not at 10:00?), and the discordance put me into a negative emotional space that I don’t want to be in while watching math for fun.
I believe I am pretty close to if not exactly the target audience. Although I found the video incredibly well made made and animated, I thought it lacked some motivation for the individual steps and why this is a useful or interesting problem until the very end.
That was an interesting video, I wasn’t really familiar with Galois fields, but this was a good introduction to them. It definitely managed to keep my attention, the 15 minutes went by quite quickly.
I also appreciated the connection to computer science at the end, showing a real, practical use case of the mathematical theory.
The animations were also nice, but one complaint I have is that the music is a little too loud sometimes, it can be distracting.
I liked this a lot! I’m a number theorist, so I’m very familiar with finite fields, and I’m surprised at the lack of information and videos on them from the traditional sources. So I’m happy such a well-made video exists about them now!
Things I liked: The motivation is clear, why we care about these things: they’re kind of like mod p, but extensions. The number of examples, especially going beyond quadratic extensions into the degree 6 extension.
Things I didn’t like (take with a grain of salt, me being a number theorist with a doctorate): It spent a lot of time describing the things, rather than saying why they were true. I understand it’s a short video, but you mention that there’s exactly one finite field of each size; an example of two possibly non-unique fields that end up being the same, and the isomorphism between them. Also, I could have wished for some mention of the fact that every finite field’s multiplicative group is cyclic, which would’ve been easy to show on the multiplicative chart you had.
Overall, a very good expository video on finite fields for an audience not yet comfortable with proofs. Well done!
Really interesting though I’ll have to watch it again later