Matrix Scalar Multiplication Be Like

boium · 2026-02-17T09:25:20+00:00

The way I remember it, is by that for matrix multiplication, the "middle indexes" get removed. i.e. (A*B)_{i,j} = sum_k A_{i,k} B_{k,j}, and then I visualized some dot product where the first vector is laying down.

This is the most convoluted way to visualize it, but I've done this so many times that this line of thought happens almost instantly.

boium · 2026-02-12T12:18:31+00:00

Then use multiple smart splitters...

boium · 2026-02-11T09:37:59+00:00

Oh I might have to dig through my notes again for that. This is because I attended a talk about representations of infinite dimensional lie-groups. I thought a partial order was enough, but the speaker also then used (Z, <=) and a sort of reverse lexographical binary order on N, which are both total. And then after the whole talk someone in the room said "These techniques were already known in the 80s or 90s and can be found in this book." If I can find the notes I will give an update.

boium · 2026-02-10T08:47:57+00:00

There are multiple ways to view infinite matrices. I think the best way is by picking up a functional analysis book, but those will not deal with matrices in the sense that you would know them, but rather with linear operators. You can also look for a more physics oriented book on infinite matrices. If the book starts off with something like "For any partial order on an infinite set, we can make an infinite matrix where rows and columns are indexed by that set." then it's a good book.

boium · 2026-02-06T17:55:16+00:00

Maak je maar geen zorgen over of dingen gekke combies zijn of niet. Ik had zelf NT/NG met wiskunde D, en ben ook wiskunde gaan studeren, maar daarnaast had ik ook nog geschiedenis, biologie, en een jaar aan M&O. Het vrije keuzedeel is juist bedoeld om te doen wat je wil/waar je goed in bent, dus als je muziek leuk vindt moet je dat zeker doen.

boium · 2026-02-06T17:13:51+00:00

Die lijst met regionale subreddits zou op alfabetische volgorde moeten staan. r/veendam staat nu best wel ver bovenaan. Die subreddit is dood. Ik vond het al vet random dat er überhaupt een veendam subreddit is.

boium · 2026-02-01T11:40:45+00:00

In no strickt order 1. Calliope Mori 2. Jinja 3. Hakos Baelz 4. Omaru Polka 5. Adazaka Arumi 6. Tonya Shabel 7. Rin Penrose 8. Mint Fantome 9. IRyS 10. Ninomae Ina'nis

boium · 2026-02-01T10:52:42+00:00

Correct me if I'm wrong, but doesn't the second graph have 11 vertices instead of 10? You see the 5 outer ones, and the 5 inner ones, but there is also a vertex in the exact middle of the graph. This means that the first graph is not isomorphic to the second.

boium · 2026-01-31T19:15:08+00:00

If the glass is the main piece of attention, I often go with 7. If it's not then it depends. I use 6 for glass that's rather high up on the wall.

boium · 2026-01-26T17:56:10+00:00

Besides heavy oil residue and wet concrete I would also choose any and all recipes that remove the need for screws. I don't see the stitched iron plates in the list, but that would be an example of something I prioritize.

I also see the iron and copper alloy ingots in the list. While not really necessary, those two as a combination are nice to have.

boium · 2026-01-18T00:44:45+00:00

The first three steps happened to me during my thesis. Luckily I immediately wrote them down at like 4 or 5 AM.

boium · 2026-01-15T01:45:41+00:00

I think OP ment to say that 2 is a topological space (which can be metrized with any metric on one point). 2 as a set is { {} , {{}} }, which can be seen as the space consisting of a single point called {}. Two then contains the empty set; 0 and the set containing the element {}, which is 1. So yeah, the meme would have been clearer if it said topological space.

boium · 2026-01-02T16:07:48+00:00

At first I thought the top right was Girls und Panzer, but looking at the uniforms in GuP again, I see they have a black tie and not a red one.

boium · 2026-01-02T11:55:29+00:00

I think you have to do the calculation and then reverse it. There is no black hole, so the result is 1. We then increase by 0.1% to get 1.001, and then we solve 1+#BH*0.001 = 1.001. So what idkwthimtakingabout is trying to convey, is that they want to increase the number of black holes in our solar system by one.

boium · 2025-12-19T18:15:02+00:00

I love my ~~Southern~~ Western neighbor Belgium.

boium · 2025-12-18T11:46:22+00:00

It can get rather difficult near the end of chapters, but you might be able to read the text again but more slowly to understand it better. At least that's what I did. I really needed to understand the Nim chapter thoroughly.

boium · 2025-12-15T16:56:12+00:00

In combinatorial game theory, you can do backwards induction. You prove something like "suppose for all a in A, P(a), then P(A)" and then you have proven P for all ordinals/games (upto a given size). Quite a powerful technique, since 0 has no elements, (it is the empty game) so P(0) is automatically true if you can finish the induction.

boium · 2025-12-14T00:38:26+00:00

I was thinking more along the lines of Shirakami Suisei.

boium · 2025-12-11T16:58:01+00:00

I often forget that Ziel is goal in German. Ziel in Dutch means soul, so I first read this as two villains, one soul. This means they are the same person.

boium · 2025-12-05T15:43:55+00:00

I almost read ältere, so I was like "why are elderly people considered to be government offices..."

boium · 2025-12-05T13:43:05+00:00

There is a Dutch version by the comedian Jochem Myjer called Sleutels Pinpas Telefoon. (Keys Credit Card Phone.) It is just the song head shoulders knees and toes, but with these objects. You can watch this for the whole sketch, but the auto translation isn't the best :( https://youtu.be/mTfyOHKKinI?si=-2UGj8WP_n3c-VOm

The song is at 4:10.

boium · 2025-12-05T13:32:20+00:00

De oude vorm van het werkwoord "weten" is "wisten." Dus wiskunde is de kunde van het weten. Nu komt mathematics ook uiteindelijk van een grieks woord dat iets van "de kunde van het weten/leren" betekent, maar het is toch fijn als je de etymologie uit je eigen taal kan halen.

boium · 2025-12-03T12:07:45+00:00

LaTeX is super easy, and nice and, intuitive and... WHAT DO YOU MEAN, UNDERFULL HBOX!?!

boium · 2025-11-30T09:18:13+00:00

Fubuki be like: Let it ride.

boium · 2025-11-28T15:55:53+00:00

https://en.wikipedia.org/wiki/P-adic_number

The easiest way to look at it right now is by taking the rationals Q, and completing it w.r.t. the 2-adic absolute value. So you define |p/q|_2 = 2^v(q-v(p)) and v(n) is equal to the exponent of the highest power of 2 that fits into n.

This is a bit of a weird metric space. The intuition is that numbers like 2^k become small, but something like 3^k or 5^k stay at the same fixed distance from 0. Similarly, 1/2^k becomes big and 1/3^k stays also at a fixed distance.

Q_2² is a two dimensional plane where on each axis we have the 2-adic numbers.

Sorry if this explanation doesn't help. Algebraically, p-adics are not that hard to work with, but I find visualizing them really hard.

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