Latest Posts by bsdndprplplld - Page 6

everybody cries doing their math hw, those who claim they don't just haven't met that hw yet

this unlocked some ancient pain lol

hey guys quick question

tips for studying math

I thought I could share what I learned about studying math so far. it will be very subjective with no scientific sources, pure personal experience, hence one shouldn't expect all of this to work, I merely hope to give some ideas

1. note taking

some time ago I stopped caring about making my notes pretty and it was a great decision – they are supposed to be useful. moreover, I try to write as little as possible. this way my notes contain only crucial information and I might actually use them later because finding things becomes much easier. there is no point in writing down everything, a lot of the time it suffices to know where to find things in the textbook later. also, I noticed that taking notes doesn't actually help me remember, I use it to process information that I'm reading, and if I write down too many details it becomes very chaotic. when I'm trying to process as much as possible in the spot while reading I'm better at structuring the information. so my suggestion would be to stop caring about the aesthetics and try to write down only what is the most important (such as definitions, statements of theorems, useful facts)

2. active learning

do not write down the proof as is, instead write down general steps and then try to fill in the details. it would be perfect to prove everything from scratch, but that's rarely realistic, especially when the exam is in a few days. breaking the proof down into steps and describing the general idea of each step naturally raises questions such as "why is this part important, what is the goal of this calculation, how to describe this reasoning in one sentence, what are we actually doing here". sometimes it's possible to give the proof purely in words, that's also a good idea. it's also much more engaging and creative than passively writing things down. another thing that makes learning more active is trying to come up with examples for the definitions

3. exercises

many textbooks give exercises between definitions and theorem, doing them right away is generally a good idea, that's another way to make studying more active. I also like to take a look at the exercises at the end of the chapter (if that's the case) once in a while to see which ones I could do with what I already learned and try to do them. sometimes it's really hard to solve problems freshly after studying the theory and that's what worked out examples are for, it helps. mamy textbooks offer solutions of exercises, I like to compare the "official" ones with mine. it's obviously better than reading the solution before solving the problem on my own, but when I'm stuck for a long time I check if my idea for the solution at least makes sense. if it's similar to the solution from the book then I know I should just keep going

4. textbooks and other sources

finding the right book is so important. I don't even want to think about all the time I wasted trying to work with a book that just wasn't it. when I need a textbook for something I google "best textbooks for [topic]" and usually there is already a discussion on MSE where people recommend sources and explain why they think that source is a good one, which also gives the idea of how it's written and what to expect. a lot of professors share their lecture/class notes online, which contain user-friendly explenations, examples, exercises chosen by experienced teachers to do in their class, sometimes you can even find exercises with solutions. using the internet is such an important skill

5. studying for exams

do not study the material in a linear order, instead do it by layers. skim everything to get the general idea of which topics need the most work, which can be skipped, then study by priority. other than that it's usually better to know the sketch of every proof than to know a half of them in great detail and the rest not at all. it's similar when it comes to practice problems, do not spend half of your time on easy stuff that could easily be skipped, it's better to practice a bit of everything than to be an expert in half of the topics and unable to solve easy problems from the rest. if the past papers are available they can be a good tool to take a "mock exam" after studying for some time, it gives an opoortunity to see, again, which topics need the most work

6. examples and counterexamples

there are those theorems with statements that take up half of the page because there are just so many assumptions. finding counterexamples for each assumption usually helps with that. when I have a lot of definitions to learn, thinking of examples for them makes everything more specific therefore easier to remember

7. motivation

and by that I mean motivation of concepts. learning something new is much easier if it's motivated with an interesting example, a question, or application. it's easier to learn something when I know that it will be useful later, it's worth it to try to make things more interesting

8. studying for exams vs studying longterm

oftentimes it is the case that the exam itself requires learning some specific types of problems, which do not really matter in the long run. of course, preparing for exams is important, but keep in mind that what really matters is learning things that will be useful in the future especially when they are relevant to the field of choice. just because "this will not be on the test" doesn't always mean it can be skipped

ok I think that's all I have for now. I hope someone will find these helpful and feel free to share yours

So the exponential function is given by

which evaluated at a real number x gives you the value eˣ, hence the name. There are various ways of extending the above definition, such as to complex numbers, or matrices, or really any structure in which you have multiplication, summation, and division by the values of the factorial function at whatever your standin for the natural numbers is.

For a set A we can do some of these quite naturally. The product of two sets is their Cartesian product, the sum of two sets is their disjoint union. Division and factorial get a little tricky, but in this case they happen to coexist naturally. Given a natural number n, a set that has n! elements may be given by Sym(n), the symmetric group on n points. This is the set of all permutations of {1,...,n}, i.e. invertible functions from {1,...,n} to itself. How do we divide Aⁿ, the set of all n-tuples of elements of A, by Sym(n) in a natural way?

Often when a division-like thing with sets is written like A/E, it is the case that E is an equivalence relation on A. The set of equivalence classes of A under E is then denoted A/E, and called the quotient set of A by E. Another common occurence is when G is a group that acts on A. In this case A/G denotes the set of orbits of elements of A under G. This is a special case of the earlier one, where the equivalence relation is given by 'having the same orbit'. It just so happens that the group Sym(n) acts on naturally on any Aⁿ.

An element of Aⁿ looks like (a[1],a[2],...,a[n]), and a permutation σ: {1,...,n} -> {1,...,n} acts on this tuple by mapping it onto (a[σ(1)],a[σ(2)],...,a[σ(n)]). That is, it changes the order of the entries according to σ. An orbit of such a tuple under the action of Sym(n) is therefore the set of all tuples that have the same elements with multiplicity. We can identify this with the multiset of those elements.

We find that Aⁿ/Sym(n) is the set of all multisubsets of A with exactly n elements with multiplicity. So,

is the set of all finite multisubsets of A. Interestingly, some of the identities that the exponential function satisfies in other contexts still hold. For example, exp ∅ is the set of all finite multisubsets of ∅, so it's {∅}. This is because ∅⁰ has an element, but ∅ⁿ does not for any n > 0. In other words, exp 0 = 1 for sets. Additionally, consider exp(A ⊕ B). Any finite multisubset of A ⊕ B can be uniquely identified with an ordered pair consisting of a multisubset of A and a multisubset of B. So, exp(A + B) = exp(A) ⨯ exp(B) holds as well.

For A = {∗} being any one point set, the set Aⁿ will always have one element: the n-tuple (∗,...,∗). Sym(n) acts trivially on this, so exp({∗}) = {∅} ⊕ {{∗}} ⊕ {{∗∗}} ⊕ {{∗∗∗}} ⊕ ... may be naturally identified with the set of natural numbers. This is the set equivalent of the real number e.

30 I 2023

in a fortnight I will have two oral exams and one problem-based exam

the first oral will be for complex analysis and we are supposed to choose three topics from which the professor will pick one and we'll have a chat. I chose meromorphic functions, Weierstrass function and modular function. I have already received my final score from homeworks, which is 73%. combined with 74% and 100% from tests, I am aiming for the top grade

the rest of exams will be for algebraic methods. a friend who already took this course told me that when someone is about to get a passing grade, they get general questions and the professor doesn't demand details of proofs. when I asked him if we are supposed to know the proofs in full detail or if it suffices to just be familiar with the sketch, he told me that if I will only know the sketch I will sit there until I fill in all the details. lmao that sounds like he wants me to get a top grade. ok challenge accepted

so it seems like I have a chance to ace everything. if I achieve this and do it again next semester I can apply for a scholarship. studying for the sole purpose of getting good grades doesn't feel right, the grades should come as a side effect of learning the material. buuut if I can get paid for studying then I might want to try harder, I enjoy being unpoor

the next two weeks will be spent mostly grinding for the algebraic methods exams, this is what I'm doing today

Me: *Removes my cat from my lap to do something else.*

My cat: Father is…evil? Father is unyielding? Father is incapable of love? I am running away. I am packing my little rucksack and going out to explore the world as a lone vagabond. I can no longer thrive in this household.

(Points at the function I'm doing my thesis on) this is my son who has every disease

Julie D’Aubigny was a 17th-century bisexual French opera singer and fencing master who killed or wounded at least ten men in life-or-death duels, performed nightly shows on the biggest and most highly-respected opera stage in the world, and once took the Holy Orders just so that she could sneak into a convent and shag a nun.

(via Feminism)

ah yes my boy tom cardy. everyone must listen to him, he's the best

I need everyone to see this ABSOLUTE MASTERPIECE

moreover tiktok adhd content is not even good lol most of it is videos themed "things I didn't know were adhd" and they actually are personality traits and it's not helpful at all with anything

just saw a post complaining about how hard it is to find adhd resources for adults and one of the comments said “tiktok has a lot of adhd tips” as if telling someone with adhd to enter the algorithmic quicksand of perpetual dopamine hits isn’t the most insane thing you could suggest for someone with adhd

The chili plant made a deal with their God to only be consumed by things that could spread its seeds and fly. The chili received capsaicin, making itself painful to eat for mammals, but not birds, and all was well for the chili.

Then the human shows up, tastes it, and likes the pain. So now there's this flightless fucking mammal eating the chili. Like not even a fruit bat or anything, a flightless fucking mammal chomping on the chili.

What the fucking shit, God, cried the chili, I specifically requested the opposite of this.

Now hold on, wait a moment, replied the God who talks to plants but has no idea what the fuck these apes are going to do next. It might be something cool.

And in a flash of a second, in barely fraction of the time that chili took to develop capsaicin, the humans went from walking across land bridges and rowing little boats across small waters, into building ships that could cross oceans. More humans tasted the chili, and liked the pain. They took the seeds with them, and planted it elsewhere.

See? They spread the seeds.

They're still not flying, said the chili, still feeling insulted and betrayed.

But before the conversation was over, the humans were still not done fucking around and nowhere close to finding out. The ships became machines, and another machine was invented, capable of flight. Now, not only were the humans farming chili on continents far too far away for any of the birds that originally ate it could dream of flying, but the chili flew with them to lands where it could possibly not grow, so that humans over there could also eat it and enjoy the pain.

You see? They spread your seeds and fly.

It doesn't count as keeping a promise if you only manage it by a fucking accident, said the chili, still somewhat insulted. But nonetheless, the chili thrived.

21 I 2023

so the test I had today, our professor went crazy with grading it and we all had our scores by midnight

I don't think I ever scored 100% before, but here it is

I was insanely lucky. yesterday I was watching some series (and by that I mean Young Royals, not Fourier) and I had a thought you know might as well give them elliptic functions a quick read. today one of the easy problems required to only know the basic definitions and properties, have I not spent those 40 minutes reading I would probably not solve it. the other easy problem was solved by picard's theorems, my favourite, which I tried to use with every given opportunity so now it's as they say: when your only tool is a hammer every problem looks like a nail. and today it actually was a nail. two other problems were just objectively easy and the last one took a lot of my time but it was "my type" of problems, so I enjoyed working on it and I had some good ideas thanks to solving about 20 similar problems before

so that's how it feels to reach above my goals. I dreamt of this moment and it feels exactly like I thought it would. ah feels good man

in my country having a diagnosis is highly confidential, too. there is no such thing as "the government knowing about your diagnoses" unless you get evaluated for disability documentation (I have no idea how to translate this to english), which is your choice. besides, who knows when the diagnosis will be useful? waiting for a diagnostic appointment takes several months and is very expensive, so taking an opportunity to sort this thing out when it's possible is good. depending on where someone lives, it can be very harmful to say that having a diagnosis somehow creates disadvantages

at my university the support program for people with asd has been introduced two years ago. it took me almost a year to get everything done, a year of unnecessary suffering. treatment for depression with or wihout adhd can be completely different and having it on paper that in your personal circumstances ssri might not work can save so much time. when someone suspects adhd and the situation calls for introducing medication, it's nice to be able to try right away, not wait several months for a diagnosis. those are just some practical examples of how you never know when diagnosis might be useful

and the validation reason, yeah, that too, it's beneficial to have someone work with you through that stuff. moreover, with professional support there comes someone suggesting solutions and forms of help that one might not even thought of. there are shitty doctors, but there are good ones too, and I think we should talk more about how to find the right ones instead of demonizing getting help

By the way. Before you rush to get a professional diagnosis for a Brain Thing you should really weigh your options. Like do you just want to "prove it" or will this actually give you access to treatment you can't have otherwise? Are the treatment options available worth having the government know you're neurodivergent? Because sometimes it's better to keep things off the record because unfortunately we still live in a very deeply ableist society and you might not want to have more real material oppression stacked against you than you have to

why is deciding on a title for my thesis so hard

19 I 2023

this week is kinda crazy

I have a complex analysis test on saturday and the professor said that it will cover the entire semester. thank god I might get away with not knowing anything about analytic number theory lmao

I had troubles sleeping lately, it takes me about 3-4 hours to fall asleep every day. I sleep a lot during the day and it helps a bit but I still feel half-dead all the time. every time I fall asleep my brain can't shut up about some math problem

for the algebraic methods course we were supposed to state and prove the analogue of Baer criterion for sheaves of rings. I was the only person who claimed to have solved this, so I was sentenced to presenting my solution in front of everyone. the assertion holds and I thought I proved it but the professor said that the proof doesn't work, here is what I got:

he said that we cannot do this on stalks and we have to define a sheaf of ideals instead. when I was showing this I had a migraine so no brain power for me, I couldn't argue why I believe this to be fine. whenever two maps of sheaves agree on each stalk they are equal, so if we show that every extension on stalks is actually B → M on stalks, then doesn't that imply the extension is B → M on sheaves?? probably not, but I don't see where it fails and I'm so pissed that I was unable to ask about it when I was presenting, now it's too late and this shit keeps me up at night

I enjoy sheaf theory very much and I can't wait to have some time to read about schemes, I have a feeling that algebraic geometry and I are gonna be besties

during some interview Eisenbud said that when deciding which speciality to choose one should find a professor that they like and just do what that professor is doing lol. I feel this now that I talked some more to the guy who taught us commutative algebra. since my first year I was sure that I will do algebraic topology but maybe I will actually do AG, because that's what he's doing. is having one brain enough to do both?

anyway I'm glad that my interests fall into the category of fashionable stuff to do in math these days. my bachelor's thesis is likely going to be about simply-connected 4-dimensional manifolds, which is a hot research topic I guess. I won't work on any open problem because I'm just a stupid 3-year, not Perelman, but it will be a good opportunity to learn some of the stuff necessary to do research one day

Master Control Program

A minimal 74 knot on the simple cubic lattice

(source code)

sn

℘²

I think "high value person" can be interpreted as "someone who is liked by everyone and perfectly adheres to social norms" but also as "someone who wants to find their core values and to this end tries many different approaches" and many other things. some of the things listed are pretty good, such as "take care of themselves" or "doesn't equate their worth to sex", some are unnecessary: "perfected first impressions" or "ALWAYS well-dressed". naah, who cares lol

the thing with self-improvement or other forms of conscious existing (I just invented this term, by that I mean something like chosing which parts of oneself to keep and which to change) is that one must start somewhere. it's nice, in general, to have social relationships, sex life or hobbies and I see this list as a guideline for increasing the probability of achieving those and other things in a certain way

in my opinion it's really important to keep in check with oneself, ask if the cost of being likeable and elegant is worth it. some people derive pleasure from wearing nice clothes and make-up, I am not one of them and for me that would be too much of a sacrifice. I guess most people would hate to have my lifestyle: I basically do math all day. it is my decision to so, it's fun, and I hate it when someone assumes that it's bad just because they wouldn't enjoy it

hence I see this controversial list as goals of someone who genuinely wants to be perfect. and yeah I do think that most of those things are completely unnecessary, I don't consider this set of characteristics as a "high value person" but maybe some people do. a part of self-improvement for me was realizing that I don't care about most things and this post reminded me that there might exist people who care about everything. have they not yet realized that they actually don't care? idk, maybe they do care

but yeah if someone came to me and said that this list objectively defines a high value person then I would laugh lol I will respect everyone's values if they respect mine

did i tell u guys i got into an argument on twitter bc i said foxes are dogs and someone tried to bring up their actual fuckin. classification or whatever and i just said “foxes are dogs cause they are fluffye” and they kept arguing with me. the entire time i was like “you will not survive the immigration to tumblr you are lucky we are not there right now”

rb this with ur opinion on this shade of pink:

I read this and it got me thinking that it's funny how many goals and standards people tend to have. my only goals are to have fairly good health and to improve my math skills constantly. maybe it's my obsession, maybe it's the fact that I just gave up long time ago on femininity, social skills, so called emotional intelligence and how I present to other people

besides… why does this sounds like I'm supposed to only date men lmao

13 I 2023

two days ago I went to the 0th term exam for commutative algebra and received the highest possible grade!

the thing I noticed when studying for it was that the topics that used to be fairly ok but not very clear became completely intuitive. the best example of this would be fibers of maps induced on spectra. it feels so good when after trying to understand something for two months everything finally clicks and I obtain a deeper level of understanding

also I realized that making pretty notes actually doesn't help at all, so I switched to making more messy, natural ones. maybe I can no longer look at them and admire the work of art, but I think the principle behind it is that the more I focus on making my notes pretty the less attention I pay to actual information processing

so maybe these ^ don't look as good as they could and they are probably hardly useful for anyone other than me lol but the benefit is that I started learning really fast compared to how it was going when my notes were a work of art

currently I am studying sheaf cohomology and preparing for a complex analysis test (it's next week). I have two courses left to pass and I would like to ace them too, although that's rather unrealistic

the second batch of topics for complex analysis includes: order of growth of entire functions, analytic continuation, gamma, zeta, theta functions and probably elliptic functions. significantly more sophisticated than the first part of the material. for the course on algebraic methods, everything is hard lol I am waiting for the moment when homological algebra and sheaf theory become intuitive

next semester I am going to take algebraic topology (fucking finally), differential geometry, number theory, statistics and algebra 2 (mostly galois theory). I have never taken 5 courses in one semester so I'm very scared

I want to follow all of you!

[ID: a figure in a textbook that has curved arrows to look like vectors in a field. The figure caption reads, "Is this a vector field? No. It's a picture" /end]

Shortest math paper ever.

And with so much impact! It just disproved a widely accepted theorem from the year 1769 in 5 rows!!!

I'll never publish anything even remotely badass like this! But I want it so much!!!

the human experience is so crazy. at any time i want, for free, i can comprehend the beauty and the horror of my own fragile existence, the cosmic insigificance and personal significance of my experiences, the impossibly vast yet laughably tiny boundaries of my own consciousness, and feel sick to my stomach with anticipation for everything i have yet to understand and grief for everything i have yet to lose.

A monoid? Oh, you mean a monad on a one point set in the bicategory of spans of sets?