Archived threads in /sci/ - Science & Math - 31. page
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ITT: we post our favourite biographical books of scientists and/or mathematicians. Pic related is mine
spoiler alert.....
.....dirac was probably autistic
>>8182845
not sure if this is the right place to ask, but does anyone here know about swollen lymph nodes? basically both of my 'midjugular' ones have swollen up (i think) in the past couple of days and im wondering if thats how it works? like does one swell and then the ones connected to it follow or should i be worried its something else? i have a doctors appointment book but its not for a couple of weeks
>>8182723
Edema is just excess fluid. It depends on what you have.
>>8182743
it doesnt look like edema, more two pea sized bumps on my neck
>>8182754
Not particularly educated on physiology but as far as I understand, lymph nodes swell up all the time, especially if you are at all sick. The lymph system is for "cleaning" and so there are endless reasons it could be overloaded.
Hello /sci/, and welcome to the second lecture in my Brave New Algebra series. Today we will be discussing category theory. This won't be as careless as yesterday's lecture, but it is NOT going to be super duper careful either. You've been warned. All of this stuff has been fully formalized and carefully handled in a variety of great textbooks (Categories for the Working Mathematician by Mac Lane is pretty good). This lecture is meant to familiarize people with the language and methods of category theory. My goal is not a starkly rigorous handling. With that said, let's begin.
I will be fixing a suitable Grothendieck universe U for this discussion, for those curious. When I say small, I mean U-small. An arbitrary category need not be U-small here, but it will be U'-small for some sufficiently large universe U'.
A category C consists of a U'-small set of objects, which I will denote C_0, and a U'-small set of arrows or morphisms, which I will denote C_1. This notation should remind you of objects being 0-cells, and arrows being 1-cells. We will handle this generalization later on.
There are parallel functions s,t: C_1 -> C_0. We call s(f) the source or domain of f, and t(f) the target or codomain of f. A pair of arrows (f,g) is called composable if s(g)=t(f). There is a binary operator called composition ∘: {(f,g) : (f,g) is composable} -> C_1 which is associative....
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The elements of C[X,X] are called endomorphisms of X. The subset of C[X,X] consisting of the isomorphisms is called the set of automorphisms on X, Aut(X). (Exercise: show that Aut(X) satisfies the group axioms.) With this, we call Aut(X) the automorphism group of X.
If r∘s=Id(X), we call r a retract of s (a left inverse), and we call s a section of r (a right inverse). A morphism f is called idempotent if f∘f=f. (Exercise: show that, if s is a section of r, then s∘r is idempotent.) We say that such an r and s split this idempotent.
A monomorphism is an arrow...
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A category C is called small (by our use of universes, this is technically U-small) if C_0 is a small set and C_1 is a small set. It is locally small if C[A,B] is a small set for all A,B in C. (Exercise: show that a small category is locally small.)
We will now examine some of the categories which we will be working with most heavily.
The category Set has for objects U-small sets, and Set[A,B]=B^A, the set of functions from A to B. (Exercise: check that Set indeed forms a category. Is it small? Locally small?)
The category Grp has for objects (small)...
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Does browsing /sci/ make me smarter than everyone else?
>>8182142
It makes you just smart enough to qualify to be my sandwich maker.
Can you prove the formula for volume of sphere
If yes then you're probably a fucking genius
>>8182142
nah, not just browsing... you have to fight with someone, and believe that your right
What's gonna happen at CERN? Are the worries of a black hole forming or the world exploding valid? general knowledge will be appreciated
>>8182075
>What's gonna happen at CERN?
Protons are gonna get smashed together.
>Are the worries of a black hole forming or the world exploding valid?
No
>>8182075
>What's gonna happen at CERN?
Particles are going to be accelerating
Are the worries of a black hole forming or the world exploding valid?
No.
>>8182088
Why not?
Question for chemists from a physics-fag. How the fuck do you grasp your notation? Like seriously, the way you read molocules and shit is fucking unlegible.
>>8180110
there are naming conventions you have to learn. in chemistry there is currently a discrepancy between generations, as the old fucks had a system put into place, but the fresh meat redesigned the standard to be more intuitive.
most everyone knows the new notation because its really easy. i dont know why old people insist on using the older words to cause confusion. some are just easier to say I guess.
>>8180136
You happen to know the name of the two notation sets? Would like to find out which one I'm being taught.
>>8180139
IUPAC handles the naming conventions for current chemistry education and is named "IUPAC notation" accordingly if i remember correctly. I dont know what the old notation is called, but sure tell me what you are being taught.
hey /sci/,
any clues?
one of these space balls?
>>8178608
Pipe bomb?
>>8178608
>space balls
Piece of satellite.
Hello, /sci/, No dark matter guy here again.
Long video in which I argue against a comment defending the current black hole model.
https://www.youtube.com/watch?v=8nwS708KOtk
i like the video
>>8172611
Finally someone standing up against this nuts concept? I'll watch your videos later
>>8172611
Good OP!
Sick and tired of people taking a mathematical equation as proof that black holes and dark matter exist. All fucking nonsense.
since i couldn't find one, dump your lingering questions without fear of looking a fool.
for instance, what is this molecule, and can i wear this shirt around my in-laws? it's been a while since ochem
i have no idea about chemistry, but i summed the amounts of letters in your picture and googled it
https://en.wikipedia.org/wiki/Capsaicin
>>8161859
basically it says "hot." don't wear it around your in-laws.
I couldn't get into Spivak Calculus, and Apostol's introduction to proving Archimedes just left me confused and I have no idea of what these guys are doing.
So I am obviously too dumb for these two. Is there some other book that kind of gives me the type of thinking required for this type of math? Induction, proving, etc.
Everything in life is dependent on something else in order to function as we know it. However, in conversation, when bringing up dependency what are the prerequisites for it to be relevant to the context at hand?
Basically, how "dependent" does something have to be, or what thresholds does it have to pass in order to be brought up?
>>8183754
Be a nigger
Say "you didn't build that"
Get a Nobel Peace Prize
Passive facilitation versus direct impact.
https://en.wikipedia.org/wiki/M%C3%BCnchhausen_trilemma
Why some people (mathematicians mostly) say that "pi is the answer for everything"? What does it mean or is it just a metaphor?
>>8183201
>is it just a metaphor?
No, it's literally the answer to everything. Every single constant can be reduced to pi.
>>8183211
what
>>8183201
No mathematician ever said that, the closest thing will have been a math undergrad who will probably drop out.
I asked /g/ and /diy/ and they couldn't tell me shit so i'm hoping on some engineers here.
i just got an arduino uno from my parents and started playing around with it, now my brother (who works in some electronics business) brought me a bunch of stuff to build around and i don't really know what it is or what i can do with it.
I'd appreciate every little bit of information from you guys.
can someone tell me what's going on in this picture? Both sides seem identical to me, they both end up aproacching 1^infinity
>>8183128
>graph paper
Kill yourself.
>>8183128
They are not the same function.
how the fuck do you get euler's number from any of that?
As a physcist, are there any humanitarian missions I can help with using my expertise?
MSF only wants doctors (unsurprisingly), but I really want to help people if I can.
You could build a better car and pay for condoms in the developing world so that the niggers can stop breeding like rats.
lol jk they will not use them.
Seriously, just spend your money on your own happiness. Or take more days off.
>>8182807
>i want to help people
"spend money on yourself and go on holiday"
i dont think you understand how this works, friend
>>8182824
You can help people by not being an idiot who makes the world worse through incompetent retarded altruism. Believe it or not, the people who "really want to help people" usually cause the worst screwups and idiotic conflicts.
What is the most important math to know backwards and front?
>>8182582
Elementary Algebra. Important for what?
addition and multiplication of numbers 0-9
calculus is the only important one
