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00:03
does the fundamental theorem of finitely-generated modules hold for any non-PID rings?
Hi @Ted
hi @user127001
How are you this evening
doing pretty well ... enjoying my last night before lots of days/nights of grading final exams
How many classes did you teach this semester?
00:13
two official, plus one class with one student
Oh, how does the one-student class work? Is it math research or something?
no, I taught the Spivak Calculus class to a high school student
Ohhhh wow
I tried that and failed :(
I don't remember teaching you!
Haha
Tried to self-study it on my own and I remember I was in the library and started crying quietly because I didn't understand epsilon-delta after a week or so
Then I just gave up
00:15
I don't think self-study works very well for most students ... Pretty much everyone I've ever taught that course to would have bombed trying to do it on their own.
A good teacher can actually be a significant plus :D
Not to mention getting weekly feedback on written homework, exams, etc.
Everyone always told me "self-study, self-study, self-study"
Nobody was really that helpful in community college
I am one who learned a lot from teachers ... so I try to reciprocate as a teacher.
Self-study can be really frustrating
@Mike does a lot of self-study and then he comes here and bombards us with questions :P
@Ted rude
00:17
lol
What do you expect from me if not rudity?
My friend's calc 2 exam lol
pretty pathetic ... both the exam and his performance, although I don't see why (g) is wrong.
oh, the teacher is putting an x on everything because there are no equal signs ... but there were some actual integration errors. Horrid.
It looks to me like he got docked ... yeah
Actually it looks like the only one that was wrong was (d)
No, (d) is right, too. Actually, I don't think any were wrong.
But might as well give a test on multiplying two-digit numbers. What sort of course/test is this?
00:23
Oops, you're right. I didn't say that.
Calculus 2
Am I supposed to engage yet again in rudity?
it's not even a high-school level test, @user127001.
Haha, I didn't even take pre-calculus in high school xD
good for you :P
Oh... looks like it's Chris's test.
his sister should teach him about integrals.
00:25
smacks @Mike
lol
I think I barely managed to pass the state exam for algebra 2
so you're more motivated now, @user127001
Motivation, desperation, similar things I guess
I think not doing more academics when I was younger affected how well I learn as an adult
I'm kind of slower compared to a lot of other people
I'm no expert in educational psychology ...
I see people of all different speeds at all different ages ...
I wish I had some natural abilities in something that I can be good at
I'm bad at everything so I chose the thing I'm the least worst at
00:28
Hey guys
I got slightly better grades in math than the other subjects I failed so yea, that's how I chose my major :p
Have you gone to the career center to take one of those aptitude tests to see what it tells you?
hi @Fernando
No I haven't tried that
I have some sweet students in my senior-level diff geo class and I keep wondering how they've gotten almost to the end of a math major. I just can't understand how.
00:30
Hi @Ted
Future mathematicians of America, ladies and gentlemen
How're things this evening in BA, @Fernando?
Rainy but good
We're supposed to get serious thunderstorms/tornados here ...
@Pedro must be on hiatus :)
@TedShifrin Hey, here I am!
00:32
That's really scary. That kind of stuff isn't really commonplace here.
Oh, look, @Pedro be here!
@TedShifrin I'm trying to convince someone that pedagogy is a null set of courses in higher mathematics.
I am not sure you'll agree though.
I'm not sure what you mean.
When the level of a course is such that teaching techniques or whatever becomes absolutely irrelevant.
I don't think it is ever irrelevant. The students who took my advanced grad course last fall might disagree, but I doubt it.
00:35
And it is the professors' experience with such topic and knowledge of the topic (rather than knowledge of teaching techniques) what really counts.
Someone with little connection to mathematics can hardly devise an improvement in the teaching of a mathematics course.
Mostly true, and I'm not a big fan of pedagogy courses. But I still disagree with your point.
It is the people that deal with maths everyday that know how to transmit it, to my view.
I've sat in courses taught by experts who could not communicate and didn't want to be there, and it was basically frustrating and a waste of time.
No, @Pedro, that is wrong.
@TedShifrin Well, that will always happen, regardless.
If the guy doesn't want to be there, less will he want to take a pedagogy course...
There are plenty of star researchers who are gifted teachers -- partly because they care -- but there is no implication.
I agree that the ideal is a bright, engaged researcher who is also a gifted teacher.
00:39
@TedShifrin I guess so. But I don't think any pedagogy course can improve the way I transmit mathematics.
I've never taken a pedagogy course.
I don't even know what a pedagogy course would consist of
I think a lot of teaching talent is innate. Some comes from experience and thinking.
And I also agree that we shouldn't have education majors teaching in high schools, but there is definitely something for them to learn about teaching and how learning works. But of primary importance is knowledge of and enthusiasm for the subject. Those are often lacking.
@TedShifrin Agreed.
Did Alex sort out his $\bigwedge$ thing?
Well, he thought something was wrong, and it wasn't. And I explained something to him. So I think he's ok.
Ram
Ram
00:47
Hi All, Hi @TedShifrin, my Prof. cancelled my seminar today. I felt terrible.
Which seminar @Ram
why did s/he cancel it, @Ram?
Ram
Ram
I am supposed to give a talk on bounds on least primes in arithmetic series.
@TedShifrin, his train was late by 3.5 hrs. Can't help. But we have to (its a group seminar course) read 4 more sections.
that's quite a train ride
so is there going to be a make-up meeting?
Ram
Ram
Nope, others are not so interested (..from Davenport. Initial plan was to finish davenport in 2 months and start reading Iwaniec. ). But due to scheduling conflicts we just able to do only 40% of original plan :-(
00:52
Well, it often happens that one doesn't cover all one intends. Particularly happens in seminar talks and classes that are not well-organized :)
heya @Karl
Ram
Ram
Yes, but Davenport is not a hard book, we are not supposed to spend this much time on it.
01:35
Quick question: is the cokernel of a map all of the elements in the codomain that do not get mapped to by any element in the domain?
Not exactly @Alex.
You're talking about vector spaces, right? @Alex
Yeah. I just looked up the wiki page, and saw the definition.
should have at least done that before asking, sorry
@user127001 wow. that infuriates me.
@AlexanderGruber Got marked down for no equal signs...?
SIGH. Then people wonder why other people dislike mathematics.
Sorry guys, I was having a bad day. So, I marked down lack of equals signs.
01:50
@PedroTamaroff i don't understand why so many math teachers needlessly abuse their students
@AlexanderGruber Yeah, they should be impaled.
either they take no pride in what they do at all or they are sorely misguided. i run into stuff like this all the time.
@AlexanderGruber Indeed, those people ruin maths for so many others.
SIGH.
That guy totally deserved full marks.
The exam is quite boring.
You cannot expect somone to show work if you give those problems.
the entire first year mathematics is done completely incorrectly if you ask me, especially below math/science/engineering major-level calculus
it's all grinding and rote memory, 90% of the people don't even know what any of it means
not that that's the case here. it just reminded me of some related insanity i saw today.
ORLY?
What did you see?
01:55
@PedroTamaroff actually, i shouldn't say publicly what it is because it's somebody i work with.
@AlexanderGruber Oh, OK. Then don't tell me.
@AlexanderGruber Did you finish proving that one isomorphism?
@KarlKronenfeld yeah pretty much, now i am working on the next problem
there is a detail of the other one that i need to touch up but i'm putting it off till later
01:58
Do you have another beastly commutative diagram to show us?
@AlexanderGruber. I agree with you in how they decide to teach mathematics in junior years.
@KarlKronenfeld not yet. :)
Kids constantly think that mathematics is about memorisation, counting and shapes. Then they realise that there are these weird mathematical structures and can't seem to comprehend them properly.
@eXtremiity i think it literally could not be taught worse if someone were trying deliberately to teach as badly as possible.
02:00
Hahaha.
i grew up with really atrocious math instruction (with only one year in exception). i never took past geometry in high school.
I sat down with my student last night and explained to him that he must disregard his current "feel" of mathematics and start to realise that there's more to it.
Oh wow.
i never saw calculus until i was 24, heh.
@AlexanderGruber VERY BANE
SUCH REFERENCE
So what were you studying prior 24?
02:03
@eXtremiity i was an artist.
That's incredible.
When did you decide to do mathematics?
Or continue.
@eXtremiity well, i realized suddenly that i didn't know anything worthwhile... i had a skill, and i enjoyed it, but that's not the same thing as being educated
so i went back and picked physics because it was the hardest sounding major
and after a couple years i realized the thing i liked about physics was math
the class which really cemented that for me was algebra, so, i kept going with that.
You think well.
ended up with the double major, graduated, and here i am in grad school.
@eXtremiity thanks!
What were your majors?
02:07
physics and math
(and a minor in Chinese, haha)
Ahhh, fantastic!
Do you still draw every now and then?
@eXtremiity very frequently
I love anime.
Makes me want to draw.
you should take up the fountain pen. it's easier than it looks
@AlexanderGruber Look at dis.
02:09
basics of anime aren't too hard, the inking makes it look incredible without much effort
Got some German ink there. It's da bombz.
@PedroTamaroff DUDE, i knew it. Lol
You use fountain pens too, @PedroTamaroff ?
@eXtremiity Yes.
@AlexanderGruber WHUT
I think I will invest in a fountain pen.
02:10
@PedroTamaroff you had to be a fountain pen guy.
YAS
I wasn't at first. But the trace is as smooth as fuck.
It's great for my hand. =)
@eXtremiity start with a lamy safari fine nib.
I write cursive.
Is that ok?
@eXtremiity that's more than okay. that means you're going to love it, and probably have an easier time with it than most people.
unless you're left handed.
Fantastic. I usually use fine ball-point pens. They're great when new. But the friction increases after a while.
02:12
@PedroTamaroff it's such a varied skill, too. how long ago did you start using them?
And that's annoying. I'll head to my nearest stationary shop soon.
@AlexanderGruber Like a year ago. But I want to learn some calligraphy.
@AlexanderGruber Raises ink-covered hand
@eXtremiity it's a totally different world, man. you're going to hate using ballpoints after this.
I am quite decent at fraktur though. =)
@KarlKronenfeld =D
02:13
:D !!!
@AlexanderGruber Ballpoints feel like writing with glue. UGH.
I'm so excited ^.-
i got addicted to pens in art school, my primary medium was/is pen drawing
i'm still only so-so at calligraphy, though. i want to learn to use a flex nib better.
Calligraphy looks cool. Medieval.
Game of Thrones xD.
if you learn to write with an italic nib you can do fraktur
02:16
Thick.
did you do that?
I don't believe it.
@PedroTamaroff no, i just grabbed it off google images as an example of fraktur
oh
I don't do that kind of fraktur.
But I have a midpoint pen.
And a thin one.
Both give cool outcomes.
@PedroTamaroff absolutely
once you start getting into it, @eXtremiity, there are a lot of subtleties to the type of ink and whatnot you put into it
How often must you replace ink?
02:19
@AlexanderGruber I like black ink since it doesn't leave marked traces of where you started or finished writing.
@eXtremiity i do it about once a day but i write maybe 30 pages of math notes daily
Blue does.
@AlexanderGruber Ditto here. =)
@PedroTamaroff you mean shading?
@AlexanderGruber Guess so.
@eXtremiity it's not hard to reload your ink, though. you just take the converter out of the pen and dip it in the bottle.
02:22
Awesome. Can't wait to try it out
@AlexanderGruber DAYUM.
@PedroTamaroff i like slightly shaded inks when writing, but only slightly. drawing you can get some great stuff.
I want to learn calligraphy. =)
@AlexanderGruber WHOA.
02:26
WHOA
means?
@Sush (it's an expression of awe or amazement)
@anorton, Ok!
@AlexanderGruber, I am inspired by you!
@Sush oh yeah? are you gonna get a fountain pen too?
@AlexanderGruber, no, i mean i am nutcase in math now. But, i hope i will do good if i keep practicing.
You took Calculus in 24.
I still didn't take analysis, i am 21.
@Sush yeah! go for it. you will.
02:30
I was feeling ashamed, but your case of taking calculus @24 is inspiring.
@AlexanderGruber
@Sush there's nothing wrong with starting late. most people don't even run the race.
:)
02:47
@AlexanderGruber I prefer this one
that pen is ridiculous
probably costs an eye and a leg
@PedroTamaroff now that's a flex nib
wait that's not true. it's a dip holder, you can see it on the side.
you can get those for like $15.
@AlexanderGruber I will buy a pen like this
sooner or later
yeahhhh that's what i'm talkin about
02:54
I know a place where they sell them.
The day I dropped by I had already spent all my money on a painting
@Alexander 4/10, should have drawn a smiley face
@PedroTamaroff what's it look like?
what painting?
dunno how to say "grabado" in english, though
"I have know the $H^†_1$"
LOL @Jacobsons
"The going-down theorem."
That's the name of the theorem...
03:03
Well, sounds naughty to me.
that's your own fault.
The "lying-over theorem" sounds lazy.
Also, $H_1$? Are you doing group homology?
@PedroTamaroff oh i LOVE it
who is the artist?
03:05
@AlexanderGruber Local redhead artist
Can not find a single fountain pen at my Uni stores T_T.
@PedroTamaroff very cool
@eXtremiity does amazon work where you're from?
@AlexanderGruber She did some "dissections" of Picasso's Guernica, IIRC.
That was the minotaur/bull part.
And it is drawn in a steel plate, then dipped in ink (different kind of inks give stronger or softer printings) and pressed onto paper
quite quite technique
@eXtremiity buy this and this and this
03:09
What's the convertor for?
@PedroTamaroff printing is so cool. i've never been able to do it.
@AlexanderGruber I know a place where they sell Lami, but I like Parker's steel.
@eXtremiity it's so that you can refill the pen using an inkwell instead of cartridges.
@PedroTamaroff yeah - parkers are the other good option for starting pens
(and advanced pens too of course)
@PedroTamaroff have you tried any of noodler's stuff?
@AlexanderGruber What's that?
@PedroTamaroff it's a brand, they make pens and inks.
03:12
@AlexanderGruber (My Parker fountain happens to come with the "refill" system, but some don't. I should find out if they sell the converter separatly, I need it for my other pen)
@AlexanderGruber Ah. Googles...
what i really want to get is a TWSBI. that will be my reward for passing quals.
So pretty .
my impression is that noodler is an insane person who makes ink that's mediocre at best.
Yes! There's a stationary shop warehouse on the way home from Uni. Definitely making a detour :p.
To eager to wait for Amazon delivery ^_^.
@eXtremiity haha nice. what time is it over there?
03:16
1:15pm.
There?
@eXtremiity 11pm.
Great time to do maths.
03:52
i don't understand this problem:
Suppose $V$ is a real vector space with $d=\dim V$, $\mathcal{B}:V\times V\rightarrow k$ a nondegenerate symmetric bilinear form. Recall that any symmetric bilinear form extends to a symmetric bilinear form on the exterior algebra $\wedge V$ of $V$ by the formula $$\mathcal{B}\left(v_1\wedge \cdots \wedge v_k, w_1\wedge \cdots \wedge w_k\right)=\operatorname{det}\left(\mathcal{B}\left(v_i,w_j\right)\right).$$
Suppose now that $\omega =v_1\wedge \cdots \wedge v_d\in\wedge^d V=\operatorname{det}(V)$. We say that $\omega$ is an orientation of $V$ if $\mathcal{B}\left(\omega, \omega\right)=1$. Show that $V$ has exactly two orientations, of opposite sign.
@AlexanderGruber Show the dimension of $\wedge^d V$ is one.
Check Spivak's Calculus on Manifolds for motivation on orientation, I guess.
That book is very clear.
@PedroTamaroff hmm
@PedroTamaroff okay i can show that. that part's easy.
@AlexanderGruber Right.
so the other orientation is given by any transposition $\sigma\in S_d$ acting on $\omega$ in the obvious way
Now if $\omega \in \bigwedge^d(V)$.
And $w_i=\sum a_{ij}v_j$
$v$ a basis.
Then $\omega(w)=\det(a_{ij})\omega(v)$.
Sorry.
Sorry.
Sorry.
04:08
hahaha
So far, that is correct.
$w$ is one basis right? and $v$ is another?
No, $\omega$ is just some set of vectors.
My point there was $\omega$ is just $\det $ times a constant.
i mean the $w$ in $\omega(w)$
I mean $\omega(w_1,\ldots,w_d)$.
04:10
right... yes! okay yeah
i am seeing that
I think Spivak's definition of orientation is different though.
Can anyone help me how to show $(y\sin(x), z\cos(y), xy)$ is surjective or not
Spivak says the following: having fixed $\omega$, this $\omega$ divides all bases of $V$ into those with $\omega(v)>0$ and $\omega(v)<0$.
Those are the two orientations.
@PedroTamaroff hmm.
@AlexanderGruber That is all for diff. geo.
04:13
@PedroTamaroff i'm taking that next year by the way
@AlexanderGruber Do you mean $\det(\mathcal B(v_i,w_j))$?
@user127001 let's see
@PedroTamaroff oh, yeah.
@user127001 Think about coordinates.
Something like that.
i had my mind on calculating $\mathcal{B}(\omega,\omega)$
@AlexanderGruber I think something of that sort is called the Gram matrix.
04:17
@user127001 try $(2,0,1)$
@Alex I'm trying to learn how to show it algebraically (no counterexamples)
@user127001 That's how you show it algebraically.
@user127001 but you can't show it algebraically if it's not true.
I mean without any specific numbers
The word "counterexample" means "prove something is not true". Kinda...
04:21
@user127001 my inspiration was, the last coordinate is xy, so if you set that equal to $1$ you get that $y=1/x$. so that means the first coordinate is $\sin(x)/x$.
And $\sin(x)/x$ is bounded....
so you could get an answer without specific numbers by figuring out the range of $\sin(x)/x$, then saying that for any $a$ that isn't in that range, $(a,0,1)$ can't be obtained
it's a little overpowered but that might satisfy your desire to do it without a specific example
I don't know how to show that $sin(x)/x$ is bounded
@user127001 $|\sin x|\leqslant 1$.
And $x^{-1}\sin x\to 1$, $x\to 0$.
Ok, if a function is supposed to be surjective, how can I show that?
04:31
@user127001 to show a function is surjective, you have to take an arbitrary element of the codomain and show that it is the image of some element of the domain
i.e. for $f:X\rightarrow Y$, take any $y\in Y$ and show that there exists an $x\in X$ such that $f(x)=y$
@user127001 to show that a function is not surjective, you only need to find one element of the codomain that is not the image of an element of the domain
i.e. show that there exists a $y\in Y$ such that $f(x)\ne y$ for all $x\in X$
04:53
"It is well-known to the sort of people who know these sorts of things that..."
@Mike DAWG.
Suppose $E$ is a ring, $R$ is a subring, and $u,v\in E$ and $M,N$ are finitely generated $R$-modules, and faithful $R[u]$ and $R[v]$-submodules of $E$ respectively. It is clear then $MN=\{mn,m\in M,n\in N\}$ is a finitely generated $R$-module, and a $R[u+v]$ and $R[uv]$-submodule of $E$
I gotta be up in 6 hours
dammit
I am missing the part that it is faithful.
@FernandoMartin Why so early?
04:55
CA brah
@FernandoMartin It's 11 a.m.
I know, I live far, far away
I gotta leave at 9.20
In a strange kingdom.
I don't understand your question @Pedro
@FernandoMartin I want to show that if $M,N$ are finitely generated $R$-modules and faithful $R[u]$,$R[v]$ submodules of $E\supseteq R$ a ring, then $MN$ is a (f.g.) faithful $R[uv]$ and $R[u+v]$ submodule.

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