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7:00 PM
OK, lunchtime. Time for this bonzo to disappear.
 
@TedShifrin yeah, but when doing some substitutions, it is actually easier not to change names. At least, I find it so in substitutions where the limits of integration are being affected
 
what are you having for lunch @Ted
 
@TedShifrin bon appétit
 
@robjohn small question, how do you get to that substitution, what's the rationale? (I mean I get that it works but...)
 
I always miss Ted.
 
7:22 PM
@jcora originally, I did it in a couple of steps (in the comment above), but once I knew where I was going, I knew I wanted to map $-1$ to $a$ and $1$ to $b$. From there it is not too difficult to get $\frac{1-x}2a+\frac{1+x}2b$
It is essentially the Lagrange Polynomial
 
7:58 PM
I don't like how some books will show results and then prove they work without actually telling you how they thought of the particular substitution or Ansatz or whatever
just this past semester a professor taught me a perspective on how to prove things involving inequalities that really helped me
he said if you have a certain inequality, you try to "break it" by making the statement as strong as possible
which might, for example, turn a weak inequality into an equality
I never looked at it that way before
the context was something involving proving something was an inner product, i dont remember what it was exactly
 
@GFauxPas I'm guessing I already know whether you like Rudin or not
 
I just ordered real and complex analysis today actually
by mail
 
"I don't like how some books will show results and then prove they work without actually telling you how they thought of the particular substitution or Ansatz or whatever" All rudin is like this
 
oh :(
unfortunate
 
How come you are ordering that book? Have you read his principles of mathematical analysis?
that's the pre-req
 
8:18 PM
@GFauxPas how is your ordinal studies?
 
@LeakyNun when you prove things do you think in terms of logical symbols?
 
I don't know
 
@TedShifrin I think the answer is yes, everything is linear. The best way to organize this is by fixed point sets. A cheap reduction is to use big technology: (I believe, but need to think about it) Smith theory says that $\text{rk} H^*(M^G) \leq \text{rk} H^*(M)$. Fixed point sets are submanifolds. So your fixed set is either empty, point, or $S^k$. You then organize by normal bundles of the fixed set, which have an action by the group of interest, and see if you can embed these in $S^4$.
 
@LeakyNun I see, where have you learned most of the foundation stuff that you know?
 
in the logic room :P
 
9:26 PM
@Fargle: Did we miss something of consequence? :)
 
lol, not really.
 
So it was merely pro-active?
 
10:14 PM
@LeakyNun almost done with what I decided I wanted to study now
 
what are you going to study?
 
adult Rudin assumes you've read baby Rudin? they're not independent?
measure theory
 
are you familiar with metric spaces and baby rudin stuff?
 
let me check the table of contents
 
at all universities, measure theory has pre-requisite analysis 2 at the level of baby rudin
 
10:18 PM
most of it, i don't know about differential forms
i've taken analysis ii
 
no need for those
that's good
then most likely you can do measure
 
i'm using a book by Folland
for measure theory
adult Rudin I got to study for my written qualifying exams
in January
 
oh wow
qualifying for what
 
well, they're offered 3 times a year, but I'm aiming for the one in January
graduating. but if you get an A, you're eligible to apply to the PhD program, and I hope to do so :)
you can try more than once
 
@GFauxPas: By NO means try to learn multivariable analysis/differential forms from baby Rudin. It's sucky.
 
10:20 PM
what about adult Rudin
 
@TedShifrin hahahah finally someone on my side!
 
differential forms are not on the exam anyway
 
I've said that for 40+ years, @Maximus.
 
A lot of people have this cult following with regards to that book
 
it has three sections: real-valued functions, complex-valued functions, and liner algebra
 
10:21 PM
Of course, I'm now fond of my own text on that material :P
 
Ted has a book on that
 
over 3 days, each section gives iirc 3 hours for 5 questions
yes I bought it :)
 
Adult Rudin is idiosyncratic, @GFauxPas, but there are places where it's natural to have real and complex supporting one another.
 
what is that exam for?
getting into grad school?
 
2 mins ago, by GFauxPas
graduating. but if you get an A, you're eligible to apply to the PhD program, and I hope to do so :)
I'm in grad school
 
10:22 PM
oh wow
 
Thanks, @GFauxPas. Perhaps you'll keep me out of the poor house. (Totally joking.)
 
Ted does your book have anything on Mobius transformations or on projective geometry? I didn't find any but I didn't look very hard
lol
 
No. There's stuff on that in Chapter 8 of my algebra book, however.
 
Max, I wasn't sure if it was bootleg because it wasn't ridiculously expensive. it was around $45
turns out it's legitimate, but it's "only for sale in India" and illegal to sell outside of India, which the vendor website neglected to mention
oops
 
hahaha
yeah they have lots of international editions
 
10:24 PM
"Abstract Algebra: A Geometric Approach"?
 
yes, @GFauxPas.
 
do you need a hard copy? like reading from physical copies?
 
yeah but this isn't just international, it is specifically India, and most books say "only for sale outside of the US" rather than explicitly saying "it is illegal to sell in the US"
 
I prefer real copies
 
10:25 PM
I am trying to simplify the volume difference of the B_n which are n balls
 
partially because I do a lot of my studying on Shabbos, the Jewish Sabbath, and I don't use electronics on Shabbos
 
and I get that long binomial sum and I have no idea how to simplify it further
@GFauxPas ah I see, that's nice I like physical copies as well
 
lol the guy at proofwiki.org has been going through Knuth's exercises on binomial coefficients and putting them all up on the site, maybe you can find it there
just this month
 
Haven't seen your classmates lately, @GFauxPas. I guess Antonios is off to Greece.
 
what's an example of uniform convergence
 
10:27 PM
I've actually been studying together with one of my classmates weekly for the writtens, but I forgot his handle here
 
Oh, um, I know who you mean. The guy who bitched about the horrendous manifolds class I helped with some.
 
that sounds like him. he didn't mention complaining to you, but he complained to me
 
JoeShmo
 
right , yes
 
He complained here all the time.
He liked my lectures :P
So how can I not like him? :D
 
10:29 PM
proofwiki.org/wiki/Category:Binomial_Coefficients Maximus this has dozens of identities, maybe you can find a clever one
he's really amazing, that user. prime.mover
 
@GFauxPas Thank you so much
 
a bit grumpy sometimes (he'll admit that) but very talented
and industrious
and funny :)
 
I get grumpy with you too, sometimes, @GFauxPas :)
 
he gets grumpy with everyone :P
 
Uniform convergence example?
 
10:31 PM
oh I can be a difficult student, but I'm pretty sure my professors prefer an annoying student to a complacent one
that doesn't actually care about the course that much
 
@GFauxPas: I had a particularly annoying autistic student (presumably) in my class that got videoed. He was truly disruptive to the point where I had to yell at him to shut up. He was constantly asking off-topic questions, whether to show off or to pursue his pet topics. So I don't agree with you all the time.
 
all my questions are on topic
well, almost all
 
@geocalc: Any power series on a closed interval inside its interval of convergence.
 
sometimes I try to get my professors to talk about their professors
I'm good at it
 
Outside of class that's fine.
 
10:34 PM
but usually my questions are about the material
 
An occasional personal anecdote in class can be motivating.
 
i'm pretty sure my classmates enjoy it too
I don't mean all the time
I think about the question I'm about to ask and consider whether or not other people might have the same question
 
I have a pet topic
 
or whether the answer will elucidate other concepts that I don't think everyone in the class is clear on
 
@GFauxPas you were Ted's student?
 
10:36 PM
alas, no
except in the sense that I frequent the mathematics chat room at stack exchange
but not in his university
like asking the professor how he thought of a step in a proof if it's not immediately obvious
"how did you know to do that?"
or "how would we know to do something like that on an exam?"
 
hahahah yeah that's the best question
 
or one of my favorite questions
"why is that obvious?"
 
I have a good question
 
"this obviously converges"
"obviously we can assume the region is compact"
etc
what is your question geocalc
 
at least you have good culture, at my uni some profs pretend you just have to know stuff without studying it
 
10:39 PM
Hi everyone
 
Those can be good questions. On the other hand, often the answer is to pay attention to how proofs go and model from experience.
heya @Alessandro. NOW finally done? :D
 
Wow, now I have to call you Mr. Alessandro. Congrats!
 
I only need to finish writing my thesis, but that's also almost done
 
You've learned a ton of stuff, @Alessandro. I remember where you were when we started. Congratulations.
 
10:41 PM
or another question I like
I ask for an example
 
Officially I'll finish in mid July with a short presentation on my thesis, but I'm now done with exams
 
sometimes they're not ready for that question
 
Professors often don't give enough examples ... or enough concrete homework questions.
 
textbooks too
 
10:42 PM
^ true that
 
have that problem
 
My question is such: can you take a function and exchange it's variable for a paremeter???????
 
But students really need to work out examples themselves. Too much time meant memorizing proofs and not wrestling with concrete examples/counterexamples.
@geocalc33: Your question makes no sense. Uniform convergence is about a sequence or series of functions.
And I have no idea what it means to exchange.
 
Like for example f(x)=x²
 
what do you want to replace with what?
 
10:45 PM
R=x
 
the name of the variable doesn't change anything
 
Where R is a parameter
 
$x \mapsto x^2$ and $R \mapsto R^2$ mean the same thing
maybe you mean something like
parameterization of a contour
?
 
A parameter just means another variable. You are talking about a two-variable function.
 
do you mean like the kind of substitution done in integration by substitution?
 
10:52 PM
No. He's thinking of a function build out of the Riemann zeta function $\zeta(s) = \sum n^{-s}$ ($s\in\Bbb C$, well, really, an open subset thereof), so it becomes $f(x,s)$. It simply is a two-variable function.
 
S can't just be a parameter and not a variable?
It must be a two variable?
 
what's the $x$ mean there?
 
Yes, it must be two-variable. A parameter is always another variable.
 
oh I think I see what he's asking
 
Suppose you did something like $f(x,s) = x^2\zeta(s)$ or $f(x,s)=\zeta(s)^x$ (which isn't really well-defined ... but ...)
 
10:55 PM
Then why is it called a parameter if it's just another variable
 
A parameter is a "letter" which is free to be set equal to various values. You know about parametric equations for curves or surfaces? Parameters are just variables.
 
Ok
I'm going to write my thesis on parameters
 
What kind of thesis?
 
Phd
 
Um, no, you're not.
 
11:03 PM
Why not
 
That's like saying you're going to write a thesis on the quadratic formula.
I thought you were still in high school?
 
No I graduated college last yr
 
Wow.
 
Wow what :)
 
werent you just studying for some high school standardized test?
 
11:05 PM
I can't say this nicely, but I would expect you would have learned more as a college math major.
 
No lol
I was a statistics major
 
Ah.
 
And I've never been that great at math
It's always been difficult for me
 
So you're talking about a Ph.D. in stat?
 
No probably math I didn't like statistics
And first I'll try a master's
 
11:09 PM
How many upper-division maths did you take?
 
diff EQ, calc 1-3, linear alg.
 
So none of that is upper-division. You most likely can't get into a masters program without two years of upper-division math first.
 
Oh no
Does upper division usually start at real analysis
 
Real analysis is often the hardest course a math major takes.
Abstract algebra, some applied stuff, complex analysis, real analysis.
 
So what should I do?
 
11:15 PM
You need to take a few courses like Intro to Higher Math, which begins to teach you to write proofs, and beginning abstract algebra. If you can't get solid A's in those, graduate school in math is not appropriate.
 
Sounds good
 
how important is knowing abstract algebra? I mean, i took it, and got an A, so I can't know for sure what I would be missing if I didn't.
 
Hi, @TedShifrin I haven't checked in here for quite a bit. How's it going?
 
hi @amWhy. I'm just dispensing gloomy advice, as usual.
@GFauxPas: I generally advised most of my students to take algebra before analysis, because the proofs in algebra — for the most part — are not as laden with quantifiers and are therefore a little more straightforward.
 
@TedShifrin Sometimes gloomy advice is honest advise, and the most important advise.
 
11:25 PM
done
 
I see
 
@GFauxPas depends on what you want to do. I'd say it's vitally important, but that's just me
 
@geocalc33: In a few words, I don't in this day and age cavalierly encourage people to go to grad school in math unless they have a real talent and passion. Perhaps a masters in applied math might be a reasonable choice. Regardless, your stat background and solid experience with programming would probably get you better — or comparable — jobs in the real world.
2
 
Who started that
*starred
 
pffft "real world"
 
11:34 PM
Actually, of all the things I've said in this chatroom, that might be the most important.
 
@geocalc33 Is starring off-limits in this chat? I just ask because in many, many chat rooms on MSE, starring or "pinning" a message is very common.
 
There's plenty of starring in here. Sometimes of inanities, sometimes of bad puns, and very occasionally of mathematics :P
7
 
@TedShifrin Just like most chat-rooms :P
 
@GFauxPas: You can pffft all you want. Prospects for a career in academia grow dimmer by the year. More and more colleges and universities are hiring adjuncts at crap salaries rather than pay a somewhat reasonable salary to tenure-track faculty.
 
no I meant
 
11:38 PM
Now I'm sounding downright grumpy, but American Ph.D. students have been depressed about the situation for a while now.
 
well, it was more of a joke
 
I need to shut up. I'm becoming the starboard.
3
 
should I star that comment
 
I knew someone would say that.
 
I was told that many mathematicians become applied mathematicians to make money and then go into academia when they can afford it. if its possible
 
11:41 PM
@TedShifrin I'm responsible for only the first star (one star). Seems your comments are appreciated.
 
but the low salary for professors in America is a problem
 
It's very hard to go into academia from industry (in mathematics). Unless one has a stellar publication record. Being removed from publications and teaching experience and the ridiculously competitive job market makes it very difficult. Far easier to try academia and leave in a huff for industry.
 
Hmmmm
 
the problem with academia imo is that there's way too many phds vs. positions
 
See my comments above re adjuncts.
 
11:43 PM
hence why i'm not interested in going down the postdoc route
 
Good points being made all over the place
 
(well, that's one reason. there are others as well)
 
Physics is worse in that regard than math, Semiclassic. Math has so much service teaching to do. Everyone has to take some math. Physics, not so much. It's the premeds that keep you guys busy in the service arena.
 
Yeah.
Not that I'm doing a great job yet figuring out "what's next"
 
And engineers have to take physics (along with math). But that's still not a huge fraction of the population, across universities.
 
11:44 PM
here, SAP hires people with a pure math academic background, I've seen it happen to some people who had postdoc positions here
 
I need to make my CV not look like s***
 
LOL, @Semiclassic.
 
I think I'm going to take a long break from math
 
I apologize if I said anything rude along the way, @geocalc.
 
oh, now I realized you said into academia from industry @Ted
 
11:46 PM
I meant to, anyhow, @Mathein.
 
academia -> industry is a better pipeline afaik
though the culture shock is real
 
that's true of course and probably everywhere, not just US
 
Those of us who live and die to be dedicated teachers are in a different category, of course.
There are still small and liberal arts colleges that want dedicated teachers, but the research requirements have ramped up a bit there since my day because there's such huge supply ...
 
yeah. that's at least one route I should keep in mind
I feel like I'm a little better situated that some physics grads, since my research was stuff that involved paper/pencil/mathematica rather than some dedicated experimental lab or a huge colloboration
so a bit easier to sell that as being accessible to undergraduates. but there's a lot of speculation in there
 
@TedShifrin Absolutely, this is true. But research requirements allow for research in the teaching of mathematics, and/or mathematics education for undergrads.
 
11:50 PM
@TedShifrin about teaching, one of my students who is aiming for a high school teaching degree (don't know how to say that in English), offered to give me some feedback, since she learns a lot about didactics of course in the specialized courses they take besides some bachelor classes. It was very helpful and encouraging
 
At smaller colleges, you mean, @amWhy? True.
 
@MatheinBoulomenos I firmly believe that no one truly understands the math they've learned unless they are able to teach it well.
@TedShifrin Yes, indeed.
 
That's great, @Mathein. I've tried to give you some comments occasionally, too, but as you know I think you've improved and you definitely care about communicating and not being incomprehensible. :)
 
Hi TEd
 
Wow ... hey there @quallenjäger
 
11:52 PM
Some intense conversation going on in here.... hi all
 
@Ted the only negative point she had was my messy work on the blackboard, but I've already improved on that
I'm going to buy some colored chalk and try to work with that
Hi @ÍgjøgnumMeg
 
hello @Mathein :)
 
I am a big advocate of clever use of colored chalk. That and neat organization are both very helpful. (I got sneered at by a colleague when I spoke about this shortly after coming to UGA. Of course, he was about the worst mathematician and worst teacher on the faculty.)
 
my professor of topology told me about a professor he had that used to be a chemist but lost his hands in a lab accident, so he went into mathematics instead, after he learned to write on a chalkboard with artificial hands
 
@Mathein: At the beginning of algebra, I like to use colors to code cosets.
 
11:55 PM
I brought multiple colored pens with me to my Calc II exams that had iterated integrals
or was it Calc III idr
Fubini's stuff
 
@TedShifrin I that, too. When I write proofs, I tend to intersperse some commentary/justification for an equality/analogy/connection to other exercises etc. I'll try to use colored chalk to separate that stuff from the main proof more clearly
 
when my number theory professor thought a theorem was particularly important, he would say things like "this calls for colored chalk" and write the theorem in a color
 
So my problem with colored chalk at the moment is that it's kinda scratchy and is a pain to erase. Legend has it that Hagoromo colored chalk is better but I've never used it and also money
 
What is an algebra of real functions?
 
Hi @Daminark
 
11:58 PM
coughs Dry wipe white board pens coughs
 
That's crappy Crayola chalk, Demonark, not good stuff.
 
Might not be a bad idea to do those sorts of drawings that require it on the back board so that there's less of an eraser problem
 
@quallenjäger a space of functions you can add, multiply and multiply by constants, I'd say. (Though you could have e.g. convolution instead of pointwise multiplication)
 
@ÍgjøgnumMeg yo
 
@Daminark hey man
 
11:59 PM
That's just outta line
 
Someone call mods
 
quallen, it's going to sound like a non-answer but the answer is , a space of real functions endowed with an algebra
 
That's my question, is the multiplication defined pointwise?
 

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