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9:00 PM
and not much exciting on the physics side this week either. hrmph
 
I will be going to see the doc for meds in a few hours time.
I went off meds for a few months.
 
Maybe this time I will just take them till I am completely well, even if I am not sure whether they work.
 
did you taper off?
with one I'm on, I'll pretty much have to taper if I'm to function while getting off of it. (if I miss a dose in the morning I notice it by the afternoon, and I'll sleep awful in the evening)
 
Well, I think I just stopped taking them one day, because I got fed up.
 
9:02 PM
ah.
 
@SteamyRoot I see things went well ;)
 
Yup ^^
 
Anyway, I am going to give myself one last shot at trying to be well.
Because I really want to get well so that I can do mathematics again.
 
for me, my goal is basically to get a stable enough sleep schedule that I can have energy during the day
when I muck that up the rest is hard to keep together
 
@Semiclassical How often do you attend seminars?
 
9:05 PM
For me, it's more of dealing with disturbing thoughts of anxiety nature.
 
not often this semester so far
 
In general better sleep = better you methinks
 
for me, it's the fact that my writing anxiety is bad enough when I'm rested
when i'm not, it's even worse
 
I am now at my lowest point again, but I hope things will go uphill from now.
 
plus when i'm tired I usually find an excuse to go take a nap somewhere, and when I wake up I usually find myself feeling really jittery
so it's not a good/healthy cycle
 
9:07 PM
The thing is sometimes you feel so tired all of a sudden you have no choice but to sleep.
 
ugh, yeah
 
And sometimes you want to sleep but you just cannot.
 
which is bad when you're in transit
and you have to walk just far enough to get to a place you can lie down
What I find the strangest about anxiety, though, is how physical the experience is
one talks about it in mental health terms, but
 
Right now, I need to let go of the past and start afresh.
It's painful when I think of all the time, money etc I have lost.
 
ugh, i'll drink (my coffee) to that
 
9:10 PM
I do hope this is the final lap of my struggle. I have said that many times, but I will say it again!
Oh I am still waiting for the publication of the fourth edition of Merriam-Webster's Unabridged Dictionary.
The third edition was published in 1961, lol.
 
Hey @Perturbative!
 
@Daminark Nifty, lol.
Hello Ted and Mike, lol.
 
Hi Jasper, Demonark, et al.
 
9:26 PM
There was Hurricane Harvey and then Irma, now there is Maria.
 
José was in between
 
Jose Carreras is one of my favourite tenors, but I never liked Maria Callas.
 
G'night, Mike.
 
I listened to The Three Tenors 2002 Yokohama, and it seems all three were sick that night, because their voices were not great.
 
9:31 PM
Heya! @TedShifrin, @Daminark
 
hi Pert
 
@SteamyRoot Mourinho?
 
0
A: Natural Deduction Problem: Predicate Logic with Identity in a Gentzen-style system

Kenny Lau01. ∀x[Qx↔[∃y[[Rxy]∧¬[x=y]]]] premise 02. ∀xQx premise 03. ∃x∃y∀z[[z=x]∨[z=y]] premise 04. ∃y∀z[[z=a]∨[z=y]] assumption 05. ∀z[[z=a]∨[z=b]] assumption 06. Rcd assumption 07. ¬[c=d] assumption...

72 lines
it was a hell of a journey
 
@LeakyNun Did you use the same program again?
 
@Jasper no, I wrote it myself
 
9:39 PM
@LeakyNun Then that's amazing!
@LeakyNun You are going to fly off very soon, right?
 
@Jasper 9 days later
it was like 100 lines on my first attempt and i optimized some lines
 
LOL
Maybe you will solve P vs NP one day.
 
The broken sleep cycles are becoming an epidemic in this room.
 
it definitely helped me train natural deduction @Jasper
 
We need Ted to tell them when to go to bed.
 
9:42 PM
It's hopeless, Jasper.
 
I just learnt those rules today lol
It's 5:42 AM now
 
It's 11:43PM now here
 
@LeakyNun Yeah, I see you behind that iceberg.
 
@Jasper lol
 
@Perturbative Do you also sleep after midnight?
 
9:44 PM
@Jasper Only during holiday periods
 
On many days some time ago, I went drinking at pubs with a friend after midnight.
 
During normal weeks I try to get to bed by 9:30
Emphasis on the try ^
 
9.30 is a little too early, lol.
Maybe 10 is still OK, lol.
 
@Jasper I gotta be up by 5:30 in the morning though
 
@Perturbative Oh why so early?
I guess you need to travel to school.
 
9:47 PM
I've gotta be at uni by around 6:50, (because my parents have to drop me off at campus and get to work), then lectures start at 7:45
 
Wow, strange timing you have there.
 
@Jasper I feel like I can prove anything now :P
 
@Daminark If you had a 7:45 lecture, would you go to it? :p
 
@KasmirKhaan This is what justifying every step looks like /s
 
I think that lectures should not start before 9, lol.
 
9:48 PM
Demonark won't even go to a 10:45 lecture.
 
lmao
 
I had a student/advisee many years ago who refused to take any of my classes before 11 AM.
 
I go to lectures only if the teaching is of a high enough standard, lol.
 
I guess I'd be spared your attendance at my lectures, Jasper :)
 
What do you think of eating raw eggs @ted?
 
9:50 PM
@Jasper Like that scene in Rocky?
 
I have them now and then, but some people tell me I shouldn't do that.
 
I guess the only time I do that is if I make homemade mayonnaise.
 
@Perturbative Can't remember which scene, lol.
 
It is somewhat of a health hazard.
 
It becomes more of a hazard if you eat them with the egg shells
 
9:53 PM
Sigh.
 
Hi @Dodsy lol.
 
Hello.
The drama is real here, Jasper.
 
Hi Nate.
 
Hey Ted.
 
NOOOO drama.
 
9:54 PM
Howdy yall.
 
heya @PVAL
 
What happened that day? Who flagged?
 
I agree @TedShifrin
 
NOOOO drama.
 
So I found out today that my linear alg class is 100% tests.
 
9:55 PM
No drama, just some normal talk now, lol.
 
not a single assignment.
 
I personally think that is crap, Nate.
 
Me as well.
 
I actually like it if there is a single final exam at the end of the course.
 
You said this is a newbie instructor?
 
9:56 PM
@Dodsy I feel ya, every math course I've taken has been 100% tests (along with an exam)
 
But I understand the idea behind a more continuous assessment.
 
I believe in weekly homeworks, evaluated however, so that students get feedback and learn to write a bit. Two or three exams and a final.
 
Oh of course the homework should be marked, yeah.
 
He's a postdoc who is piggybacking off some other instructor who also does not know what he is doing. I felt bad for him today though. He was explaining mod arithmetic and somebody critisized how he taught it, and laughed at him..
 
These days in low level classes, most homeworks are on computer and one gets instantaneous feedback. Great for computation. Bad for writing mathematics.
 
9:57 PM
@TedShifrin What's your opinion on take-home final exams?
 
UGH. We have to use mapleTA to do quizzes for lin alg.
 
Are you using the James Stewart text @Dodsy?
 
@Jasper Yes, quite.
 
Nate: Maybe you could get together with other students and politely request a different policy. Ask the undergraduate coordinator/undergraduate department head, if necessary.
 
Pls pls no more Stewart
 
9:58 PM
@Perturbative: In an advanced course that's small and where I trust people, maybe. But in this day and age, it's too tempting to cheat (witness MSE).
 
@Dodsy He died a few years ago. He lived in an expensive house made from his money made from that textbook.
 
@TedShifrin I'm unfortunately not prepared to lead a spearhead towards education reform in the mathematical sciences. :(
@Jasper that canadian bastard.
 
I'm not suggested mass reform.
Postdocs vary rarely get adequate teaching mentoring.
 
I haven't told you guys my favourite calculus text yet, lol.
 
Yet another thing we took seriously at UGA.
It had better be mine, Jasper.
 
9:59 PM
no of course not, I was over-embellishing your point. :)
 
I like Wilfred Kaplan and Donald Lewis's Calculus and Linear Algebra I and II.
But this book is almost unheard of.
 
Almost?
 
It's freely downloadable from the Michigan University archives, and is a very affordable paperback.
 
@TedShifrin That's fair, I remember seeing the course outline or one of the Harvard math courses that had a take-home final which made me think if it was done regularly
 
Yeah I feel bad for the postdoc. I think he knows a lot of mathematics and probably would be considered like many of you here who has a real love for math. But he has to do things based on what the other instructor is doing and seems to be trying his best. And that's really all that matters.
 
10:01 PM
Kaplan wrote an advanced calculus book a half century ago or something.
 
Yeah, I don't like that one.
 
Nate: Is the linear algebra all computation or are there some proofs?
 
What makes you like/not like a calc text?
 
Jasper has arcane tastes.
 
@TedShifrin computation :(
 
10:02 PM
And, unlike me, he totally disregards examples and exercises.
 
What makes me like or not like a math book is whether it contains things I like or not, lol.
 
I'm pretty sure the main difference between the 8th and 7th edition of Stewarts text is that the colors are different and the exercises have been rearranged (but not changed)
 
Officially, one is supposed to change 20% of the text upon revision.
 
I completely disregard James Stewarts examples and exercises, to be honest.
 
Poll: classical logic or intuitionist logic?
 
10:02 PM
@LeakyNun I'll vote what you vote.
 
lol
 
Nate: There are interesting computations in linear algebra, to be honest, as long as one has some idea of why one is doing them.
I recommend my lectures :P
 
Hey @AlessandroCodenotti
 
@Dodsy What text are you using for linear algebra?
 
@Perturbative I received the 7th edition for free! I got all of my books free and saved 500 dollars.
@jasper david poole.
 
10:03 PM
@Dodsy That's great!
 
Never heard of him.
 
but the recommended edition was the 8th.
And I asked the prof who said that the only difference is that 1.4 and 1.5 turns into 1.5 and 1.6.
I haven't felt behind yet.
 
Also check your uni's library, if you ever need any other books, without a doubt they should have almost any book you need
 
@Dodsy LOL
There are also many books on Russian servers...
 
Yes, for sure. But it seems that mathematics teachers here really want to save students money, my next semester math teacher (tyana something..) assigned readings from a textbook freely available online from the UWO library!.
@Jasper :O heathen.
 
10:05 PM
well, Nate, I'm willing to explain linear algebra concepts to you if you get curious.
 
@TedShifrin his textbook is terrible.
That'd be great! I'd appreciate that Ted.
 
It is very strange that first year math and science textbooks in American universities are mostly very expensive...
 
And, seriously, you might enjoy my lectures (most of the linear algebra is separate from the multivariable calc).
 
@Jasper They're expensive everywhere
 
Okay, that'd be great.
I'll take a look on your youtube.
@Jasper Yes, for James Stewart 8th, David Poole and University Physics with Modern Phsyics, the bill was 540 dollars.
And as much as I love physical textbooks, I needed to be practical.
 
10:08 PM
@Dodsy You can read the Feynman Lectures at feynmanlectures.info
 
I know I sound like an author when I say this, but in truth book prices are ridiculous, but for the most part they've inflated like everything else (college tuition, automobiles, housing, etc.) ... at least in the US.
 
My calc teacher said something very feynmenesque today.
 
Feynman is NOT a good place for a first-year physics student to learn physics.
 
@TedShifrin oh yes, for sure.
 
University Physics with Modern Physics is to physics students what James Stewart's Calculus text is for math students
 
10:10 PM
He was talking about how $f(xy)=f(x)+f(y)$ (or something similar, suspend your disbelief) and someone argued that the equation was pointless and my teacher said that he thought the equation was nice and had to add it to his box of tools.
 
Huh?
 
You can watch Ramamurti Shankar's Fundamentals of Physics I and II lectures on youtube @Dodsy
 
It's actually a fundamental functional equation ... LOG.
 
Yes. For sure.
I forget the exact thing that the student had a problem with.
I just heard my teacher saying he thought the equation was really beautiful.
 
In fact, in the Calc Theory course I started with that to get to the integral definition of log.
 
10:11 PM
And mentioned having a box of tools.
 
It's an example of a group homomorphism, Nate.
 
I like that idea.
Oh I see.
 
Yes, and make sure you have a sandbox to play in, too.
 
haha :)
you bring the trucks, I'll bring the gi-joes, Ted.
 
it's important to play in a mathematical sandbox and fiddle with examples.
 
10:13 PM
Oh, yes.
It's fun to play with numbers.
I'm going to do some linear algebra tonight :)
 
@Dodsy I will bring the food, lol.
 
Thanks Jasps.
@TedShifrin my physics tutorial was a joke today.
 
look for good things and concentrate on learning/understanding.
 
That's a good plan.
 
it's too easy just to criticize everyone.
 
10:24 PM
Yeah maybe I'm being overly negative.
 
In this $\phi$ has to be the canonical map $\phi(x, \alpha) = \phi_{\alpha}(x)$ correct?
 
Sure.
I don't know what $\phi(x,\alpha)$ means.
They said it explicitly. $\phi\big|_{\partial D_\alpha} = \phi_\alpha$.
 
@TedShifrin $\phi$ is a mapping from the disjoint union of the boundaries of the closed $n$-cells
 
I know what it is.
How are you writing it as a function of two variables?
 
That's how the disjoint union was defined in my text
I'll explain now
 
10:33 PM
Oh, they put the $\alpha$th set at coordinate $\alpha$ in a product space?
For doing topology that's overly pedantic. Just think disjoint union.
 
No no, it's defined slightly differently, it doesn't have the product topology on it (well not explicitly)
$\bigsqcup_{\alpha \in A} X_{\alpha} = \{(x, \alpha) | a \in A \ \text{and} \ x \in X_{\alpha}\}$
 
Bah. Restriction to an element of the disjoint union should be clear enough.
Yes, that's precisely what I wrote in words.
If you understand what you're doing, yes to what you said, but you should think of it more concretely.
It makes sense to identify $X_\alpha$ with the stuff in the $\alpha$th slot and just write restriction.
 
Ahh okay
 
10:54 PM
@TedShifrin I've finally accepted that there's no hope of an exact solution to the integral curve problem in the general case. I've tried way too many methods of playing with the equation, but it always comes down to an unsimplifiable diff eq. Can you think of which numeric approximation methods would be best for approximating $\frac{dp}{dt} = F(p(t))$?
 
Any numerical scheme should be reasonable. Just usual Euler should do something for you.
Mathematica can do it easily and draw a picture if you're in 2D or 3D.
 
I feel like I'm doing things backwards, though. Originally, I wanted an exact form of $p(t)$ so that I could perform optimization on it. Now, I'm numerically approximating it, so that I can optimize on the approximate, and then hope that the optimum I find is approximate of the true optimum.
 
Well, I'm lost in the original mission.
 
I wanted to convert a standard gradient descent problem into a single-parameter gradient descent problem.
And then solve it using Newton's Method
 
I have a feeling a good numerical analyst would know what to tell you immediately.
 
11:04 PM
Probably tell me to use the KISS method
Keep it simple, simpleton.
 
I am a total ignoramus.
Well, I was telling people earlier that they were making everything too hard.
Yeah, yeah, I got it.
 
I wish I could spend more time on this project. They've got me teaching this semester and I'm not willing to half-ass it.
My adviser says it's cool to pursue this in my spare time, though, so it's what's getting the least attention
 
I'm sure it's just a matter of finding the right person to ask for 15 minutes.
 
Usually, yeah.
"Oh, yeah. This paper solved exactly what you're trying to do. It's called ...."
"This was proven infeasible by a French mathematician from Spain."
Something along those lines saves a lot of time.
 
If you want to take a few minutes to TeX up a cogent statement, I'll happily send it to one of my smart ex-students who's writing his Ph.D. on numerical PDE.
 
11:18 PM
I'll see if I can write something up. The benefit of having a one-parameter closed form is that it's efficient to calculate, which makes solving minimization problems computationally easy. Without that, any additional overhead we incur trying to approximate the one-parameter closed form must remain less computationally expensive than gradient descent OR it must be more precise/accurate given the same amount of computation spent (if we ran gradient descent for as long, which is better?).
@TedShifrin This will take me some time to formalize, but that's the gist of the problem.
 
I'd do better with a concrete, concise question. And I can pass it along.
 
That'll take me some time. Tomorrow, I'll see if I can have a write up; it's my day off.
 
Don't hurry on my part. I'm just volunteering to try to pass it to someone who might know.
 
Hullo
 
Hallo
 
11:24 PM
I do appreciate it either way. Thanks for humoring me, at the very least, :P
 
So I thought I know how disjoint union spaces work, but I guess I don't
In the image above, the author says that we usually identify $X$ with its image $X^*$
 
This is saying exactly what we said.
 
Okay wait but hear me out
 
Maybe I should wait until I get my martini :P
 
Lol :p
 
11:30 PM
I wonder if that'll get flagged. Oh, I didn't say that.
 
$U \subseteq \sqcup_{\alpha \in A} X_{\alpha}$ is open iff $U \cap X_{\alpha}$ is open in $X_{\alpha}$ for all $\alpha \in A$
 
A good example to think about is the hawaiian earring and it's non-$\Bbb R^2$ realization.
Do you know what I'm talking about?
 
(x^2-3x+6)/(x^3+8x)
 
But if we identify $X_{\alpha} = X^*$ as the author says, then the definition is circular since $X^*$ would have to inherit the subspace topology from the disjoint union
And if we don't, then $U \cap X_{\alpha}$ is always disjoint
So every subset of the disjoint union would be open in that case
 
Huh?
 
11:34 PM
I hope I'm making some sense
 
So let's talk about my suggested example.
 
I'm trying to integrate (x^2-3x+6)/(x^3+8x) via partial fraction decompositualization, But, I end up with A(x^2+8)+Bx^2+Cx = (x^2-3x+6)/(x^3+8x) and I'm not sure its possible to solve...
 
Okay I know the hawaiian earring, not sure about its non-$\mathbb{R}^2$ realization
 
So remove the common point from the Hawaiian earring.
Now take $X_n = \{(x-1/n)^2+y^2=1/n^2\} - \{(0,0)\}$. Take the disjoint union.
How do the topologies compare?
 
I factored the denominator from (x^3+8x) to x(x^2+8)
 
11:37 PM
I.e., disjoint union space versus subspace topology.
@10Replies: What are you trying to do?
 
Okay just give me a few mins to work it out
 
@TedShifrin Trying to do partial fraction decomposition to integrate (x^2-3x+6)/(x^3+8x)
 
Oh. OK. So you factored correctly. Now just crank the algorithm.
No, you're not doing the algorithm correctly.
 
that gives me A/x +(Bx+C)/(x^2+8)
 
$\dfrac A{x} + \dfrac{Bx+C}{x^2+8} = \dfrac{x^2-3x+6}{x(x^2+8)}$
Now what?
 
11:41 PM
Thats where I'm stuck... Normally I would multiply both sides by x(x^3+8)
 
Yes. And what will the RHS become?
 
Oh... I forgot the x^3
 
No, you left the denominator!
 
which means I can actually make it zero
and then solve
 
What $x^3$?
 
11:42 PM
I had x^2-3x+6 = a(x^2+8)......
instead of x^3
 
You should get $A(x^2+8) + x(Bx+C) = x^2-3x+6$. Quadratic = quadratic.
 
Now I can actually plug in an X to make half o f it zero
 
There is no $x^3$.
 
ohn
How do I solve it then?
 
So what do you get when you compare like terms?
 
11:43 PM
@TedShifrin $X_n$ describes one circle in the hawaiin earring, am I taking the disjoint union of all those $n \in \mathbb{N}$?
 
Combine?
 
No. @Perturbative
 
@Perturbative: I took the origin out of all the circles so we'd have disjoint.
Oh good, Balarka is here to take over for me. :)
 
Oh I didn't realize you were helping Perturbative.
Carry on/
I slept for too damn long
 
@10Replies: So do you get $A+B=1$, $C = -3$, and $8A = 6$?
I gave him a concrete question, Balarka.
We're comparing subspace topology and disjoint union topology.
 
11:45 PM
Aha, OK
 
I don't usually think about this stuff.
 
I remember having a nice time figuring out why the Hawaiian earring philosophically and mathematically should not be the wedge of countable many circles.
 
I removed the origin so we could do disjoint union, but otherwise the same thing.
(I think)
 
I remember Balarka wanted to get himself a Hawaiian earring as a present.
 
I don't remember that.
 
11:53 PM
I don't like earrings, so I will settle for a Hawaiian pizza instead.
 
I cannot stand pizza with pineapple on it.
 
I can't stand pizza with earrings on it.
 
I see the room is degenerating again.
 
The worst is earrings with pineapple on it.
 
@TedShifrin If you remove the origin you don't get the disjoint union topology on countable many intervals though.
 
11:54 PM
Too heavy. Ear injury is inevitable.
3
 
I'm confused, Balarka.
 
Yo @Balarka
 
Oh, I see. I should be taking disjoint union of circles of radius $1/n$ with the origins all identified? Versus the subspace topology?
 
Yeah pizza with pineapples are the Antichrist as far as I'm concerned
 
Finally, Demonark and I agree on something.
Except for his horrid syntax.
 
11:57 PM
@TedShifrin Disjoint union of circles with the origins identified is exactly the same as the countable wedge of circles, isn't it?
The reason if you remove the origin from earring you don't get the disjoint union of intervals is because the Hawaiian earring is the one-point compactification of the topologists' comb.
 
Yeah, @Balarka. I was trying to keep out the quotient space stuff.
 
Ah, ok, then we're on agreement.
 
If you guys hate pizza with pineapples on it, just stop calling it pizza. Maybe you'll be able to taste how awesome it truly is.
 
I wanted Perturbative to see that the usual subspace topology on the earring (minus the point) didn't give the disjoint union topology.
 
Got it!
 
11:58 PM
I'm right, right, right?
 
Absolutely.
 
Also @Perturbative I'd never sign up for 7:45 classes without good reason. We don't even have them here
 
Whew. :P
 
Oy @Daminark
 
I once taught a winter quarter precalc class at UGA that started at 7:50.
 
11:59 PM
What time does elementary school class start in America?
 
The guy who was supposed to teach it got fired for giving away the uniform final exam to his students the previous quarter.
 
I think our classes start at 8:30, and even classes at 9 and 9:30 have messed me up. I'm trying this year to keep it post 10:30
 
Depends on the school, I think, Jasper.
 

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