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20:00
true scotchman :)
hmm im not a topologist or set theorists. I do consider myself an algebraist actually
@SineoftheTime calculus - 2 < algebra
dont cry baby kisses
;)
can I flag you for moderation attention because you're an algebraist?
20:04
i challange you to find a set that is not a box without repetition :)
@SineoftheTime before you start a battle , look at my pic
@mick the role of steorids when using a keyboard is less than epsilon
ah yes , but what is epsilon
for all epsilon > 0 ?
+
see im an algebraist now
i switched from calculus to algebra
@mick I feel sorry for you :(
20:08
lol why
beacause you're an algebraist
im also into calculus baby ;)
@mick there we go
@Koro who is the teacher ? Do i know him or her ?
@Koro interesting set of topics. this could be a very computational class. i would try to find out if there is a requirement to do work in any particular programming language, and maybe opt out if it's not one you know already.
20:18
What is the dual of $L^2(0,T;H_0^1(U))$?
@SineoftheTime https://math.stackexchange.com/questions/4568778/how-to-evaluate-the-integral-int-01-frac-ln-left-fracx12x2-rig

my gift for you

notice no empty set used :)
Is it $L^2(0,T;H^{-1}(U))$?
Hades's father, Chronos. Primordial God of Time
if I am infinitely old , can i have a father ?
This integral reminds me of a girl who just posts the end result and no works.
20:21
i have $q\in L^{\infty}(\Omega)$ $q\geq 0 a.e x\in \Omega$, how to prove that $||u||_{H^1_0(\Omega)}$ is equivalent to $\int_{\Omega} |\nabla u(x)|^2 dx+\int_{\Omega} q(x) |u(x)|^2 dx$
@Vrouvrou it's easy. no?
the inequality $\int q(x) (u(x))^2 dx\leq c \int_{\Omega} (u(x))^2 dx$ is very easy
but the other side i have no idea
It's certainly false as stated. What if $q=0$ everywhere?
@TedShifrin Poincare inequality says that $||u||_{H_0^1}$ is equivalent to $$||\nabla u||_{L^2}$$. No?
$q(x)\geq 0 a.e $
yes PNDas
oh
then it is very easy
20:27
Don't you need some hypotheses on $\Omega$ for that to be true?
bounded
@TedShifrin Hmm bounded open
And we were not told such hypotheses.
theorems have hypotheses now?
Well, perhaps I'm old-fashioned.
20:29
At least I found another person who is doing Sobolev spaces.
I knew all that stuff in grad school, but that was a long time ago.
And a PDE person in the chatroom.
@TedShifrin in functional analysis course?
@leslie Went on a walk with MIT alumni yesterday and on the walk was a mathematician whom I'd met back in the 70s who is now retired from UCSD. Several complex variables person.
@PNDas I'm guilty of this myself
No, I never took a course, but we were doing geometric analysis and unbounded operators in several seminars.
20:32
I often leave things out since they seem "obvious" but clearly it's not a good idea
Hades, speaking of leaving things out (like justifications for a "trivial proof") ... can you do that trapezoid problem yet?
@冥王Hades But that girl posts only the end result.
@TedShifrin Yeah, I found a proof, it relies on taking an arbitrary point inside the square, that is not P, and proving that the property of 3 equal areas can ONLY be true if and only if the fourth area is equal to the rest as well
Its pretty ugly though. I'm trying to simplify it
That's sorta the gist of the proof that the guy who corrected me posted.
But you were making cyclic quadrilateral claims. I don't see how cyclicity is helpful.
I didn't see his answer but I wouldn't be surprised. That's the only way to prove it as far as I can see
@TedShifrin it isn't. Not unless ratios of lengths are known
20:36
Serves me right for attempting to answer a geometry question. But the OP who posted it was truly not far along in geometry. His efforts were ... things like opposite angles cut by a transversal.
@TedShifrin cool. we drove munchkin up to the snow yesterday. she was complaining for weeks about seeing it but not being able to go to it. so she went there now.
Oh, did you get stranded in the San Bernardino mountains in 12 feet?
@TedShifrin Pete Arantes? Yeah, I've answered many of his questions before. He isn't an expert in geometry, that's all I'll say
no, although, haha, they did close the road going in to where we went, while we were there. nice of them to let us out.
Well, by your standards, I'm far from an expert, too. But ...
I'm surprised they let you in without chains, then.
20:38
@TedShifrin I'm not an expert either, lots to learn for me. I just purchased a big Olympiad geometry book and oh boy I've got lots to learn for sure.
That's why it's so much fun
Well, eventually you should learn a broader scope of mathematics.
Unless all you intend to do is competitions.
Yeah, I will probably aim for a Masters after spending a few years in the industry (you can do that right?)
Well, even for an undergraduate degree in math, your strength in classical Euclidean geometry is far more than needed.
@PNDas I'm guilty of similar stuff. Posting "proof without words" in geometry, when I believe its obvious, when in reality it isn't
@TedShifrin To be honest I don't even know where I got this "strength", but its fun so I'll take it. That said, I also do enjoy other areas of math as well. I really like calculus for example
So far you're listing high school mathematics subjects :D
Not college/university.
20:43
Noob question: what is the geometric interpretation of the inclusion $\Bbbk[x^2]\hookrightarrow \Bbbk[x]$? Is it the branched cover $z\mapsto z^2$? If so, what is the geometric interpretation of the squaring map $A[x]\overset{x\mapsto x^2}{\to}A[x^2]$?
The latter map is far from a ring homomorphism, so why should it have a meaning?
@TedShifrin Wait, which High school is teaching calc 3?? Where do I sign up?
I don't understand why the latter map is not a ring morphism - I am defining the image of the generator $x$ as the polynomial $x^2$.
In the US plenty of high schools are in fact teaching crappy calc 3 classes. But most college calc 3 classes are pretty crappy, too.
@TedShifrin Yours made perfect sense to me.
I wouldn't call it crappy at all
20:46
No, that is an advanced course taken by a handful of the best students at a handful of colleges/universities. That is not what calc 3 in the US is at all.
We did learn quite a bit of vectors in my Japanese high school but that's probably the farthest "college-level" math we did in high school.
@Arrow So this is not "the squaring map."
Agreed, my name was poorly chosen.
a nice definition of vector is related to equivalence classes
@TedShifrin So that course is only for the best among the best? Are all of those who attend it expected to understand it all completely?
20:48
Of course not.
@TedShifrin What if you, yes you, were to sit in your own class as a college student? How would you fair?
(If I were one of those students, I'd call your classes "The Ted Talk")
fare? I don't know how to answer that question. Do you mean me as a college freshman as I actually was?
well, $A[x]\rightarrow A[x^2],\,x\mapsto x^2$ ist just an iso then
@TedShifrin yep
I would have done all right, but certainly not aced it. I did take Rudin real analysis as a freshman and did fine in it.
I suppose you could think about projecting the parabola $y=x^2$ to the $y$-axis.
20:52
Evans only defined Bochner integral and Banach space valued functions in the appendix. But he is using their properties without even stating. It's making me mad.
@TedShifrin You'd get an A on it, probably?
@Thorgott the target should be $A[x]$ instead of $A[x^2]$
Yes, Hades, I have given a lot of As to students in those courses over the years. They were not perfect, but they went on — not surprisingly — to be our best majors. Even some with B's from me have gone on to graduate school and done well.
yes, this is a branched 2-fold cover $\mathbb{A}^1\rightarrow\mathbb{A}^1$
It's already 2:25AM here.
20:56
@TedShifrin I wish I had some talent for rote learning classes too such as world history or something, those classes are really damaging my GPA
If $A[x]\overset{x\mapsto x^2}{\to}A[x]$ is the branched 2-cover, what's the inclusion $A[x^2]\hookrightarrow A[x]$?
I spent half an hour proving this💀
@Arrow they're the same thing essentially
the former map is a composite of the latter and an isomorphism
Are we supposed to learn how to prove the Dirichlet integral in Real Analysis?
@Thorgott ah, jolly good. The iso "straightens the parabola" and translates between the projection from the parabola to the y-axis that @TedShifrin mentioned and the 2-cover given by the squaring map.
21:03
I'm looking at our course outline and it has this in it
@冥王Hades the convergence or the value of the integral?
@SineoftheTime its probably both
the convergence is straightforward
We already proved the Gaussian integral
to compute the value, depends on which tecniques are you allowed to use
21:04
Why does every nice looking integral have a $\pi$ in it
i wouldn't care much about the dirichlet integral (i assume this is sin(x)/x). it might be an OK homework exercise.
the gaussian integral actually comes up in fourier analysis, most of the other integrals are just the calculus version of these complicated trapezoids and triangles, i.e. if you're me you file them under who gives a shit.
@leslietownes it's can be used as a good example to show Leibniz rule
@leslietownes yes it is $\frac{\sin(x)}{x}$
@leslietownes trapezoids and triangles? I give a shit! Me, right here!
yeah, i mean, it takes all kinds of people to make a world.
i'm not in any sense against the dirichlet integral. i just don't see why it would have to come up. you could spend your life doing analysis and never know or care about it.
Yeah I'm a weirdo, never had friends 💀
@leslietownes Looks fun to me so, why not?
21:09
it's a less destructive habit than a lot of other things i could think of.
@leslietownes like punching your expensive monitor and breaking it because you lost an online game. Yeah....wonder who would do that...
i periodically return to polya and szego's problems and theorems in analysis, because it's a cool book, but sometimes i think - man, there's tons of really complicated stuff to learn that you might never use.
although i did steal an idea from those books for a proof once.
Its not stealing its inspiration /s
@冥王Hades i hear that is pretty common, unfortunately.
my daughter has the use of a tablet, and when the volume on one of her shows is off, or the stream stops and she gets some error, she nerd rages and her instinct is to slap the screen. it is instinctual.
@leslietownes It is very common. Its even gotten me into some trouble for uttering a lot of colorful words in the voice chat after losing due to bad luck
21:16
i curse in traffic pretty frequently. my daughter can do it too. someone cut us off on the freeway and my daughter, about 2 and a half years of age, immediately said "this f---ing guy!" it was heartwarming and also inappropriate.
@leslietownes Same. Although thankfully in Japan you pretty much never have to curse in traffic
i don't mind my daughter's cursing if it's contextually appropriate, and not gratuitous. she called someone a mother f'er in traffic the other day, and i was like, when you're right, you're right.
my wife is a little more, uh, prescriptive when it comes to this kind of thing.
how are you even driving in japan? don't they have functional transit infrastructure?
@leslietownes they do. An excellent subway, in fact....for people who don't mind sitting with others/being around strangers
I'm not comfortable with that. I get anxious
ah, OK. i didn't regularly drive until i was almost 30, and it felt like taking a major L. still does.
I wish I was allowed to speed a little though. That's all I dislike about driving in Japan
21:24
most of the routes i drive are heavily patrolled, but 10-20 mph over a posted limit is not uncommon as long as it is the flow of traffic and not one person innovating.
I like to innovate
well, best of luck. :D
My V8 engine demands to be pushed harder
my 2003 wrx is on its last legs
head gasket issues, not worth fixing, but it is a beaut to drive in the hills
bright yellow probably wasn't the best choice if colour to stay under the radar
my radar detector went on the blink a few years agoi
or driving like an irishman
21:36
every irish person lives with the illusion that they are rally drivers
conceit was what i meant, but my old brain also needs a head gasket replacemnt
I'll faint if I get so much as a scratch on my car
you need to get beyond that to get full value from the car:-)
22:05
I'm gonna take it out on track someday even though Audi A7s aren't exactly built for tracks
 
1 hour later…
23:31
Least insane geometric proof 💀
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