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18:07
wolololo
I get my best ideas when I ought to be sleeping
don't forget what the lead singer of deep purple has done recently
floyd is love, floyd is life
Where have I ended up? XD
18:10
roger waters-kun...
@AndreasAlmgren at hell, no problemo for you
Nice, at a warm and cozy place, then :)
@MikeMiller senpai
18:37
I wish airports had more than half an hour of internet access...
I'm back
Some do
Which one are you at
Hey! Anyone willing to give an undergrad some class advice?
Dallas Love Field
What dooes the number under a user's name mean, when you search them at "Users"? (so not the reputation, nor the badges)
18:39
I mean I guess my flight is taking off in just a bit more than half an hour anyway
@user115185 I might be alright with helping out, though there are some in this room that are more qualified than I
@Dam
oops
@Daminark So I'm finishing up Analysis 2, and I'm trying to decide if its a good idea to take a graduate intro to manifolds, or just move on to other topics
What did you cover in analysis 2?
Topology on $\mathbb{R}^N$ and $\mathcal{C}$, F and G derivatives, G differences
Class isnt over yet
In which country do you study?
Frechet and Gateaux derivatives?
18:44
@AlessandroCodenotti USA
@Daminark yeah
The prof says ive got the prereqs, but is being kind of cagey on whether its actually a good idea
So for an intro to manifolds, you need to have a good grip on multivariable calculus, and depending on how the course is done, possibly point-set topology
(oh never mind btw, I've found it)
What other topics would you be doing?
@Daminark Just finishing the semester on derivatives and optimization, we won't be covering integration, which im kind of worried about
Yeah that could be a bit of a problem
What other classes do you think you'd be taking if you don't do manifolds?
18:51
I'd either do grad numerical analysis, or catch up on CS classes (double major)
Joe
Joe
Where can i post a mathematical observation as apposed to a question?
@Joe Here would be good
Joe
Joe
oposed*
opposed*
@user115185 merp
Well I mean catching up on CS doesn't sound too bad
Joe
Joe
Would i just post it as a question?
18:54
@Daminark Yeah, true
So I'd say to find out what book they're using and what the professor for manifolds is going to be assuming as prereq knowledge. If it's something you could self-study, consider whether you want to wait until you get other classes down first and handle CS for now, or make the jump
Like, given sufficient self-studying of integration I'd think it's totally reasonable to do a G&P class
But if it's Lee or smth, I'm iffy
Hey @AliCaglayan!
hey @Daminark
How's everything going?
very good, how about you?
Thanks, @Daminark!
18:58
I'm doing well, about to board the flight back to Chicago
@Daminark where were you?
Hi @Ali
Texas, for spring break
hey @MeowMix
How are you?
19:00
i'm good
returning to uni on the train atm
found some interesting reading material on some algebraic knot invariants
and I wondered if anybody categorified them (they were from the 80's)
So they're algebraic variants?
they had so I am reading that now
@Daminark have you heard of Quandles in knot theory?
supposedly they can classify knots
No, I was just making a (k)not pun
its still flying over my head
can you be knotty and just tell me?
If it's not invariant, then it's variant :P
19:03
ahhhh
thats pretty good
@AliCaglayan what's flying over your head? :O
Haha, thanks!
a halo?
@SoumyoB Daminarks jokes
too advanced for me
@SoumyoB spooky
19:04
I'm knot sure I can keep up
reminds me of the two-line horror story I once read-
"You can look ahead, left, right or back. But wherever you look, don't look above, she hates people looking at her when she's watching them"
Or a six-word story: "Baby clothes for sale: never used"
damn
that escalated quickly
kaboom baby
19:08
@AliCaglayan you scared me
"Blood, guts; death"
boring
@BalarkaSen careful there are kids here
but blood
good, very good
Lol I mean, it's easier when you don't immediately associate a word with a concept. Right now the only thing I know that's in the neighborhood of algebraic geometry is that Zariski topology is a thing
19:11
@Daminark Zariski topology is weird if you think of it in terms of topology
I think thats mostly because its not Hausdorff
you just try to shrug off the nonHausdorffness
good punchlines
Yeah Zariski gets things done however
It really shines when you apply it to affine schemes
You start to do some powerful things
i think it's cool if you think of it as something which has a good sheaf on it
which is what the structure sheaf is
I just saw someone suggest calling multiples of three "threeven"
19:24
@Daminark if you're going to read alg geo on the flight don't talk about blowing up planes
multiplies of 0: "oven"
5
does anyone by chance know the opposite expression for a quadratic scale? I am just using square root to calculate my scale value... just wondering if there is a specific expression for such a scale
I'll make sure to avoid that
Though I'll be focusing on group theory
nobody here focuses on probability theory :(
except me that is
Well I'll be doing some measure theory next quarter
It won't be probability heavy, I know last year they did more geometric measure theory and all
19:31
@Daminark I hope you'll do things further in probability theory
oh :|
But like, there's a chance that a bit will come up, if only in side remarks. Still, I think I'll end up an algebraist
I see sigh
don't feel pressured, I can be the lone probabilist here, I'm used to it now
I mean it seems like probability can be pretty dank, as much as I have a preference I still intend to have some exposure to everything
The multiples of 7 would be the sevenven ?
i cannot seem to select that this question is actually a duplicate
19:34
what
-1
Q: In a differential equation, is recursion allowed?

TheGreatDuckTake the following ordinary differential equations. $$y'(x^2) + y(x) = x$$ $$y''(y'(y(x))) = x^{x^x}$$ $$y''(5) + y(x) = x$$ Is there anything wrong with any of these as differential equations? I know that nonlinear equations can result from terms consisting of various derivatives of $y$ mult...

I mean doesn't that mean that even numbers are multiples of e?
e=2 confirmed
could some people maybe place the remaining close votes?
@Daminark My C* buddy @JoshuaKeneda also suggests Murphy's book.
I suspect he won't get that ping.
@Daminark what kind of multiples of e?
of course 2 is a multiple of e.
e^ln(2) = 2
19:40
Alright, I'll look into that. C* algebras are connected with operator theory, right? Because I felt that the part of functional I liked the most was the stuff on spectra at the end, so that'd be fantastic
what is C*?
some kind of new programming language?
C* algebras are algebras of operators on Hilbert spaces.
oookkay then...
Nice
Ok so looking at the book, I'll want to know a bit more complex, but I'll pick up some on the boot camp so that's good.
Thanks @Mike!
Sure, @Daminark, I'm trying to get that punk to join the room
19:52
Haha
Feel the power of the 90's
That reminds me of
That song is featured somewhere in that video
like 30 seconds in
Hi @TheGreatDuck
20:05
Hey @Meow!
Hi @Dami
I've moved on.
Probably a good idea, infinite dimensions are tricky
OH MY GOD
I just read that miniguns are legal in the US
I'm so eager to go there now
I mean they're small so there shouldn't be a problem, right? -said the summer child-
if I was born in America as a citizen my home would look like an arms dealing market
20:09
your mind makes it real
Are they as small as the hands of your president ?
let's not get political here
Sorry, could not resist :p
To be fair that was quality
I can ridicule the DNC too, but I just choose not to offend people on here. It belongs to a different place
20:11
i hope to be good at math one dayyy
You are surely right
I honestly have no doubt you will Zach
I get demotivated too much
Given time I'm sure you'll turn out well. A lot of it is drive, and you definitely have that
Apparently my topology puzzle from a while back (two disjoint compact sets that each have simply-connected complement even though their union doesn't) is already well-known
Nobody in my life supports me. But it's not like I'm entitled to any.
20:14
in the sense of being an exercise in a textbook somewhere
Plus I have y'all :]
(By a guy named Pugh?)
Oh Pugh is a quality analysis book
You could have been famous Akiva
I like it better in many respects than Rudin
20:16
Is Pugh a guy or a book ? I'm confused
I thought people just call books by their author
Because saying "Topology" is a lot more vague than specifying "Munkres'"
Oh yeah it's the guy, he wrote "Real Mathematical Analysis"
@Meow to be fair, Munkres also has a book called analysis on manifolds so you'd prob want to specify already :P
Then there was Pough, who wrote "Real Mathematical Analysis," but the Fake one, so it was "Fake Real Mathematical Analysis"
20:17
I have a fat book at home simply titled "Geometry". (And yet I don't remember any of the three authors' names…)
Hey guys, quick question. Suppose I have an overdetermined (n > m) system of polynomial equations
f_1(x_1, x_2, ..., x_m) = 0
f_2(x_1, x_2, ..., x_m) = 0
...
f_n(x_1, x_2, ..., x_m) = 0
I've used numerical methods to find an approximate common root of (f_1, f_2, ..., f_n). Is there some way I can check if there is an actual root somewhere near this approximate root?
say the word baby
Have you guys read "Math" by "J.L. Professorton and R.M.Tenure"?
The situation I want to avoid is that the zero sets of (f_1, f_2, ..., f_n) very nearly, but do not quite intersect at (x_1, ..., x_m)
What about "Book" by "Author"?
20:18
:D
@DavidZhang what do you mean by polynomial equations ?
@Akiva Hartshorne!
Lol jk
Yeah, polynomials over what ring?
Equations of the above form, where each f_i is a polynomial function.
@MeowMix Who needs support when you have Ted-cercises?
(jk)
20:20
They all have integer coefficients, and I'm looking for real solutions.
I'm not actually sure if it matters that it's overdetermined, but I say it in case it helps
@Akiva I don't know anything about this stuff, so would we say $f_1, \dots, f_n \in \Bbb Z[x_1,x_2,\dots,x_m]$?
Or is that wrong notation
@Meow Mix Yeah, that looks right to me.
I think that's good
Now that Rotman is going all Galois mode it'll be tricky to follow but it's been damn helpful. Just need to pick up all the series stuff and then I'll prob revert soon to analysis
If we get some good problems in (geometric) measure theory I'll be sure to pass them along
One thing that I know works in the case of a single equation is interval arithmetic. If I let y_i = [x_i - epsilon, x_i + epsilon] for some suitable small epsilon > 0, then I can use interval arithmetic to determine if 0 \in f_j(y_1, y_2, ..., y_m)
But in the case of multiple equations it's possible that each of them is satisfied at some different nearby point
20:35
you don't even know what you are messing with here boy
sweet dreams, i'm walking a little, i'm too stressed out
20:51
Bye Null
Given the lack of responses here I've posted my question to Math.SE proper: math.stackexchange.com/questions/2204342/…
Am I correct to say that we could have also considered $t=\sup[a,b]\cap U_1$?
@Astyx I found inequalities for the k s, but I didn't found the values yet.

$\prod_i (k_i \cdot 2^6+1)=2^{2^5}+1$


$k_i \cdot 2^6+1\mid 2^{2^5}+1 \\ \Rightarrow k_i \cdot 2^6+1\leq 2^{2^5}+1 \\ \Rightarrow k_i \cdot 2^6\leq 2^{2^5} \\ \Rightarrow k_i \cdot \left (2^2\right )^3\leq \left (2^2\right )^{16} \\ \Rightarrow k_i \leq \left (2^2\right )^{13} \\ \Rightarrow k_i \leq 2^{26} \\ \Rightarrow k_i\leq 67108864$


$k_i \cdot 2^6+1\leq \sqrt{2^{2^5}+1}\\ \Rightarrow (k_i \cdot 2^6+1)^2\leq 2^{2^5}+1 \\ \Rightarrow k_i^2 \cdot 2^{12}+k_i\cdot 2^7+1\leq 2^{2^5}+1 \\ \Rightarrow k_i^2 \cdot
@Astyx How can we find the $k_i$s?
21:07
Compute low values and hope for the best is an option
@ShaVuklia it seems so
I would have to know what the definitions they are talking about are to be sure
@Astyx oh yea I wrote that out: So we have two open subsets $U_1$ and $U_2$ that satisfy the following conditions: $(I\cap U_1)\cup(I\cap U_2)=I$, $(I\cap U_1)\cap(I\cap U_2)=\emptyset$, and $I\cap U_1\neq\emptyset$, $I\cap U_2\neq\emptyset$.
That's not possible is it ?
I have seen at wolfram that the smallest k is 100. Is there maybe also an other way to find k? @Astyx
@Astyx which part is not possible?
@Evinda You've seen wrong
@ShaVuklia the existence of such $U_1, U_2$
21:11
@Astyx well yea, that's what the proof is about I think
they assume such $U_1$ and $U_2$ exist, and then derive a contradiction
Oh right, fair enough
Oh it is 10. @Astyx
Sounds more like it
I'll go now, good day/night to you
@Astyx And then we just divide $2^{2^5}+1$ by $10 \cdot 2^6+1$ and find the other prime which is 6700417, right?
A ok, good night :) @Astyx
what does the bar (|) in "f_t | A = identity map" mean
21:25
restricted to
f_t(x) = x if x is in A
thanks Mike. I appreciate it.
Hi @Dami again
21:48
Hey @Meow, finally back in Chicago
21:59
never start a fight if you can't end it, i'd say
Hey guys!
Just a quick question, we know that $B = A^{-1}(I - A^{-1}CD)$ can be expressed in $B = (A - CD)^{-1}$
Because distributive, but how come we can't do this:
$B = A^{-1}BC^{-1}(I-C^{-1}BA^{-1}D)^{-1}$ ?
It's just a friend's notes, I'm failing to see how this is not valid. Trying to help out some underclassmen by helping them make some linear algebra notes (for statistics) :)
Substitution doesn't seem like there's any wrong steps
$B=A^{-1}(I-A^{-1}CD)$ does not imply $B=(A-CD)^{-1}$ does it?
If you use the property that $(AB)^{-1} = B^{-1}A^{-1}$
And treat $A$ as $A$, $B$ as $I-A^{-1}CD$, I think it does work out.
22:12
you think?
Oh shoot, my bad I forgot an inverse sign.
I meant: $A^{-1}(I-A^{-1}CD)^{-1}$
$B=(I-A^{-1}CD)^{-1}A^{-1}$ implies $B=(A-CD)^{-1}$
Oh hmm, I see. A left multiply doesn't work in this case. Let me check again
the machinery used for factor analysis is a big pain
ah I see. Got it. Thanks!
I didn't catch that error in the notes. Friend accidentally left multiplied when he was supposed to right multiply from distributing terms
@Dami Cool :]
22:31
Hi :)
I have a tiny question: We know that given a subespace S with dim(S) = n-1, of R^n, we can extend S basis to a basis of R^n with a good choice of a vector. Can we do the other way around? Take a basis for R^n and reduce it to get a basis for S? I'm not sure, I think it's not true...
You can't do that. Consider $\mathbb{R}^2$ with the standard basis and let $S = \{\lambda (1,1) | \lambda\in\mathbb{R}\}$
@Daminark Thanks, intuitively, why does that happen? :/
That's what I can't seem to explain to myself
surely you can visualize why with Daminark's example in R^2
Hmm... Arctic, I mangled around with the equations and arrived at something of the form:
$(A - BC^{-1}B^T)X = -BC^{-1}$
If we are trying to separate X, then it would become: $X = -(A-BC^{-1}B^T)^{-1}BC^{-1}$ right?
22:38
Can we not apply our rule here?
As in it becomes:
$X = -(CB^{-1}A - CB^{-1}BC^{-1}B^T)^{-1}$
Cancelling out we get $X = -(CB^{-1}A - B^T)^{-1}$?
@Matti Note that your ability to go one direction is not a function of any deep connection between a subspace of a vector space and the whole thing
Alright. Not sure why didn't simplify it to that last step. Thanks!
22:39
The reason why you're able to do it is that any basis is linearly independent
So you can always translate things up
@Daminark Thanks
But there are so many possibilities, so if you imagine two subspaces with different bases, you can translate either of them up, but given a basis, you can't take any random subspace and say "We got our basis by extending this", you might've gotten it from somewhere else
22:59
Hi :) I'm stuck on a convergence in probability question and have read that there's a specialised form of Chebyshev’s Inequality for counting random variables: $P(X=0)\leq Var(X)/E(X)^2$. I can't find any other references for this online though?
So Laci asked Boller to forward the message to the math list host, with a description of his "Algorithms in Finite Groups" class and everything. The prereq is first quarter of algebra, and we apparently have to get a permission form from the department head
@Dami What are your topics of interest?

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