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00:00 - 19:0019:00 - 00:00

12:54 AM
If there are relationships between all of $x,y,z$, is it possible to reduce this to a single number?
 
1:13 AM
Well, it's not easy to establish a direction relationship. What I'm describing are more correlations that you see when trying to minimize particular quantities. It's entirely possible to have excessively high values in all three quantities.
There are also situations where the correlations break, I should mention.
For more context, the tournament is for this game: https://store.steampowered.com/app/558990/Opus_Magnum/
The three quantities are "how fast the solution to a puzzle is, the total cost of parts used in a solution, and the area that the solution occupies on the board"
Obviously, using fewer parts results in a smaller board area used, and should also result in cheaper solutions.
 
This is all wayyyyyy too hard for me.
 
XD
Fair enough. I guess there's an obvious solution that I am going to feel stupid for not seeing?
 
Why are you guessing that?
 
Because I interpreted your comment as sarcasm
 
Hell no.
I am rarely sarcastic in here.
 
1:21 AM
Fair enough. So this is actually a more difficult problem?
 
Don't ask me. I am not engaging.
But I'm guessing yes.
 
Ah, fair enough.
 
Hi @Ted
 
heya a @Balarka
 
1:39 AM
hi chat
 
hi JoeShmo
 
i did all the exercises for complex final. now ive got nothing to do and im looking for more exercises
 
So you come here to exorcize?
 
accessorize
following up on conversation last night -- under $z \mapsto \frac{1}{z}$, $-1 \mapsto -1, 1 \mapsto 1, 0 \mapsto \infty$
i.e., $y=0$ gets mapped to $y=\infty$?
 
yes, yes, the real axis goes to itself
For some reason I was restricting to the $y$-axis in my head for all that
I was not in good mental form and left.
 
1:43 AM
but now im confuzzled
 
why are you confuzled?
 
my brand new claim is $y=0 \mapsto y=\infty$
where the latter is probably not even a line
 
LOL, no, no, the point $0+0i$ goes to $\infty$.
 
but the point $0$ lies on the line $y=0$, and the point $0 \mapsto \infty$. how do we reconcile?
 
Reconcile what?
 
1:47 AM
so on the one hand we claim $y=0 \mapsto y=0$ under $z\mapsto \frac{1}{z}$. On the other hand the point $0 \mapsto \infty$, where $\infty \notin y=0$
 
Oh, oh, because all this is going on in the extended complex plane.
 
thought so, so $\infty$ is identified with...?
well, no
 
$\infty$ is the point at $\infty$, of course.
 
well i thought $\infty$ is the boundary of the complex plane identified as a point
 
So?
 
1:51 AM
the topology being defined by the stereographic projection
 
One-point compactification is the right way to say this
 
yuh
no, all it is is $0$ doesn't map to $0$
which isn't a problem
 
huh?
 
I am probably lacking the right terminology to convey my point (order preserving bijection is perhaps what i am getting at?)
but basically $z\mapsto 1/z$ doesn't preserve order. I.e. I probably made the mental error to think that $0$ should map to $0$ (since the line itself remains invariant)
 
Where is there an order-preserving bijection?
 
1:54 AM
there isn't one
 
On the reals, $f(x)=1/x$ is increasing on the negatives and decreasing on the positives.
 
where in fact it sorta inverts the line
 
it inverts the two rays separately
 
yuh!
that makes sense
 
it's sorta like: I was just telling my calculus kidlets today that $f'=g'$ only implies $f=g+c$ when the domain is connected ... if you have different components, the $c$ can change from component to component.
 
1:56 AM
did you break their little brains?
 
that's my goal
otherwise I have no purpose
Of course, I didn't use that language.
 
oh. then what did you say? in fact, how else can you say that?
 
I talked about different intervals.
 
oh. fair
single variable calc. right
 
Yup. I used $f(x)=\tan x$ as the example. And asked, what if $g'(x)=f'(x)$?
 
2:00 AM
so how many future fields medalists do you have in your class
 
None.
I had an amazing kid last year.
 
and?
the chat is acting up for me. for you too?
 
Nope.
 
so why was the kid so great?
you know, you could create an IMO team out there
 
Just amazing intuition and knowledge. He actually was one of the 10 national winners of a high-school-level competition.
 
2:03 AM
thats awesome!
 
I offered to "teach" my best student this year my multivariable math class as an independent study course next year. We'll see if he's good enough to do that.
 
most kids need some tough love
really wish i had a resource like that when i was growing up here
back in israel there's tons of ex-soviet mathematicians that drool over working with mathematically inclined kids
 
Yup, JoeShmo. Plenty of them are here too
Some of them are not the greatest teachers.
 
yup
oh they are bulldozers
 
Well, interestingly, my ex-colleague at UGA who was unquestionably a star researcher (Russian) was too easy on kids, because he didn't want to be bothered.
 
2:08 AM
lol. well my teachers let us have it. and i think we liked being treated like adults
its a bit different in the land of the free
 
I didn't pamper students, but I also tried to be sympathetic and encouraging, while pushing hard.
But most universities don't encourage faculty to spend time behaving like that.
 
thats how you raise a generation of participation trophies
(by not behaving like that)
 
Huh?
 
Genuinely curious: What are the advantages to taking a multivariate math class as an independent study course?
 
if youre not pushing hard, or youre too nice unnecessarily, you end up raising wimps (i think)
@Dair learning math
 
2:12 AM
@Dair: Better than taking what the high school would offer, since I'm willing to spend the time.
 
@TedShifrin Ohhhhh... The persons in high school.
 
Yes, very much so.
 
I was like: Independent study is like 1 - 2 unit P/NP usually...
why would you do that when you can get credit for 4 units lol.
 
Sadly, my book is way better than what most college courses are.
But most college courses aim for the general science/math/engineering student, not for someone who is particularly strong in math.
 
Don't forget econ
 
2:14 AM
Econ is usually in a weaker track, unless it's students who know that they want to do PhD's.
 
shouldn't these students major in math anyway?
 
Hmm interesting... I had a friend that was Econ/Math. He said the econs had to take multi...
 
No, JoeShmo.
 
Math is too competitive as it is and it isn't even popular lol.
 
@Dair: This depends on country, of course. But, generally, yes, econs need some computational multivariable, but only serious math if they're going on to graduate work.
Graduate econ really does use some serious math analysis.
 
2:18 AM
@TedShifrin Btw, I started messing around with some math stuff recently today. Probably wasting my time, but it was fun lol. Been doing too much CS started missing the math. :(
 
math > CS
 
Which math were you missing, @Dair?
 
@TedShifrin Basically anything. I was looking at some stuff by Euler, in particular the Euler Prime Product theorem and was just wondering if there was a way to generalize it to Gaussian Primes. I basically came up with nothing after a couple hours of working, but found out there was one after extensive google.
 
I haven't thought about that.
 
Basically I've been a bit tired this past few days. Haven't really been doing a problem solving grind, but just looked at some results and thought: "Is there a way to generalize this?" That's why it's probably a waste of time. Still kind of fun.
 
2:23 AM
No, that's really laudable. That's how people think to discover "new" math.
 
I have to decide what I want to do today, mathwise
 
Try doing math.
 
Good point
 
Math? Crazy talk.
 
I'm here to help :)
 
2:25 AM
Isn't Balarka supposed to be un-unsleeping?
hi @Fargle
 
Woke up after 2 hours of sleep
 
Hey @Ted
 
Damn, Balarka. I don't want you sick.
 
sleep > math
 
I mean I had slept before, just not at the right time
I am still sleeping like 9 hours a day
But literally on daytime
 
2:26 AM
Oh, OK, then I won't complain.
Do you miss classes and such?
 
Nope, nothing like this happens when I'm in the uni. It gets auto-fixed.
 
oh, you're on holiday now?
 
Yeah, winter
Still got 3 weeks left
 
OK, I'll shaddup.
 
2:28 AM
It's only 'cuz I care.
 
Thanks!
 
I'm about to disappear to cook dinner.
 
whats on the menu
 
Enjoy.
 
scallops, JoeShmo
 
2:30 AM
bon apetit
 
LOL
 
i made my first attempt at a sous vide brisket last night
it came out way better than i had actually expected
 
Sous-vide is a definite trend. I have never done it.
 
geez so many expert cookers on the math chat lmao.
Meanwhile I can barely toast toast correctly.
 
I would have been a serious chef if not a mathematician.
 
2:32 AM
so i dont have a machine. i cooked it on low temperature for 2 hours and then fried
 
Ah, interesting
 
i think i should have cooked it for 1 hour on low temperature
and then fried
the trick is when you fry it, you don't actually want to cook it anymore. you just want to caramelize the outside
 
I think the actual sous-vide machines keep it much more controlled and low temp.
Right.
 
so put it on high, and keep it on each side for about 10 secs
yes
the actual machine would make for a much better result
 
Yup. Although I've still been fed overcooked things.
Not in restaurants. Just in homes.
 
2:34 AM
gotcha. the experiments that have gone wrong huh..
yeah brisket is a tough cut. if you overcook it, it becomes unedible
 
hi chef ted
 
Well, the curing/marinade helps, JoeShmo
 
mhm
 
Hi Leaky ... what you been cooking? And why are you up at 3 AM?
 
my first attempt. i hear pressure cooking in coke is a good idea
 
2:35 AM
i'm back home @Ted
 
@JoeShmo: The "instant pot" pressure cookers are the new wave.
Where were you, Leaky?
 
home as in hong kong
 
Ohhhh
JoeShmo, I have often made pot roasts by braising them in a mixture of coffee and broth.
oh hell, now Demonark is here
 
>:)
 
huh! that sounds interesting
 
2:37 AM
Oh wow they changed things
 
They did?
 
What has changed?
 
Chat looks different for me, it's pretty much messages on a contiguous white background (aside from mine which are still in a blue box)
 
Can you send a screenshot?
 
Mine is blue for me and beige for everyone else. Is that a change? THis seems the same to me.
 
2:38 AM
 
@Daminark that's what mine looks like, and always has (as I recall).
 
This looks like it always has? (except there is no side bar)
 
I'm using it on a different machine than usual, maybe that's what's changed?
 
Some of these sites adjust based on the screen size.
 
Yup.
 
2:39 AM
Browser/extension?
 
Oh it was my screen contrast
 
smh
 
rolls $3\pi/2 + 7$ eyes.
 
lmao
 
This one was set at 75, changed it to 50 and now it looks normal
 
2:41 AM
Well, to me, what you described is normal.
 
So I'm guessing that on my actual computer it's 50
 
I'm gonna go cook dinner. Demonark is a mess.
 
I have my screen contrast cranked up to 100
 
Cya @TedShifrin
 
Cya, all.
 
2:42 AM
Lol, this is a new device! Now it at least has vaguely beige boxes around each message
 
bye ted
 
is your new device a tablet?
 
Nope, my dad's computer
 
Rip.
 
It's pretty similar to mine but slightly worse (e.g. i5 instead of i7), and also he has a really wide screen since he usually has two windows open at once
 
2:46 AM
Lol Mac?
 
Chromebox
 
Woah. wtf. haven't seen one of those in forever lmao.
I know they exist but i don't think i've ever seen one out in the wild
Fascinating.
Don't get me wrong: there is anything wrong with a chromebook, just kind of hipsterish. I need to get dinner too lol. Cya.
 
@Balarka Gromov is quite something
@Dair lol I know, I was just reading some transcript and didn't notice your message, see you!
 
@Daminark What did you encounter from Gromov
 
"Everything was known and was obvious, he just wrote it down"
 
2:57 AM
Ah yeah
Gromobvious is the opposite of obvious to normal people
 
Do you guys think a novice could learn from these notes
Just some really nice looking commutative algebra notes I've found online (the only ones that seem to have detailed proofs, so good for self-study).
 
It's tricky to glean that from a quick look because whether something is user-friendly really depends on the writing style
Though at least based on the contents it definitely seems to start completely from scratch?
 
It does seem to start from scratch, though I'll have to look up what those diagrams etc mean. The first few chapters couldn't possibly use a lot of category theory, could they?
From what you could glance.
 
Commutative diagrams are a fair bit easier than category theory, it's just about saying one composition of maps is equal to another
 
I was thinking that, but I was made suspicious by the preface "we freely use the language of category theory" I was like oh no.
First 6 chapters seem to correspond to Steps in Commutative Algebra
By Rodney Y. Sharp.
Man, these notes prove everything. I'm 100% gonna use them.
Thanks @Daminark
 
3:46 AM
rolls D finite eyes
 
Why are you rolling your eyes at us, mate? @Secret
 
Because the messages go from chrome stuff all the way to category theory, and the transition is so steep that I get a headache lol
 
4:04 AM
lol
 
user131753
@AlessandroCodenotti: See the following post,
 
user131753
16
Q: What is a logic ?

alpheccarI am not interested in the philosophical part of this question :-) When I look at mathematics, I see that lots of different logics are used : classical, intuitionistic, linear, modal ones and weirder ones ... For someone new to the field, it is not easy to really see what they have in common fo...

 
5:10 AM
@NicholasRoberts thanks! sorry, I have been distracted and missed your message before
 
5:35 AM
hey, if I have a function f(x) cont on [a,b] and diff on (a,b) and know that f''(x)>0 (so f'(x) is increasing, i.e. f'(b)>f'(a)) and a define a new function piecewise g(x)=f(x)-f(a)/x-a if a<x=<b and g(x)=f'(a) if x=a, then is it true that g'(x)>0 on (a,b) as well?
doing it by cases it doesn't seem like this is necessarily always the case
 
 
3 hours later…
8:33 AM
The cayley graph of Zp X Zp has a square mesh structure. Cayley graph of Zp X Zp X Zp has a cubic structure. How can we call the structure of Zp X Zp X ...X Zp , n times?
Can we call it a n dimensional grid?
 
It's more like a lattice on the n-torus
 
Ok, thanks a lot. I want to use that word to explain something to another person. Thanks again. :)
 
 
2 hours later…
10:25 AM
yeah it isn't really a square...
 
11:17 AM
Thanks :)
 
 
3 hours later…
1:48 PM
 
 
1 hour later…
2:49 PM
I usually am a fan of Wikipedia's math articles, but they're only as good as their sources
and the supposed limits it gives here are a prime example where the result cited is nonsensical as written.
(if you take a limit with respect to some parameter, said limit should better not be a function of said parameter!)
 
Aren't people who write wikipedia pages meant to know what they're talking about ?
 
well, to be fair in this case, the error is in the original source
it cites a technical report from 1992, and said report does indeed contain the erroneous results
 
Huh right
 
that said, someone who actually understood the formula should have recognized the issue and not included it as such
 
Yeah
 
2:56 PM
The correct meaning is that, when they say (for instance) $\lim_{|\mu|\to\infty}f(\mu,s)=F(\mu,s)$ they mean $\lim_{|\mu|\to 1} \frac{f(\mu,s)}{F(\mu,s)}=1$
That's a perfectly legitimate statement, but the two are very much not synonymous
(You can say that $F(\mu,s)$ represents the 'limiting behavior' of $f(\mu,s)$ but that's not what $\lim$ is supposed to denote)
@astyx going to post this on the talk page:
"The section on "Limiting behavior" states several limits, which are (modulo possible typos) found in Wood 1992. While the title (correctly!) frames these as the limiting behavior of the polylogarithm, the text (following Wood) misleadingly presents them as limits of the polylogarithm.
But the polylogarithm either vanishes or diverges in each of these instances. More formally: The text indicates that f(mu,s)->F(mu,s) as mu or s is varied appropriately, when in fact it means that f(mu,s) ~ F(mu,s) i.e. f(mu,s)/F(mu,s)->1 in the appropriate limit. (The only exception is the fifth statement, w
 
 
1 hour later…
4:22 PM
Hopefully someone will read it
 
4:56 PM
For a semidirect product between Z3 and Z5 X Z5, where Z5 X Z5 is the normal subgroup, if we consider a cayley graph with respect to a generator set with two elements say s,t, if order of both elements is 3, Why does st^(-1) always belong to Z5 X Z5?
 
I don't think that's true
if (s,t) generate the group and have order 3 then so would (s,t^2)
but st^(-1) and st can't be both in Z5 x Z5
 
@BuddhiniAngelika As usual this has nothing to do with any Cayley graph, so just ignore the graph
 
Thanks @LeakyNun and @TobiasKildetoft. I found it in the proof in page numbered 43, in this articlehttps://amc-journal.eu/index.php/amc/article/view/177
The proof for groups of order 3p^2, under case 2, the first 4 lines
Please help me to understand this
 
it's saying WLOG we can assume st^-1 in Z5xZ5
 
I don't understand why we can assume like that...
 
5:09 PM
yeah, the WLOG is necessary
It says why
 
@BuddhiniAngelika think of s' and t' as elements of Z/3Z
 
Please explain to me..
Ok, and then ...
 
since they have order 3, they are not the identity
then it is clear that either s' = t' or s' = t'^-1
 
Ohh, so it's because the subgroup which is not normal is Z3 , if it was some other Zq this assumption can not be made
 
yes
 
5:17 PM
Thank you very much @LeakyNun
Thank you very much@TobiasKildetoft
:) :) :)
 
 
2 hours later…
6:49 PM
For a semidirect product between Zpq and Zp, where Zpq is the normal subgroup and p > q, the commutator subgroup can be Zp or Zq or Zpq , right?
I mean we have to consider all 3 possibilities if no other condition is given right?
 
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