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12:00 AM
@PeterTamaroff I still don't see where $k$ went
 
@Alizter why was the question about my sexuality?
 
@Twink What are you talking about?
 
you asked me why did I go parading my sexuality this morning
 
@PeterTamaroff How did you like brilliant?
 
¬¬
and you were the one who said there were high school students here and that we shouldn't be talking about that
 
12:14 AM
@Alizter I am not a fan of problem solving, really. Looks nice, though. Neatly organized, nice graphs, nice platform and so on.
 
@Twink When did I say that?
 
i like brilliant.org for high school students who go to competitions
but only that
 
@Twink If you can link that I will give you a cookie.
 
not for academic learning at university
¬¬
 
@Twink That was either Jasper or AlecTeal who said that I am pretty sure
 
12:17 AM
ok
im watchin my soap opera
I wanna know how to have ideas quickly to prove things
:(
or at least have them, it doesn't matter if it's not quickly
 
How do you tackle problems like this?

What is the smallest positive integer that can be expressed as the sum of eleven consecutive positive integers, the sum of twelve consecutive positive integers, and the sum of thirteen consecutive positive integers?
 
@Alitzer that's too high school :S
ask something of real analysis
or measure theory
I mean... those question can make you think a lot... but.. in the end... they're for nothing
 
@Twink I can ask what ever I want. I am trying to get to grips with a topic that I am not too familiar with and maybe, just maybe, I can learn something like a new technique.
 
why are you so upset? :S
don't be like that
be a nice guy
 
@Alizter Isn't the smallest number expressible as the sum of N consecutive positive integers just the sum of the N smallest positive integers?
 
12:33 AM
@KevinDriscoll you seem to be a nice guy
 
@Twink thank you
 
Maybe phrasing the problem like this will help:
$$\sum^{13}_{k=n}k=\sum^{14}_{k=m}k=\sum^{15}_{k=p}k=a$$
Find $a$.
 
i can't see the forumules
:S
 
OH! I see @Alizter. The number must be expressable as MULTIPLE sums. That was 1 question and not 3 related questions.
 
12:35 AM
which one do i have to download?
 
@KevinDriscoll Yes :)
 
@Twink instructions are on the page
 
@Twink Non its a bookmark
 
ok thank you
 
@twink you don't actually have to 'install' them, just put them on your bookmark bar and click it when you need it
@Alizter It seems like we can derive some additional constraints on the sequences of numbers
 
12:42 AM
@KevinDriscoll like... ?
 
@Alizter The difference between the first sequence and the second is 0. Same for all other pairs
 
maybe you can use the formule n(n+1)/2
 
@KevinDriscoll Are they not the same number?
 
for the first k+13 integers
 
@Twink Triangle numbers won't help
 
12:43 AM
and then rest the first k integers
with the same formule
and you'll change your summatory for a formule ¬¬
 
@Alizter Yes, they are the same number. Which is precisely why their difference is 0. I don't know if its relevant.
 
they'r not triangle numbers
 
@KevinDriscoll Thats like saying the difference between x=x is 0 :-P
 
@Alizter a tautology to be sure, but arent all mathematical facts tautologies?
 
the first summatory can be changed for the difference between the first k+13 natural numbers and the first k natural numers
and similar for the others
 
12:46 AM
@Twink I don't understand, maybe if you could LaTeX it I could see it
 
and you can use tthe formule n(n+1)/2
take the index n of your first summatory
calculate the first n numbers
with n(n+1)/2
then calculate the sum of the first n+13 numbers
and take the difference
 
@Twink oh I see $\sum_{k=n}^{n+10} k = \sum_{k=0}^{n+10} k - \sum_{k=0}^{n-1} k$
 
between the sum of the first n+13 numbers
 
this would be for 11 numbers
 
and the sum of the first n numbers
 
12:48 AM
but you get the point
 
and you can replace your summatory for that
well maybe it's 14 i dont know
fix it xD
 
Which we can write as $\frac{(n+10)(n+11)}{2} - \frac{(n-1)(n)}{2}$
 
ues
yes
yes @KevinDriscoll
that sum
 
@twink you can edit your posts by mousing over it and clicking the arrow
 
and you'll get fornules
instaed of summatories
 
12:51 AM
@Twink I think you mean summations, but yes
 
i dont know if it can help its just an idea
yes summations xd
sorry i dont speak english very well
 
@Twink The problem then is that you'll get 3 quadratic equations that each depend on a different starting number, say $n_1, n_2, n_3$. I'm not sure you can progress from that
 
$$13n_1+78=14n_2+91=15n_3+120$$
 
each equation is = a
solve each
maybe?
 
Subtracting each formula from each other one seems to give a set of 3 quadratic equations in 3 unknowns
@Twink its the same idea, that way you also can find a set of 3 quadratic equations
Sadly, non-linear algebra is much more difficult than linear algebra
As the quesiton implies, the solution of such a set of equations is not unique
 
12:56 AM
$$13n_1+78=14n_2+91=15n_3+120$$ ??
and the ^2?
 
@TedShifrin Hello again, hope your dinner was good
@Twink There should definitely be quadratic terms, not juse linear ones
@Twink oh wait I see, the quadratic terms cancel
 
its def linear
 
So this defines a plane in 3D, no?
Oh too many equal signs, no way
 
Ah yes it is a plane! Good job, brain.
 
1:03 AM
Good night all
 
So now you have a constrained minimization problem
ah, going to bed alizter? good night
 
nite
 
1:15 AM
o/
NOOOOOOOOO
 
@AlecTeal o7
 
Salute?
 
no what
j
salut comment ca va
 
@AlecTeal Indeed
 
i have a question, why aren't there girls here?
only guys
 
1:34 AM
j
 
Have you ever seen what it is like to a be a woman online? Even if people are not aggressively obnoxious to them, they are often passively obnoxious. And entering a math den would be disaster.
 
@ThomasAndrews Hmm. Amy seems to do fine, though.
 
@Twink It is entirely possible there ARE girls on MSE who just choose not to express their gender. But I also agree with Thomas. You can't admit to being a woman on the internet without a stream of lewd and rude comments flying your way. I don't think you'd have problems from MSE though.
 
Yeah, I'm not saying this isn't a welcome place, just that a woman wouldn't necessarily expect it to be.
 
@ThomasAndrews that's crap
Girl gamers are like "Everyone on the Internet is mean to me because I'm a girl"
They mean to say:
 
1:42 AM
Crap? Really? That's how you want to express yourself?
 
"Everyone on the Internet is mean to me"
 
@AlecTeal You can elevate the level of discourse, pal.
 
@AlecTeal I have personally investigated a number of the streams of female games on Twitch.tv and found that almost universally they are subject to attacks that revolve primarily around their gender. Low-quality male streamers are ignored. Low-quality female streamers are ridiculed. Of course you don't have to take my work for it. Go to Twitch.tv and look at the chat of any female streamer
 
No seriously, everyone is a dick on gaming forums and such. A girl comes a long and expects to be exempt from that proud tradition :P
 
It is either heavily moderated or filled with terrible comments
@AlecTeal I do my fair share of friendly trash talking in Halo. Personally, I'm convinced that what I see women subjected to is entirely different.
 
1:45 AM
@AlecTeal It is precisely that attitude - everybody is a dick - that caused me to stop online gaming, except for contract bridge, where the players are statistically more mature.
 
@KevinDriscoll and @ThomasAndrews yes Halo - Xbox Live is bad - it's all like "Haha suck my dick gay boy" - yes, that'd make me the gay one.... no offense @Twink maybe.
 
@ThomasAndrews I'm a bridge player myself!
 
I haven't played much in a long time, but I have a bridge web site: bridge.thomasoandrews.com with a lot of stuff that might be interesting to mathematically inclined bridge players :)
 
@ThomasAndrews Looks great! Enjoying the read.
 
If it was just Halo, I wouldn't mind, because I don't play that game, but virtually every online game I've ever played other than bridge was filled with racist words, homophobic words, etc. Most of that is just teen boy stupidity, South Park had a funny joke about that many years ago. Cartman had learned a friend had a crush. Cartman: You like a girl? You're such a fag! That's the level of it, most of the time.
But it is still tiresome to these old ears.
 
2:03 AM
@ThomasAndrews Sadly, yes.
 
lol
no @AlecTeal im not offended, thank you
but i can see you're a victim of some homophobic clichés
for comparing being rediculed with being gay
 
I think he was saying he was ridiculed as gay in online games. That's the go-to insult against other games, sadly.
 
why would it be ridiculous to be gay?
 
In the same way that Cartman think's it's gay to like a girl. It's just a sad teen-boy insult.
 
a word that should be erradicated from insults and offenses
now the use the word gay to criticize everything
 
2:10 AM
Of course, but teen boys are not particular bright.
 
that makes children associate the word gay with something bad
and that's why they grow up being homophobic
 
That's more than a bit simplistic!
Surrounded by homophobic parents and religious bigotry ... Perhaps more to the point.
 
It's usually the more offensive words starting with f that are used to imply the other player's homosexuality. "Gay" is more often used for "lame" nowadays.
 
@TedShifrin Truer words...
 
@TedShifrin Yeah. I'm wondering why my linear algebra book has little content on the range of a matrix! =/
 
2:14 AM
mine too
 
Don't blame me, @Peter .. But some of us call that column space :)
I use the word image, btw
 
@TedShifrin Wait.
I mean the dimension.
 
i don't understand why multiplying a matrix by another matrix which is invertible doesn't change the rank of the first matrix
 
Not the space itself.
 
@PeterTamaroff: that's almost always called the rank
 
2:16 AM
Whose book are you using, @Peter and @twink?
 
and i had to use that in one exercise and i wasn't even in the propierties mentioned in the book
a local book
 
@Twink What is the relation between ${\rm rank}\; (AB)$ and ${\rm rank}\;A$?
 
you won't know it
 
Ok ... I'm guilty of writing my share of local books :D
 
it's a book from my school you won't know it :p
and it's not online
 
2:18 AM
What's your school?
 
madrid university
 
@Twink I'm from Argentina.
 
Ah, cool. So many Spanish speakers here ....
 
@PeterTamaroff You can't associate with him, he's a peninsulare
 
xD
 
2:20 AM
I'll revert to lecturing in French :)
 
bonjour
 
I suppose thatt means I should try greeting Ted in Chinese again
 
smack @Kevin
 
哎呀!!
 
@KevinDriscoll Ah?
 
2:21 AM
@twink, it is almost morning there!
 
yes
 
对对对
 
@TedShifrin @Twink Really? I thought it was only like 3AM there
 
4 22
 
So rank is intrinsic to the linear map ... Independent of matrix representation. Lots of beginning courses don't get there.
 
2:23 AM
@AnthonyCarapetis I used to make fun of my roommate for compulsively repeating 對 on the phone
 
omg a taiwanese heiroglyph, fancy
 
I really should have learned Chinese in grad school, since half the geometers were Chinese.
 
hahah @AnthonyCarapetis I basically only type in Chinese to my taiwanese-american friends and they have trouble reading the simplified characters
which is funny to me because mainlanders can read traditional just fine usually
 
@KevinDriscoll: right. My entire vocabulary was picked up living in beijing for two months so I know about 50 simplified hanzi and that's it :p
 
@TedShifrin That's half the reason I learned it. Now my boss is Chinese.
@AnthonyCarapetis I can hardly understand people from Beijing. They speak so quickly and with so many 'r's......
 
2:26 AM
So he can't swear at you :)
 
儿儿儿儿儿
 
@TedShifrin I'm sure if he were creative he'd figure something out
 
interestingly the geometers were exactly the people I didn't have to speak chinese to while I was there :p
 
McDonalds delivers to your house if you live in the city in China! Isn't that crazy!?
 
Ah, Jon Stewart comes back tonight. (Sorry, American TV.) Guess I'll stay up to 11:30 tonight.
 
2:28 AM
Ha ha ... Nap at work in the morning?
 
We're having a crazy week at the office, anyway - we are moving to a new office at the end of the week.
 
Exciting!
 
We had a crazy day at the office today as well......a girl moved into the office across the hall. I don't think we've had a female on the 5th floor since 19-ought8
 
I'm sure she won't get any unwanted attention :)
 
Haha, I saw more grad students stop by her office today than people that have stopped by my office just to chat in 2 years
I'm not sure if its disturbing or not. I'm also not sure if that fact that I'm talking about it is disturbing or not. Overall confusion.
 
2:40 AM
Yeah, I get that. A long time ago, I once shared a small enclosed office with an attractive woman. I realized any discomfort was my own, but I did ask her not to wear such strong perfume. :)
 
Should we ring up the psychologist, @Kevin?
 
My advisor in grad school left mathematics to get a PhD. He still didn't learn to deal with women.
(PhD in psychology, I mean.)
Actually, I think he got an MD. But he still had problems talking with girls.
 
We math people are singularly bad at people! :)
 
@TedShifrin I don't think that would help. To be honest I've been thinking about gender issues a lot lately both in general and how it relates to my personal life. I'm not at all sure what to think.
 
It's people's fault for not being rational agents!
 
2:44 AM
Yeah, unfortunately, adulthood is a graduation into rationality. I sometimes think it is just getting used to being adolescent.
 
Haha @AnthonyCarapetis I want to Duke so I had to hear from Dan Ariely pretty frequently about how people are predictably irrational
 
Ah, understood (partly) @Kevin. One of my students from years ago (who transferred from Tech,actually) is now transitioning M to F. All sorts of issues some of us deal with.
 
Sigh, I meant to say, "adulthood is not a graduation into rationality..."
 
See, you're a mass of contradictions, @Thomas :)
 
I had a relative come out as transgender a few years back. Another case where I realize my discomfort is entirely my own.
 
2:50 AM
Another of my math students went from lesbian to M between undergrad and grad. Seems very happy now.
 
I have a friend transitioning MtF at the moment, hardest part for me is getting out of the wrong pronoun habits
 
@TedShifrin Yes, that is one sticky wicket. I was reading a blog for trans people a few days ago and was particularly distressed to see that one commenter insulting people who cross-dress and "just liking to play on the weekends." Makes me wonder if we'll ever grow out of our in-group/out-group mentality
 
It's very difficult, @Anthony. You're not alone.
 
Also, I realize my above comment could be interpreted that I'm unsure what my gender is and that's not the case. I'm quite clearly a cismale. I just meant thinking about how I treat others as it relates to their gender
 
Okey dokey @Kevin. I hadn't completely jumped to any conclusions :)
 
2:52 AM
(He was a deeply introverted man - so introverted, than when people talked about Aspergers, I always thought about him. When I met her, she was so outgoing and friendly and talkative, and I realized that he had been introverted out of fear of exposing herself. It was cover. She waited until her parents died to come out, afraid of parental rejection.)
 
Agh, back to parents again. But I guess @twink has gone to sleep.
 
@ThomasAndrews Illustrates a perfect point about how quickly these things move socially. A few years ago it was all the trans community could do to get people to say "transgender" or "transgendered" instead of "shemale" or some such. But now "transgendered" and "transgender" themselves are falling somewhat out of favor. My feeling is "trans" is the preferred adjective these days.
So it's all a mess of changing conventions. I find myself understanding at least 1 reason why it is comforting to have strictly-defined gender roles. The norms are always obvious.
 
I have a hard enough time referring consistently to the person who was my uncle as "she." Still feels odd.
 
That I totally understand. Personally, I've never known anyone pre- or mid- transition. Or perhaps I have and didn't notice; in which case good for both of us.
 
Yeah, one advantage if nerd-dom is that, sometimes, we just miss stuff that would cause others to be awkward. Or we are just always awkward, and no more or less awkward with "different" people. :)
 
2:58 AM
Night, folks. I applaud the open convo here :)
 
Have a good one @TedShifrin
 
3:37 AM
Are there any conditions under which $(i x)^{u+iv} \neq (i)^{u+iv}*(x)^{u+iv}$?
 
use polar coordinates
to figure out the conditions
 
3:54 AM
@TedShifrin I haven't, what's up?
 
@anon thanks
@twink he's long gone
 
lol ok
do you guys think gays are born gay or become gay?
 
@Twink I think that's like asking if you are born a musician or you just learn to play an instrument
 
so you think gays become gays?
 
@Twink No I think the question is ill-posed
 
3:59 AM
do you intend to do this gay fixation thing indefinitely twink?
 
hmm..
lol
hi anon
how are you?
just that....
i just wanted to know what mathematicians think about the gays
 
seems legit
 
there was a very famous gay mathematician
Alan Turing
:D
but he was chemically castrated when they found out he was homosexual
he developed boobs and some secondary effects
and he died
all because the stupid homophobic British
he could have made a lot of things and invent new mathematics but they killed him because he was gay
 
yep
 
recently the british government apologized for what they made to him
 
4:11 AM
the cyanide poisoning is generally thought to be suicide IIRC
 
yes but he did because of what the government did to him
he was happy with a partner
and when they found out what he was, they forced him to get chemically castrated
that's why he did that
 
naturally though this is irrelevant to your purposes here, which is amusement
so it makes the gravity of the current topic a bit ironic
 
my purpose is not amusement
i make math questions
and try to help others too
 
a subset of your purposes, not all of them. pedantic.
 
but it's the subset of the largest cardinality
 
4:17 AM
indeed
 
and don't call me pedantic
because i haven't been disrepectful to you
 
there is no way to tell if this is a real conversation to you, or just fun play. the latter seems more plausible.
 
think whatever you want i don't care
see, i'm too much older and smarter than you are, you might be as smart as I am when you get to be my age, but you're not there now
so when I ask you a question, you give me an answer
 
I don't see why users take up long-term trolling. it seems too time-consuming for too little pay-off.
 
4:44 AM
@anon There's a problem for $\pi < \theta < \frac{3 \pi}{2}$ thanks to the branch cut of the complex log it seems
@anon I feel like there should also be a problem with the 4th quadrant but there doesn't seem to be
 
5:04 AM
err lol thats not what I meant I meant $\frac{\pi}{2} < \theta < \pi$
 
5:26 AM
I think I've seen enough @Twink.
24 hours to cool down should chill your head.
Your own site's mods will decide what to do with him when its lifted.
 
@MadaraUchiha Thanks for stopping by, what brought you here, flags?
 
@KevinDriscoll A lot of them, yes.
 
@MadScientist Howdy, I've seen your posts on meta, but I'm pretty new to the chat
@MadaraUchiha Tonight or early this morning/last night?
 
@KevinDriscoll Both
Last time I thought it would be enough for an auto-suspension, but I saw he came back this morning
 
@MadaraUchiha Ah okay. Can't say I wasn't annoyed at times.
 
5:32 AM
@KevinDriscoll Aside for the abusive parts, the fact that he's deliberately steering the conversation into the realm of the (far) off-topic, is enough for a short suspension
 
@MadaraUchiha Agreed. Issues of sexuality sometimes come up here casually, but its not something I want to be talking about 24/7
 
Doing it twice and with such a dubious subject is warranted for a longer one
 
welcome back @AnthonyCarapetis
 
what are you doing around so late?
 
5:39 AM
?? it's 3:40pm here
 
@AnthonyCarapetis Hahaha forgive my Americo-centricism
You must be in the Phillipines or Australia maybe
 
@Kevin: heheh, a better question would be what I was doing around here 12 hours ago :p
Australia is correct.
 
When you abbreviate Australia, do you type Aus or Oz?
 
usually Aus
or "straya"
why abbreviate it when it's already one syllable in aussie english
 
haha, yeah i've heard "stralya" before
side note, The Philippines are further west than I thought
 
5:50 AM
Yeah, you were probably going for Micronesia or something
 
I think I'd rather go for an adult beverage
 
 
1 hour later…
ADR
7:12 AM
Hi, is it true that if f: M \to B is a submersion then for any function g: B \to N we have that if g\circ f is smooth then f is smooth?
 
@ADR: I assume your definition of submersion only requires $C^1$?
also that sentence doesn't make much sense, I assume you mean "if f is a submersion and (for any g, gf is smooth) then f is smooth"?
you probably also want some restrictions on the g for that condition to ever actually hold
 
ADR
@AnthonyCarapetis my definition of submersion is that is differential at every point is surjective, the statement im trying to prove is this: Let $f: M \to B$ submersion: A map $g: B\to N$ is smooth if and only if $g\circ f$ is smooth
 
7:29 AM
@ADR: Oh, that's different, and your submersion must be smooth then. One direction is just the fact that compositions of smooth maps are smooth.
The other direction is harder. Have you seen something like the "local normal form" for submersions?
 
ADR
@AnthonyCarapetis hmm, like the Jacobian matrix of $df_p$ has rank n relative to one choice of coordinates?
where n is the dimension of B
 
@ADR: you need to know that at least locally, you can find a submanifold $\Sigma$ of $M$ such that $f$ restricted to $\Sigma$ is a local diffeomorphism. Restricting $g \circ f$ to $\Sigma$ will give you what you want I think.
 
ADR
@AnthonyCarapetis the image of the submanifold $\Sigma$ is all B?
 
@ADR: locally. So the image of a small enough open set in $\Sigma$ will be an open set in $B$. Since smoothness is a local property that's all you need anyway.
 
ADR
@AnthonyCarapetis ok, any reference on the proof of the submanifold $\Sigma$?
 
7:47 AM
@ADR:have a google for the "constant rank theorem"
I think it follows pretty easily from the implicit or inverse function theorem
 
 
1 hour later…
8:50 AM
wtf i just got an "audit"
i said "leave open" because it wasn't spam and although i didn't understand it maybe op would fix
that is shit
SE is supposed to publish user actions not audit them or whatever
 
@DanBrumleve they recently started having "test" reviews in the queues
 
just because i default to leave open doesn't mean i run a reviewer bot
 
the reason is that there are a lot of people who robo-review and approve a bunch of stuff that should not be
@DanBrumleve no, but if you press leave open on something that is really poor quality, then that is not the right review option
 
if i get really confused i skip
but if i am somewhat confused and there is hope and the time frame is short i leave open
occasionally i vote close
i'd rather be shamed by a data.SE link than audited or whatever tf
stop look it's gotta go
just post the data
 
But if you do not feel you understand it, why choose leave open rather than skip?
 
8:59 AM
because of the likelihood
when i do understand it i vote to reopen 80% of the time
when it just looks pretty legit i guess close votes are unjustified as usual
so audit attempts to refute null hypothesis good luck
too much closing
 
given how poorly formed some questions are, maybe a lot of closing isn't a bad thing
 
deleting fine closing no
 
@DanBrumleve that makes no sense
why would it be better to delete than to close?
and how would you have that deletion take place?
 
deleting is a harsher action as it's harder to undelete
 
when questions are crap they should get deleted
 
9:09 AM
and if it's bad but can be salvaged with editing?
 
when they are dupes they should stay open and be merged after the fact somehow
 
What about a vote to merge them into community wiki?
 
@TobiasKildetoft Hey I have a question
 
@user38268 sure
 
If I have two morphisms $f : X \to Y$ and $g : X \to Y$
of schemes
How is the map $(f,g) : X \to Y \times_S Y$ obtained?
$X,Y$ are schemes over some base $S$
@TobiasKildetoft I am not getting it from the universal property
 
9:16 AM
I would expect from the diagnal map from $X$ to $X\times_S X$
 
Right that's what I guessed
@TobiasKildetoft Is it clear that if I have the map $(f,g) : x \to Y \times_S Y$ and the diagonal $\Delta : Y \to Y \times_S Y$
Then the fibered product $X \times_{Y \times_S Y} Y$ is just the set of all $x \in X $ such that $f(x) = g(x)$?
 
isn't that the pullback?
 
@DanielRust It's not clear because now X,Y are schemes
 
@user38268 My algebraic geometry is poor so I'll just sit by the sidelines :P
 
9:21 AM
@DanielRust The reason is because in Liu's book he says it is sometimes dangerous to be arguing set theoretically
for example because $X \times_S Y$ is not a set of pairs
 
@user38268 That seems like a reasonable stance
 
is some complicated thing made out of gluing lots of affine schemes together over and over again
 
@user38268 so even if you can identify it with those points, you also need to know what the scheme structure is on it
 
Ok hmmm
Actually suppose we know that the set of all $x$ such that $f(x) = g(x)$ is open and dense @TobiasKildetoft
 
does the fiber product satisfy some universal property w.r.t $f$ and $g$?
 
9:25 AM
are your schemes separated?
 
well if you want for my purposes I want $Y$ to be separated over $Y$
If I call the fiber product $X\times_{Y \times_S Y} Y =: V$
Then if $Y$ is separated over $S$, the projection $V \to X$ should be a closed immersion by stability under base change @TobiasKildetoft
 
Some quick linear algebra:

How to find integer solutions $\forall n$?
$$13n_1+78=14n_2+91=15n_3+120$$
 
00:00 - 10:0010:00 - 00:00

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