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00:00 - 21:0021:00 - 00:00

12:13 AM
@skull did you know that when the lights out is less dangerous?
 
12:43 AM
aaaaaaa
aa
 
1:01 AM
@Ethan May I ask, why?
 
1:20 AM
The world seems to have failed to end.
 
1:43 AM
The 21st isn't over yet for me
 
2:09 AM
y
 
2:36 AM
HI
 
 
2 hours later…
4:30 AM
d
3eed
aaaaaaaa
 
Hey
 
lol
know anything about functional equations
solving em
 
no
 
oh
think this statement is reasonable, if is f(x) is continuous and $f'(x)\leq 1/x$ for all postive x, then $\sum_{k=1}^{n} f(k)$ is assymptotic to $f(n)n$
 
huhuh?
 
4:43 AM
do you think that statement is reasonable
 
what do you mean by asymptotic
 
the ratio of the two as n-> infinity is equal to one
 
is it true for log x?
 
yes
I think its true for all functions
just a guess lol
 
can you prove it?
 
4:44 AM
no but it seems obvious hueristically
 
give me the proof.
 
ok think of it like this
any function with a derivative of 1/x
will be increaseing, but increaseing at a decreasing rate
its derivative is approaching a constant value namely zero
lol to lazy
just a curriousity
 
@Ethan Did you mean $f'(x)\le\frac1x$ or $f(x)\le\frac1x$
 
@Ethan Have you seen proofs like this: math.stackexchange.com/questions/263192/…?
or look in georges' answer below @Ethan
 
the first 1 robjhon
 
yes?
 
uhm wtf
think this statement is reasonable
wait
Let f(k) be any integer function satisfying atleast, f(ab)=f(a)+f(b), when gcd(a,b)=1, if
$$\sum_{n=1}^\infty \frac{f(k^s}{k^s}$$
converges for all s>1, then
$$\sum_{k=1}^n f(k)=\sum_{p\leq n} f(p)[\frac{n}{p}]+o(n)
fuck sake
aaa
Let f(k) be any integer function satisfying atleast, f(ab)=f(a)+f(b), when gcd(a,b)=1, if
$$\sum_{k} \frac{f(k^s)}{k^s}$$ converges for all s>1, then
$$\sum_{k=1}^n f(k)=\sum_{p\leq n} f(p)[\frac{n}{p}]+o(n)$$
 
5:12 AM
aaaaaaa
If f(x) is monotonic and continuous on the interval $[1,\infty]$, and $f'(x)\leq\frac{1}{x}$ on the interval $[1,\infty]$,

is $$\sum_{k=1}^n f(k) $$ assymptotic to $$nf(n)$$
 
5:37 AM
hi guys, quick question, flag this as too localised? math.stackexchange.com/questions/263547/…
hmm, perhaps not, I guess the proper way forward is to answer with general methods instead of the specific solution
(and also edit the title to something better, which I just did)
 
6:11 AM
Im guessing it doesn't have an closed form integral
id try to simplify the integral til you get it to somthing thats easyier to see weather or not it converges for a given a
 
 
2 hours later…
8:29 AM
Why is $\gcd(0,0) = 0 \ne +\infty$?
 
@DumbCow a gcd of n and m is a number such that d|n and d|m implies d|gcd(n,m). If n=0=m then 0|n and 0|m implies 0|gcd(n,m) implies gcd(n,m)=0.
 
8:55 AM
Ah!
Thanks @anon! Does anyone understand Blankship's Method by the way?
 
never heard of it
 
@anon: Check it out; have you heard of Bezout's Lemma?
 
course I've heard of Bezout's
 
Yup, so we have $\gcd(a,b) = xa + yb, x,y\in\mathbb{Z} $
 
well, (gcd(a,b))=(a)+(b), in terms of ideals
 
9:00 AM
Blankship's helps us find the $x$ and $y$.
 
so extended euclidean algo?
 
Yes.
How can I fix this Chrome problem with M.SE?
 
which prob?
 
It freezes when I am typing an answer.
 
happens with me way too often
dunno what the 'fix' is
 
9:57 AM
@anon: Sorry, it's Blankinship's Method*
 
 
2 hours later…
user19161
11:32 AM
@DumbCow How does it freeze?
 
user19161
@BenMillwood I think it is fine. Many mathematical problems are highly specific in some sense.
 
user19161
@DumbCow I have not come across defining the gcd of 0 and 0 before.
 
@Ethan someone reverted your question. If you want, you can post the summation question separately.
 
12:11 PM
This Dirichlet series:
$\sum _{n=0}^{\infty } \left(-\frac{1}{6 n+2}-\frac{2}{6 n+3}-\frac{1}{6 n+4}+\frac{1}{6 n+5}+\frac{2}{6 n+6}+\frac{1}{6 n+1}\right)$
converges to zero.

I have tried to modify it to make it reveal something about the Riemann zeta zeros but the set of tools in my toolbox is limited and I have not gotten far.
This is another one:
$\sum _{n=0}^{\infty } \left(-\frac{1}{10 n+2}+\frac{1}{10 n+3}-\frac{1}{10 n+4}-\frac{4}{10 n+5}-\frac{1}{10 n+6}+\frac{1}{10 n+7}-\frac{1}{10 n+8}+\frac{1}{10 n+9}+\frac{4}{10 n+10}+\frac{1}{10 n+1}\right)$
that also converges to zero.
 
user19161
1:05 PM
@MatsGranvik I hope you solve the Riemann Hypothesis soon! =)
2
 
@MatsGranvik: You're pretty dope :)
 
1:22 PM
What do you think of my answer here?
 
@DumbCow Look at Asaf's answer, it encompasses what you said, and then goes a bit further.
 
Sorry, didn't see his answer :P
Man... why do I give so simple answers that they seem stupid?
Or rather, unexplained.
 
@DumbCow you are 13.... you will learn... patience is the key.
 
Sometimes, though, it's annoying how people answer so simple questions with unbelievable ways.
 
looks can be deceptive, simple is not that simple sometimes. :-)
 
1:36 PM
Is it just me or does everybody see encrypted text instead of the normal one on the menu bar of the site?
 
@DumbCow no encrypted text here
 
@MatsGranvik Sorry, summed from n=1
 
@robjohn Thanks for checking though.
 
When I hover over something, it turns into the original text.
 
2:10 PM
$$
\sum _{n=0}^{\infty } \left(\frac{1}{10 n+1}-\frac{1}{10 n+2}+\frac{1}{10 n+3}-\frac{1}{10 n+4}+\frac{1}{10 n+5}-\frac{1}{10 n+6}+\frac{1}{10 n+7}-\frac{1}{10 n+8}+\frac{1}{10 n+9}-\frac{1}{10 n+10}\right)\\
-\sum_{n=0}^\infty\frac{5}{10n+5}-\frac{5}{10n+10}\\
=\log(2)-\log(2)
$$
 
2:25 PM
There is one in between:
$\sum_{k=0}^\infty\left(\frac1{8n+1}-\frac1{8n+2}+\frac1{8n+3}-\frac5{8n+4}+\frac1{8n+5}-\frac1{8n+6}+\frac1{8n+7}+\frac3{8n+8}\right)$
 
@robjohn this one I have not seen before. How did you find that?
 
@MatsGranvik The same as I showed above: it is the difference of two alternating harmonic series
@MatsGranvik You can do one for each even integer $>2$
 
kan
Wow what with this place just seeing all the chaos for the past year!
 
Ok, I am not sure I understand how. The ones I mentioned are from the matrix a(GCD(n,k)) where "a" is the Dirichlet inverse of the Euler totient function.
http://oeis.org/A191898
 
for 4 you get
$\sum_{n=0}^\infty\left(\frac1{4n+1}-\frac3{4n+2}+\frac1{4n+3}+\frac1{4n+4}\right)$
 
kan
2:38 PM
Well, I popped in to wish you guys an advanced Merry Christmas... Have fun!
@robjohn My special wishes to you. :)
Catch you guys later!
 
@robjohn This destroys my previous belief that the earlier ones for Mangoldt Lambda [6] and Mangoldt Lambda [10] and so on, were the only ones.
 
@kan I swear I read "pooped"
 
@kan You got out too quickly... Happy Holidays to you, too!
@MatsGranvik Do you see what I did above?
 
@robjohn I will look at it. I am not so great at understanding things though.
 
@MatsGranvik The first line is the alternating harmonic series written in one way, the second line is also the alternating harmonic series written in another way.
@MatsGranvik so you get $\log(2)-\log(2)=0$
@MatsGranvik The one for 8 could even get trickier...
@MatsGranvik $\sum_{k=0}^\infty\left(\frac1{8n+1}-\frac3{8n+2}+\frac1{8n+3}+\frac1{8n+4}+\frac1{8n+5}-\frac3{8n+6}+\frac1{8n+7}+\frac1{8n+8}\right)$
 
2:49 PM
How different is real analysis from complex analysis?
 
Nice question: If $f(t + k) = f(t)$, can we assume that $f((t + k) + k) = f(t)$?
 
@MatsGranvik which now that I look at it, is just the one for 4 written twice.
@DumbCow If the first statement is true for all $t$, then yes
 
@robjohn Do you have an explanation for that conclusion?
 
@DumbCow $f((\color{#C00000}{t+k})+k)=f(\color{#C00000}{t+k})=f(t)$
 
Oh yes :D
 
2:56 PM
@DumbCow You could inductively show that $f(t+nk)=f(t)$
for $n\in\mathbb{Z}$
 
@GustavoBandeira there is a question on main about it.
 
@robjohn Yes, I see that :)
 
@JayeshBadwaik Really? Can you send me the link? It's not me being lazy, I'm on my mom's house, internet is REALLY SLOW
 
@GustavoBandeira I was searching for the link till now. Here
 
@JayeshBadwaik Really? Can you send me the link? It's not me being lazy, I'm on my mom's house, internet is REALLY SLOW
 
2:59 PM
See Robert Israel's answer in particular.
 
@DumbCow One can also write the condition as $f(t+k)-f(t)=0$ so that $$f(t+nk)-f(t)=f(t+nk)+\sum_{i=1}^{n-1}(-f(t+ik)+f(t+ik))-f(t)$$ $$=\sum_{i=0}^{n-1}(f(t+(n+1)k)-f(t+nk))=0.$$
 
@JayeshBadwaik Thanks
 
@peoplepower Yes, I see... periodic function :D
 
I am going to shop now, but this should work also:
$\sum _{n=0}^{\infty } \left(\frac{k}{3 k n+k}+\frac{k}{3 k n+2 k}-\frac{2 k}{3 k n+3 k}\right)$

which is a similar sum for log (3).
to the shop
 
@MatsGranvik yes, cancelling the $k$, that is $\log(3)$
 
3:13 PM
@robjohn: How did you become such a genius? >_<
 
@MatsGranvik $\sum_{n=0}^\infty\left(\frac1{6n+1}-\frac1{6n+2}-\frac2{6n+3}-\frac1{6n+4}+\frac1{6n+5}+\frac2{6n+6}\right)=0$
 
4:03 PM
@robjohn Have I phrased this correctly? (just been confusing myself after a Christmas drink!)
 
4:47 PM
@OldJohn Looks good to me.
 
@robjohn Thanks
 
Holy cow.
 
@JonasTeuwen Moo
 
@JonasTeuwen Holy moo
 
Robjohn became good at mathematics like most people who are good at mathematics have become good at mathematics: work hard. There are no shortcuts 8-).
@OldJohn Yes @robjohn Ya!
It is like raining non-stop!
 
4:49 PM
@JonasTeuwen same here
 
@JonasTeuwen Send some rain here!
 
Yes, but that is like the UK.
 
Mats needs a hat...
Otherwise, the first six in the avatar bar have hats.
 
Mariano, say something!
 
@robjohn Yes, definitely. Could you ban him if he refuses to do that?
Or reset the avatar 8-).
 
4:54 PM
I'm jealous of y'all :P
 
@DumbCow why?
 
Because we are chimps and not cows, maybe?
2
 
@robjohn That's because you know mathematics -- a lot more.
 
No non-hatted people may speak ... until @MarianoSuárez-Alvarez does
 
@DumbCow He is also much older.
 
4:59 PM
@JonasTeuwen According to my philosophy, age doesn't matter :)
 
Then your philosophy is wrong.
 
@MatsGranvik have a hat!
 
According to philosophy, no philosophy is wrong; it's just how you experience it.
 
That's a pretty stupid philosophy. I don't buy that shit.
Sounds like the hokum Sokal and Bricmont wrote about 8-).
 
lol
 
5:04 PM
I need to buy a high speed train ticket for tomorrow to Belgium, I'll tell them that in my philosophy it is free.
And not 120€.
 
@JonasTeuwen Your philosophy appears to be internally inconsistent. There's a contradiction between "it is free" and "need to buy".
 
@HenningMakholm I can buy it for 0€.
 
lol
 
@JonasTeuwen Does that fit the definition of "buy"? We may need to enlist the help of a native English speaker.
 
@HenningMakholm Maybe if I first pay for it and then get a refund.
 
5:08 PM
speaks fluent English, gibberish, esperanto, ...
 
They...must...be...fuqing...kidding...me.
'Unable to process request.'
That is the only error.
Now it is 'You are not authorized for this page.' < want to buy.
This means it must be free, right?
 
Everybody trying to book tickets at the same time - overloading the server?
 
Last year they charged me 6 times and I got the ticket 6 months after I had to take it!
First they send an apologies letter with 'here are some free vouchers'
But the vouchers were missing.
They however refused to give me the address of the helpdesk.
 
@JonasTeuwen Good grief - that is worse than Virgin rail in the UK!
 
@JayeshBadwaik: lol
 
5:14 PM
Why do I need to print the bastard???
I don't have a printer.
One time I was on the airport, and I had an e-ticket on my tablet - fine in Amsterdam. Same carrier in Madrid NAH PRINT IT.
Back to the end of the bloody line.
15 minutes before boarding.
And of course the gate was like a 10 minute walk away!
Added to the hate list: Easyjet, NS Highspeed.
(can get a print from them but 25€ booking costs, assholes)
 
@HenningMakholm You have been trolled.
 
Have not!
 
@HenningMakholm nuh huh!
 
@HenningMakholm comments are often designed purely to confuse, I think (well, most of mine are!)
 
5:24 PM
Why does it seem to be so hard to build an online ticket sales before you cancel the 'human' desks?
 
Hello!
 
@JonasTeuwen Can you get it from SNCB instead?
 
@HenningMakholm Good idea!
 
@dumb hi Parth!
 
Whenever I need international train tickets I always end up buying from Deutsche Bahn. Our local DSB doesn't really seem to be interested in selling.
 
5:28 PM
@Charlie Hello :)
 
@DumbCow how are you?
 
@Charlie I'm fine; enjoying the weekend. And you?
 
@DumbCow same. enjoying holidays
 
@HenningMakholm It is pretty strange. Then you complain to the guy at the counter and they say 'don't complain to me! call this number <...> 25 ct/minute'
 
@Charlie No holidays yet... a week more :(
 
5:32 PM
@DumbCow which holiday?
 
Holidays are evil.
 
Why so?
 
@JonasTeuwen we slow down...
At least i have two months of vacation :P
 
Oh, you're on Winter Break?
Charlie, I mean.
 
@MWarsi no:P is summer hrre!
 
5:37 PM
Hello peoples of the math.
 
@PeterTamaroff hola Pedro!
 
Summer?! Yikes. Where are you, mate?
@Peter
@PeterTamaroff Hola Pierre!
 
@MWarsi south america
 
Or rather, my bad. *Salut, Pierre.
 
@Charlie The vacation, I mean.
 
5:38 PM
Holidays are great to work, the only asshole whining to you is yourself!
 
@DumbCow oh.. you know what's funny? Cow in portuguese is "vaca" so vacation sounds like cowation hehe
 
@MWarsi Do I know you?
Does anyone know who is responsible for the analyitic proof of FTA?
 
@Charlie Haha
@PeterTamaroff Yello!
 
@PeterTamaroff rockstar. oh! Sorry, that's gta. (I couldn't help sorry...)
 
@Charlie You play GTA?
 
5:43 PM
What the hokum is an 'analytic proof'?
 
@DumbCow :D
 
@DumbCow I'm currently playing Hitman:absolution.
 
@Charlie You still have a chance.
 
@JonasTeuwen The opposite of a synthetic one?
 
5:44 PM
@Charlie Oh my.
 
@DumbCow why "oh my"?
 
@HenningMakholm Perhaps.
 
@PeterTamaroff que diablo és. eso?
 
@Charlie You're too adventurous...
 
@Charlie OK, the animation is damn creepy, but the song is a classic
 
5:47 PM
@DumbCow it's a really good game!
 
@Charlie Obviously it is!
 
@peter la vaca estudiosa? Hahaha
 
@Charlie Yeah. DO you understand the lyrics?=
 
@PeterTamaroff yes, of course
How cutie! Everyone with christmas hats
 
6:26 PM
@Charlie Not quite cute enough - we are aiming for an unbroken line of hats on the avatar bar :))
 
@OldJohn we're nuts
 
@Charlie I'm an almond and demand equal respect.
 
@Charlie Of course - it is a prerequisite to be here
 
@OldJohn Did you see what I asked above?
 
@PeterTamaroff about FTA?
 
6:32 PM
@JonasTeuwen I mean the proof using continuity, compactness, Weiertrass theorem, infimums, closed disks, &c
@OldJohn Yes.
 
@PeterTamaroff hahaha
 
@PeterTamaroff Not sure - I know that Gauss and Cauchy were in on it in the early days - but I think their proofs were later shown to have gaps
 
@OldJohn Didn't Gauss give 3 proofs?
I have one in a book.
 
@PeterTamaroff I believe so - and I think none of them would be accepted today as complete - but then nobody had developed the necessary topological machinery in his day
 
@OldJohn Right.
I eco what a friend told me once: He said that when he learnt some songs he loved in the guitar, they lost their mystique. I feel somehow something similar here: when I see the proofs of some theorems, they seem to lose their mystique, their flavour.
They become mundane to me.
Which is something kind of bittersweet.
 
6:39 PM
@PeterTamaroff I get the same feeling sometimes, in a way - reading Gauss in D.A. - his arguments seem fresher in some way that I find hard to define - although his arguments can be a long-winded by modern standards.
 
@PeterTamaroff how? See the proof is what makes the theorem so beautiful!
 
for instance he didn't have the concept of a group - so he proved almost the same thing 3-4 times in D.A. when a modern book would just say "follows from Lagrange's theorem", I think
 
@Charlie Well, yes. But at the same time, it is like when a magician reveals his trick.
 
Must go eat - back in a bit
 
6:41 PM
@HenningMakholm Hahhaah, nice.
 
@HenningMakholm haha how cute! Thanks!
Now i have a hat too :)
@jayesh you should put a hat too...
 
How many votes are allowed in a day?
 
@DumbCow 40, I think.
 
@HenningMakholm I see.
 
@DumbCow Here it says 40, but only 30 of those can be on answers.
 
6:54 PM
@HenningMakholm How can I see the number of questions I've voted on? =/
 
So now we have our six-hat lineup. Now if only robjohn or Mats would say something...
@DumbCow It on the bottom right of the "summary" tab on your profile page.
 
something
 
@MatsGranvik It was solved by sled instead, it seems.
@DumbCow (But it doesn't distinguish between question and answer votes for the "today" column. Strange).
 
hmm
 
@DumbCow wouldn't it be muu?
 
6:59 PM
@Charlie lol
 
@DumbCow :D
 
@MatsGranvik: you didn't like the hat I made for you?
 
@robjohn The picture was a bit blurry.
 
@MatsGranvik I took you picture, which is blurry, and added a hat to match. If you have a sharper gravatar, I could add a hat to that.
 
The image you linked to was much larger than this one above.
 
7:12 PM
What is a rollback?
 
@MatsGranvik so it would probably be less blurry when sized back down.
@DumbCow when an edit is undone
 
@robjohn thanks
 
7:26 PM
@robjohn Most honorable. Do you think you can answer my question about FTA?
 
Is this a new record - 7 hatted avatars in a row? (How sad are we!)
 
@OldJohn There was 8 for a brief interval before Charlie left.
 
@HenningMakholm Henning.
 
@HenningMakholm darn - missed it
 
Why is $\det(XI_n-CAC^{-1})=\det(CXI_nC^{-1}-CAC^{-1})$?
 
7:33 PM
@PeterTamaroff That's my name. Don't wear it out.
 
@HenningMakholm Your name cannot be worn.
 
user19161
Wow, so many hats!
 
@JasperLoy probably the hattiest room on MSE?
 
user19161
@OldJohn Yes, also the nuttiest. Everyone is a nutcase here...
 
@JasperLoy apart from an odd banana
 
user19161
7:36 PM
@OldJohn Have you heard of banana nut crunch? =)
 
2 mins ago, by Peter Tamaroff
Why is $\det(XI_n-CAC^{-1})=\det(CXI_nC^{-1}-CAC^{-1})$?
 
@JasperLoy yep - we have that here
 
user19161
Wow, I thought I would get less than 100 today, but I still got over 100 in the end.
 
@Everyone Hohoho. Santa in the sun!!
 
user19161
@JayeshBadwaik No hat!
 
7:37 PM
@JasperLoy there is a hat. Refresh please. :-)
 
5 mins ago, by Peter Tamaroff
Why is $\det(XI_n-CAC^{-1})=\det(CXI_nC^{-1}-CAC^{-1})$?
 
@PeterTamaroff Is X a scalar?
 
@HenningMakholm It is a variable. It is in the context of the characteristic polynomial of a matrix.
They are proving it is an algebraic invariant.
 
@PeterTamaroff Yes, but is it a scalar variable?
 
Well, $\chi_A(X)=\det(XI_n-A)\in K[X]$
It is.
 
7:41 PM
ahh, then $CXI_nC^{-1} = XI_n$
 
@PeterTamaroff In that case $CX=XC$, so $CXIC^{-1}=XCIC^{-1}=XI$
 
I was thinking about it as a matrix =P
This is because $\alpha (AB)=A(\alpha B)$ for matrices, right?
 
Yes. Multiplication with scalar is commutative.
 
That is what you mean by $CX=XC$
@JayeshBadwaik I was thinking about $X$ as a matrix...
 
@PeterTamaroff yeah, got that.
 
7:44 PM
@JayeshBadwaik Do you happen to know who is responsible for the analytic/topological proof of FTA?
Do you, @HenningMakholm ?
 
@PeterTamaroff no.
 
Maybe I should ask on main,
 
may be.
 
@Jayesh: Do you like Apostol?
 
7:59 PM
@DumbCow yes. its good. I prefer spivak though.
 
@JayeshBadwaik His writings are pretty difficult for me :(
 
@DumbCow yes, that can be a thing. btw, is this your first course in calculus?
 
@JayeshBadwaik No, not really.
I want to cover calculus in depth.
 
@DumbCow okay, where did you study from first?
 
Paul's Notes -_-
 
8:02 PM
ohh. I haven't read that I think.
 
It's a website which is not too great
 
yes, I know. never read that though. when I was 13, I taught myself calculus from rd sharma. :P
 
Just a bunch of lecture notes
 
what do you know in calculus?
apostol is good though
are you reading from it?
do you find it readable?
 
I am right now.
 
8:05 PM
its readable?
 
Yes I do, but visually, I find the some-bold and some-regular print really disturbing.
Maybe -- I'm just on the prologue, so I'd have to read some pages before I make a decision.
 
hahaha.... that's too early
you can try apostol though, its a good introduction.
 
where did you get that!
 
Look at how some words are bold and some are italic and some are too huge.
 
8:07 PM
you have a bad printing
There is a wiley international student edition
available in india
which is around Rs. 300-500 (I forget) but quite cheap
buy that
 
eh, I'm reading an ebook provided by one of the well known users here :D
 
:P
I have that ebook too. :P
I know where it came from.
 
Be what you want cuz a pirate is free... you are a pirate!!!
 
wait a little bit
 
What was it?
 
8:13 PM
@PeterTamaroff I think that post was left vacant at the last ICM. It was felt that the various proofs of the FTA are now mature enough not to need constant caretaking.
 
@HenningMakholm What is the last ICM? International Congress of Mathematics?
 
@HenningMakholm lolz.
@PeterTamaroff yup.
 
I posted.
 
8:46 PM
@DumbCow mailed.
 
I feel underdressed in this chat without a santa hat.
 
@MikeSpivey Well, that gravatar is unhattable!
 
@PeterTamaroff I'm not sure. If robjohn can hat his mean square my gravatar should be hattable. :)
Of course, a santa hat would probably clash with my outfit. ;)-
 
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