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12:01 AM
@skullpatrol II suppose that depends on how recent counts as "new". Nothing I've been doing recently really counts as new.
Specifically, I've just been doing a lot of computations with spectral sequences to find the cohomology of various BRST operators in order to understand 2D conformal field theories with $\mathcal W$-algebra symmetries. This was all well-understood by both physicists and mathematicians in the 80s, so in a sense I'm doing rather ancient stuff.
The "new" thing is that we're trying to reinterpret the results and generalize them in the framework of the AdS/CFT correspondence and specifically conformal bootstrap methods. That probably isn't particularly interesting to mathematicians though.
It's a version of the holographic principle which says that quantum gravity on Anti de-Sitter space (basically Lorentzian signature hyperbolic space) is equivalent (in a somewhat precise way) to a conformal field theory in one less dimension.
 
Sounds deep.
 
the wiki article is
 
@skull Remember the question I asked that day, about doing something right but illegal? I am still thinking about it.
 
yep
be the change you want to see in the world
@JasperLoy
 
@skullpatrol Is that a quote from somewhere?
 
12:13 AM
yes
Ghandi
 
In history are there any famous examples of people who did what they thought was right but was illegal?
 
yep
 
Can you give me one?
 
what Ghandi did was illegal according to british law
 
OK, and what was it he did? Pardon my ignorance.
 
12:17 AM
refused to obey british laws in india
watch the movie
 
I see.
 
12:49 AM
hi all
                                         hi all
                         any active people               here?
@JasperLoy
@JasperLoy
 
Hi @user3222184
 
 
2 hours later…
2:30 AM
@Hakim Hey, Hakim.
 
Does anybody know how to install MacTeXtras?
Hey, @MatsGranvik!
How are you?
 
fine thanks.
I don't use Macintosh.
Googled that, I don't know that software at all. Macintosh or Windows.
 
Ah. No prob. It's a bit bothersome when amsmath isn't enabled for some reason.
|^_^|"
 
2:57 AM
YEAH!! Just hit 10k! :D
(I feel so powerful!)
 
good job :D
 
4:05 AM
How does one improve on an asymptotic?
$$\prod _{i=2}^{\text{nn}} \frac{1}{1-\frac{1}{b_i}}$$
$b_i$ is a complex number, the product is the constant in the asymptotic for another sequence.
 
 
1 hour later…
5:36 AM
thamokin purpth & sthudyin analythisth
J/k
it was Trainwreck
Hey, any one know wtf happened to anon?
@anon
 
@EnjoysMath what
 
5:59 AM
Just hadn't see you post in a while.
^_^
You're probably out seeding the world like Khan.
 
I have other accounts
 
<-- namely
 
You'd probably overflow the user rating bytes if you didn't :D
Then you'd be back at < 1000 conservatively since you probably pull in a crap load of points fast or something, because you are a super math genius
 
haha
thanks
 
sthuper sthmart bro
You're welcome
 
6:46 AM
@Chris'ssis I finally got $$\int_0^1\arctan(x)\log(1+x)\,\mathrm{d}x=\frac\pi8(3\log(2)-2)+\frac12\log(2)-‌​\frac18\log(2)^2-\frac{\pi^2}{96}$$
$$
\begin{align}
\int_0^1\log(1+x)\frac{\mathrm{d}x}{1+x^2}
&=\int_0^1\log\left(\frac2{1+x}\right)\frac{\mathrm{d}x}{1+x^2}\\
&=\frac\pi8\log(2)\tag{1}
\end{align}
$$
$$
f(a)=\int_0^1x\log(a+x)\frac{\mathrm{d}x}{1+x^2}\tag{2}
$$
$$
\begin{align}
f(0)
&=\int_0^1x\log(x)\frac{\mathrm{d}x}{1+x^2}\\
&=\frac12\int_0^1\log(x)\mathrm{d}\log(1+x^2)\\
&=-\frac12\int_0^1\frac{\log(1+x^2)}{x}\mathrm{d}x\\
&=-\frac{\pi^2}{48}\tag{3}
\end{align}
$$
$$
\begin{align}
f'(a)
&=\int_0^1\left[\frac{ax+1}{1+x^2}-\frac{a}{a+x}\right]\frac{\mathrm{d}x}{1+a^2}\\
 
The great anon
 
7:02 AM
@anon No, really? ;-)
 
;-) is the smiley I hate most.
I wonder why people star the chat guidelines.
 
solidarity
 
7:51 AM
I just starred the chat guidelines, It makes me feel like I'm some sort of authority that has approved of the document rather than just a mere subject of it's terms.
@JasperLoy: Yes, 2B is a pencil. Is it the same as a #2 pencil?
@anorton: Congratulations on the 10k. I wish you many more k's in the future.
@skullpatrol: What Gandhi did just goes to show there's a large prime gap between illegal and immoral.
@JasperLoy: All he did was manufacture dirty salt as an opposition to the heavily taxed and monopolized good salt made by the British . Actually, all he did was pick up and claim responsibility for the dirty salt illegally made by the sweaty guys that followed him. The only reason he would have been guilty of it in court would be because he walked from his ashram to that damn place with a very large group of Indians saying that he did it.
 
Well said @Nick
 
8:09 AM
@skullpatrol: I wouldn't blame him for not having the time too dig up a hole in the beach to naturally let the sea water fill into it and the sun evaporate that water leaving fresh sea salt... the one that contains all the yucky gross stuff like your kids pee from your last visit to the beach.
@skullpatrol: No, I seriously wouldn't blame him, he was so busy winning against Martin Luther King during that time.
Now, enough with my conspiracies.
@skullpatrol: How was your day?
 
Fine thanks
 
@skullpatrol: You were right about reciting stuff. I feel a whole lot more confident about what I know.
Now, my current battle is against my slow speed and thinking capacity.
 
@Nick I don't know.
@robjohn You are not sleeping yet?
 
@JasperLoy have an idea please
 
@Vrouvrou Sorry, I am not too good in math. =)
 
8:53 AM
Greetings
@robjohn I have a similar approach excepting the fact that I don't use the differentiation under the integral sign.
@robjohn I think it's a nice integral. :-)
 
@Chris'ssis How often do you go jogging?
 
@JasperLoy I go jogging almost every day (like 1 hour or so).
 
@Chris'ssis Ah, you must be very fit then. I have become fat.
 
@JasperLoy It also helps you to be in a good frame of mind. Well, it's never too late to start going jogging. :-)
 
@Chris'ssis When you publish your book, will your name also appear as Chris Sis?
 
9:02 AM
@JasperLoy lol, no. :-)
 
@Chris'ssis How did you do it?
 
Just do it. Nike.
 
@Chris'ssis I was having trouble with $$\int_0^1x\log(1+x)\frac{\mathrm{d}x}{1+x^2}$$
 
@robjohn Look at my proof below. There I evaluated that integral.
 
Using the $x\mapsto\frac{1-x}{1+x}$ substitution did not help there.
@Chris'ssis ah, you did the same thing, but just hid the differentiation with a double integral
 
9:08 AM
:-)
 
Wow, Chris Sis is a genius.
There are too many geniuses in this chat.
Others are Ethan and Balarka.
 
@robjohn However, one can do it without differentiation or double integral. You simply try to get the series in my proof and then compute that in a different way by using the generating function of the harmonic number.
 
@Chris'ssis Now I am thinking maybe you and Cleo are the same person.
 
@JasperLoy are you kidding, right? :-)
(I hope I'm better than Cleo :-))))))) - because I also have proofs :D)
Hey, joking here again ... ;)
 
Cleo is also very mysterious, and both Cleo and Chris start with C.
 
9:18 AM
@Chris'ssis I have another way starting with the integral hiding the differentiation... Let me write it up...
 
J.M. no longer comes to this chat.
 
9:40 AM
@Chris'ssis Ah, it didn't pan out. I got a $0-0$. More work would be needed.
@JasperLoy I haven't seen J.M. for a long time.
 
The terrible Taiwanese drama my mum is following has 900 episodes, sigh...
I am still looking for the perfect calculus book, one with all the applications and proofs. Most of the current books lack one or the other.
 
some one can help me?
 
Huy
What do you need help for?
 
9:56 AM
@robjohn here is a more advanced version
$$\int_0^1 \arctan(x) \log^2(1-x) \ dx$$
 
0
Q: How find the maximum the postive integer $n$ if such $w(n)+\varphi{(n)}=1+\pi{(n)}$

china mathQuestion: if the postive integer $n$ such $$w(n)+\varphi{(n)}-\pi{(n)}=1$$ find the $\max{(n)}$, where $\varphi{(n)}$ is Euler's totient function (Euler function) $\pi{(n)}$ is prime-counting function (prime-counting function) $w(n)$ is represents the number of distinct prime fact...

 
@Shisui Did you include \usepackage{amsmath} in the preamble of the document?
 
@Chris'ssis with a minus instead of a plus?
don't know if that makes much of a difference
 
@robjohn yeah, and the logarithm is squared.
 
10:13 AM
@JasperLoy: I don't know either. And I'm the person that randomly knows that $$111111111\space \times\space 111111111\space = \space12345678987654321$$
@Chris'ssis: Is $\log^{2}(x)$ accepted notation for the square of the logarithm function?
 
11
Q: What's the correct notation for log squared?

Roronoa ZoroI ran across these two notations for the log function (squared), which one is more conventional. $\log^2(n)$ or $[\log(n)]^2$

@Nick that way it's OK.
 
@Chris'ssis: Who would confuse that for $\log(\log(x))$ ? Good gracious.
Hey, that's funny $logolog(x)$
Might just be the new trolololo.
 
r9m
10:29 AM
oh ! I have seen various texts use $f^{n}$ instead of $f \circ f \cdots \circ f$, but they always mention that it is for the sake of convenience :|
@Chris'ssis Hi :-)
 
Oh my! In my world, $f^{n}$ usually means the nth derivative of $f(x)$.
 
r9m
derivative is $f^{(n)}$
 
Convenient :D
 
@robjohn in a way or other, one needs to prove this result $$\int_0^1\frac{x \log^2(1-x)}{1+x^2} \ dx = \frac{35}{32}\zeta(3)+\frac{1}{24}\log^3(2) -\frac{5}{96} \pi^2 \log(2)$$ and this doesn't seem easy at all.
@r9m Hi :-)
 
@r9m: Random question, how long does it take you to count till a billion?
 
r9m
10:34 AM
@Nick never counted that far .. I remember counting till 100 when I was 5 years old .. never after that :P
 
@r9m: Just goes to show. Not even big math people can count till big numbers. But can you estimate how long it would take.
@r9m: Truth is no one has ever really counted to a billion. mathsisfun.com/activity/count-billion.html
 
r9m
@Nick I'd have a foaming mouth before I could count till $\frac{1}{100}^{th}$ of that :P
 
@r9m: No that starts right after 10,000
 
r9m
@Nick I'd rather have my mouth foaming 'coz of a poisonous snake bite than have the same from counting till a billion :P
 
@r9m: It's too hard to combat that logic.
 
10:43 AM
@Nick That's odd... If you can count to 100 in 25 seconds, you should be able to count to 1 billion in 8 years (without break or sleep).
 
r9m
@Nick It ain't logic .. it goes to show that I'd prefer sheer bad luck to counting till a billion :P
 
@robjohn: From a scientists point of view, you'd have comparatively lesser physical evidence to support you hypothesis.
 
@Nick Their assumption was that you are counting at the same rate as for 100 in 25 seconds. Sleeping 8 hours a day would add 50% to the time
 
I just asked a question on main ... math.stackexchange.com/questions/872472/…
 
@robjohn: They'll have lots of evidence about the sleeping part.
 
r9m
10:55 AM
@Chris'ssis my God ! another crazy integral !! :D ..
 
Well, I'm off to bed.
I'm gonna go comatose for a few hours, hallucinate vividly, and then maybe suffer amnesia about the whole experience.
 
@r9m :D It's a really cool one.
 
@Nick Hello.
 
@BalarkaSen: .... Ah blast from the past! Thanks for waking me up with that ping.
 
Long time no see.
Wattcha been upto?
 
11:00 AM
Long time no math.
Studying so much that my brain hurts. Unable to frm sntnces
 
What are you studying?
Heck typos.
 
You are not serious, are you?
 
I got 480 rights in 5 minutes
I need some way to wake up don't I.
I'm effectively attempting to cut down my calculation time by 80%
 
Are you sitting for some exam?
 
11:04 AM
Yup the first terminal of 12th
 
Oh noes.
 
If I don't get a 100 marks on this simple exam, I could never live with myself.
 
I got second terminal in 15 days in here. 9th.
 
I have it tomorrow morning! I have 4 hours left to finish 2 chapters inorder to stick to my schedule
 
Tomorrow morning?!?!
 
11:06 AM
I am still looking for the perfect calculus book. Any recommendations?
 
What subject?
 
It's not that I haven't learnt the chapters, it's that I had an anxiety thing. @skull helped me solve a part of it.
@BalarkaSen: Math. Why would I otherwise be watching techmat for 3 digit multiplication tricks
 
@JasperLoy I learned cal from Piskunov.
And i think it's a great book.
 
@BalarkaSen Title?
 
@JasperLoy Integral and Differental calculus, probably.
@Nick ha
don't they let you guys use calculator?
 
11:09 AM
I am FAT
 
@JasperLoy: The only calculus book I've ever finished in my life was Arihant's Differential Calculus by Amit M. Agarwal
 
@Nick Who is Arihant?
 
@BalarkaSen: ... Nope. I can actually do multiplication as fast as a calculator because of that.
 
@Nick Multiply 1317 by 1968.
 
@JasperLoy: An Indian Publishing Company with the motto Inspiring Minds Inspiring lives
@BalarkaSen: 2591856
 
11:11 AM
@BalarkaSen Unfortunately many teachers here think that is all there is to math.
 
@JasperLoy Sad.
Here's the case too.
 
@BalarkaSen The teachers here are stupid but they think they are smart, lol.
 
@Nick I dunno let me check.
 
@BalarkaSen: Yeah 4 digit is harder
 
opens up calculator
 
11:12 AM
I cheated, I used paper
 
yup. it's fine.
 
Don't have enough money for a calculator :(
I can do 3 digits in less than 10 secons though
 
131 with 678
 
Too many geniuses in this chat, I feel so stupid, lol.
 
Dividing stuff in chem and physics is hard though.
@BalarkaSen: 88818! :D
 
11:15 AM
I am going to take a nap.
 
r9m
@Chris'ssis :-) did you do to the limit problem, the one with $tan \dfrac{k\pi}{2n+1}$ ? :)
 
I think I need to lie down now too. XD
 
Sorry was away for a while.
Yeah, go to nap @Nick
 
r9m
@Nick where are you from ? :)
 
India.
 
11:16 AM
@BalarkaSen: In a sec, I need to revise formulas from matrices (That's why I'm doing all this multiplication)
 
@Nick You have math next day?
 
@r9m: The country where people usually do math
 
Yeah, it seems there are too many Indians doing math these days.
 
@BalarkaSen: Yup, that's what I said.
 
@r9m that might be done by a clever application of the trapezoidal rule. I'll put a proof on paper after I finish my work on a certain type of series.
 
r9m
11:17 AM
@Nick okay .. then what is the unusual thing about the country you are from ? :-)
 
@BalarkaSen: Yeah but no one is a number theorist at your age.
 
@Nick I am not a number theorist.
Just studying stuffs.
 
r9m
@Chris'ssis oh ! thanks :-) .. did you see robjohns solution ? :D
 
@r9m: It has Balarka
 
@r9m by the way, I have some news ... I might have an elementary way for $$\lim\limits_{n \to \infty} \dfrac{(-1)^nn^2}{n!} \sum\limits_{k=2}^{n}\binom{n}{k}(-1)^kk^{n-1}\ln k$$
 
11:18 AM
@BalarkaSen: As are we all.
 
r9m
@Nick oh ! you are from India too ? :D
 
@Nick I think there is a guy who is doing quantum field theory, algebraic geometry, topos theory and higher category theory all at once.
 
@r9m: No, I'm from India One.
@BalarkaSen: He must have twin.
 
@Nick Twin?
 
r9m
@Chris'ssis oh !!! superb !!!! Subarashii :D
 
11:20 AM
@BalarkaSen: Well, I can't see a person doing all those things at once (unless there's some wierd calculation that requires it)
 
@Nick He is in MSE. 13-year old.
 
@BalarkaSen: What I would give for a brain like that.
I'd like totally give away my brain for his brain. Yeah, totally.
 
I'll keep my brain, thanks very much.
Shisui changed username.
 
@JasperLoy I didn't notice that it wasn't there but I included it very shortly after I posted the message. Thanks!
 
r9m
@Chris'ssis please show it to me when you put things in paper :-)
 
11:24 AM
@BalarkaSen: Hey, I'm not a freaky alien who eats smart people brains so that he can do math. Why would you suspect that?
 
why my "aha" is starred in the starboard?
 
And no one liked my rant about Gandhi or my philosophies on sleep. Definitely a math chatroom.
 
@Nick You should try creating a philosophy chat room.
 
@BalarkaSen: And listen to the random poetic musings of madmen on acid. No thanks!
 
r9m
@BalarkaSen sorry that must have been a slip of my hand .. my mouse pointer is behaving erratically :|
 
11:28 AM
@Nick Here's a problem for you : Find an integer such that sum of the factorial of it's digits is equal to the integer.
 
@r9m ok ;)
 
@r9m aha
now don't star that again!
 
r9m
:P .. you caught me almost in the act :P okay :P .. it was too tempting :P
 
Yeah, let's just star the old one again
 
bangshead
1 min ago, by Balarka Sen
@Nick Here's a problem for you : Find an integer such that sum of the factorial of it's digits is equal to the integer.
You should try it too.
 
11:30 AM
@BalarkaSen: That's too easy!
0!
1!
2!
 
OK, OK, enough. Find such an integer with more than 1 digit.
 
r9m
@BalarkaSen thank you :) .. but I'll have a cup of coffee please :P
 
@BalarkaSen: Ok, I'm stuck
There doesn't seem to be any two digit numbers such that the sum of the factorial of each digit is the number itself.
 
There ain't any.
 
...
 
11:32 AM
Hint : 3 digits does the trick.
 
1! + 4! + 5! = 145
Got it :D
 
Yes.
Well done.
 
... I don't think I can get anymore
What are these called?
 
There is precisely one more of such number.
It's 6 or 7 digits I think.
 
There are things called Armstrong numbers which are similar
 
11:34 AM
40585 = 4! + 0! + 5! + 8! + 5!
5
 
Holy moly!
 
@r9m and there is one more thing to add in terms of news ... I recently came up with a second elementary proof to math.stackexchange.com/questions/554003/… :D
 
And there are no more of these (prove that yourself)
 
r9m
@Chris'ssis Great :D ... now that I have my speakers on .. the pings sound like sthonk .. :P lol ..
 
Well, I'll spill the beans. They are called factorions.
 
11:36 AM
@BalarkaSen: That's such a cool name!
 
@r9m By the way, why my question here is not highly upvoted? math.stackexchange.com/questions/872472/… It's marvellous ...
 
OK, I guess I have to go now.
Byes.
 
Bye! Thanks for letting me know about Factorions
:D
 
r9m
@Chris'ssis I (+1)ed it the moment I saw it :-)
 
@r9m Yeah, I realized that $+1$ came from you. :D
 
11:38 AM
I'm now gonna do over 9000 matrices and determinant problems
 
r9m
@Chris'ssis shouldn't have said that ... votes are private in M.Se you know :P XD
:P BBL
 
@r9m: I said nothing.
 
r9m
@Nick good one :P LOL
 
Now, let me go read Al Jibr by AlGore-izmi so that I may in future know when not to find Al Iksh
(Yup, I need a nap)
 
r9m
12:32 PM
 
1:31 PM
@r9m No, not before showing me this one. However, my ways use no polylogarithm. :-)
 
Hello. I am a bit new to Math.SE. I see that some questions don't have actual answers as answers, but instead have hints on how to solve the problem. Why is that? Is it because the questions are too simple? Should I, too, refrain from actually answering certain questions?
 
@Chris'ssis It's a pity that many question/answers that are marvelous are not highly upvoted in MSE.
(+1)
 
1:46 PM
@BalarkaSen Yeah, that's really true ... (unfortunately)
 
@eiterorm visite MetaMath.SE for discussions about policy :-)
 
@skullpatrol I was just wondering if there's any consensus on this. I'm not too interested in the discussions. =)
 
r9m
@Chris'ssis okay ! :D
I was watching the Goku vs. Super-man thing :P troll lol
 
@Chris'ssis I've noticed that mostly surveys get highly upvoted in MSE rather than real answers.
I've thus stopped posting answers in MSE.
 
@eiterorm there is no uniform agreement
 
1:53 PM
@BalarkaSen For a while (some many months) I didn't post any question, answer ... then I changed my minds and said to myself to do it once in a while.
 
Yeah, posting answers/questions once in a while is good. Making it a habit to earn rep points is bad.
Many people just go out of their comfort zones to do that, resulting in wrong answers.
Also, LHFs are a bad idea. I personally never answered to LHFs, if ever commented on any.
 
If $A$ is any set of real numbers, define a function $C_{A}$ as follows: $$ C_{A} = \begin{cases} 1, & x \text{ in A} \\ 0, & x \text{ not in A.} \end{cases} $$ Now I need to find expressions for $C_{A \cap B}$, $C_{A \cup B}$ and $C_{\mathbf{R}-A}$ in terms of $C_{A}$ and $C_{B}$. Where do I start?
 
@Khallil What have you tried? Do you have a good idea?
 

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