Mathematics - 2015-01-26 (page 1 of 4)

Modded Bear

00:00

My teacher forgot to upload my grades and now I'm going to have a week full of bureacracy and paper work to fix the f***ing mistake.

Clarinetist

@DonLarynx - Yeah, that's what I'm doing... I'm trying data science, but it is going to require quite a bit of work. Hopefully it'll all work out at the end.

Don Larynx

@ModdedBear: Looks like it should be easy for you, as that requires no strength :)

Modded Bear

mabye, but paperwork is like kryptonite.

Daniel Fischer

@evinda A red-black tree? Also not something I know the rules of, I'm afraid.

Don Larynx

@Clarinetist that's good! But also engage in one more area, preferably outside mathematics in general. Otherwise, you'll be worried about spending your life dealing with numbers.

Modded Bear

00:03

For example calisthenics

sports is the best hobby imho

@DonLarynx yeah, cardio is for girls

although I do sneak into the pilates classes once in a while.

Clarinetist

@DonLarynx - True, true indeed. It's just hard to do *anything* really, when you work full-time and are expected to progress through exams. If I could do anything with my life, it would be some combination of the following:

1) Piano lessons and/or composing
2) Teach math/statistics/actuarial science at a university
3) Publish an actuarial textbook or study manual

Don Larynx

@ModdedBear or should I say Dr. Fernandez, for the week being, you will be okay. Send me some extra kryptonite in case you are winning in our next challenge.

Alex Wertheim

@Clarinetist: you are a pianist, then?

Clarinetist

@AlexWertheim - Yes, and clarinetist. Clarinet for about 11 years now (been on a hiatus since I graduated last May) and Piano for about 5 years, but off and on. I'd like to improve my piano skills.

Modded Bear

@DonLarynx you better not slow down in PE. Because when I decide to punch, I will punch hard.

Alex Wertheim

00:07

@Clarinetist: neat. Working on any piece in particular at the moment?

Don Larynx

If you ever decide to. Ha

Clarinetist

@AlexWertheim - Just trying to get back to composing at the moment. It's just hard to be inspired when I live in a city where everything seems to be business and insurance.

Don Larynx

What city is that?

Clarinetist

Des Moines, IA.

evinda

@DanielFischer A ok...

Alex Wertheim

00:09

I could see how that might be difficult. Doesn't seem like there's much soul or romance in business/insurance. :)

Clarinetist

@AlexWertheim - Nah, not really. :P Especially when you're an actuary out here. Silence permeates the departments I've been in. You only talk to people when you have a question or if there's a department outing. And even those outings, dang, they're awkward as heck.

Alexander Gruber

Okay let me tell y'all a thing and get some reactions

Alex Wertheim

How comes your prep for the subject GRE?

Clarinetist

@AlexWertheim - Right now, I'm not really sure what to do with that exam. I'm definitely going to take the General GRE again. My Q score wasn't bad, but not the best either.

Alex Wertheim

@Alexander: is it a story all about how your life got turned upside down?

Clarinetist

00:14

The only reason that I've been switching between YES, I'M GOING TO TAKE IT and I MIGHT NOT is because I don't know if I'm going to have the time right now, and I don't know if I necessarily need it for what I want.

Alexander Gruber

@AlexWertheim Now I'd like to take a minute just sit right there

I'll tell you how I'm going to calibrate some particle detectors using combinatorial optimization.

Alex Wertheim

:)

@Clarinetist: I see, makes sense. Well, whatever you decide, good luck!

Clarinetist

Thanks @AlexWertheim

Modded Bear

@AlexanderGruber that's awesome

Alexander Gruber

So, suppose we've got a machine with a bunch of keys, say 100 of them, call them $\text{k}_i$. Whenever a key is touched, it sends a signal to the machine, saying $\text{k}_i$ was touched at time $t_i$.

We can't personally go in and press any of the keys, but every once in a while, some person will come in and randomly press a bunch of keys and leave. Then we get that data

Modded Bear

00:18

so a person goes in at time $t$ and presses a subset of the keys simultaneously?

or at different times?

Alexander Gruber

@ModdedBear We'll say that every time a person comes in and presses a bunch of keys, that constitutes an "event", and events restart the clock.

Modded Bear

ok, so then the buttons get pressed at different times by the person right?

Alexander Gruber

So if they only pressed one key during an event, it would always register as time $0$

right

Modded Bear

ok

Alexander Gruber

We'll assume that the events are far enough apart that they're distinguishable.

Modded Bear

00:20

k

Alexander Gruber

So, the problem is this, we think that each individual key may have a different activation time. In other words, if somebody came in and all the keys were pressed at once, the times the machine recorded for each key would be their "true zero," $\text{z}_i$. These are assumed to be consistent

But, we don't know what they are

Modded Bear

when you say all the keys where pressed at once you mean by the same person right? not at the same time.

Alexander Gruber

I mean, at the same time.

Modded Bear

oh ok

then the machine would tell you all the keys got pressed at the same time. Or not?

Alexander Gruber

So, I'm saying, if we had an experiment where someone pressed $k_1$ and $k_2$, the $t_1$ and $t_2$ couldn't be trusted, because $z_1$ and $z_2$ may be different. Does that make sense?

@ModdedBear Yeah. It'd record times for all of them.

Modded Bear

00:24

ok

I didn't get that "true zero" part

Samuel Yusim

what happens to t_i if key i gets pressed more than once

not that I have any idea what you guys are talking about

Alexander Gruber

Basically the event timer may start recording times differently for different keys. If $k_1$ and $k_2$ were pressed both at once, maybe we would see $t_1=1$ and $t_2=2$, which is non-desirable.

@SamuelYusim All but the first one would be dropped. Good question (Meaning, only the time of the first press of each key is recorded)

Modded Bear

ok, I think I'm getting it

so if you press six keys at once you'll get times $1,2,3,4,5,6$?

Alexander Gruber

@ModdedBear we'll get $1,2,1+(z_3-z_1),1+(z_4-z_1),1+(z_5-z_1),1+(z_6-z_1)$

whatever those may be

Modded Bear

oh, I got it

each key takes up a certain ammount of time to activate?

So some are slower than others?

Alexander Gruber

00:30

Exactly

And we don't know what the activation times are

All we have is the actual data the machine gives us, and we can't measure the "true" times the keys are hit

So one would think this would be a hopeless problem. We are blind because we can't trust our own eyes

my idea is this

Modded Bear

wait

Alexander Gruber

ok

Modded Bear

ok, sorry

I'm ready

Alexander Gruber

So if we kept looking for events with $k_1$ and $k_2$ in it and we always found data like [event 1: $t_1=2$ , $t_2=3$], [event 2: $t_1=12$ , $t_2=13$], [event 3: $t_1=8$ , $t_2=9$] etc

it'd be pretty obvious that $k_1$ was $1$ second ahead of $k_2$

Modded Bear

wouldn't one event be enough?

Alexander Gruber

00:36

It would if we were 100% sure that they were pressed at the same time.

Modded Bear

oh right

ok

I got it

Alexander Gruber

My idea is this... within a single event, it isn't possible to tell how accurate the timing delay we get is. But, timing delays should be transitive.

$k_1$ should always be $z_2-z_1$ ahead of $k_2$, $k_3$ should always be $z_3-z_2$ ahead of $k_2$, then $k_3$ should always be $z_3-z_1$ ahead of $k_1$. Within a single event, we would measure $t_2-t_1$ and $t_3-t_2$ and $t_3-t_1$ for these values

Don Larynx

How does $(n+1)(n)(n+2)(3n+5) = (n)(n+1)(n-1)(3n+2) + 12n(n+1)^2$ I just don't see it.

Alexander Gruber

But over multiple events, we can measure those values and compare $t_2-t_1+t_3-t_2$ from one event to $t_3-t_1$ in another event.

Modded Bear

makes sense

Alexander Gruber

00:43

the closer those two values are, the more likely it is that it's the real $z_3-z_1$

so i'm trying to figure out if that's really a good way of looking for those $z_j-z_i$'s or not

finding the most consistent set of measurements would amount to finding a minimal spanning tree on a graph with vertex set $\{k_i\}$, with edges weighted by $t_i-t_j$ over all events

@DonLarynx how bout by interpolation?

in $\mathbb{Z}[n]$?

Don Larynx

interpolation? How do I do that? In $\Bbb{Z}[n]$

Alexander Gruber

@DonLarynx both sides are $4^\text{th}$ degree polynomials. If they agree at 5 points, they are the same.

Pedro Tamaroff

@AlexanderGruber Hehe, $\Bbb Z[n]$ looks so weird.

Alexander Gruber

they're both the same at $0$ and $-1$, that's obv

Don Larynx

But if they agree at only 5 points, they don't necessarily agree for six. Wouldn't this make them not the same?

Modded Bear

00:52

@DonLarynx if two polynomials $P$ and $Q$ of degree $n$ agree in $n+1$ points they are the same

becuase the polynomial $P-Q$ of degree $n$ or less would have $n+1$ roots. Thus $P-Q$ is the zero polynomial.

Don Larynx

Wow @Modded I learned that last semester. WTH?

Alexander Gruber

plugging in $n=1$ gives $48=48$, check

then $-2$ gives $0=-2\times -1 \times -3 \times -4 + 12\times -2 \times 4 = 0$

then pick your favorite number for your 5th and you'll be doin good

Ted Shifrin

@Alex!

Alexander Gruber

@TedShifrin Hola

Ted Shifrin

Back still better?

Alexander Gruber

00:58

Yeah! Biked to the gulf this week.

Ted Shifrin

Oh, I'm so glad for you.

Alexander Gruber

@TedShifrin So I just gave in and ordered a dip pen

Ted Shifrin

LOL, I still use my Parker 51 that's 50+ years old. @Pedro and several of my students are fountain pen devotees.

Alexander Gruber

@TedShifrin Yeah, I am too.

Ted Shifrin

Nerds unite :)

Alexander Gruber

01:09

@TedShifrin if you ever get to Cincinnati you should check out Appointments.

Ted Shifrin

OK

r9m

01:54

@Chris'ssis ?? -_-'' wha was dat?=P

Kevin Driscoll

My lab mate uses a fountain pen

I use an electronic pen and a writing tablet. Paper is soooooo 2000 and LATE

Modded Bear

electronic pen and tablet is for noobs lol

r9m

@KevinDriscoll what kind of lab is it ?

Kevin Driscoll

@r9m My lab?

r9m

@KevinDriscoll yes

Kevin Driscoll

02:07

Technically, its in our minds. We're theorists.

So by lab mate I really mean we're in the same group and share an office

r9m

@KevinDriscoll what kind ? :)

Kevin Driscoll

@r9m We do Cold Atom Theory

r9m

@KevinDriscoll that sounds totally cool, although I have no idea what a cold atom is (pardon my ignorance)

Kevin Driscoll

@r9m Usually we consider alkali metal atoms, although with our particular research it doesn't really matter. By cold we mean they are in the micro to nano-kelvin scale

Which means they could be a billion times colder than outer space

r9m

@KevinDriscoll wow!! cool !!!

Julian Rachman

02:17

Hey. I have always had this speculation: when is a mathematician considered a mathematician amongst the mathematics community?

Kevin Driscoll

They're cooled so much because at the scale almost all classical motion is suppressed. The atoms act essentially as ideal quantum mechanical objects

r9m

@KevinDriscoll I see ! I just started reading the wiki page :)

Julian Rachman

Hey. I have always had this speculation: when is a mathematician considered a mathematician amongst the mathematics community? I.e., They can create a website and such.

Don Larynx

That's called a web designer @Julian

Julian Rachman

No. Like can create a website for their work. Like I consider myself an amature and that I cant create a website because it will make me look stupid

Don Larynx

02:24

Make you look stupid amongst whom, @Julian?

Julian Rachman

And I asked another question too: when is a mathematician considered a mathematician amongst the mathematics community?

Don Larynx

When they produce a work, @Julian.

Julian Rachman

Idk. It is just that like the website will look stupid if you dont have any work. but i have written notes and have one expository. but that is it.

i have a blog now, but I have been looking at personal webpages and they are better than a blog to me. But I have only seem ones for people that have published a paper. and that makes me wonder...

@Don

Don Larynx

02:42

You have nothing to prove to anyone but yourself @JulianRachman. Some notes and an expository is better than nothing.

Julian Rachman

That is true. But then I want to display it so should I use a webpage? Or should i wait till i have more or a publication? Because i was told like dont get it unless you have published something

@Don

Don Larynx

Remember owning a website costs money, it's basically e-land. Land costs money. Ask yourself if it will be worth it.

Julian Rachman

I found one that is free and can be programmed from scratch using HTML.

I can send you the link if you would like

But I think I will stick with my blog for now. It was just a hunch.

:)

@Don

Samuel Yusim

03:08

the universal property of tensor products is weird and while kind of cool I can't say I like it yet

whenever I use it I get a bad feeling for some reason

user105491

03:34

@Samuel It becomes more natural once you think of it in terms of category theory

r9m

I am grieved to declare that yesterday I broke the 344 consecutive days visits to M.Se ! :(((((( disaster !!

user105491

basically it then becomes the existence of a map that leads to the commutativity of a triangle

user105491

See en.wikipedia.org/wiki/Universal_property#Formal_definition for example

user105491

@r9m That is a lot more than my personal high!

user105491

:-)

r9m

03:37

@SanathDevalapurkar I wanted to reach 365 somehow ! I couldn't login yesterday :( da** our servers :((

user105491

i feel for you

user105491

are you at a university?

r9m

ya ... the uni with possibly the worst internet service in India :(

user105491

ah, you're in india?

user105491

i used to study there

user105491

03:39

until i moved to the us with my parents

r9m

I see :) ..

@user153330 I hope there was no actual mating involved ! =P rofl

Kevin Driscoll

03:57

I dont know what I would do if our internet went down

Id be very much beside myself

sometimes we have a minor outage in the middle of then night

even after midnight, they already have people working on it

walkar

I know that feeling. When a page takes more than a couple of seconds to load I get a bit nervous. In some places, we've definitely been spoiled by consistent and speedy access to the world at large.

Don Larynx

The probability that you get a particular number on one roll is 1/6 . Roll it 6 times to get a probability of 1.

True or false?

r9m

When I go back home from the uni in the summer/winter vacations .. it's a 28 hr journey by train .. no internet :P most of the time I stare out of the window but after sunset I simply stare at my co-passengers until they freak out! :P

walkar

@DonLarynx False.

r9m

@DanielFischer are the mod duties are affecting the tropical rainforest ?!! :O

nywy .. Time to watch 'we'll never have paris' .. :D bbl

Don Larynx

04:15

@walkar false. How come?

r9m

@robjohn many thanks for the answer at the integral ineq problem :-)

Julian Rachman

Hello!

walkar

04:34

@DonLarynx Presuming each roll is independent, the probability that the number will not be rolled is 5/6, each roll has independent probability so to find the probability of the number not occurring after repeated rolls we multiply the chances together. (5/6)(5/6)...(5/6) six times gives us 15625/46656 chance of not rolling it after six tries. The probability we will see it at least once in six rolls is then 1-15625/46656 = 31031/46656.

@DonLarynx That, of course, assumes the dice is fair.

Don Larynx

05:20

Thanks @walkar

mathguy

05:43

Could someone recommend a book to practice probabilities based interview questions? It doesn't necessarily have to be geared toward interview questions, but I want to know about how to calculate things like expected values and related topics (I don't honestly know what related topics there are in probability). I have a basic knowledge but would like to become comfortable with the topic.

walkar

@DonLarynx No problem! Next time ask it as a question instead of on chat so I can get some rep from it, eh? Hahaha!

mathguy

To clarify on my original post, when I say 'practice probabilities based...' I meant to say 'learn probabilties based...'

Kevin Driscoll

05:58

@mathguy Im not sure anyone here would know. Those kind of questions usually get asked in wallst or consulting type job interviews.

mathguy

@KevinDriscoll Well it was worth a try =/....but yea that is what i was going for

Kevin Driscoll

@mathguy Ya sorry. Most of the people who hang out in chat are academics. I dont know everyones background though so there may be someone.

infinitesimal

►

Sayan Chattopadhyay

06:31

Hi people

I have a question that requires a proof .....can someone give me

The question is ......can every perfect number be expressed as the sum of three positive cubes .......

If someone has the proof or gets the proof send me on my email.....the paradox [email protected]

No space in the emil

Email*

user91500

@ABeautifulMind Hi!

A Beautiful Mind

@user91500 Hello!

user91500

@ABeautifulMind How is my new picture?

A Beautiful Mind

@user91500 It's nice.

Chris's sis

07:59

@r9m That was taken from the picture above my message. ;)

Najib Idrissi

08:14

@user153330 I have no idea who she is... Why?

@user153330 (re this message)

This has got to be the strangest question I've been asked here, by the way

Daniel Fischer

08:40

@r9m Yes, not entirely unexpectedly. But in the last days I've started finding time to look for questions again and even found a couple to answer.

Chris's sis

08:59

@robjohn the answer to that nested radical is not $\sqrt{2}$ (I initially made a typo). Anyway, it's nicely solved!

evinda

10:22

@DanielFischer Good Morning!!!
I am looking at collisions when we have a hash function... We can treat the collision with the method seperate chaining. We symbolize with n the length of the dictionary and with m the size of the hashtable.
In a structure of hashing with chains, of n elements, the median number of elements that are saved in a chain is a=n/m (load factor).
So is n the number of possible values that we can get from the given hash function? Or have I understood it wrong?

Daniel Fischer

10:45

@evinda n is the number of elements in your hash table, and m the number of buckets, as I understand it.

evinda

@DanielFischer So for example if we want to insert the keys 6, 9, 14, 17, 5, 7, 16, 20, 18, 19, 4, 11 in a hash table with 7 positions and we are given the hash function h(k)=k mod 7, then is m equal to 7 and n equal to 12? Or have I understood it wrong?

Daniel Fischer

@evinda That's how I understand it.

evinda

@DanielFischer Nice... Thank you :)

infinitesimal

Is Mathematics More Art Than Science?

John Doe

Hi all

Balarka Sen

11:09

@user153330 LOLOLOL

@TedShifrin Listened to what? I am studying homology right now :P

Huy

11:37

Mathematics Advisory
Proposed Q&A site for people who are on the path to higher mathematics and want advise on certain techniques, future topics, reference requests, and "road maps" to related fields.

Really?

Hi @BalarkaSen. How's your studying going?

A Beautiful Mind

@Huy Isn't that already covered by this site?

Huy

@ABeautifulMind: Exactly my thoughts. I was just quoting it, see JulianRachman's starred message on the RHS.

A Beautiful Mind

@Huy OK, I am definitely not supporting it.

Huy

@ABeautifulMind: +1. How's your day so far?

A Beautiful Mind

@Huy Not good. I am planning for my future now, giving myself a few more years to get well and enter grad school. Also, making sense of what has been happening the last few years.

Huy

11:44

@ABeautifulMind: I'm by no means a psychologist but doesn't thinking about it every day just make it worse?

A Beautiful Mind

@Huy It depends on what kind of things you think about, and how you think about it.

Huy

@ABeautifulMind: Ok. I hope you're making it better, then.

Sayan Chattopadhyay

anyone got the answer to my question

Huy

@ABeautifulMind: Have you seen this? i.imgur.com/SJfTrr5.png

Sayan Chattopadhyay

@ABeautifulMind u got the answer for the question

A Beautiful Mind

11:46

@SayanChattopadhyay No.

Sayan Chattopadhyay

is it tough

A Beautiful Mind

I am not in the mood to look at questions now, sorry.

Also, my knowledge is limited to simple arithmetic.

Sayan Chattopadhyay

So can anyone solve it

so can anyone in this chat solve it

Huy

@SayanChattopadhyay: No, nobody.

Sayan Chattopadhyay

thanks then

Ramanewbie

11:55

hi

Sayan Chattopadhyay

hi

Ramanewbie

what's up ?

Huy

The sky.

Ramanewbie

@Huy lol

Sayan Chattopadhyay

so what do u guys do .......i mean profession?

Huy

12:02

Teacher.

And you?

Sayan Chattopadhyay

Student

Huy

Is that considered a profession?

Sayan Chattopadhyay

nope i was asking yours

which field in mathematics r u a teacher in

Huy

I teach at high school.

Sayan Chattopadhyay

oh......but u will love a topic right

Huy

12:05

@SayanChattopadhyay: I like mathematical physics, but that's a bit too advanced to teach at high school. I currently teach linear algebra at high school.

Sayan Chattopadhyay

oh i love number theory

Ramanewbie

@SayanChattopadhyay I'm at school, too

Sayan Chattopadhyay

which country ramanewbie

Ramanewbie

France, like @hippa

Sayan Chattopadhyay

Oh your name sounded like indian

Ramanewbie

12:10

@SayanChattopadhyay @hippa gave me this account so he choose thye name, in fact he told me it was a joke to make @ted upset...

Sayan Chattopadhyay

@Huy did u get something on the question that i wrote

Huy

@SayanChattopadhyay: I don't really care for number theory, sorry.

Sayan Chattopadhyay

oh ........fail then

i have to now break my head out on this question

Ramanewbie

@SayanChattopadhyay where and what level are you studying ?

Sayan Chattopadhyay

10 grade,India,bangalore

Ramanewbie

12:13

ok

Sayan Chattopadhyay

and you

Ramanewbie

I don't know... in France we don't talk "grades"!

I should ask ted again

Sayan Chattopadhyay

Then what do u talk

For "grades"

Ramanewbie

we say "5th, 4th, 3rd, 2nd, 1st" etc

Sayan Chattopadhyay

so u are

Ramanewbie

12:16

I'm on what we call "second"

Sayan Chattopadhyay

I am 10th then

Ramanewbie

yes.

how old are you ?

Sayan Chattopadhyay

15

Chris's sis

@r9m how is it going?

r9m

@Chris'ssis ya I saw that ... quite alarming =P lol

@Chris'ssis good good not bad .. :)

Chris's sis

12:17

@r9m That was taken from the picture inside. ;)

Ramanewbie

@SayanChattopadhyay I'm 14 then

Chris's sis

@r9m Do you wanna see my last creation?

r9m

@Chris'ssis YES!!!!

Chris's sis

@r9m ^^ I'll include it in my book.

Sayan Chattopadhyay

@r9m did u get anything from the question i posted

r9m

12:18

@Chris'ssis haa!! Sweeeet ! :D

Chris's sis

@r9m Thanks :-)

r9m

@SayanChattopadhyay which one?

Sayan Chattopadhyay

This one I have a question that requires a proof .....can someone give me
The question is ......can every perfect number be expressed as the sum of three positive cubes .......

r9m

@SayanChattopadhyay okay :) lemme see .. thanks

Huy

@r9m: Are you familiar with Lie groups?

Sayan Chattopadhyay

12:20

Thanks a lot coz i want an answer

Ramanewbie

@Chris'ssis are you ok with your book ? is it nearly finished ?

r9m

@Huy not exactly

Sayan Chattopadhyay

Lie groups what r those

Chris's sis

@Ramanewbie I have all I need to it. It's just a matter of time for arranging things and make all looking amazing.

Sayan Chattopadhyay

@Chris'ssis what kind of book

Ramanewbie

12:22

@Chris'ssis You're sending it to @hippa right ?

Chris's sis

@SayanChattopadhyay A collection of amazing integrals, series and limits.

@Ramanewbie I'll give him a copy of my book, yeah.

Sayan Chattopadhyay

Wow feels like its going to be interestig

interesting

Ramanewbie

@Chris'ssis Then I'll be able to read it for free e_e

Chris's sis

@SayanChattopadhyay I have thousands of questions and solutions created by me, so if the readers will love my book there will also be other books, if not, it's OK. I simply want to publish a book because I put much work in this area and I wanna see my results in hand under this form. :-)

Sayan Chattopadhyay

THEn try my question

will you @Chris'ssis

Chris's sis

12:27

@SayanChattopadhyay I don't get your point.

Sayan Chattopadhyay

well i thought of a question and the question is can every perfect number be expressed as the sum of three positive cubes .......

Chris's sis

@SayanChattopadhyay that sounds interesting.

Ramanewbie

@Chris'ssis @SayanChattopadhyay isn't that the great theorem of Fermat ??

Sayan Chattopadhyay

i have checked it for almost 9 perfect numbers

its the cube of every perfect number not perfect number

You should try it @Chris'ssis and also u @Ramanewbie

Ramanewbie

@SayanChattopadhyay @Chris'ssis have you seen my post just above ?

Sayan Chattopadhyay

12:33

Its not the great theorm of fermat

Chris's sis

@Ramanewbie you mean en.wikipedia.org/wiki/Fermat%27s_Last_Theorem ?

Ramanewbie

@Chris'ssis @SayanChattopadhyay yes, my bad, I was mistaking with that..

Sayan Chattopadhyay

Fine not a problem

Chris's sis

@SayanChattopadhyay There are tons of problems I should try, and I'll also try this one, but after finishing the work on my book. There are many things to do, it's a real adventure to publish a book! (especially for someone that has no background in mathematics like me) :-)

Sayan Chattopadhyay

its the cube of a perfect number which can be expressed as the sum of three cubes@Ramanewbie

Ramanewbie

12:35

@SayanChattopadhyay a perfect number is a number for which the root $\in{Z}$ right ?

Sayan Chattopadhyay

it will be good if u try

a perfect number is one whose divisors accept itself add up to the given number

Ramanewbie

oh ok I see

Sayan Chattopadhyay

For example 6=1+2+3 and 1,2,3 are its divisors

r9m

I take that back ... lemme work my chances with google (@Chris'ssis knows how obnoxious a googler I am :P)

2

Ramanewbie

Yes I see, but I'm doing a maths exercice right now, I may think of it a bit later !

Sayan Chattopadhyay

12:38

well r9m i want the proof

that it can be expressed as sum of three cubes

r9m so is what i am saying right

i have googled it already

Chris's sis

@r9m :-))))))))))))))))))))))))))

Sayan Chattopadhyay

@r9m i have tried everything

r9m

okay .. :) I'll take my chances anyway ;)

Ramanewbie

@SayanChattopadhyay what have you tried ?

Sayan Chattopadhyay

so is what i am saying legit or right

googling, going to india's most prestigious institution by bunking my school for this question and much more

so tell me @r9m is what i am saying right

Ramanewbie

12:43

@SayanChattopadhyay but have you searched by yourself ?

Sayan Chattopadhyay

i have searched every book possible

worked for 8 weeks for this question without doing my schools work

now mathoverflow and mathematics stack exchange r my only hope

U got something @r9m

r9m

@SayanChattopadhyay I'll let you know when I find something :)

Sayan Chattopadhyay

where will u let me know

take my email

[email protected]

r9m

@SayanChattopadhyay I'll ping you in chat .. that'll inform you (you'll get a red bubble in your chat tab :) .. )

Sayan Chattopadhyay

Fine and thanks

Balarka Sen

12:51

@Huy Homology looks complicated.

Sayan Chattopadhyay

homology is complicated

Balarka Sen

Objects in singular chain complexes looks huge. I have no idea how Hatcher plans to compute singular homology of very non-simplicial objects.

Sayan Chattopadhyay

Balarka u interested in number theory

Balarka Sen

@SayanChattopadhyay You're familiar with homology?

@SayanChattopadhyay Sure.

Sayan Chattopadhyay

if u r pls help me in this question

Balarka Sen

12:53

What is the question?

Sayan Chattopadhyay

that the cube of every perfect number can be expressed as the sum of three cubes

r9m

@BalarkaSen man you make me feel like I have jelly in place of grey matter =P

Sayan Chattopadhyay

u from wesstbengal

@BalarkaSen even me

Balarka Sen

@SayanChattopadhyay Looks interesting -- I have no idea.

Sayan Chattopadhyay

Pls try doing it

Balarka Sen

12:55

I have to run a program then :P

Sayan Chattopadhyay

program?

Balarka Sen

Yeah, well, I'd search for counterexamples by coding.

Sayan Chattopadhyay

fine and when will u finish with it

well then there is one more question which i found during my research

Balarka Sen

technically, never, as I can't search every cube in the whole world

Ramanewbie

@BalarkaSen what language would you use, Python ?

Balarka Sen

12:57

PARI. Way better than Python in case you're on number theory.

Sayan Chattopadhyay

Are there infinitely many N3 (especially for prime N) that cannot be expressed as a sum of three positive cubes?

Ramanewbie

ok

Sayan Chattopadhyay

because i found that cubes numbers more than 100000 have 94% of having their sum written as cubes

Three cubes

Balarka Sen

@SayanChattopadhyay Probably yes, but I have no proof.

Transcript for

$Mathematics$ Mathematics