Mathematics - 2013-02-23 (page 4 of 5)

Orange Harvester

11:00

@Ethereal to prevent spambots from automatically scanning them possibly as hyperlinks.

Ethereal

@OrangeHarvester oh, I see.

Orange Harvester

Its an arms race, spambots mature, you have to adapt. (Captcha etc etc)

Ethereal

@OrangeHarvester Yes, I see that everywhere.

Now they have moving captchas.

user19161

Did any of you get many spam emails the past week or so?

Orange Harvester

I instead like an intelligent personalized question about the site better. For example, what is the color of the tiger that is displayed in the green colored link above?

@JacobBlack no.

user19161

11:04

I have a feeling that some email addresses have been hijacked.

user19161

Because I got a few spams of a similar nature.

user19161

All were from people I know sending out mass emails, and then they said they did not send them.

user19161

So it must be some address hijacking.

Orange Harvester

Okay. I hope you did not get any from me? Also, be aware of address spoofing.

Ethereal

I think they are from Tumblr.

Orange Harvester

11:06

I am not on Tumblr. Hahahaha!

I prefer my blogs to stay upright.

Ethereal

Yeah, Tumblr is now just for hosting pics/GIFs.

user19161

I see many lies everywhere. When one lie is told, ten more have to be told to cover it.

user19161

Therefore, do not lie. QED.

Orange Harvester

@JacobBlack Are you fairly familiar with literature on math logic?

user19161

@OrangeHarvester You want book recommendations?

Orange Harvester

11:14

@JacobBlack Not just that. A path too. I know squat about the approach I should take. I know very basic set theory and a cursory (not rigorous) knoweldge of ZFC. I do not know how to proceed from there.

Ethereal

@JacobBlack I never lie; I only hide.

user19161

Read Mendelsen's Mathematical Logic.

user19161

Another great choice is Goldrei's Propositional and Predicate Calculus and his Classic Set Theory.

user19161

Look at these three first for all introductory logic/sets.

Orange Harvester

@JacobBlack Okay.

@Ethereal Lying by omission that is.

user19161

11:16

I think it is OK to speak on books even if you have not read them seriously.

Orange Harvester

@JacobBlack Yes.

user19161

As long as you know a fair bit about the topic and have looked at the books for quite a while.

user19161

Therefore, I shall continue to give book recommendations in this chat. QED.

Orange Harvester

QED.

Ethereal

Can somebody other than the OP award a bounty to an answer?

Orange Harvester

11:18

There are too many bad books to leave studying from them to experimentation.

@Ethereal Yes. My only bounty is gotten that way.

Ethereal

@OrangeHarvester How?

I see that "start a bounty" button under the comments of the question.

user19161

@OrangeHarvester Many of the books I like are not the standard recommended ones.

user19161

I recommend them because I have looked at 9000 books for any common topic.

Orange Harvester

@JacobBlack I see.

Ethereal

@JacobBlack Why do you use only the number 9000 for saying "large amount"?

user19161

11:20

And when I look at a book, I look out for various things, like whether it has this or that important theorem or proof.

Orange Harvester

@Ethereal $\infty$ is so commonplace.

user19161

@Ethereal Internet meme.

Ethereal

@JacobBlack Really?! Never heard of it.

user19161

For example, I can tell you that Lee's Riemannian Manifolds has the best treatment of Hopf's Umlaufsatz and Gauss-Bonnet Theorem.

user19161

His Topological Manifolds has the best treatment of classification of 1-manifolds and 2-manifolds.

user19161

11:22

His Smooth Manifolds has the best treatment of Stokes and Frobenius' Theorems.

user19161

So guys, my book recommendations are not bullshit.

Ethereal

Guys, I want to award a bounty on an answer.

Orange Harvester

@Ethereal Yes, that is the correct way. I think there is a time limit before you can start a bounty on the question.

Ethereal

@OrangeHarvester No, answer.

Orange Harvester

@Ethereal Its the same thing.

The bounty is always given to an answerer

math.stackexchange.com/faq#bounty

Ethereal

11:37

thx.

BenjaLim

@Sanchez You don't hang out much here anymore do you

user19161

@BenjaLim How are your classes?

BenjaLim

I think I got a good mark for my algebraic number theory one which just finished @JacobBlack

But everything else has just begun

@JacobBlack And with Fulton I've done like 10 exercises

It's not that hard

user19161

@BenjaLim OK. Milne also has notes on ANT, I am sure you know that.

BenjaLim

@JacobBlack yes.

@JacobBlack But my lecturer advised me not to run too fast

Nimza

12:21

Hi! If $a,b$ are symbols and $G$ is an arbitrary Abelian group, is it possible to say in general to what equal $(aG+bG) / (b-a)G$ ?

:8237566 Jayesh, $a$ and $b$ aren't numbers here :(

Orange Harvester

Ahaa. I had anyway made a mistake there.

@Nimza If they are members of group $G$, then they can be represented as such because of isomorphism with $\mathbb{Z}_m^{+}$ for some $m$.

If not, I am not sure! ;-)

Nimza

@OrangeHarvester $a$ and $b$ are simplexes here, I'm computing homology group)

Orange Harvester

I see.

Nimza

Actually $H_0(\tau^1;G)$

user58512

13:19

hi

peoplepower

hi

user58512

hows it going

peoplepower

Great, are you feeling better?

user58512

yes thanks

user19161

@user58512 Hi!

user58512

13:22

hey

user19161

@robjohn Your comment on that guillermo post shows you did the right thing. Also, the deleted post there gave me yet another shock. =)

user58512

I have got to do lots of work today

user19161

@user58512 Just apply force in the right direction. W=F.d

robjohn

@JacobBlack it looks similar, but the sources are different enough to make me wonder.

user19161

@robjohn I am slightly traumatised seeing all these deleted posts. I think I should stop reading them. =)

skullpatrol

13:25

Traumatised :\

user19161

Yes, some things affect some people more than others.

robjohn

@JacobBlack I was looking at mine today. I have about 5% deleted posts. Mostly, my answers were close to already posted ones. A few I noticed were just wrong :-)

2

skullpatrol

Don't you think you're being a bit overly dramatic?

user19161

@skullpatrol Maybe, but it affects me more for various reasons.

skullpatrol

I respect your reasons pal.

user19161

13:29

No, I don't try to be dramatic, I am just being myself.

user58512

I missed a few days because I was ill so I have to use the weekend to catch up

user19161

Let me just give you an example. If a person has been told many lies by someone who abused him for many years, he is more likely to be affected than others by lies in future from different people.

user19161

If a random stranger told him a lie, he is not so affected compared to if a friend told him a lie.

user19161

Hey @skull do you still do weights these days?

user58512

this is so annoying math.stackexchange.com/questions/307151/…

he wont clarify his question so its unanswerable

user19161

13:36

@user58512 Haha, don't be too annoyed. =)

skullpatrol

@JacobBlack On the internet nobody knows you're a dog.

user58512

I wanted to answer it though

user19161

@skullpatrol You are certainly not a dog to me...

skullpatrol

@JacobBlack What makes you think I lift weights?

user19161

@skullpatrol I think you mentioned it right?

skullpatrol

13:38

@JacobBlack No.

user19161

OK, never mind. I did weights before though.

skullpatrol

@JacobBlack For how long?

user19161

@skullpatrol For a couple of years.

skullpatrol

@JacobBlack Did you gain any weight?

user19161

@skullpatrol A little bit only, but I definitely looked better.

skullpatrol

13:43

@JacobBlack Did you feel better too?

user19161

@skullpatrol Well, I can't compare because there is no sample X and sample Y side by side. =)

skullpatrol

@JacobBlack Compared to before you started.

user19161

@skullpatrol Well, maybe a little.

user19161

@skullpatrol I saw that Robusto comment about you being me!

Orange Harvester

I feel awesome after I exercise.

Before I exercise though, I feel lazy.

skullpatrol

13:46

@JacobBlack Nice detective work Sherlock :-D

user19161

@skullpatrol I know more things than you think! =)

skullpatrol

@JacobBlack I think more things than you know! =)

user19161

@skullpatrol Yes, like ... =)

skullpatrol

@JacobBlack Just a joke.

user58512

group theory web.bentley.edu/empl/c/ncarter/vgt/images/cd-any21-3.png

user19161

13:49

@skullpatrol Well, we all think about ... =)

skullpatrol

@JacobBlack True dat ;-)

@OrangeHarvester I think we all feel lazy before exercise because our body doesn't want to work that hard.

peoplepower

@user58512 Took me forever to realize that mess was abelian. :)

user58512

lol

I only realized from the labelw

user19161

@peoplepower I was only admiring the picture...

user19161

@user58512 You like to use lol like me, lol.

peoplepower

13:56

@JacobBlack What I don't like is that the order 7 element has a more prominent circle than the order 3 element does. We need three dimensions!

user19161

@peoplepower I saw you commented on Chris sister answer.

user19161

She just answered, bumped the post and that gave me a couple more votes.

user19161

I was wondering where the votes came from.

peoplepower

Hah.

Tim

I have some low hang fruits to pick

hah

user19161

14:00

@Tim Haha!

Tim

@JacobBlack Can you pick them?

user19161

@Tim I am taking a break from this site. Too much has happened on this site.

Tim

@JacobBlack Then have a nice break

user19161

@Tim Which areas of math are you interested in?

Tim

@JacobBlack analysis

and others

user19161

14:02

@Tim You prefer real or complex?

user58512

he does stochastic stuff

Tim

I prefer soft not hard, Justin Bieber

I am learning stochastic stuff, not doing

I am a layman

user19161

@Tim Ah, I prefer real but Old John prefers complex!

Tim

both real and complex are hard to me

too overwheim

too detailed

user19161

The epsilons and deltas can get overwhelming.

user58512

14:03

why does a sharp 2-transitive group of size p have a p-cycle?

I have this proof it just says "let x be a p-cycle"

Khromonkey

What do people mean by fishing expedition?

user19161

@Khromonkey Context.

Orange Harvester

@Khromonkey Blind Exploration. Main purpose might be to spend/waste time rather than doing something.

Khromonkey

Sanchez asked marino what he thought about a questionand he said he thiught it was a fishing expedition

Oh

Orange Harvester

That's not to say things cannot come out of it, but they are not obviously visible.

Khromonkey

14:09

Well i have to go see u guys later

Orange Harvester

later

user58512

help :(

Orange Harvester

@user58512 do you really think I am qualified to help you? You are too far ahead of me.

user58512

oh cauchys theorem

if i have an element of order p in a group of order p(p-1) is it a p-cycle?

I was wrong earlier about size p, should be p(p-1)

no it's not, this follows from aspecial lemma

I need to know better about normalizers and centralizers, what should I do?

Orange Harvester

Read a book on algebra?

group actions in specific

user19161

14:22

@OrangeHarvester Haha, you were not pinged!

user58512

given a p-cycle, how many conjugates does it have in S_{p+2}?

I know that the conjugate of (a b c) by pi is (pi(a) pi(b) pi(c))

Orange Harvester

@JacobBlack I was the only one talking then, and khromonkey went off, so I assumed I was.

peoplepower

@user58512 Equivalently, you can ask how many distinct p-cycles can one form with p+2 symbols.

user58512

that's easy!

peoplepower

The conjugacy class of a p-cycle is the set of all p-cycles; I think you will find that easy to show as well.

user58512

14:26

(p+2 choose p)/p

I think I got it wrong

(p+2 choose p)/(2p) makes sense because you choose p from p+2, then you have account that a p-cycle could be written in any p turns round, or its inverse

but that gives (p+1)(p+2)/(2^2 p) and the proof says its (p+2)!/(2p)

this is good youtube.com/watch?v=4r6H9mUgcA8

Orange Harvester

@user58512 YEAH!

@user58512 You play badminton?

user58512

15:17

I want to accept both answers, two people helped me :(

user19161

@user58512 Just upvote both and then choose one. I am sure one is slightly better than the other. =)

user58512

15:29

this is good though I am actually getting through the proof, last time I tried none of it meant anything because I had a cold

@JacobBlack, do you search for some answers in mathematics

user19161

@user58512 Meaning do I want to know some answers very badly?

user58512

yes

user19161

Not really. I am happy to enjoy whatever math I like, no holy grail.

user58512

ok

user19161

There is already so much math that one cannot learn in a lifetime!

user58512

15:39

this is so great, math.stackexchange.com/questions/297443/… many different proofs

user19161

@user58512 math.stackexchange.com/questions/249016/… I gave three here to another question. =)

user58512

those are all good

user19161

Well, you can try to answer these questions too and get some points. =)

user19161

@user58512 I don't get it.

user58512

obama let the meteroite hit russia

Charlie

15:48

@jacob hiiiii

user19161

@Charlie One i will do.

Charlie

@JacobBlack do what?

user19161

@Charlie Is that a joke?

user19161

I am not sure, so I ask.

Charlie

@JacobBlack I'm not understanding...

user19161

15:50

"Will do" is a rather standard expression.

user19161

It means "one i will suffice or be good enough".

Charlie

@JacobBlack ah I just said Hi

user19161

@Charlie Yes, and I was making a little joke. Sorry, I guess I am too deep...

Charlie

@JacobBlack your joke was.so deep that I could not find it

user19161

@Charlie Yes, I told you, not many people in this world get me...

Charlie

15:53

Is @skull around?

@JacobBlack if you try to explain

Skull's comment in the other room is making me laugh until now

user19161

Oh, I won't bother going there, one room is enough.

Eric Gregor

are you guys familiar with matrix calculus?

i'm looking at the first answer here: math.stackexchange.com/questions/20694/…

Charlie

@orange tickles tickles tickles

Eric Gregor

i think he meant product rule rather than chain rule, and i get $d(x^tAx)=d(x^tA)x+x^tAd(x)=Ax+x^tA^t$, which doesn't seem to add up

Orange Harvester

@JacobBlack What is to be done before? Set theory or predicate logic? Or first set theory, then logic, then set theory again?

user58512

16:12

one down!

Charlie

n-1 to go

Orange Harvester

Rita

Charlie

What the...

Orange Harvester

I thought we were writing nonsense, so I wrote the title of the song I was listening. Rita by beatles. :P

Charlie

Facepalm

awllower

16:23

Hello everyone!

user58512

hi

Charlie

Hello!

awllower

I am still wondering if one can find the book class field theory by Artin and Tate online. Maybe some one knows how?

Charlie

@skull

awllower

I am referring to this book.

Charlie

16:41

@awllower you couldn't find it anyhow?

Nimza

Hey guys, who is familiar with basics of homological topology? I'm not agree with one thing in wiki

amWhy

@robjohn I "pinged you", or rather commented below one of your answers. Please let me know if you've any objections!

awllower

@Charlie:
Yes I endeavored to do so without any success...

Charlie

@awllower oh.... Some books are very borinf to find

awllower

Indeed.
As I cannot even find the book on sale on internet, I cannot recommend to my university.
So bad...

Peter Tamaroff

16:53

@Charlie Did you sleep?

Charlie

@PeterTamaroff a little

Peter Tamaroff

@Charlie Good.

Charlie

:)

user58512

ok I have 8 pages of work left to do

user19161

@user58512 To read through you mean?

user58512

16:57

yes

user19161

As long as it is not 8 pages of exercises, phew!

user19161

That might take 9000 years.

Charlie

Hi @jacob

Peter Tamaroff

@amWhy Can you help me with algebra?

robjohn

@amWhy It does look quite similar, but you've just expanded the steps that were collected into a single step. Your answer is better than it used to be, and that is what counts for the site.

Frank Science

17:04

I'm staying up now!

amWhy

17:21

@robjohn Thanks, robjohn. I don't want to step on toes!

user58512

omg I cant be bothered doing all these proofs I just want to eat cake

robjohn

17:41

@user58512 I just had a couple of scones... does that count?

user58512

only to 2

user19161

17:52

@OrangeHarvester Do logic then set theory. Mendelson treats both topics.

user19161

@user58512 I like tiramisu.

user19161

@robjohn After scones come brownies in the ... .

robjohn

@JacobBlack how lovely

user19161

@robjohn Together with some lemonade. =)

Charlie

@JacobBlack oh my god! Don't say it... I want it now!

user19161

17:57

@Charlie You want brownies and lemonade? lol

Charlie

@JacobBlack and tiramisu and everything

Peter Tamaroff

I made a question

Sanchez

18:13

@BenjaLim, I actually feel like you came here less often :P

Tim

hello Sanchez

Hi Jacob! Do you remember you have mentioned some sites for ebooks?

Sanchez

Hi @Tim

Tim

THanks! Sanchez

Sanchez

Are you looking for ebooks?

Tim

Yes. The one I frequented has not been working for a week

probably it has been taken down

the one I was using is gen.lib.ru.ec

I am searching for a book Convergence Structures and Applications to Functional Analysis by R. Beattie, H. P. Butzmann

Sanchez

18:18

that you may want to take a look.

(Remove all the non-alphabets except ., of course)

Tim

and Probability With a View Towards Statistics by J. Hoffman-Jorgensen

Yes, I am now using lib.gen.info. However it doesn't necessary have the same collection as gen.lib.ru.ec. The two books are not found on it.

Thanks

Sanchez

Hm I see. For the books I need this site usually doesn't fail me.

Tim

Yes, most of the time. I agree

Should I delete the link addresses too?

why

too late to delete

I so miss library.nu

When it existed, it was one of the happiest time in my life

When it was gone, it was one of the darkest moments in my life

Sanchez

haha

That's why you should delete links at these public places

Tim

Is someone spying on this chatroom?

anon

18:25

chat pages are indexed by google

the future is unknowable

Sanchez

which increases its (perhaps unwanted) publicity

Tim

Will I be prosecuted for publizing the pirate sites?

user58512

no

Tim

I will keep my identity in secret then.

anon

that feeling when the homework you thought was due yesterday was postponed over the weekend

:freedom:

Bartek

18:27

Hello. I have a simple group theory question: if $xy$ is a conjugate of $yx$ in a group, does it mean that $x$ and $y$ commute?

Sanchez

No

Hint: find an example in the symmetric group.

Orange Harvester

@anon heaven.

Bartek

@Sanchez Thanks!

user58512

@anon, im the opposite.. have to lots of catching up

anon

It's just an hour of deathly boring fundamental form calculations for differential geometry.

Tim

18:29

@anon It is analysis again

@OrangeHarvester: What ebook sites do you use? Does India have some ebooks sites?

anon

I feel like there is only a handful of students on campus that actually prefer doing proofs to calculations.

at least it's analysis applied to something geometric, so there's a visual element to it

:)

Tim

@OrangeHarvester What sites do you use or like?

@OrangeHarvester I didn't know it is so popular.

@anon Can I say topology is part of soft analysis?

Sanchez

@anon, I liked to do proofs more in the past. But somehow I like to do calculations more now.

Orange Harvester

@Tim it is I think.

anon

@Tim What do I look like, a category theorist? (ba dum tss)

user58512

18:33

I just think calculations are proofs

Tim

@anon JB said you are a god?

anon

bananas say things, yes

user58512

@anon, so what are you plans this weekend

Tim

enjoy freedom

anon

ladyfriend's bday party tonight. otherwise, math and nostalgia.

Orange Harvester

18:37

@anon yes, are you free this weekend? If yes, we can go out for coffee.... err.. jacob is gonna kill me now, and user58512 too... okbye :P

user58512

nostalgia?

anon

oh, you know. watching things I used to watch as a kid. for old times sake.

user58512

oh that is nice

anon

a recent question on MSE today just gave me the perfect idea for undergrad research. too bad the deadline for a proposal was like a week ago. >:(

user58512

anon what are you looking for in mathematics?

anon

18:41

math?

it's like asking, "what are you looking for in that fried chicken?" why, I am simply enjoying the chicken.

user58512

ok

anon

of course getting paid for things I would have done anyway is a very nice bonus. having to wait a semester is a lost opportunity though.

pourjour

hi

anon

I sense this is what you were getting at.

Charlie

@pour hi Soufy

pourjour

18:45

@Charlie how are u? :D

Charlie

Good, and you @pour?

pourjour

@Charlie I don't feel good these days I'm depressed

Charlie

@pourjour oh! Why?

pourjour

@Charlie I don't know maybe because of the exams

Charlie

@pourjour hmm :(

pourjour

18:49

:(

while I'm resolving an exercise I get this result $M(z)\in (D)\Longleftrightarrow \alpha \equiv \frac { 3\pi }{ 4 } [2\pi ]$

Charlie

@pourjour drink a cup of tea

pourjour

@Charlie It's in vain

@Charlie maybe I must take some pills of anti-depressing

Charlie

@pourjour noooooo

pourjour

@user58512 can u help to understand this result

@Charlie why

user58512

what is it?

pourjour

18:54

@user58512 $M(z)\in (D)\Longleftrightarrow \alpha \equiv \frac { 3\pi }{ 4 } [2\pi ]$

user58512

what is M D and alpha

Charlie

@pourjour it's dangerous

Arkamis

Good afternoon

Anyone have a moment for a brief question?

Charlie

Good afternoon

Arkamis

I need to find a bound for $\sin(zt)/t$ for $z\in \Bbb C$, $t \in [0,1]$.

pourjour

18:58

@user58512 M is a set of point and $(D) = {M(z)/ arg(f(z)-i) \equiv \frac{\pi}{4} [2\pi]}$

user58512

@Arkamis, that is unbounded for nonzero imaginary z

Arkamis

well, shit

That's what I figured.

user58512

@pourjour, I can't read this

pourjour

$f(z)=\frac{iz}{z-i}$

user58512

whatis M(z)

Arkamis

18:59

ok, so related problem

I need to show that I can exchange the order of integration:

Transcript for

$Mathematics$ Mathematics