Mathematics - 2013-03-08 (page 3 of 4)

Peter Tamaroff

16:00

@robjohn I recall when I was little, I repeated "$e$ a la $i\pi$ mas uno es igual a zero" (i.e. $e$ to the $i\pi$ plus one is equal to zero) but I had no idea what it meant. I probably heard it from my father.

robjohn

@PeterTamaroff when did you finally understand it?

Peter Tamaroff

@robjohn When I learned about complex exponentiation probably.

robjohn

@PeterTamaroff In high school, I remember proving $e^{ix}=\cos(x)+i\sin(x)$ using geometrical properties of complex multiplication. I have reproduced that proof in one of my answers...

@PeterTamaroff There

Peter Tamaroff

@robjohn Let's see...

@robjohn Interesting.

robjohn

@PeterTamaroff It uses $\lim\limits_{x\to0}\frac{\tan(x)}{x}=1$

Peter Tamaroff

16:13

@robjohn So?

user19161

I just answered a lovely question, yay!

robjohn

@PeterTamaroff That is about as much as is needed.

Peter Tamaroff

@JacobBlack Lovely? That is to be determined.

robjohn

@JacobBlack this one?

user19161

@robjohn Yes, some lhf!

user19161

16:14

@PeterTamaroff Not as lovely as you Pedro!

Peter Tamaroff

@JacobBlack Good, good.

But the "number theory" tag is wrong!

user19161

@MathGems, I'm using the EISENSTEIN'S CRITERION & WHAT I'VE USED IS A WELL KNOWN COROLLARY OF EISENSTEIN'S CRITERION — AKASNIL CHAKRABORTY 14 mins ago

user19161

Wow, plenty of caps there!

Peter Tamaroff

@JacobBlack Caps hurt my eyes.

user19161

@PeterTamaroff Even his name is all caps.

user19161

16:23

Hey @kan!

robjohn

@KannappanSampath: you snuck in :-)

@KannappanSampath: how are things today?

user19161

Ooh did our ping of kan bring in kar? =)

robjohn

@JacobBlack probably not, they don't match to 3 characters.

user19161

@robjohn Yeah, but it happened at the same time.

user19161

I think that inequality question will soon become very hot, hehe.

robjohn

16:27

@JacobBlack coincidences do happen :-)

user19161

@robjohn Miracles happen too. =)

Kannappan Sampath

@robjohn Fine!

robjohn

@KannappanSampath Great! I didn't see you come in. I was probably out.

Kannappan Sampath

I just walked outside a bit before going to do some math.

Jayesh Badwaik

@robjohn Have you played the broderbund software's prince game?

Kannappan Sampath

16:30

So, could not reply early.

karsnen

What is linear mapping two vectors?

Kannappan Sampath

@karsnen oops! I am afraid that makes little sense.

user19161

@karsnen A vector is an element in a vector space, and a linear mapping is a function from a vector space to another that preserves addition and scalar multiplication.

karsnen

Sampath -> Hmmm Yeah. Even that what I thought untill someone told me that I had to linear map vectors in order to solve my problem which is here gamedev.stackexchange.com/questions/50543/…

Jacob : Hmmm

Peter Tamaroff

@KannappanSampath Hey.

user19161

16:34

@karsnen Ah you should always provide the context when asking.

Peter Tamaroff

@karsnen Use @[name] to ping users.

Kannappan Sampath

@PeterTamaroff Hi!

Ilya

@robjohn: hi, how are you?

Kannappan Sampath

How are you doing? @Peter || @Ilya Hello! How are you? Long time since we spoke.

robjohn

@JayeshBadwaik I have not. is it any good?

Ilya

16:35

@KannappanSampath yeah, have not seen you for a while. I'm fine, what about you?

robjohn

@Ilya Hey there! doing pretty well. It rained here pretty hard last night.

Peter Tamaroff

@KannappanSampath Good. Starting uni in a week.

Kannappan Sampath

@PeterTamaroff Oh, I seel

karsnen

@[Jacob Black] so if vector A is a child of B and if B moves to an arbitary position - how to transform A so that it could preserve the distance/angle and scale with B. Yeah I should have provided context.

@[Peter tamaroff] Sure will do.

Ilya

@robjohn oh really ;) spring refreshing rains?

Kannappan Sampath

16:36

@Ilya I am doing good!

@karsnen no braces after @, like others and I ping users in our messages.

Jayesh Badwaik

@robjohn It is an old game Prince of Persia is the full name. It was released around 25 years ago. I thought you might have played it some time, since you were involved in programming and all.

robjohn

@Ilya needed desert rains. We've been having drought conditions for several years now. We are glad for any rain we can get.

karsnen

yeah @kann

user19161

@kan So you will reach 20k soon eh?

karsnen

yeah @KannappanSampath - roger that.

Kannappan Sampath

16:37

@JacobBlack Let's see.

Having exams and all that!

robjohn

@JayeshBadwaik Oh, I think I may have gotten Prince of Persia 25 years ago.

user19161

@karsnen Ah, I am too tired to think now, I will let the rest help you.

karsnen

@jacobBlack no problem.

Jayesh Badwaik

@robjohn I see. It was my first PC video game in 1996. I still play it sometimes on dosbox.

This is the actual link to the game I am talking about.

karsnen

@JayeshBadwaik that was really a good game. Were you able to compelte it in 60min?

Jayesh Badwaik

16:40

@karsnen I can complete it in around 40 minutes. My best being 35 minutes. :-)

Kannappan Sampath

Later, folks.

Jayesh Badwaik

later

robjohn

@JayeshBadwaik When I got PoP, I think I was using a MacPlus or MacII. Still using a 28K modem :-)

Peter Tamaroff

@KannappanSampath What are you up to?

robjohn

@KannappanSampath Come back soon!

Dominic Michaelis

16:44

hi

peter you are 19 ?!

robjohn

@DominicMichaelis hello

Jayesh Badwaik

@robjohn Heh, cool. :-) I was using a 56K modem alright when I played that game. But my processor was Pentium I I think. It had that manual turbo/normal mode.

Peter Tamaroff

@DominicMichaelis Aye. I'm closer to 20 though.

robjohn

@JayeshBadwaik Perhaps I am remembering it from a friend's computer since it only seems to have been on the PC back then.

@PeterTamaroff You're about a year younger than my son. He turns 21 in June

Peter Tamaroff

@robjohn July 6$^{th}$, 1993

robjohn

16:53

@PeterTamaroff June 3, 1992

Gustavo Bandeira

@PeterTamaroff You're from 92? I thought you had my age.

Peter Tamaroff

@GustavoBandeira I just wrote it is 93!

Arkamis

Wow

I just read this email subject as "Public Safety prepares Tomato Preparedness Drill"

Jayesh Badwaik

HaHahahahahahhaa

Arkamis

It was "tornado"

Gustavo Bandeira

16:54

@PeterTamaroff Oh, I was counting with the time you were fabricated.

Jayesh Badwaik

@GustavoBandeira just like you? ;-)

Gustavo Bandeira

@JayeshBadwaik Nope. I was always alive on earth.

Peter Tamaroff

@GustavoBandeira LAWL

user19161

Ladies and gentlemen, I have capped for the day, thank you for your support.

user58512

17:52

hi

Arkamis

hi

Charlie

hi

@Arkamis Hi Ed

Arkamis

@charlie Morning :)

Charlie

@Arkamis :) 14h54

Arkamis

?

oh

I always say morning.

temporally-based greeting seem outdated in the electronic world.

Charlie

17:55

Good day seems a good option

@Arkamis how's your rib?

is it broken?

Arkamis

sore, but not as bad

it still is hard to sleep in some positions, and it's brutally painful whenever I sneeze

Charlie

ooooouch

you need a doctor

Arkamis

Nothing they could do

Just gotta let it heal.

Charlie

but you have to see what happened

if it is really healing

or won't hurt you

user58512

@TobiasKildetoft, sorry I missed you

Charlie

18:00

aaawn

Tobias Kildetoft

@user58512 did you see my hint to one of your questions?

user58512

no

oh yes I did!

Arkamis

@Charlie No, but then they'll tell me not to play hockey!

I have at least two more games, hopefully four more.

user58512

I was about to try it but I didn't get around to it yet

Charlie

@Arkamis if you hurt it again it can even cut your internal organs... then you will have problems

@Arkamis really, you must take care of it

Arkamis

18:04

Unlikely, it's not broken off, it's just cracked. Or it could be cartilage. Also, if I puncture a lung, then I'll be forever known as the guy with the booming slapshot that played until he punctured a lung, and no one will ever mess with me.

user19161

I have some unexplainable physical pain too.

user58512

@TobiasKildetoft, I dont really know how to useit

Charlie

@Arkamis okay, you who knows....

Tobias Kildetoft

@user58512 what subgroups of index 2 are there in $S_n$ in general?

user58512

i think A_n is one

Jayesh Badwaik

18:06

@Arkamis after you puncture a lung, I am not sure if it will be possible to mess with you. :P

Tobias Kildetoft

@user58512 right. Are there others?

user58512

I don't know

Tobias Kildetoft

@user58512 note that the commutator subgroup of $S_n$ is $A_n$

user58512

yeah

Tobias Kildetoft

and any subgroup of index 2 will contain the commutator subgroup

(this is true for any group)

user58512

18:07

wow ok

Charlie

@JacobBlack have you seen a physician?

user58512

why?

user19161

@Charlie Yes, they made some guess as to what it is.

Tobias Kildetoft

@user58512 any subgroup of index 2 is normal, and the quotient has order 2 so it is abelian

Charlie

@JacobBlack "guess"..ahh...

user19161

18:09

@Charlie But I think no human really knows for sure.

user58512

I didnt know a subgroup of index 2 was normal

Tobias Kildetoft

@user58512 that is a very standard exercise

Charlie

@JacobBlack if you insist, maybe you will find out

Tobias Kildetoft

(it generalizes nicely to any subgroup of index p, where p is the smallest prime dividing the order of the group, is normal)

user19161

Wow @tobias is an expert in groups!

user58512

18:10

if H is a subgroup of index 2, then H^g is too and meets H so it has to be H or the whole group

Tobias Kildetoft

math.stackexchange.com/questions/164244/… has several different proofs of the generalization

user19161

@tobias Where do you study groups from?

Tobias Kildetoft

most of them uses group actions (including the one by myself, though that is somewhat hidden)

@JacobBlack what do you mean?

user19161

@TobiasKildetoft Like what book do you read?

Tobias Kildetoft

@JacobBlack depends on what I need

for some things, I know I can find them in some notes written by my previous advisor

user58512

18:13

ah

Charlie

@skull Hi!

user58512

aH = H = Ha for a in H

Tobias Kildetoft

for things about actions of groups on other groups, I usually look in the one by Gorenstein

skullpatrol

@Charlie Hi!

Tobias Kildetoft

for p-groups, there is of course Berkovich

user58512

18:13

so aH = Ha for a in G, because there are only two cosets and H already used up half the elements

Charlie

@skullpatrol How are you?

Tobias Kildetoft

for character theory, I tend to look in Isaacs

@user58512 right

user58512

that's really nice

user19161

@TobiasKildetoft Wow, so many sources!

skullpatrol

@Charlie Fine thanks, how are you?

Tobias Kildetoft

18:14

@JacobBlack yeah, I don't really know a good source for introductory stuff

Charlie

@skullpatrol Fine :)

skullpatrol

@Charlie :)

Charlie

I changed my pic again

skullpatrol

Orly?

Charlie

@skullpatrol yarly

user58512

18:17

now G' is the smallest normal subgroup such that G/G' is abelian

so if H has index 2, $H \lhd G$ with $G/H$ abelian so $H$ contains $G'$

Charlie

@skullpatrol this one Skull

Henning Makholm

Argh. Trying to install an upgraded Java, but java.com insists on redirecting me to plain http and an insecure download. Is Oracle deliberately trying to kill this thing?

user19161

@HenningMakholm Not many sites use java these days, at least the ones I visit.

user19161

In fact, I can do without it altogether.

Henning Makholm

@JacobBlack Never mind websites -- our development IDE (Eclipse) runs on top of it.

user19161

18:22

Ah, programmers!

user58512

index 3 seems harder

Charlie

:P

user19161

Oh well, people should just use Python for everything!

Tobias Kildetoft

@user58512 consider the map you get by letting the group act on those conjugates

Charlie

@Skull ?

user58512

18:23

S_6 acting on the conjugates of X_5?

Tobias Kildetoft

and use this to show that $S_6$ does not have any subgroups of index $3$

user19161

I see that Julien has become a coloured square, yay!

Tobias Kildetoft

@user58512 but I need to go now

user19161

The coloured squares are taking over MSE!

user58512

bye ,thanks a lot!

Charlie

18:33

@JacobBlack why not circles?

skullpatrol

...or skulls?

Charlie

@skullpatrol Yes!

skullpatrol

@Charlie I am on patrol for those skulls and when they get here I'll be waitin'

Charlie

@skullpatrol Great!!!

Arkamis

18:51

Jeez, my poor parents

they were expecting 4-6" of snow from this storm.

They got 14.

Charlie

oh my!

Arkamis

in addition to the 30+ they got a couple weeks back

Charlie

things are ugly, then...

Arkamis

Yeah, they're ready for spring.

Charlie

aah

Arkamis

18:53

This snow was heavy and wet, too.

Charlie

ooh

Arkamis

Hopefully my lazy brothers will help them shovel this time around.

skullpatrol

That much snow in March?

Arkamis

@skullpatrol yeah, not unheard of, really.

I've seen snow in mid-may

skullpatrol

Must be pretty far North or South.

Arkamis

18:55

New England

Dominic Michaelis

finally my internet seems to work again

Arkamis

technically, the may snow was in upstate NY

rcnj.org/2002/05/20/0859239.html

user58512

hi @DominicMichaelis

Charlie

@DominicMichaelis good

Dominic Michaelis

19:12

when will people learn that complex analysis is not difficult analysis

Charlie

@DominicMichaelis it's not?

Dominic Michaelis

no complex analysis is analysis in the complex field

user58512

complex analysis is difficult

Dominic Michaelis

but difficult real analysis is not complex analysis

Charlie

it's all math, guys, of course it's difficult :P

user58512

19:14

@DominicMichaelis, do you know group theory?

Dominic Michaelis

@user58512 not good but a bit

user58512

ok

I wonder what I should do

skullpatrol

@DominicMichaelis When people hear "complex" analysis they think of "complicated" analysis.

Dominic Michaelis

what is the problem ?

@user58512 if you are lucky a friend of mine willhelp you

Ethan

19:38

Does any one know what hybridization is required at the central atoms of $O_3, GaH_3$ and $So2$

user58512

math pls ethan

Charlie

@Ethan is it homework?

Ethan

yes

Charlie

really?

Ethan

Yes, is there a chemistry chat room?

skullpatrol

19:41

Yes.

user58512

no

Ethan

is anyone in the chat, and if so can I get a link please

Charlie

@Ethan there's no one there

skullpatrol

The Periodic Table

Haikus are awesome / Chemistry's even better / So pull up a chair

1

The last message was posted 1 day ago.

Charlie

I was so good in chemistry, in school

skullpatrol

19:49

Why didn't you go further?

Theorem

anyone here familier with euler lagrange equation ?

Charlie

@skullpatrol meh, lack of interest

user58512

yes

Theorem

@Charlie hi

@user58512 hi

@user58512 : i am reading some variational calculus , and trying to find when does actually euler lagrange equation give me the extremal .

user58512

I think it always does

Theorem

19:51

if a functional is $C^2$ , is that sufficient ?

user58512

I don't know, I just used it to get answers

Charlie

@Theorem Hi Theo!

Theorem

But there is a problem with the uniqueness , euler lagrange equation doesn't say anything about uniqueness

@user58512

Sgernesto

20:13

hi, i had this idea, it would be cool if there was a directory of webs related to math

Arkamis

proofwiki.org?

Sgernesto

you know anyone?

since some answers to questions here are lists of webs

all of them should be together

a wiki with lists of mathematics websites

Arkamis

Lists of websites are no longer maintained, because about 10 years ago it was realized that the internet is too vast, too dynamic and changes too often, so the maintenance of such a list would be basically impossible.

Sgernesto

what about considering only the websites listed here

skullpatrol

Couldn't that "maintenance" be programmed?

Arkamis

20:19

@skullpatrol Such a tool exists; some call it Google.

skullpatrol

@Arkamis Good point.

Charlie

:P

skullpatrol

Hi @Ethereal

Charlie

@EventHorizon What happens if we get too close to you?

skullpatrol

Will time stop?

Charlie

20:29

@skullpatrol there's no return...

skullpatrol

...kinda like this room...

The Blackhole of Productivity.

Now we have an event horizon.

Great

>8(

...

..

.

Ethereal

@skullpatrol I have heard that joke before... hmm

Arkamis

20:45

Meta.Math.SE I think could be leveraged for a large-scale psychology study.

skullpatrol

@Ethereal Which joke?

Arkamis

There is nothing quite like watching people who, for a living, craft arguments from base principles and carry them out to a logical conclusion argue.

Ethereal

@skullpatrol Blackhole of productivity.

Gustavo Bandeira

0

A: What does the uppercase greek symbol pi mean for sets?

this website is usless if your trying to find out what pi means in greek don't go here bad bad website

Arkamis

lol

skullpatrol

20:53

What $\pi$ means in Greek?

Gustavo Bandeira

@skullpatrol Banana

skullpatrol

Yep.

Henning Makholm

@GustavoBandeira And another one.

Arkamis

Yep

Gustavo Bandeira

Yes.

skullpatrol

20:55

Ya.

Gustavo Bandeira

Yay! They should comment more.

I'll flag and earn reputation.

Put the rep, put the rep, put the rep in ma hand!

Henning Makholm

Um... flagging doesn't earn you rep.

4

The Periodic Table

Transcript for

$Mathematics$ Mathematics