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12:00 AM
Yummy :-D
thanx
 
12:14 AM
Congrats. I go to bed.
 
anybody know any good 2nd isomorphism theorem problems?
 
which are you defining to be second?
HN/H=H/(H\cap N)?
 
12:29 AM
@AlexYoucis Good question.
I am trying to determine $\langle \alpha,\beta\rangle$ where $$\alpha=\left(\begin{matrix} 0& 1\\-1&0\end{matrix}\right)$$
$$\beta=\left(\begin{matrix} 0& 1\\-1&-1\end{matrix}\right)$$
Note $\beta^3=\alpha^4=1$
But $\alpha\beta$ has infinite order.
since $$\alpha\beta =\left(\begin{matrix} 1& 1\\0&1\end{matrix}\right)$$ so $(\alpha\beta)^n =\left(\begin{matrix} 1&n\\0&1\end{matrix}\right)$
Also $\alpha,\beta\in {\rm SL}(2,\Bbb Z)$
@AlexanderGruber So?
What do you call the 2nd iso. thm.?
 
@AlexYoucis @PeterTamaroff $2^\text{nd}$ one for me is $HK/K\cong H/(H\cap K)$.
 
@AlexanderGruber You missed an $H$ up there.
 
yeah :P
just realized that
 
@AlexanderGruber I liked how Jacobson used it to prove: Let $G$ be a group, $S$ a $p$-Sylow subgroup. If $H$ is a $p$-group with $H\subset N(S)$ then $H\subseteq S$.
How dangerous can a sugar overdose be?
 
user19161
12:46 AM
@PeterTamaroff A or B is logically equivalent to not A implies B. Just draw a truth table to verify.
 
@JasperLoy What about "xor"?
Or is that the one you mean?
 
user19161
@PeterTamaroff I don't know what xor is.
 
@JasperLoy Exclusive or.
A or B, BUT NOT BOTH.
 
user19161
In math, or is always used in the inclusive sense.
 
user19161
Unless otherwise stated.
 
12:47 AM
@JasperLoy Well, that's why the author wrote either $A$ or $B$.
 
user19161
@PeterTamaroff Either doesn't add anything to the meaning actually, as far as I am concerned.
 
@JasperLoy I didn't know that. I thought it meant exclusive or. =/
Good.
 
user19161
Sure, some layman will say either adds the exclusivity to it, but I don't subscribe to that linguistic theory.
 
user19161
OK I just did 5 edits on my own old posts, let's hope that same guy does not complain again.
 
@JasperLoy OK. The author wrote this:
Let z be an element of a ring for which there exists w≠0 such that zwz=0. Show that z is either a left zero divisor or a right zero divisor."
 
user19161
12:50 AM
I am hoping for this to be my final round of edits, which will take a few days to complete since I have 400 posts to look through...
 
user19161
@PeterTamaroff I interpret that the same way with or without the either, that is, in the inclusive sense.
 
@JasperLoy Yes, now I see.
 
@JasperLoy what are you editing?
 
user19161
@PeterTamaroff If I wanted to be exclusive, I would manually add but not both.
 
Because the proof assuming it means just "or" went swimmingly well.
 
user19161
12:52 AM
@AlexanderGruber Just trying to format my old posts into better shape.
 
What an awesome word "swimmingly" is.
People should know about it.
 
@JasperLoy i found some embarassingly bad ones of my own about a year ago, haha
 
@AlexanderGruber Man, I was looking at some of my old questions.
 
user19161
@AlexanderGruber Exactly, after one hangs around here for a while, one realises that he wants to rewrite things in a better way.
 
I said $\lim\limits_{n\to\infty}$ was an abuse of notation because $\infty \notin \Bbb N$.
I insist on the use of $\lim$ alone.
 
user19161
12:53 AM
Again, note that one can edit at most 5 old posts a day, so with that limit, one should not be afraid of bumping.
 
I don't like $n\to\infty$.
 
@PeterTamaroff i like that.
@PeterTamaroff lim all the way
 
@AlexanderGruber You like that I don't like it, or like what I don't like?
:confus:
 
@PeterTamaroff i like $\lim$ instead of $\lim_{n\to\infty}$
 
@AlexanderGruber Right.
@AlexanderGruber Well, I can accept $\lim\limits_{n\to\infty}$, but $\lim_{n\to\infty}$ is bonfire worthy.
 
12:57 AM
@PeterTamaroff how about stuff like $\frac{1}{n}\rightarrow 0$
 
@AlexanderGruber Hmmm, yeah, it's OK.
@AlexanderGruber Do you have any idea on the subgroup I talked in ${\rm SL}(2,\Bbb Z)$?
About half an our ago.
 
user19161
Why is the -1 times -1 post still being upvoted? Nobody is bumping it!
 
@AlexYoucis You?
 
@PeterTamaroff i'm not sure: what's the question?
 
We have three @Alex in here!
 
1:03 AM
@JasperLoy google it. maybe it got linked from somewhere.
 
@JasperLoy Which one?
 
user19161
@PeterTamaroff The one that got me the gold badge!
 
@AlexanderGruber To determine $\langle \alpha,\beta\rangle$.
 
@PeterTamaroff ah, hm let me think about it
 
user19161
"we are offline"
 
1:04 AM
"Stack Exchange is currently offline, we'll be back shortly!"
Buuu!!!
 
user19161
BOO!!!
 
@AlexanderGruber See above the above.
 
user19161
Luckily we are already logged into chat!
 
$\alpha^2\beta=\beta\alpha^2$
$\alpha^4=1$
$\beta^3=1$
$|\alpha\beta|=\infty$
 
@PeterTamaroff what do you want to know about $\langle \alpha, \beta \rangle$?
 
1:08 AM
@AlexanderGruber What it is.
I want to determine that subgroup.
Entirely.
Describe it, write it down, whatever you like to call it.
=)
 
@PeterTamaroff right: so you want a presentation, or a formula for the elements, something liek that.
 
@AlexanderGruber Right.
Like I did here
Except this time it is infinite.
 
user19161
@AlexanderGruber And I wonder WHERE.
 
user19161
Maybe it came out in the monthly newsletter or sth, haha.
 
user19161
1
Q: Question on Q&A's

ClaytonMy friend gave a fun problem to me that went as follows: A. For how many of these questions is zero the answer? B. For how many of these questions is one the answer? C. For how many of these questions is two the answer? D. For how many of these questions is three the answer? ...

 
user19161
1:20 AM
Guys, this question is BOSS!!!
 
user19161
@PeterTamaroff Goodnight Pedro, I am going to bed.
 
@JasperLoy Byes.
 
1:39 AM
interseting how $b^a=-b$
 
@AlexanderGruber Ah?
 
@AlexanderGruber Tell me interesting group theory things
 
@AlexYoucis HAHAHAHAHA
 
@AlexanderGruber interseting: interesting word ;-)
 
@PeterTamaroff oh i meant $\beta^\alpha=-\beta$ with your matrices
@amWhy i ain't never purported to be able to spell, darlin'. :)
 
1:49 AM
@AlexanderGruber hehehehe...
 
@AlexanderGruber That is $\alpha\beta \alpha^{-1}=-\beta$ yes?
 
@AlexYoucis so if i've got a normal subgroup $X$ of $G$ such that $G/X$ has all sylow subgroups cyclic or generalized quaternion, i believe that $\ell_F(G)$ is bounded by $4$.
 
@AlexanderGruber What is $\ell_F(G$?
 
@PeterTamaroff i think it doesn't matter - should be both
@AlexYoucis the fitting length of $G$.
 
@AlexanderGruber Hmm, interesting. I don't see the connection between cyclic and generalized quaternion. What property do they share that allows you to (hopefully) deduce this?
 
1:51 AM
@AlexYoucis unique elements of order $p$.
 
@AlexanderGruber Ah, hmm. Interesting indeed.
@AlexanderGruber Tell me another! Or let me ask you a question :)
 
@AlexYoucis yes indeed :)
@AlexYoucis did you decide on a school yet?
 
@AlexanderGruber Not officially, but probably Berkeley. You?
 
@AlexYoucis good choice. me, probably florida.
 
@AlexanderGruber University of Florida?
 
1:54 AM
@AlexYoucis yeah, at gainesville
@AlexYoucis it's where john thompson's at among other things
 
@AlexanderGruber Yeah, I knew Thompson was there. Is he still taking students?
 
@AlexYoucis i don't think he can advise, but he's still cranking out papers.
 
@AlexanderGruber Ah, cool cool. So I assume that you are pretty hard-set on doing finite group theory?
 
@AlexYoucis somewhat. i'd like to study it more in grad school anyhow. but who knows, i may find something else i like more.
 
1:58 AM
@AlexanderGruber That's fair enough dude. I wish I knew more finite group theory!
 
@AlexYoucis so you'll be going to school with qiaochu then. did you meet him when visiting?
 
@AlexanderGruber I did not. I mostly hung out with my berkeley friends. We're not really interested in similar things anyway
 
@AlexYoucis how do you have berkeley friends already? did you REU there?
 
@AlexanderGruber No, but I did an REU where a lot of Berkeley students attended
 
ahhh, cool
 
2:01 AM
Tell me where I can learn more interesting group theory
:)
 
you should buy isaacs book :)
it's definitely what taught me most
 
I've looked at it a lot!
Do you mean group theory, or character theory?
 
i meant his finite group theory book
his character theory book is great too, but i do have another i prefer
 
Yeah, I need to read those both more
what are you interested in again--besides finite group tehroy?
 
@AlexYoucis graph theory, cryptography
 
2:05 AM
Ah, interesting! Cool stuff!
 
im trying to get into ring theory lately too but i don't know too much about it yet
(noncommutative i mean)
 
Graph theory is something I also knew I wish more about
That's something I've actually read a bit about
both of TY Lam's books
 
i just started on lam's
 
both Lam and Bergman are at Berkeley
 
i'm diggin his writing
 
2:07 AM
which is interesting
 
wow, yeah. i'm definitely jealous. berkeley wouldn't even have looked at my app twice i'm sure.
 
@alex Though I don't know much about it, I'm interedted in whatever connection there is between Special Functions and Lie Theory.
 
@PeterTamaroff There is definitely connections! For sure. It isn't the most common interaction though
 
@PeterTamaroff that is cool. i think lie theory is awesome too, i want to study it more. we don't have any classes at my uni on lie theory atm
 
@AlexanderGruber Don't be too jealous. You have Thompson!
 
2:08 AM
@AlexYoucis Have you heard of Truesdell's Essay?
 
@PeterTamaroff I have not.
 
@AlexYoucis this is true :)
also warm weather, i'll tell you that made a huge difference in my decision
(not that berkeley doesn't of course)
i feel like lack of winter is going to double my productivity
 
@AlexanderGruber I feel like it will halve mine!
 
@AlexYoucis oh yeah? winter person?
 
Definitely. Snow is so...mathy.
 
2:11 AM
@AlexYoucis i suppose there is a certain sense in which constant sun and beaches will lower my work output.
 
Haha, yeah man. Florida should be awesome!
@AlexanderGruber Any interest in geometry?
 
@AlexYoucis i really don't know enough yet to say. algebraic geometry is a big thing though, it's on my list of things to look into.
and a lot of people with similar interests to mine seem to enjoy it
 
Haha, that's respectable
sure, sure
 
so what are your primary interests at this point?
 
@AlexYoucis It is called "An Essay Towards a Unified Theory of Special Functions."
 
2:15 AM
@AlexanderGruber I'm interested in a bunch of things. I'm doing like seven mathematical things this term haha
@PeterTamaroff Link me?
 
It is based a the functional equation $$\frac{\partial}{\partial z}
F(z,\alpha)=F(z,\alpha+1)$$
 
Where $F$ is...
 
@AlexYoucis Well, many different functions!
@AlexYoucis I can give you the full thing.
 
sure, send it on over
 
@AlexYoucis are you purely algebra at this point? i seen some complex analysis on your blog sometime ago
 
2:18 AM
@AlexYoucis Here
 
@AlexanderGruber I'm pretty off of pure algebra. Number theory, algebraic geometry, complex geometry, algebraic groups, etc. are more my current interests
@PeterTamaroff ohgodtypewriterfont
 
@AlexYoucis It is awesome!
Awesome typewriter font!
I bow to the guys who wrote with that before.
 
@PeterTamaroff ohgodwy
 
@AlexYoucis HAHAHA
@AlexYoucis I want to read that some day.
And understand it.
And work on it.
 
@PeterTamaroff I can respect that, but I would rather not.
 
2:22 AM
After paying some poor soul to TeX it up.
@AlexYoucis Do you think it is too old, expired in some sense?
 
@PeterTamaroff I don't really know what it is, and I am nowhere even close to knowledgable about a field (I used to be into special functions and read parts of the book by Askey) so I can't say
 
@AlexYoucis Aha. What did you do again?
 
hmm?
 
@AlexYoucis I mean, what is your research area?
IIRC, you're "mathematically" older than I am.
 
I don't know yet. Probably something approximating arithmetic geometry
 
2:28 AM
@AlexYoucis What is that?
 
@PeterTamaroff Algebraic geometry minded towards arithmetic (number theory) problems
 
Like the guy who proved FLT? Wiles?
 
Yeah, that had an arithmetic geometry flair to it
not that I understand his paper haha
 
@AlexYoucis Hahhaha, right.,
 
hey here's something i was wondering about earlier today
what area of math is fractal geometry a part of?
is it its own thing?
 
2:32 AM
I miss caveman :-(
 
does anyone here know about L functions?
 
@AlexanderGruber I believe so. I don't know how many people actually study it. The very few I have encountered were very, very analytic. Fractal people are very proud of some fact in fractal geometry which is equivalent to the GRH
 
@AlexYoucis that explains why i've never seen it.
 
@AlexanderGruber Yeaaaaaaaah
 
Is there a proof of the non vanishing of $L(1,\chi)$ that doesn't use complex analysis?
 
2:34 AM
@Ethan Kind of. There is one that minmizes the use of complex analysis, but it has a fairly advanced flavor
 
Hi @Argon wazzup?
 
@κρανίοπεριπολία Not much! And how are you?
 
@AlexYoucis how 'advanced' could you give me an idea of what tools are used?
 
@Argon Fine thanks.
Yo @JasperLoy
 
user19161
@κρανίοπεριπολία Hey hey.
 
2:36 AM
@JasperLoy Hey hey hey
 
user19161
@Argon Fun fun fun fun.
 
user19161
Indeed.
 
@JasperLoy Almost (sorta) Friday here too!
 
@Ethan It involves a bit of algebraic number theory--see here mathoverflow.net/questions/25794/…
 
user19161
2:37 AM
@Argon Is it a big occasion for you?
 
@JasperLoy Well, it is Rebecca Black day.
 
user19161
@Argon I mean for the Jewish people.
 
It happens around 52 times per annum
@JasperLoy Not particularly. It is part of an 8-day (7-day in Israel) holiday though, that began Monday night.
 
user19161
@Argon Ah, then it is HUGE, lol.
 
2:39 AM
:)
 
user19161
Perhaps a miracle will happen in my life this Good Friday...
 
@κρανίοπεριπολία Hahahahahah :)
 
I refuse to use ${\Bbb Z}_n$ for the cyclic group of order $n$, especially if $n$ is prime.
 
user19161
2:41 AM
@anon So what do you use?
 
@anon do you $C_n$?
 
whats $Z_n$
 
@Ethan ${\bf Z}_n$ is the cyclic group of order $n$.
Don't you know about groups? You're talking about Dirichlet characters and stuff...
 
I don't know about groups
 
user19161
A group of people is any set of two or more people, lol.
 
2:49 AM
@Ethan Then how did you get to characters?
 
user19161
@PeterTamaroff They were cartoon characters, lol.
 
@JasperLoy Totally unfunny!
 
user19161
@PeterTamaroff Yes, that is why it is so funny.
 
@JasperLoy I got no upvotes yet =/
 
user19161
@PeterTamaroff I have some coins to spare the beggar...
 
3:02 AM
@JasperLoy Well, I think it is worthy of coin.
 
i did not think this guy was gonna stick around
 
user19161
@PeterTamaroff Anyway, I changed my mind. I think I will retire from MSE, lol.
 
@JasperLoy the pension's not very good man
 
@JasperLoy Yeah, right.
"The kid who cried "wolf!"."
@AlexanderGruber What do you think of my answer, Alex?
 
@AlexanderGruber yes
@PeterTamaroff linked to the wrong one, but fine
 
user19161
3:07 AM
@PeterTamaroff Hehe, still begging for coins!
 
@anon Yeah, I just noticed.
@AlexanderGruber LAWL. The guy said $\Bbb Z_9^\times$ was't a group. I'm curious about what he was thinking.
 
I've never seen this question math.stackexchange.com/questions/176760/… no I didn't downvote your answers
@JasperLoy, you are extremely rude and cruel
 
@caveman Hey, you're back!
 
@PeterTamaroff it appears correct. :)
 
@Ethan
If you want a proof of the non vanishing of $L(1,\chi)$, you can consult Apostol's "Introduction to Analytic Number Theory", Chapter 6.
 
3:15 AM
@PeterTamaroff I don't have the book
 
@Ethan Give me a sec...
 
@PeterTamaroff he once got into an argument with me over whether a question was stupid or not (which was "what graph is the petersen graph isomorphic to")
 
itself
 
and ended it with "Alex you should go to bed you looks like sleepy"
 
@Ethan Here
I'd recommend you go through all the Chapter
 
3:16 AM
@PeterTamaroff can you get me more books?
 
down the rabbit hole
 
It starts out from scratch defining what a group is, and works nicely.
@Ethan Hey! Finish that one up first!
 
its not loading ffs
 
@Ethan Sure?
 
nvm I think its working now
 
3:19 AM
@Ethan I do recommend also that you look at previous chapters, since he uses some analytic derivations (some integral formulas and asymptotic) stuff from them too.
@anon What is your notation for the matrix ring of a ring $R$?
 
For a matrix ring I use $M_n(R)$.
You want to be pretty careful with how you define it if $R$ is noncommutative.
 
@anon What needs care?
$(M\cdot M)_{ij}=\sum_{k=1}^n M_{ik}N_{kj}$, yes?
 
Fun fact: for polynomials over a noncommutative ring, f(x)=g(x)h(x) as polynomials does not mean f(a)=g(a)h(a) for a given a in R (i.e. evaluation is no longer a ring homomorphism R[x]->R)
 
@anon LOL.
 
$(M\cdot N)_{ij}$, yes. you can't interchange the M, N terms around.
 
3:34 AM
Do you know what I have used, so much, over the last year and half of my mathing, something that seems so pivotal to every area of mathematics (that I am interested in?)
Ooops, haha, sorry guys, I thought this was Gchat
apologies
 
"Babe caught me sleepin"...
 
hahahahaha
yeah, you think so?
 
heh heh
 
I can be passive agressive, but tha'd be a whole new level
haha
that was a very appropriate reference though
 
@anon What is the problem?
 
3:51 AM
@Argon Hello! Haven't seen you for awhile!
 
Hi @amWhy nice to see you.
 
@κρανίοπεριπολία Hello! Back to the keyboard!
 
4:08 AM
@κρανίοπεριπολία Yes, indeed!
 
4:25 AM
@amWhy I get the impression of a central moment of clearly seeing the question.
 
4:37 AM
@anon
Let $R$ be commutative. Then $AB=1$ implies $BA=1$ in $M_n(R)$.
 
4:50 AM
@anon I'm trying to see who to work that up above.
I have that $$\sum_{k=1}^n a_{ik}b_{kj}=\delta_{ij}$$ and want to show $$\sum_{k=1}^n a_{ki}b_{jk}=\delta_{ij}$$
 
5:03 AM
@AlexanderGruber
I have a silly question
 
Why cannot we define determinants in non commutative rings?
Where $$\det A=\sum_{\sigma\in S_n}{\rm sgn}\sigma \prod_{k=1}^n a_{k,\sigma(k)}$$
 
i don't see why you couldn't
it may just be that it isn't as useful as it is in the commutative setting
 
Maybe.
"It is easy to convince ourselves that the main formulas on determinants, which can be found in any text on linear algebra, are valid for determinants of matrices over any commutative ring. Thus if $R$ is commutative we can define for $A = (a_{ij})$ the ..."
 
actually for example, i have used determinants in group rings.
i think that just says that so long as a ring is commutative, the determinant info will work as well as it did in $\mathbb{R}$ or $\mathbb{C}$ in linear algebra class
 
5:07 AM
@AlexanderGruber Did you see what I asked above?
@AlexanderGruber Yep.
30 mins ago, by Peter Tamaroff
Let $R$ be commutative. Then $AB=1$ implies $BA=1$ in $M_n(R)$.
 
hm
good question
 
@AlexanderGruber Maybe I should ask on main?
I wanna try myself though.
However, I doesn't seem that easy.
I have an idea.
Suppose $AB=1$. This means $BABA=BA$, so $BA(BA-1)=0$, or $A(BA-1)=0$.
(upon left $A$ multiplication)
@AlexanderGruber Since $R$ is commutative $\det(AB)=\det A\det B=\det B\det A=\det(BA)=1$
 
5:34 AM
Hi there?
Where can I go to learn about the implicit function theorem?
 
@JonnyQuiznos: www.youtube.com/watch?v=xtgTckGMuWE,
 
5:54 AM
@PeterTamaroff You clearly know that doesn't imply that BA is the identity though right?
 
@Eugene Gods, yes.
@Eugene Think you can help?
 
let me think on it
oh
do this straight
might work
i dunno though
did you try that?
 
Does anyone know of the implicit function theorem?
I have a quick question
 
@Eugene Ah?
@Eugene Do what?
 
I have a function x^3+3xy^2+2y^3 = 1. and I need to find where it may not be possible to solve for y as a smooth function of x in
some neighborhood of the point?
 

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