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00:00
okay - i need something
It's late here ...
2-simplices (edges) can be directed by making them into ordered pairs, i.e. you can have two orientations $a\rightarrow b$ or $a\leftarrow b$
and 3-simplices have that whole clockwise/counterclockwise orientation thing going on
@Chris'ssis The asymptotic behavior of the sequence in this question does not happen until $n\ge3.2197\times10^{70683}$. As this comment notes, that number is much larger than the number of atoms in the universe (by a LOT).
@AlexanderGruber ya?
how is orientation defined for n-simplices in general? (i'm only looking for the restriction of the orientation to discrete types of things, no crazy manifold stuff if possible)
00:03
@AlexanderGruber equivalence classes of orderings on vertices
@Mike under what relation?
r9m
r9m
@robjohn is there a trick to get the polynomial $\frac{M}{6}(x-x^3)$ in math.stackexchange.com/questions/353947/… .. ? I tried to apply your way to a similar problem and didn't know how to get the poly
if you can get from one ordering to another via an even permutation, they're equivalent
$[v_1, v_2, v_3, v_4] \sim [v_3, v_4, v_1, v_2] \sim [v_1, v_3, v_4, v_2] \not\sim [v_1, v_3, v_2, v_4]$
okay, so the equivalence classes for orientations of $[ u_0, \ldots , u_n]$ are in bijection with the orbits of $A_{n+1}$ on $\{0,\ldots, n\}$?
yeah
i frankly can't say why we do that, but it's definitely what's done
i guess we only want two orientations and that's the natural way to make it so
00:06
o god, i'm excited, this is gonna be nuts
go on.
@r9m I knew the extreme function would be odd and $0$ at $0,-1,+1$ and so I used $x-x^3$ then scaled to get the max of the third derivative right.
i've got this insane idea about sylow systems
a math god is whispering in my ear, i have to go write things, i'll be back
@AlexanderGruber Godspeed, Alex!
00:22
okay how does that relate to the orientation (n-1)-faces?
for example an oriented 3-simplex [abc] could have boundaries [ab] [bc] [ca], does it always work like that?
in other words, is the boundary map also functorial on oriented simplices?
Hello Alex.
@PedroTamaroff hi
how is it going?
@PedroTamaroff stellar
@AlexanderGruber $[abc]$ is a $2$-simplex;) We have $$\partial [a_0,a_1,\dotsc,a_n] = \sum_{i=0}^n (-1)^i [a_0,\dotsc, \widehat{a_i},\dotsc, a_n],$$ where $\widehat{a_i}$ means that vertex is omitted. Whether that is functorial, maybe I can answer if I know what functorial means here.
00:29
@AlexanderGruber Cool. What are you up to?
@DanielFischer i mean does that map respect orientation?
(there's more in functorial but that's mainly what i'm interested in)
@PedroTamaroff i'm inspired.
@AlexanderGruber The $(-1)^i$ tells you about the orientation (together with the listing order inherited from the parent simplex).
so what you're saying is that $\delta[a,b,c]=[ab]+[cb]+[ca]$?
Funny I just learnt this today.
@AlexanderGruber No, with the induced orientation on the sides/faces, the boundary of $[a,b,c]$ is $[b,c] - [a,c] + [a,b] = [a,b] + [b,c] + [c,a]$.
00:35
@DanielFischer okay, that's what i thought.
how many nonisomorphic directed graphs are there on 5 vertices?
@AlexanderGruber Some like dis?
@PedroTamaroff good, found it using ideas from that
@AlexanderGruber Did you see my link above. It is cute as f***.
The other one.
Not the graphs one.
@PedroTamaroff that's pretty nice!
@AlexanderGruber Yeah. I am taking that combinatorics course.
00:46
@PedroTamaroff if at some point in the future you were inclined to use your combinatorial knowledge to try to count the number of unlabeled graphs on $n$ vertices with 3-colorable, triangle-free complements, that's something i would be quite excited about. :p
@AlexanderGruber hehehe whuts
rereads
unlabeled means?
I get the other part.
@PedroTamaroff up to graph isomorphism, basically. i.e. $\{\{1,2\},\{2,3\}\}$ is the same graph as $\{\{1,3\},\{2,3\}\}$.
Oh, sure.
01:05
@Mike Do you know where local rings get their name from?
@seaturtles
nop
 
1 hour later…
02:28
@AlexanderGruber
02:41
Hi @Pedro
@TedShifrin Hi Ted.
What's the news?
Because local rings are like your local coordinates on a manifold ... localizing at $P$ is working in a coordinate nbhd.
Got tired of grading diff geo homework, so going to bed.
What's news by you?
Anybody here good with proofs by induction?
You might want to look at Eisenbud-Harris sometime to see comm alg by truly geometric alg geo people.
Induction? What's dat? :)
@TedShifrin Pierre Cartier is visiting my university tomorrow! =D
@TedShifrin I read that in Lang later on, yes. Still a bit highfalutin for me.
02:46
Wow, I didn't know he was still alive ....
The unique max ideal corresponds to functions vanishing st $P$, @Pedro.
@TedShifrin If I have some arbitrary local ring, how do I relate that to a manifold...?
You don't. You asked where the name came from. Look at $k[[x,y]]$ or $k[x,y]$ localized at a point of $k^2$, etc.
Yes, that's what I asked.
@PedroTamaroff Do you know what the localization of a ring at (an ideal/a multiplicative system/a whatever) is?
@Mike Yes.
But I don't understand "Because local rings are like your local coordinates on a manifold".
02:54
My latter example is local coordinates at the point.
Howdy @Mike
Hi
You doing ok?
Yah. Tired.
I empathize.
Tomorrow I move more of my stuff... joy, moving.
03:03
Well, in a bit over a year, I have to empty my office and get rid of a lot of my house to sell it and move. Scary.
Are you going to live in a grad dorm for grad school?
Yeah.
They set that up pretty quick after committal... I know my roomie.
Ah, very cool.
First time in my life I'll get a moving truck.
Luckily, LA is close, so it won't cost much.
When I went to grad school, what little I took was in my car ... Drove Boston to Berkeley.
Well, where I'm moving is unfurnished, and I own (some) furniture.
03:10
I'm planning to be in the Bay Area last week of July or so.
Ah, cool.
I leave at the very tail end of July... let's see if we time it right.
Ah ... Define "very tail end." :)
I move in in LA on Aug 1. So I'll be leaving either on the 30th or the 31st.
Ok, I'm planning to be there a week earlier, most likely. Need to start nailing things down and making reversations.
@Mike You will live on campus?
03:22
@PedroTamaroff Yah.
So you don't have to pay rent... just tuition?
"Just tuition".
Heh.
In tuition in perpetuity :)
Wat? The opposite.
I don't have to pay tuition... just rent.
On-campus housing is still housing, they like money.
@PedroTamaroff I got one of my textbooks for next quarter in the mail just now.
Anybody here good with graph theory proofs? :D
I can be, if forced.
03:30
:o
pokes Mike
Is that prompt enough?
..
What's your question?
@DrJonesYu The way you proceed in your inductive proof doesn't work. Not every graph (of your form) can be constructed in that manner.
In general, when you're doing an inductive proof in graph theory, you start with a graph on $k+1$ vertices and somehow reduce it to the case of a graph with $k$ vertices - not the other way around.
I guess I could put that as an answer
04:01
Mike
Do you know what he means by You're assuming the new vertex is not on one of the edges of G.
@DrJonesYu You can get from $C_3$ to $C_4$ by adding a vertex on one of the edges instead of adding a new one in the way you suggested
It's not obvious to me that every graph of your form can be obtained by adding a vertex like you wanted or by subdividing an edge
Well the proof is wrong
I just need to say why its wrong :D
"Not every graph (of your form) can be constructed in that manner."
Thanks
So the error is when they go from a graph of k vertices to k+1
04:43
anyone here who knows partitions of unity?
in what context
I guess none.
@PedroTamaroff This came today
0
Q: Partitions of Unity-Integration on Manifolds

user52932So lets say I have a $k$-manifold $M$ in $\mathbb{R}^n$, and I cover it up with coordinate patches $\{\alpha_i\}$. I can find a set of partitions of unity $\{\phi_1,...\phi_l\}$ on $M$ which is dominated by the coordinate patches (that is each of their supports has to be a subset of a coordinate ...

sorry
was posting the question
it seems to be something obvious that I am missing
04:59
@user52932 I don't understand what the question is. That's a partition of unity subordinate to that open cover, yes.
Do you mean that every partition of unity subordinate to that cover can be given by translating a partition of unity on the original manifold?
@Mike I think I was told that I can find a collection that would constitute as a partition of unity...that is $\phi_1 \dot h^_{-1},...,$\phi_l \dot h^_{-1}$ would be a partition of unity on N
I don't see how that follows immediately
Err, add them up?
These are maps $N \rightarrow M \rightarrow \Bbb R$
The fact that $\{\phi_i\}$ is a partition of unity on $M$ makes that immediate.
yeah you are right...I am dumb
should I delete that question?
if you want
I could write that as an answer
yeah that be great...Ill accept it as the answer
05:06
and no, don't call yourself dumb for that :p
its just that I have been using Analysis on Manifolds by Munkres...and suddenly the chapters have become insanely hard....
all sorts of sets flying here and there
and that's why you shouldn't call yourself dumb for it
so difficult to understand proofs...esp when there is no lecturer
yeah, thanks
the best thing i ever learned was whenever something seemed confusing, to get out a pencil and fiddle with it on paper
like for instance actually check the condition by hand that that sums to 1
a lot of the time when you start writing things become clearer
hello... has anybody heard about an e-infinity theory?
i was just reading an article and the author was talking about discrete space-time (wtf?) and mentioned this E-\infty theory
05:28
@PoliTolstov who was the author?
ji huan-he
in a paper about solitons and compactons
he's a follower of Mohamed El Naschie, who developed the "theory" you're talking about. el naschie is a crank
A,B and C are three commodities. A packet contains 5 pieces of A, 3 of B and 7 of C costs $24.50 . A packet containing 2,1 and 3 of A, B and C respectively costs $17.00 The cost of a packet containing 16, 9 and 23 items of A,B and C respectively is......" and answer is $100
But i can't understand how the answer is derived. it is 3 variables in 2 equations! so isn't the info lacking?
yes @Mike... i was reading on wikipedia about him...
huan-he appears to have done actual mathematics, but i would ignore anything he says about physics.
05:36
really? And i saw he has a lot of publication...
you can get a lot of publications without having any content to them.
it's kind of 'dangerous', isn't it? I mean, there should be more control on what is being published
only some journals care about publishing quality papers. some make money from the authors who just want to get their papers published, or some will publish anything in general
it takes time to learn which journals are of a good quality and which aren't. the journal "Chaos, Solitons, and Fractals" which you probably got that paper out of isn't a good one.
the fact that Elsevier was glad to allow El Naschie to edit this journal that he frequently published in with no supervision is a problem and speaks poorly to Elsevier
(but what doesn't speak poorly to Elsevier?)
hum... i don't know...it's a kind of "selected works"... works.bepress.com
how did you find this paper?
05:45
i was reading another paper i found on arxiv by someone name Paul Bracken ( this does not to seen a 'bad' mathematician )... and at that paper he mentioned the word 'compacton'... and i googled 'compacton' and found ji huan-he between many results
compactons, solitons, that sort of thing are real mathematical objects that are a source of study
it's just that there are a group of people who publish nonsense using those words too.
A,B and C are three commodities. A packet containing 5 pieces of A,3 of B and 7 of C costs $24.50 . A packet containing 2,1 and 3 of A,B and C respectively costs $17.00 The cost of a packet containing 16,9 and 23 items of A,B and C respectively is $100. @Mike, but how tio find it?
hum... i understand
@Mike, the info is 2 equations and 3 unknowns! so how did we get the answer $100?
@Mike, it was very enlightening to discuss with you... thank you very much.
05:59
@PoliTolstov, can you please help me?
no problem @PoliTolstov
@Mike, please help me, too!
 
1 hour later…
07:15
what do we need for $\operatorname{Aut}\left(\bigoplus_{k=0}^{n}P_k\right)\cong \bigoplus_{k=0}^n\operatorname{Aut}P_k$?
is it enough if the $P_k$ are have coprime order?
or do they need to be abelian?
@AlexanderGruber remember this merge you did? :)
@seaturtles i think that's the converse.
@AlexanderGruber the condition on the matrix decomposition of Aut(A x B x C x ...) is that the summation is sufficiently refined, i.e. the summands share no common direct factors. so given that, a necessary and sufficient condition is that none of the factors have nontrivial images in the other factors' centers
in particular this shows that if the $P_k$s have coprime orders then the Auts work out like that
but I don't think that's necessary
07:32
@seaturtles you're right, it's not.
but in any case, i'm working with a nilpotent quotient, so that's all i need.
you have any experience with wget?
I shall take that as a no
A student studying the weather for d days observed that 1. it rained on 7 days, morning or afternoon; 2. when it rained in the afternoon, it was clear in the morning; 3. there were 5 clear afternoons; 4. there were 6 clear mornings, then d=9. How did we get d=9?
@seaturtles
07:50
the only possibilities for morning/afternoon states are C/R or C/C or R/C (where C=clear and R=raining). so the number of occurences of each of these states is x, y and z respectively. now translate all of the information into equations in these variables and solve.
you should get
x+y+z = ?
x+z = ?
y+z = ?
x+y = ?
(fill in the blanks)
add the last three up and compare to the first equation
Sir, x=2, right?
@seaturtles
08:09
where are you getting that from?
Sorry, i m trying.
x+y+z=d
x+z=7
y+z=5
x+y=6
am I doing your homework?
Sorry.
 
2 hours later…
10:09
@seaturtles nope.
@AlexanderGruber Do you know of any programs that make "nicer" powerpoint presentations.
Sure, there's Microsoft powerpoints, but I've seen nicer powerpoints through adobe or something.
11:08
@DanielFischer your comment has been flagged as not constructive.Discussion closed. — Darius 1 min ago
w00t!
11:28
I'm looking for words to google. Fitting a polynomial to a set of points using least squares. The problem is that outliers gets so strong using least squares
11:40
@robjohn I am here with an official complaint. I got one downvote on an old answer on each of the last three days. Could you look into it and find the culprit? I take this as a malicious act.
11:50
I don't mind having a low rep, but this is clearly not normal.
To add to matters, I have not cast a single downvote anywhere on anyone.
This downvoter is clearly a nutcase.
@eXtremiity Powerpoint is the best. You can also use LaTeX if you want, via the package beamer, but I don't think you wanna use LaTeX.
I see. Thanks Jasper.
I like the whole rich pdf powerpoints.
They look a whole lot more professional.
Hi, I am having trouble with a problem in complex analysis. Can anyone pls help?
@Chandan. Just say the question and we'll see if we can help.
0
Q: Prove that an entire function is constant

ChandanIs the following statement true? Suppose, $f:\mathbb C\to \mathbb C $ be an entire function. $ |f(z)| $ is bounded in a region where $ \alpha\le \arg(z)\le \beta $ with $|\beta-\alpha|>\pi $. Then $f(z) $ is constant.

Ahh yes, this alludes to Liouville's Theorem. Here :en.wikipedia.org/wiki/…
In fact, the function has to be entire AND bounded.
And indeed that is the case too.
11:58
No, the function is not bounded everywhere in my problem.
Only in a sector.
I just want to know if the problem is correct.
I have also checked that there are no downvotes on the other answers or questions the past three days, so it is very suspicious.
Unfortunately, I can't seem to help you there.
@JasperLoy Maybe someone is holding a grudge.
Best way to integrate latex into powerpoint?
Suggest screen shots?
@skullpatrol Who could it be? LOL.
12:02
@JasperLoy With the possibility of "sock puppets" it is very hard to find out who.
@skullpatrol One downvote is normal, two raises your suspicion, and three is clearly malice, lol.
@JasperLoy Someone could have multiple sock puppets and wage a personal war.
@skullpatrol That's a really stupid thing to do, because I don't care about my points really.
Stupidity is infinite.
@skullpatrol This person knows that giving 3 downvotes on a day would trigger the system, but not 3 downvotes on 3 different days.
@skullpatrol I have investigated two suspects, it is not them, lol.
12:08
@JasperLoy OK, so they are "streetwise," my point is don't give them what they want by letting them bother you pal.
@JasperLoy Obviously they want to annoy you, that is clearly the intent, so by not caring you will show them that they wasted their time and annoy them.
@JasperLoy. Just ignore it.
You're getting too annoyed by this.
@skullpatrol, what's the formula for return on capital?
@Sawarnik I problem you gave me yesterday, is done. Thank you for the problem.
@eXtremiity here
Sigh. There are many variations to that formula. That is why I am confused.
Some formulas do not consider the book value of debt.
Thanks though !
12:23
np
Just answered a lhf.
13:09
@Hawk How?
@ParthKohli Here?
@Sawarnik no
@ParthKohli Oh, I forgot you are dead.
@ParthKohli So did you try the set problem I gave you without circular reasoning?
Where is the circular reasoning?
Using induction.
Oh, is induction wrong?
13:15
No. But how would you prove the principle of induction?
@Sawarnik do you not know its proof?
You tell how would you do it.
Just got my books today btw.
@Sawarnik I'm proving it for you, not for me.
Ok but this is why I say using induction is circular?
13:18
Then how would you prove the principle of induction?
I don't know the proper proof. Do you?
@ParthKohli Yea just by if you solve that problem I gave!
@Sawarnik There's a difference between not doing it your way and not doing it.
@ParthKohli Yeah, so what is your way??
That is my way.
13:24
@ParthKohli You did not show your way of proving why induction works, without which its circular?
@Sawarnik Google it.
@ParthKohli Give me the link you choose.
@Sawarnik It can be stated as an axiom. en.wikipedia.org/wiki/…
@ParthKohli Yeah, that is what I asking you!
"To derive simple induction from these axioms, we must show that if P(n) is some proposition predicated of n, and if:
P(0) holds and
whenever P(k) is true then P(k+1) is also true
then P(n) holds for all n."

This is the q I askd you, and you proved it with induction which is circular!
Do you not see the proof below that?
13:30
That is the thing I was asking you!
When is the next match?
@Sawarnik no, I proved that S = N through induction.
@ParthKohli Why isnt that circular then?
@Sawarnik look at the proof again.
I have lookeed.
@Sawarnik I expanded all the cos terms and added them and saw a very interesting symmetry with the given conditions, further manipulation yielded $p(\cos^2(x+y+z)+\sin^2(x+y+z))$ or something like that.
13:32
@Hawk Good. You are a genius seriously!
@Sawarnik not at all...but thanks that you appreciate my effort.
@ParthKohli is that meant for me?
@Hawk no.
@ParthKohli Didnt saw it. Wat wasit?
many people in this room today.
@Hawk Here is one more, if you like it: Prove that its an integer:
$$(\frac{9\sqrt{6} - 19}{6\sqrt{6}})^\frac{1}{3} + (\frac{9\sqrt{6} + 19}{6\sqrt{6}})^\frac{1}{3}$$
13:36
@Sawarnik sure those are square roots and not cube roots??
Square roots? Where?
@Sawarnik over $6$
Yeah. I think the question is perfectly fine.
Okay, I'll have to think about this really...not looking very easy
Hey guys, quick question if you have the time. I need to calculate the probability that 15 or more of a random set of 20 integers are a multiple of 5. How would I go about doing that? Bit lost at how to approach it.
13:39
@Sawarnik probably involves $x^3 + y^3 = (x+y)(x^2 - xy + y^2)$
@Sawarnik yes, I was about to say as ParthKohli...i think it uses that.
but need to re-arrange to get the proper formatting
No, might be easy.
@ParthKohli You mean to say the blah is equal to 6?
no
it's equal to
2?
@Sawarnik Sorry, I will need to go now...but will login near 9 pm...hope you will stay.
sorry, that was a little bit of rough work there. :P
13:44
@Hawk Ok bye :)
@ParthKohli Good!
I need 200 more to retire at 3k, lol.
Should be able to get there this year, lol.
14:07
@JasperLoy Why are you forcing yourself to retire?
@Sawarnik Just for fun, lol.
@Sawarnik Usually I say I will retire very often, but never really retire, lol.
I know.
14:25
Greetings
14:54
hi
@eXtremiity you can use beamer, it's like LaTeX + powerpoint.
any probability people care to take a look at math.stackexchange.com/questions/727707/… and tell me if it is clear?
I am worried I haven't explained it well
Thanks.
15:15
@robjohn Are you around now?
15:30
This chat is dead.
v. sad
and all I wanted was a probability expert :)
Hey I'm here
I'm just no robjohn
@MickLH Hi
Hi
Sorry I didn't get your question
Ill look again from my PC when I get out of bed
ok :)
I hope this isn't a permanent problem :)
15:34
I am trying to get robjohn to look at my past three downvotes, lol.
@JasperLoy You mean questions you downvoted?
@user2179021 Nope, downvotes I received, one on each of the past three days, lol.
15:45
@mike So which grad school are you going to?
15:59
@JasperLoy OK

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