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1:15 AM
@Ashwin I made some additions if you're interested ;)
 
 
1 hour later…
2:17 AM
Could someone take a look at my question:
0
Q: Apply Pohling-Hellman to calculate the discrete logarithm

Mary StarI am looking at the following example of calculating the discrete logarithm with Pohli-Hellman. The group is $\mathbb{F}_{29}^{\times}$ and we given $y=10$ and $g=3$. We want to find $0 \leq x \leq 28$ such that $y=g^x \pmod {29}$. I have done the following: The order of the group is $28=2^2 ...

?
 
2:58 AM
@Balarka, after you got offline, I had nothing to do so I skimmed the second groups chapter. There are all sorts of things with SESes in there. I had no idea you could do problems like "classify all groups of order 400 / 1024" with those (and the three Sylows)!
when are you going to tell me about that theorem?
 
3:09 AM
Why don't you just read the chapter, most of that chapter is fairly independent from the rings and module chapter @SohamChowdhury
 
I'll finish most of the exercises in this chapter first, @Paul.
Don't want to shoot myself in the foot.
I just wanted to see "what was coming up".
 
Yes, but you don't need Balarka to tell you what is going on when you can just look for yourself
 
Anonymous
@iluso I think you should now go for MO.
 
@Ashwin Haha, my last edit just kill my brain
 
Anonymous
@iluso I just know one or two theorems in Combinatorics,that's all :p
 
3:14 AM
I'm starting to think it would be better to ask my question with the factorization point of view
@Ashwin I don't know much about it either
 
is a(b)(c)(d) the same as saying a * b * c * d
 
@Dave Yep
 
ah okay thanks :)
 
@PaulPlummer no, he said he'd tell me about a certain theorem.
 
Anonymous
@iluso maybe yes,I do not know xD
 
3:31 AM
is there an online website which can list alternative ways to write a given expression
 
Purely out of curiosity, anyone know where Jasper's been?
 
Jasper the philosopher?
 
Nah, there's some guy on this site with that user name
 
haha
 
Or at least it used to be that username
 
3:53 AM
You could use wolfram, but to be honest @Dave that is a skill that everybody works on :-)
Btw what did you think of the link?
 
4:36 AM
Ha ha All 200 questions done and dusted with
 
200n
Nobody does that many?
 
 
1 hour later…
5:56 AM
@Rememberme of?
 
6:47 AM
@SohamChowdhury yes, you could.
and I'll tell you about the theorem only after you play with short exact sequences more.
You told me last night that $V_4$ and $\Bbb Z_4$ fit into the sequence. How do they? I.e., what are the maps, if they do?
 
HAIL MATHS , hey folks
 
7:11 AM
@BalarkaSen Prove that

$$\sum_{n=1}^{\infty} \frac{H_n^3}{(n+1)^6}=\frac{197}{24}\zeta(9)-\frac{33}{4}\zeta(4)\zeta(5)-\frac{37}{8}\zeta(3)\zeta(6)+\zeta(3)^3+3 \zeta(2)\zeta(7)$$
 
Not in the least interested.
 
@BalarkaSen No worry. You have the possibility to buy my book (and learn).
 
I won't, believe me.
Why would I spend money on something I don't even care about?
3
 
7:31 AM
Hello@Balarka
 
@BalarkaSen u must show the least interest about someone asking u to be
 
@Rememberme hi
 
@Balarka Are you free..... I want the intuition behind subspace topology
 
thats rude + lot of people are just fended off loads of algebra u r talkin about daily .
 
@Agawa001 who told you we talk about algebra?
 
7:34 AM
sorry if I am annoying you@Balarka
 
i just see masses of algebra daily here
 
I wasn't being rude : I have told Chris to not to ping me with her stuff because I don't find anything interesting about them. But she still does it. It's irritating.
@Agawa001 well, what you call algebra is actually called "topology" :P
 
hahaha
 
It's true that I like algebra, but I don't think I have been talking anything other than topology lately.
 
@Balarka Can I get some intuition behind it ... pls
 
7:38 AM
@Remember What kind of intuition do you want? It's a natural way to equip subsets with a topology.
 
it s still abstract algebra
 
No, it's not.
Topology is a branch in it's own.
And what's wrong with algebra? It's a beautiful branch of mathematics.
 
Sorry I got momentarily disconnected...
I want a picture
I am doing it from simmons and simmons doesnt show a diagram for how a topology on a set might look....
 
Draw a set $X$, and a subset $A$. Draw a bunch of open sets inside $X$. Now chuck out everything other than $A$.
The (bits) of the open sets lying in $A$ defines the subspace topology.
 
Okay....
SO we can imply from this right any subspace of a topological space is a topological space
 
7:45 AM
Sure, but note that there are a buckload of other topologies you can give to a subset of a topological space.
 
Yes....
 
It's just that the subspace topology is a natural way to do it.
 
Okay so in mathematical terms ...
Extending the topology to the subspace
@Balarka I also wanted to know....
How do I show that two spaces are not homeomeorphic? @AlexC gave me a question on it and I have gone nowhere in it
 
exercise : prove that the subspace topology on subset of a metric space is equivalent to the topology induced by the metric.
@Remember There is no generic algorithm to do it.
What are the spaces Alex gave you?
 
2 days ago, by Alex Clark
@Rememberme Show that $\Bbb R^2$ and $S^2$ aren't homeomorphic
@Balarka
 
7:50 AM
It's a good question. Are you familiar with compactness?
 
Yes a bit....
Did it from Rudin
 
Is $\Bbb R^2$ compact?
Rudin does sequential compactness, that's not what I want.
Do you know the covering-definition of compactness?
 
Open cover one..?
 
yeah.
 
There exists open covers $A_\alpha_i$ such that the union of these is the set.....
Sorry if it is wrong
I have to check my notes
 
7:53 AM
no, that's not it. learn compactness from somewhere.
anyway, $\Bbb R^2$ is not compact, whereas $S^2$ is (why and why?), and compactness is a homeomorphism invariant.
a better question for you to figure out would be this : show that $\Bbb R$ and $\Bbb R^2$ are not homeomorphic.
 
SO homeomorphic has this huge relation with compactness...
 
that's not huge.
 
A subset K of a metric space X is compact if every open cover of K contains a finite subcover
 
wouldn't you expect "similar looking" spaces to have "similar" properties? that's the whole point of homeomorphisms.
 
Thats the definition of compact I know
 
7:57 AM
@Rememberme If you forgot the definition of compactness, do those from Rudin again. No point in trying to figure out the problem Alex gave you.
Try to solve my problem on $\Bbb R$ and $\Bbb R^2$ instead.
 
Okay using the compactness idea?
 
No, no compactness whatsoever is needed (both are compact, so it's not useful either).
Use connectedness instead.
 
Ahh.. Okay try my best
@SohamChowdhury Well I wanted to check that what I have learned till now do i remember it or not ... So I did 50 questions from algebra,50 questions from calculus , 100 questions from linear algebra
 
That took me two days...
And now back to topology
Hi@skill
 
8:07 AM
Hi pal :-)
Sounds like a great way to build-up your stamina for calculations.
Like a marathon runner.
 
Yes it is especially in linear algebra
 
Do calculations, draw sketches, and take notes.
 
Anonymous
hey huys
 
Hi
@Ashwin if you want to get Huy's attention use the @ :-)
 
Anonymous
damn it was supposed to be guys lol
 
8:13 AM
Okay @Balarka I got it till this much (with your hint)
lets assume a homeomorphism does exist between $\Bbb{R} \to \Bbb{R^2}$So it should preserve connectedness.
Now if i remove a point from $x$ from $\Bbb{R}$ and respectively $f(x)$ from $\Bbb{R^2}$ it should still be connected( which I feel but stilll thinking for its proof) after this I cant get anything.....
Am I going the right way... ?
 
np pal @Ashwin
 
Anonymous
@Huy hows Studien gehen?
 
Huy
Busy, studying some DiffGeo and teaching today.
 
Hello@Ashwin
 
Anonymous
@Rememberme @skillpatrol hello
 
Anonymous
8:15 AM
@Huy You must be teaching high school math,right?
 
Huy
Exactly, integration right now. Today gonna teach some rules like the factor rule and sum rule.
 
Anonymous
You used to tell us how smart your students were :D
 
It so nice to see high school teachers trying to learn diffgeo ... If I go to my math teacher and ask him a doubt in top he will be like"what on earth are you speaking!!"@Huy
 
Anonymous
@Rememberme Huy is a Grad student if you didn't know :D
 
Huy
@Rememberme: If you didn't know, in Switzerland to become a maths teacher you need a MSc in maths.
 
8:19 AM
thats the thing @Huy
 
Huy
Yeah, just finishing my MSc right now asap. :D$
 
Here you need BEd@Huy
and MEd I suppose
 
Huy
@Rememberme: Plus a diploma to teach, which takes 2 additional years after the MSc, I forgot.
 
Why did you remove that @Ashwin...
Are you fearing someone here is your teacher :D
@Huy Does diffgeo involve PDE??
 
Anonymous
@Rememberme haage summane.....
 
8:23 AM
Wha??
 
Anonymous
So,you don't speak Kannada
 
Nope I dont know Kannada
 
Huy
sorry need to go teaching
 
Anonymous
@Huy cya mate
 
Ba Bye@huy
 
8:30 AM
Later pal
 
@Rememberme yes, that's the right way to go about this.
 
@Ashwin Haha, still no answers but an upvote again
 
Anonymous
8:45 AM
@iluso Ask it in MO xD
 
I'll wait 7 days as recommended by some meta post
And I'll have to rework it a bit to merge my edits
 
Anonymous
@iluso cool
 
Anonymous
@iluso do you have any other problems of such type?:D
 
@Ashwin Not really, I'm in CS and usually don't kill myself on maths :p
 
Anonymous
@iluso I am in Mech. Engg. and look at me haha
 
8:50 AM
@Ashwin Haha. Hard to survive surrounded by so much maths
 
@Ashwin i was in math faculty before i do CS too
 
Isn't it sad for Math.SE that "hard" questions have to migrate to MO ? That's killing the level
@Agawa001 My first undergradute year was in math too. But that wasn't half the level needed to answer one question here :p
 
9:28 AM
How can we find $e$ such that $ed \equiv \pmod {143}$ where $d=23$?
 
@MaryStar Isn't there a missing part on the right off your congruence ?
 
I meant $ed \equiv 1 \pmod {143}$ We are looking for the inverse of d modulo n @iluso
 
@iluso in my faculty , u rnt qualified to do CS unless u major in analysis and n.theory + cinematics + algorithmic of course , i did , and i switched to cs by my own will , now i have a strong nostalgy for the precious domain i left back :(
in fact , the real cs (not database craps and officeworks) requires alot of maths , the measure taken in faculty was fair , despite the arguing and refuting of most students
 
Whoa. Don't you mix some of them with CS ?
I'm in France and here you're doing a lot of maths during a CS bachelor's degree. A lot of student choose instead to go in "Higher School Preparatory Classes" where they literally eat maths :p
 
@iluso algorithmic is an initiating part of cs
 
9:39 AM
 
@Agawa001 Agree. But since a lot of students (here in FR) are doing a CS degree only to become programmer, the maths are strongly rejected
 
@iluso u r one of "arguing students" then , no maths are strongly required , see cryptography and AI and graph teory
 
@Agawa001 I'm not ! I won't be here if I was
 
"the maths are strongly rejected" : iluso
 
@Agawa001 By a large majority of the students, but not everyone of them
(sorry if my English wasn't clear enough)
 
9:43 AM
tu peux parler en fr ?
no it was clear
 
@Agawa001 Oui je peux tout à fait ;)
 
bbl
 
@Agawa001 bye
 
9:56 AM
Is the norm $I$ or $\mathfrak{i}$ when denoting the ideal of a Lie algebra?
 
How can we find the inverse of $23$ modulo $143$ ? @DanielFischer Is there an algorithm that we can apply?
 
10:16 AM
So, applying the extended eucliden algorithm we get the following:
$$1=-9 \cdot 143+56 \cdot 23$$
So, $$1 \pmod {143} \equiv 56 \cdot 23 \pmod {143}$$
That means that the inverse of $23$ modulo $143$ is $56$, right?
@iluso
 
hey soham
@MaryStar are u trying to solve any RSA system ;)
 
@Agawa001 Yes!! :-)
 
@Rememberme not an MEd.
@Agawa001 hey.
 
hey soham
lol chris keeps pinging balarka to evaluate some sums/integrals
 
Yes, I think it's right
You can check your answer with http://www.wolframalpha.com/input/?i=PowerMod[23%2C+-1%2C+143]
 
10:30 AM
Ok... Thank you!! :-) @iluso
 
10:43 AM
hey @iwriteonbananas, @Soham
darn, we got another star-war on.
 
11:11 AM
Does anyone has an advice about how I could reword the first two sentences of this question to put them in a more "formal" way ?
http://math.stackexchange.com/q/1315109/108062
 
11:22 AM
hey balarka
 
been doing any math?
 
yep, some probability theory, complex analysis and forms
 
oh cool, so they're finally onto forms?
 
it has been slightly boring
yes, we started yday
 
nice.
 
11:30 AM
what have u been studying?
 
multivariable, but am ill right now.
so not doing much.
 
sigh, that's no good
 
indeed, it isn't :(
hullo, @Alizter
 
Hi @BalarkaSen
 
@iwriteonbananas make sure you learn the proof of excision theorem at some point, though. it's fun.
 
11:41 AM
ok, i will. the barycentric subdivision stuff looks a bit messy though. i never felt very inclined to dive into it
next week we're going to prove the axioms for singular homology in my course, im curious to see how we prove excision there
 
it's raining over here. after days of heatwaves. woo.
 
in any case, im sure it will be the least geometric, and most abstract-nonsense way possible
 
@iwriteonbananas bah, i don't care about the whole rigor of barycentric subdivisions either. it's just a systematic way to break your simplices into smaller simplices.
 
nice
ok fair enough
btw. i feel like i always make some mistake when i apply excision lol
e.g.
say we wanna compute $H_*(D^2, S^1)$ w/ excision ( i know it's easy w/ LES but whatever )
 
as you'll learn later on, proving excision is equivalent to proving that $\{C_\bullet(X)\}$ is chain homotopy equivalent to $\{C_\bullet^{\mathfrak{U}}(X)\}$ where the latter is the chain complex consisting of abelian group generated by simplices sitting inside some open set of a chose open cover. that's where breaking of simplices comes into the play
 
11:45 AM
then $H_*(D^2, S^1) \approx H_*(D^2\setminus p, S^1 \setminus p)$
$S^1\setminus p$ is contractible
 
uh-huh, you'll land into trouble in there :P
 
yeah, i know...
 
it happened to me too. excision is not really helpful for computing things.
unless, of course, you combine it with LES to get the M-V sequence.
 
right
is $(D^2\setminus p, S^1\setminus p) \simeq (S^2, p)$?
 
the drawback of excision is that once you excise something from $(X, Y)$ to get $(X - A, Y - A)$, while the latter maybe an easy pair upto homotopy equivalent, you have to keep track of where $Y - A$ goes after homotoping $X - A$
 
11:48 AM
yeah
i've fallen into that trap many times
 
@iwriteonbananas yeah, i think so. the homotopy equivalence would be wacky :P
yeah, that's it. (D^2 - p, S^1 - p) is indeed (S^2, p).
 
@BalarkaSen $\{C_*(X)\}$ is a chain homotopy? that doesn't parse
 
is chain homotopy equivalent to
 
oh i misread sry :P
 
a chain homotopy equivalent between chains are chain maps $f, g$ going in the opposite direction, such that compositions are chain homotopy equivalent to identity (for both order, with different identities)
 
11:53 AM
right, it's analogous to homotopy equivalence
 
What happened to Jasper?
 
yes. homotopy theory with chain complexes is something interesting. i guess those abstract homotopy theorists generalize these to model categories, kan complexes, etc.
about which i know nothing of.
@Alizter he left, apparently.
 
i see
btw. i suggest you start studying chapter 3 of hatcher's book
since it won't be long until i start
:P
 
haha
ok, maybe i will.
 
hi @robjohn
 
11:56 AM
cup product intrigues me.
 
I think I have an exact formula for the probability question
in case it's of interest
 
i dont have the slightest clue what it is
 
me neither. i just know that it gives cohomology a ring structure.
 
"gives it a ring structure" ?
oh
 
yeah, cup product is something which makes $\bigoplus_i H^i(X; R)$ a graded ring
 
11:59 AM
right
 
@BalarkaSen Commutative graded even
(or is it graded commutative)
 
surely, as every ring is commutative.
:P
interesting, on a serious note.
 
@BalarkaSen Ohh, it is definitely not commutative in general, just the graded version
i.e., it is commutative up to a sign depending on the grading
 
oh, yikes.
i am only familiar with the H-space homological version of this : if $X$ is an $H$-space, then $\bigoplus H_i(X)$ is a graded ring.
 
@BalarkaSen I am not even that comfortable with the cup product, though as I recall it is a bit easier to see how it appears when one considers Hochschild cohomology (which is really just a nice way to get the usual cohomology by choosing a neat complex)
 
12:29 PM
anyone got any ideas how to approach math.stackexchange.com/questions/1321242/… ?
 
^ show some effort within question body before ur post would be closed as (whatever irelevant reason)
 
@Agawa001 oh... the numerical work is not enough?
@Agawa001 ok some more effort added :)
 
@felipa just a proposition , to avoid tragic holding
that would be harder to unhold :D
 
12:44 PM
@Agawa001 thanks. I hope what I have added is enough
 
@TobiasKildetoft interesting. i have heard that differential topologists visualize cup product by the dual intersection product in homology for low dimensions.
 
@BalarkaSen My topological understanding of (co)homology is very limited
 
yeah, I understand that you're not onto topology.
 
nor into :)
 
haha
 
12:54 PM
Is there a link between a number $n$, his number of divisors $\tau(n)$ and his total number of prime factors $\Omega(n)$ ?
 
@iluso Well, $n$ obviously determines the number of divisors and the number of prime divisors
and the number of divisors is easy to describe given the prime factorization of $n$.
 
@TobiasKildetoft Yeah, stupid question... Wrong idea
 
1:20 PM
I hope this isn't too obvious but what is the largest term in the sum $\frac{\sum _{i=0}^{\lfloor n/2 \rfloor} {2(n-2i) \choose n-2i} {n \choose 2i} {4i \choose 2i}}{2^{3n - 1}}$ ?
assuming $n$ is large
is it when i = n/4 for example?
 
1:48 PM
@AlexClark you here?
 
@Alec: No one is here.
Oh, goody. Hi @DanielF
You'll be proud of me, @Daniel: I just answered two (easy) analysis questions :D
 
Hi @Ted.
 
@TedShifrin thanks, I do love it when you try to be funny using stuff that was original waaaay back when you were my age.
 
Good. I suppose you answered them well, @Ted.
 
No, it was not original then, either. It goes back earlier than Winnie the Pooh.
Nah, @DanielF.
hi bananas
 
1:54 PM
@TedShifrin There is no "earlier than Winnie the Pooh".
2
 
hello ted
 
Shakespeare will be annoyed to hear that, Daniel.
 
hmm i shouldnt have come into this chat, i need to do this exercise
bye ted
 
bye, bananas
 
@TedShifrin Shakespeare is dead. Dead and deaf.
 
1:58 PM
Well, Alec has pointed out I'm almost dead. :)
 
@TedShifrin Rumours of your death have been slightly exaggerated.
4
 
Only slightly, yes. So, you doing ok?
 
@TedShifrin More or less. I don't get enough sleep these days, have to get up way too early.
 
I never said you were almost dead. I... I was just trying to hold banter looks away
 
Daniel: I certainly hope this place isn't making you lose sleep.
More or less, Alec.
 
2:03 PM
I honestly thought you fed off of that stuff.
I feel like a bit of a penis now.
 
Does someone think that this answer can be generalized to solve this question ?
 
@TedShifrin Nah, I'm nephew-sitting for a couple of days, and he has to be in school at 8 a.m.
So I have to get up in the middle of the night (6:30) to make breakfast.
Speaking of nephews, I have to pick him up in a couple of minutes. bbl, pml.
 
2:53 PM
Hi chat
 
@Semiclassical Hi
 
Hello @Semiclassical!
 
@felipa good morning (or whatever)
 
3:21 PM
hi @robjohn
@robjohn it looks like the answer is $\frac{\sum _{i=0}^{\lfloor n/2 \rfloor} {2(n-2i) \choose n-2i} {n \choose 2i} {4i \choose 2i}}{2^{3n - 1}} / P\left(\sum_{i=1}^n v_i w_i = 0\right)$
which is quite surprising :)
the numerator is the probability that both inner products are zero
@robjohn is it clear what I am talking about? :)
 
@felipa I know what problem you are talking about
@felipa It definitely does not work out as simply as the other problem
 
heya @robjohn
 
@TedShifrin Hey, Ted... The weather here is cloudy with drizzle... Great summer weather :-)
We had rain here two days ago
 
@robjohn the formula I gave is numerically exact for n up to 300
@robjohn so it seems hard to imagine it is wrong.. I just don't have a proof :(
 
@felipa How do you know it is exact?
 
3:34 PM
@robjohn I wrote some code to work out the probabilities that both inner products are zero exactly for small n
@robjohn it's a fun exercise in dynamic programming it turns out
if you use python I can give you the code to try
 
3:45 PM
hey @Masacroso & @Chris'ssistheartist
 
@Agawa001 Hey
 
have u dismantled that harmonica
 
@robjohn: You (we, soon) need lots more rain. I'll be a Californian again by July 24.
 
:22138812 murderer
 
@Hippalectryon :D
www.youtube.com/watch?v=KuptPgLoFyc
@Hippalectryon ^^^
@Agawa001 Do you refer to some specific series? I killed all I had in terms of series with harmonic numbers. There is no one alive. :-)
 
3:47 PM
@Ted we need rain too :)
What happens is that there's a lot of thunder and everything, a very dusty wind and then barely 15 minutes of rain. And then the next day is horrible, as if to make up for those 15 minutes.
 
Yeah, you guys need it too, @Soham.
 
@Chris'ssistheartist ur latest
 
@Agawa001 It requires much work, but it works elementarily.
 
@TedShifrin global warming , we ll make all rain come to our sahara
 
Well, most of our politicians think global warming is a liberal myth. ...
2
 
3:50 PM
global warming is just a result of people messing alot with mothernature
 
Lots of people and lots of industry, yes.
 
Don't worry, according to a recent study by Marlboro and British Petroleum, the principal cause for oil spills, global warming and lung cancer is maths :3
 
Even a lot of the people who think it legitimately exists fervently deny that we are the cause.
 
u wont touch any changes until u see the disaster made by ur own hand in a very unfortunate time in a very horrible way
thats the human nature
 
Earth is big, therefore it's too big for us to affect. QED.
 
3:54 PM
Well, and you're particularly tiny, right, @Fargle?
 
@Fargle nuclear dust is enough big
 
@TedShifrin I don't know what "particularly" is supposed to mean, haha.
@Agawa001 Microplastic is big enough, too. We're handily screwing over this planet.
 
"The mathematical life of a mathematician is short. Work rarely improves after the age of twenty-five or thirty. If little has been accomplished by then, little will ever be accomplished." Thus wrote Alfred Adler in an article "Mathematics and Creativity" in The New Yorker Magazine (1972) echoing a common belief that mathematicians tend to do their best work before the age of 30, physicists before the age of 40, and biologists before the age of 50 (though there are exceptions!).
2
I totally disagree ...
 
@Chris'ssistheartist I think what really happens is that mathematicians do their best work in the first decade or so of their professional life
@Chris'ssistheartist people who start later, do good work later
 
There are lots of counterexamples to that, @felipa.
 
3:58 PM
@TedShifrin really?
I believe there are some...but lots?
 
@felipa There have been several serious studies that proved that wrong
 
@Hippalectryon well that's intersting.. can you give a url?
 
Let $m, m_1 \in (\mathbb{Z}/n\mathbb{Z})^{\times}$. How can we find $m_2$ such that $m \equiv m_1 m_2 \pmod n$ ?
 

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