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17:04
Does anyone know: Is there a limit on how much reputation one can gain in a day?
There was a discussion on Math.SE meta once
@Thomas 200 from upvotes, accepted answers and bounties do not have any limits I guess. It is fully documented somewhere onthe site.
you might want to look there
but it is unbounded by the number of bounties
Ok, so what happens to the points? So they just never get awarded?
yeah
you just lose them
17:06
Thats not cool ...
well
How many hours left of today?
nobody gets 200 upvotes in 1 day
17:06
I just hit 245 points for today on accepted and upvotes
woah
And I have missed out on 3 upvotes since then
I would love to get 14 upvotes for a simple answer about quantors
wtf
I really do not understand Math.SEs vote distribution
Yes, I don't get why there is a limit.
probably just proportional to the users' current rep
17:09
@CBenni generally, short answer that most people can understand, to questions most people can understand, get the most upvotes
Oh well there probably is some reason
Yes, sometimes you see these long answers that actually never around to answering the specific question that the OP has.
Well the reason is that people who create fake accounts and spambots do not modify their rep to infinity
because at some point you get really massive priviledges
@Thomas no matter how active you are and how many questions you answer and ask, it would not be desirable for people to gain various moderator privileges until they have been using the site for an extended amount of time
17:10
just imagine a 20k spambot
or someone who deletes thousands of posts
@TobiasKildetoft: Yes, I understand completely. But why not just put a timelimit on each level up?
The answers I have gotten the most rep from are generally the simplest ones
4
@Thomas no idea
usually I am too slow on answering because I try to write the answer as detailed as possible
Oh well. It is all good. It had just never happened to me before.
@CBenni don't let that stop you from answering
17:12
@Thomas The factors combine, the desire to not have spambots + desire for extended time periods etc. If you can achieve stuff with as general rules as possible, then it is probably better. Actually, I am in support of weighted rep, for the first ten votes, you should get 10 points each, then for next 10 votes, 9 rep points and so on.
and then some 10k rep user comes by, writes some 2 line stuff, and gets 22 upvotes and accept
@CBenni this is why I tend to mostly answer question I know not a lot of other people will be able to answer, even though it usually means at most a few upvotes if any
@CBenni: I am definitely not fast. Sometimes I do get upvotes from simply answering the question as short and sweet as possible. Other times I notice a lot of short answers with little explanation and hten it makes sense to add a longer answer
well I am only a maths student, Idhafc about most of what is written on this page ;)
well, actually I dont really care about votes+rep
as soon as I reach 1k I am happy ;)
Yeah, you can't/shouldn't get too focused on the points :)
17:14
I really wouldnt care if it werent for the privileges
but at 1k you want 2k, then you want 5k then you ....
lol :D Well no, I wouldnt start moderating the crap out of this page
however, I like the established user thing
Oh well I will go again.
@Thomas at 2k you want 3k, as that is where you get to start voting to close/reopen
17:21
Hello, can anyone help me with a chinese remainder theorem question?
@user2175923 probably
I have X-k mod a = 0 and X+k mod b = 0 and I know a, k, and b. I wish to solve for X such that (X-k) and (X+k) are both positive
I've been at this for a very long time now and have had extraordinary difficulty getting a direct answer
@user2175923 well, given any solution $X$, you can add any multiple of $ab$ and get a new solution
so add a large enough multiple to make it positive
okay, but how to solve for X to begin with?
by using the chinese remainder theorem (I assume that $a$ and $b$ are coprime since you mentioned it)
17:30
they may not necessarily be coprime but it can be assumed there is a solution
i know how to solve it when they're coprime
@user2175923 then start with something that solves the first one and keep adding multiples of a until you get something that solves the second one
i believe my case is the same as finding the CRT of k and -k modulo a and b correct?
if you start with something positive, you will then end up with something positive
CRT?
chinese remainder theorem
X = k mod a and X = -k mod b
CRT is not something you find
user19161
17:32
@Karl'sstudents That is a nice version sung by the composer himself it seems.
I meant finding X via CRT
but still those systems are equivalent yes?
okay, so given that system, I am after a systematic way to solve for X
i know i can always eyeball it etc but I am writing a program
Hi @Charlie @Karl'sstudents @JasperLoy
@user2175923 what is your systematic way when the numbers are coprime?
17:34
The Chinese Remainder Theorem is a result about congruences in number theory and its generalizations in abstract algebra. It was first published in the 3rd to 5th centuries by Chinese mathematician Sun Tzu. In its basic form, the Chinese remainder theorem will determine a number n that when divided by some given divisors leaves given remainders. For example, what is the lowest number n that when divided by 3 leaves a remainder of 2, when divided by 5 leaves a remainder of 3, and when divided by 7 leaves a remainder of 2? A common introductory example is a woman who tells a policeman that...
see: case of two equations
user19161
@κρανίοπεριπολία Hey hey.
@user2175923 hmm, I guess one could try to generalize that based on the assumption that some solution exists
user19161
The Bridge on River Kwai is up.
but it is probably about as fast to just add multiples of $a$ to a solution to the first until you get a solution to the second
17:37
@JasperLoy Did you watch it?
user19161
@κρανίοπεριπολία Only the video you linked to.
So I would just solve for (k*b*inverse(b,a) + (-k)*a*inverse(a,b)) % (a*b)
but I can't do that if a and b are not coprime
how would I modify this?
@user2175923 not sure, apart from doing it the long way I said
what is the "long way"?
the way I just described
17:40
you said "then start with something that solves the first one and keep adding multiples of a until you get something that solves the second one"
i don't understand what you mean by this
@user2175923 you know how to find a solution to the first one?
X = k modulo b? it seems like I could just set X = b+k, and then you are saying "keep adding b to X until it satisfies the secocnd congruence" right?
@user2175923 well, until it satisfies the first congruence then, but yes
also, starting with $X = k$ seems more practical
17:57
hi @Chris'ssisterandpals
18:42
still trying to figure out this problem, can anyone assist?
Hey does anyone here know Discrete?
I'm trying to see if I'm getting this answer right
anyone here?
@user2175923, wha is the problem
@jtm22, what isthe problem
1
Q: Using Chinese Remainder Theorem for two equations with non-coprime moduli

user2175923I have \begin{align} x & \equiv a\mod m \\ x & \equiv b \mod n \end{align} Normally I would solve for $x$ by doing $(an\cdot \operatorname{inverse}(n,m) + bm\cdot \operatorname{inverse}(m,n)) \bmod mn$ but I am not sure how to modify this for when $m$ and $n$ are not coprime. Assume a s...

@user2175923 it is answered
I can't get anyone to explain this thing in a simple, easily understood way that I can actually use
It's not answered in a way I can use
18:47
@user2175923, oh right, you want to know about CRT when not coprime.
It's totally different notation with a bunch of extraneous detail that's only confusing me
How many ways are there to distribute 5 balls into 3 boxes if the balls are labeled but the boxes are not? Would this just be 1 way?
@user2175923, do you know how to derive the usual CRT?
Aaaghhhh!!!
@jtm22, i've got no idea you could probably just find that on google though
18:49
I can't
@jtm22, since the boxes aren't labelled I'd label them A,B,C and make sure A>=B>=C
try both of those combinatorics and see if one fits (k-1 choose n-1) or (n+k-1 choose k) or (n + k - 1 choose n - 1)
but I'm being told it's either 1 or not
I'm confused.
ignore what you are being told
just solve the problem to your own satisfaction
18:51
My satisfication is being right and that's what Im' trying to make sure of
do you think 1 is the answer?
@caveman I am just trying to write a program that will return the right value given the two values and their moduli, which may or may not be coprime, and assumes a solution exists
Caveman - do you?
if you're not going to answer my question I think I'll do something else
@jtm22 can you not think of more than one way to distribute the balls?
18:53
NO
It is not 1
even if the balls are not labelled either, there is more than one way
I think if it's (n+k-1 choose k) then that maeans it's (7 choose 5)
since N is 3, and k is 5
right?
How many ways are there to distribute 5 balls into 3 boxes = n=3, k=5?
5 balls into 3 boxes means the order of the balls matter but not the boxes. so you have (1)(2)(345), (1)(2)(354), (1)(2)(435), (1)(2)(453), (1)(2)(534), (1)(2)(543), etc
@jtm22, what is your reason for asking "Caveman - do you?"
Arrange the balls in $n!$ ways and then place the slashes as combinations?
18:57
so would that mean it's 7 choose 5?
yeah
multiplied by 5! that is I think.
so, 21
wait are you sure it's multiplied by 5!?
Its not multiplied by 5!. Hmm. Let me see.
user19161
Answered 3 lhf today, yay!
@jtm22 you are being rude ignoring me
19:00
No, caveman. I answered you already.
There was no reasoning for it.
7 mins ago, by jtm22
Caveman - do you?
I'm asking you why you asked me this
There was no reasoning for it, caveman.
No reason.
I don't know why I asked
that is a blatant lie
I wanted your opinion on a question, I think. I don't remember.
ok
@jasper my students are so stupid i can't believe :(
19:01
@jtm22, it's not ok
user19161
@DominicMichaelis What level are they?
first semester
user19161
Can you stop calling people rude and calling them liars when they are not clearly so?
user19161
I am sick and tired of all this nonsense.
i did read today about 80 times: "A funktion is 2 times differentialbe iff it is a polynomial of degree 2"
19:03
@DominicMichaelis why does every prof feel that his students are stupid, especially when everyone was a student once?
i am not a prof but still a student :D
@JayeshBadwaik The path behind always looks easier than the path ahead.
@Arkamis That is what I wanted to say. :-)
It is much simpler to look back and say, "I did that and it was not hard" than to say "I'm about to do this and it will be easy."
user19161
19:04
@PeterTamaroff I saw your comment, hehe.
@JasperLoy "Look at me, I am awesome, I need no words to answer!" =D
user19161
@PeterTamaroff Did you give me an upvote? =)))
@JasperLoy Yeah,.
user19161
@PeterTamaroff Good, good.
which answer?
19:06
I get 120 btw
for the boxes question
user19161
@JayeshBadwaik The one on the Cauchy Schwarz inequality.
user19161
@JayeshBadwaik Did you also give me an upvote? =)))
@JayeshBadwaik You so silly! You no gangsta.
19:08
@user2175923, I just answered it
user19161
I studied that proof in high school actually.
@jasper i did after i made an accidental downvote :D
user19161
@DominicMichaelis Ah, good good.
still need 60 reputation today :(
@JasperLoy The proof I like the best is the one considering $P(\lambda)=||x+\lambda y||^2$ when $x\neq 0$ or $x\neq \eta y$ for any $\eta \in \Bbb R$.
Kicks every other proof's asses.
user19161
19:10
@PeterTamaroff Where did you see that?
@JasperLoy I think 'twas Rudin.
hi there , any body know the answer of this question?
why the positive-definiteness of a riemannian metric implies it is non-degeneracy?
user19161
I like how Bill comments on answers and says how it is lacking and then tells the answerer to see his solution. Quite interesting!
@caveman Let's say you had x = 21 mod 4 and x=-21 mod 10
@user2175923, there
@user2175923, you can use a stack of (value,modulus) pairs and keep trying to add new ones onto it by checking whether they are coprime with what's already in the stack
19:16
FUCK YEAH!
I have a method that solves for gcd(x,y) already
i like this one here
it should be 1 for coprime pairs
so you're saying divide the moduli by g
@JasperLoy Bill is a marketing machine of himself!
@user2175923, I added a worked example
19:21
He answers and he's like see THIS link here. And it's a related answer of his, where he links to yet another answer, ad infinitum!
user19161
@PeterTamaroff Well, he called himself Professor Bill Dubuque in that meta post! I wonder where he taught at... I find him an interesting person actually.
@JasperLoy Me too. I like his answers. He's succinct and efficient!
user19161
@PeterTamaroff Yes, like me. =)))
He also introduced me to an essay that deals with differential equations, special functions and said it is related to Lie Algebra.
I am much interested about that essay.
But it is too highbrow for me ATM.
user19161
Michael Taylor's 3 volumes of PDE is BOSS!
19:23
I studied ODEs and stuff from Spiegel
user19161
There is so much machinery used in them that the appendices can form complete books in functional analysis, representation theory and riemannian geometry!
@caveman In my case, that a=b mod g thing will always hold true
but i am getting odd answers
are you saying that i can just treat it as solving for x = a mod m/g and x = b mod n/g?
@user2175923, you should just assume that your procedure takes arbitrary inputs and give an error token if there is no solution
user19161
Michael Taylor recently published a book on ODE as well.
user19161
His lecture notes on his home page are BOSS!
19:26
@jasper do you want to se the histogramm of the exam i corrected today ?
@caveman sure; so I will check if that equivalence holds and if not, no solution. so when it does, then that thing holds?
user19161
@DominicMichaelis Sure.
what thing?
oh they failed so hard :(
@caveman solving for x = a mod m/g and x = b mod n/g (only when a = b mod g)
19:28
no you threw away the condition that x = a mod g
i am confused now
the usual program (which i use when a solution is assumed) is

function crt(a, m, b, n)
   return ( a*n*inverse(n,m) + b*m*inverse(m,n) ) % (m*n)
user19161
These number sequences, who knows what is the next number? Could be anything...
this requires n,m to be coprime
what I did now is call crt(a, m/g, b, n/g) where g=gcd(m,n)
19:31
@jasper nope i said it is $\pi$
user19161
@DominicMichaelis lol
well in fact i said $\pi$, $\pi$ or $42$
I don't understand how mathgems is doing this without recursion
I see a way but it's not the same as his
caveman, how would you modify the program?
as i have misunderstood you apparently/somehow
    function crt(a, m, b, n) // input requires m,n coprime. outputs a value mod mn
        if gcd(m,n) != 1 then error "inputs not coprime in CRT"
       return ( a*n*inverse(n,m) + b*m*inverse(m,n) ) % (m*n)
19:37
right
but then now to solve for when m and n are not coprime and there is a solution
@user2175923, you start with [(a,m),(b,n)] meaning you want to find x = a (m) and x = b (n)
yes, solving for x
if m,n have gcd g you check a = b (g) then change this to [(a,m/g),(b,n/g),(a/g)]
@jasper you looked at that histogramm ?
so i first check if a%g==b%g, yes?
19:40
@user2175923, yes - now you want to solve a system of 3 equations with CRT - but you still don't know that they are all coprime
we know that m/g and n/g are coprime
user19161
@DominicMichaelis So full marks is at the top?
so you could change it to [(crt(a,m/g,b,n/g),m*n/g^2),(a,g)]
on the x axis there are the points, and on the y axis the number of students getting the points
there are no marks fixed yet
user19161
@DominicMichaelis I see, no labels at all! -1. =)
19:42
sorry got lost again
so it becomes another congruence in the form of
x = crt(a,m/g,b,n/g) modulo mn/g^2, x=a modulo g ?
@user2175923, Here is the big picture explanation: You want to solve a system of congruences - the tools you have work to either solve coprime congruences or split a congruence into coprime congruences - so we have to use these together to reduce the problem to what you can solve
yes, x = crt(a,m/g,b,n/g) modulo mn/g^2, x=a modulo g is what I meant by [(crt(a,m/g,b,n/g),m*n/g^2),(a,g)]
and then how would i solve that final congruence? are mn/g^2 and g coprime?
@user2175923, recursion
you don't know they are coprime (having checks like that built into your programs would help you a lot)
ok so i just keep checking if gcd(modulus1, modulus2)==1
@user2175923, one thing you do know is that gcd(mn/g^2, g) is strictly smaller than g
This justifies the recursion (proving it terminates)
19:49
@jasper but they really failed didn't they?
@caveman so

function crt(a,m,b,n)
    g=gcd(m,n)
    if g==1
        return (a*n*inverse(n,m) + b*m*inverse(m,n)) % (m*n)
    else
        return crt(crt(a,m/g,b,n/g),m*n/(g*g), a, g)
@caveman
I recommend not writing code like that
it's recursive
I mean lack of error checking
what's the error?
(is what I wrote wrong?)
19:51
it's only wrong sometimes
you should use else if a%g==b%g ... else throw error
function crt(a,m,b,n)
    g=gcd(m,n)
    if g==1
        return (a*n*inverse(n,m) + b*m*inverse(m,n)) % (m*n)
    else if a%g==b%g
        return crt(crt(a,m/g,b,n/g),m*n/(g*g), a, g)
    else
        throw error
this answer here is so wrong (the one i commented)
user19161
20:37
@DominicMichaelis Oh well, without the definition of "fail" and the labels, the histogram cannot be interpreted, lol.
on the horizontal line there are the points which they have
and on the y axis there is the number of students having those amount of points
27 points are the maximum by the way
user19161
@DominicMichaelis There must be something wrong about my PDF viewer then.
user19161
I see absolutely no numbers on the graph.
there are at least numbers
oh there are numbers
user19161
I am using Evince on Debian, lol.
20:42
argh i still need 40 points, i want to go sleeping :D
how can I view peoples previous names?
"recent names"
user19161
@caveman You cannot.
user19161
I really enjoy typing solutions on this site, helps me practise my LaTeX and also exposition.
3
user19161
Hey @amwhy I just sent you an email.
@JasperLoy Oh, goodie...!
user19161
Do you guys notice that on the questions that I answer, the other answers always have many votes? That is cos I upvote all the other answers, lol.
@jasper and everyone who upvotes you does it too
arg need 3 more upvotes than i can go sleeping :D
user19161
@DominicMichaelis I think we should not just upvote the first correct answer or the best answer, but upvote all reasonably good answers posted within a reasonable period of time.
yeah i guess that would be better
user19161
@DominicMichaelis No need to cap every day bro!
21:09
but i want to get those super fancy super sexy superpowers :D
user19161
@DominicMichaelis You will burn out soon! 100 a day is good enough!
user19161
Rumour has it that Debian 7 might be released this weekend, but I think it could take another 4 weeks.
soon i will have 7.500 repuation
user19161
21:38
So today I answered 5 lhf, yay!
21:55
hi
@jasper i nearly got you in the quartal scoring :)
@caveman: you should use "wiseman" nickname. ;)
hehe
Does anyone know of any questions/answers on MSE that discuss (what I hope to be correct)...
... when you go from octonions to quaternions, you gain associativity
...when you go from quaternions to complex numbers, you gain commutativity
...when you go from the complex numbers to the reals...?
Does this seem familiar, or should I start a new question about it?
you get a total order
21:58
thats a funny direction
Right. Are there any resources on MSE already?
normally you go from the real numbers to the complex and then to the quaternions and so on
4
Q: Why are properties lost in the the Cayley-Dickson construction?

HookedMotivating question: What lies beyond the Sedenions? I'm aware that one can construct a hierarchy of number systems via the Cayley-Dickson process: $$\mathbb{R} \subset \mathbb{C} \subset \mathbb{H} \subset \mathbb{O} \subset \mathbb{S} \subset \ldots $$ "Reals" $\subset$ "Complex" $\subset$ ...

YES
Thank you, Dominic
Those are exactly what I was looking for. Thanks again.
22:01
glad i can help
@DominicMichaelis: nice from your side.
@caveman: today I was thinking to prove that $\frac{\displaystyle x+\frac{x^3}{1\cdot3}+\frac{x^5}{1\cdot3\cdot 5}+\frac{x^7}{1\cdot3\cdot 5\cdot7}+\cdots}{\displaystyle1+\frac{x^2}{2}+\frac{x^4}{2\cdot4}+\frac{x^6}{2 \cdot 4 \cdot 6}\cdots}=\int_0^x e^{-t^2/2} \ dt$
@Chris'ssisterandpals, thats nice, i think you can make a continued fraction for it
of the LHS
that wont help to prove it though
isn't it sinh/cosh ?
oh right the factorials are wrong
22:10
@Chris'ssisterandpals, I cannot imagine how to proceed
@caveman: no pb. I only shared one of the problems I was thinking of today.
@Chris'ssisterandpals, I think this is a really great interesting problem
I just wish I had the skills to give some input on them
I think it is related to hypergeometric functions
can we differentiate the LHS with respect to x?
@caveman: I think we can. Does it help?
@Chris'ssisterandpals,, I have no idea if it helps
22:15
if the derivative looks easier to deal with, and we prove they have the same derivative - that might b a good start
but how would you differentiate the LHS? it looks impossible to deal with to me
well I guess you could just get it as a big product and multiply it out
@caveman: I'm not sure yet I want to do it. Maybe there is another way.
yeah that is definitely not going to make things easier
its just the first idea I had
@caveman: all ideas are precious. Thanks.
@caveman: I'll think of it tomorrow. Have a nice day! ;)
ok, and tell me if you get any further
@Chris'ssisterandpals bye
user19161
22:31
@DominicMichaelis Good! Soon you will reach 100k!

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