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1:00 PM
I suppose $f(M)$ must be at least a submonoid of $M'$? In which case the question is whether a submonoid can have a different identity element than the monoid itself.
in the case of subgroups, at least, the answer is definitely no
 
(con't) I don't know how useful to learn that the function $\phi$ is separable, but it surely will help interpret the incoming future batch of data because I don't need to worry about cross terms
 
"A submonoid of a monoid (M, •) is a subset N of M that is closed under the monoid operation and contains the identity element e of M."
hmm, so that'd forbid this scenario by definition. but that more seems like a statement that 'submonoid' is the wrong word here
 
@Semiclassical according to model theory, no
according to morality, no
according to sanity, no
 
@Semi!
 
1:11 PM
I finally understand the evanescent wave
 
@Hemi!
 
it took me a year
 
@Demi!
@Half!
 
For all $x$, $f(x)=f(x+0)=f(x)+f(0)$. Since $f$ is additive, it follows $f$ is a homomorphism between the two monoids, thus $f(e)=e'$ where $e,e'$ are the identities of each monoid. Therefore $f(0_M)=0_{M'}$
 
half full or half empty?
 
1:12 PM
half demi and half hemi
 
but it you add it all, it's just semi
#physics
 
semidemihemiclassical
 
Exactly @Semiclassical. Homos map the identity to the identity
 
@Secret i.e. use abstract unjustified stuff
(btw the answer is no, so your reasoning can't be correct)
 
1:14 PM
but how, the + is an operator in the monoid M', and we are given f(x+y)=f(x)+f(y)....

wait a minute, are those + for the different monoids?
hmmm.. let me think...
 
I don’t understand what it means.
@0celo7 I don’t understand what it mean
 
@Secret what you presented is at best circular reasoning
 
"if a function f:M->M' satisfies f(x+y)=f(x)+f(y), where M and M' are monoids, does it follow that f(0)=0?"

Given: $f_{M\to M'}(x_M+_My_M) = f_{M\to M'}(x_M)+_{M'}+f_{M\to M'}(y_M)$
isn't that is exactly the form a homomorphism is supposed to be like?
 
@Secret it's called appeal to authority
the authority here being "homomorphism"
you don't know why it's true, you just throw the word out as if it justifies anything
if you define homomorphism as that, then your argument becomes "because it's true"
 
But for any set A,B and $f : A \to B$ a homomorphism is defined as $f(x*_Ay)=f(x)*_Bf(y)$
I don't know how one can go beyond a definition
$f(0)=f(0+0)=f(0)+f(0)$
hmm...
wait what, $f(0)$ can be any idempotent and it will work. Is $f$ really not a homomorphism... ::Checks reading again::
fine, so while it satisfy the morphism property (which is the expression wrote above), nothing tell us whether it preserves identities
and hence $f$ is not necessary a homomorphism
 
1:34 PM
[Unrelated] hmm.... $f(x+y)=f(x)+f(y) \land f(0)\neq 0$ may be useful for something in one of my investigations...
 
Hi, why can we say that the determinant $\text{det}(A)$ is a polynomial in the entries of the matrix $A$? If we look at the determinant of a $3 \times 3$ matrix

$$A = \begin{bmatrix} a_{11}&a_{12}&a_{13}\\a_{21}&a_{22}&a_{23}\\a_{31}&a_{32}&a_{33} \end{bmatrix}$$

by expansion along the first row we get

$$\text{det}(A) = a_{11}(a_{22}a_{33}-a_{32}a_{23}) - a_{12}(\ldots)+a_{13}(\ldots)$$

Why is that a polynomial? There is no one variable $x$ but only different $a_{ij}$?
What is meant by "polynomial in the entries of $A$"? What are the variables here?
 
The variables are the matrix elements. @philmcole
It's a polynomial in nine variables.
Whether that's a useful statement will of course depend on the problem of interest.
 
Well, if the monoid is the natural numbers, then $f(0)$ must $=0$ if $f$ is additive, since there are no idempotents in the natural numbers except 0
 
1:50 PM
@Semiclassical so it's essentially a multivariable function $f(a_{11},a_{12},a_{13},a_{21},a_{22},a_{23},a_{31},a_{32},a_{33})$?
 
Right.
 
I see okay thanks
 
And since it only consists of products and sums of said variables, it's a polynomial.
 
I didn't know there are multivariable polynomials
okay
 
There's an additional property in the case of the determinant, though, namely that each term in the expanded determinant is degree 3 (product of 3 different matrix elements).
 
1:53 PM
yes so the polynomial has degree 3
 
That makes it a polynomial which is homogeneous of degree 3. But that shouldn't be too surprising: It implies that $f(\lambda A)=\lambda^3 f(A)$
Well, $y^2+x^3$ is degree three too. But it's not a homogeneous polynomial, whereas $x^3+y^3$ is
 
what is a homogeneous polynomial?
 
A polynomial for which each term has the same degree.
 
every term has the same degree?
right
 
So $x^3+y^2 x+y^3$
 
1:55 PM
is not
 
Sure it is. $y^2 x$ has degree 2+1=3
 
oh okay
independently of a single variable but all added together
 
Right.
The degree of a term in a multivariable polynomial is the sum of all the exponents
You could also view it as a polynomial in $x$ alone, of course, in which case $x^3+y^2x+y^3$ wouldn't be homogeneous
But insofar as it's a function of $x$ and $y$ then it is indeed homogeneous
 
okay makes sense
Thanks!
 
Again, though, this shouldn't be too surprising: If you rescale a 3-by-3 matrix by a constant factor, then the determinant should rescale by that factor^3
np
 
1:58 PM
@Semiclassical Something bad happened while processing. Do //logs to see the logs
 
ugh, bots
 
that's a bot?
what happened?
 
0
Q: Corollary 5 in Royden-Fitzpatrick's Real Analysis: Convergence in Measure

user193319 Corollary 5: Let $\{f_n\}$ be a sequence of nonnegative integrable functions on $E$. Then $$\lim_{n \to \infty} \int_E f_n = 0 ~~~~~~(5)$$ if and only if $$f_n \to 0 \mbox{ in measure on } E \mbox{ and } \{f_n\} \mbox{ is uniformly integrable and tight over } E ~~~~~(6)$$ H...

 
Nothing happened beyond my being a little annoyed to have a chatbot responding to my messages
 
@cello ???
yesterday, by cello
Is there any one who is interested in discussing about material in Kobayashi and Nomizu first two chapters
do you not understand your own words?
@Semiclassical what did you do to piss off the bot
 
2:06 PM
no clue
 
Does everybody have logs like that?
 
just the enemies of the bots
 
lol
 
Hey chat
Let $A$ be a ring (comm. and with $1$), and $M,N$ be $A$-modules, $I$ some submodule of $N$. Given a morphism $f:M\to N/I$, does there always exist a lift of $f$, i.e. a morphism $g:M\to N$ such that $f=i\circ g$?
For example I could set $g$ to send $m\in M$ to some element in the equivalence class of $f(m)$ in $N/I$, but I think with this arbitrary choice $g$ will not always be a morphism of $A$-modules...?
 
2:23 PM
@0celo7 I understand what I said. I don’t understand what you said. Can be be precise. What do your u want to say?
What do you want to say
 
I wanted to help you, butwhatever
Why make this difficult
 
You wanted to help me?? How??
 
@0celo7 mind your language..
 
christ
it's not April Fool's any more
 
2:29 PM
To clarify:
 
Please remember to keep it professional/collegiate in tone.
 
Wow, did he flag that?
 
@MetaEd Uh, that's not how it works in the chat.
Sounds like a right intervention of the situation with a wrong advice to me.
The right advice is to not talk past each other, and use the ignore button appropriately
 
From the FAQ: "Do I have to be nice? Yes. We expect community members to treat each other with respect … even when they don't deserve it."
 
Oh my god. How the heck is this a "Be Nice" situation?
 
2:32 PM
^
 
@BalarkaSen Something bad happened while processing. Do //logs to see the logs
 
1
Q: Corollary 5 in Royden-Fitzpatrick's Real Analysis: Convergence in Measure

user193319 Corollary 5: Let $\{f_n\}$ be a sequence of nonnegative integrable functions on $E$. Then $$\lim_{n \to \infty} \int_E f_n = 0 ~~~~~~(5)$$ if and only if $$f_n \to 0 \mbox{ in measure on } E \mbox{ and } \{f_n\} \mbox{ is uniformly integrable and tight over } E ~~~~~(6)$$ H...

 
@BalarkaSen YOU'RE AN ENEMY OF THE BOTS TOO
 
Made some edits
 
We don't want bots in a conversation about failure of communication, ideally
 
2:33 PM
@BalarkaSen Do you know measure theory yet
 
after 6th man
im dying of exam pressure right now
 
@0celo7 mind your language. I was not asking for any help..
 
What language? You clearly do not understand how this works.
 
guys, any idea why the height $\sqrt{x^2+y^2}$ isn't just $y$?
 
@cello 0celo7 didn't use any inappropriate language, you are misunderstanding. He's vocalizing that he doesn't want to help you - which is to be taken as a cue of respectful conversations to stop pinging 0celo7 on your side and drop the conversation.
 
2:36 PM
(I didn't get much more context than this either)
 
@BalarkaSen if you are happy being called as garbage, you can proceed for the same.
 
@0celo7 right... you do know there is a mute button?
@cello that was referring to the situation, not to you. also... mute button
 
^ that
 
ugh... why is this chatroom always three different conversations at the same time, btw?
is there some ... mutual ignoring factions thing going on?
 
Do not engage with someone you think is hostile. Flag it.
 
2:40 PM
@MetaEd which is why I'm here, you know? trying to defuse the situation after flags flew
 
@Vogel612 Absolutely. Not directed towards you.
 
There's a problem with that, because flags usually get checked off without a review, unlike this rather exceptional situation
Most 10k users in SE don't care about reviewing whether a flag is genuine (fault of the system)
It's not good advice to flag anything whenever whoever finds it hostile. That encourages misflags
3
 
sorry, but that line of logic is faulty
 
(figured the thing out btw, so nvm)
 
because if it's hostile, it needs to be taken care of
while I agree that 10k flags are a crappy solution attempt to the problem, not flagging isn't an acceptable solution either
 
2:43 PM
@Vogel612 thanks for clarification. M
 
nor is flagging everything for moderator attention
 
@Vogel612 In this case it's not, so it's pointless to bring it up. That clearly encourages flagging without discourse first.
This has been discussed in detail in hbar, the physics chat
It's worth looking up the logs if you're interested in moderation issues
 
yea physics chat is the new mos eisley
 
lol p much
 
you do know what happened there, right?
 
2:45 PM
yup
it v a n i s h e d
 
Oh I don't
Tell me more
 
they got shog9'd
 
want that to happen here?
 
the room generated so much flags and controversy that shog9 baleeted it out of existence
 
28
Q: How come our main chat, Mos Eisley, got frozen this time?

MöozMos Eisley is currently frozen#, apparently indefinitely. I assume it has something to do with the users mentioned in @Shog9's banner, but is it possible that we be told - at least in concept - what happened in our room to make it get frozen again? If the rest of you want to create a new room...

 
2:46 PM
gets really mad about sci-fi or something
 
@Vogel612 No, but that's exactly why I'm advocating discourse over flags.
 
IMO that's just hiding the problem
 
That's fine, we could have a discourse over that instead :) My idea is shared by many other else and lots of moderators in hbar that are actively trying to control the room (and succeeding)
 
@Vogel612 The lack of responsible self-moderation in each room?
 
s/each room/some rooms/
 
2:50 PM
K
I think the obvious solution here is to make Balarka our responsible self-moderator
 
I nominate myself too
 
yea the RO list here is a bit almost empty
 
Surely we will rally behind the arbiter of Justice
 
the only RO that's in here regularly according to chat is anon...
 
If I were to suggest anyone as a more active RO it would be @Semiclassical, but of course it's a decision of himself and the other room owners here
@MikeMiller No better political position than to hand all the power to someone in your alliance and thereby gaining indirect control over the system, amiright?
 
2:54 PM
I'm glad you are working out how to self-police. I will continue to monitor the room.
 
I already hate that little duck on the M.SE pages.
 
@ThomasAndrews tell it, then it vanishes
or just wait a few more hours and then it'll also be gone.
 
Last time I tried to do anything with it, it wanted my microphone access, and I love Stack Exchange, but am not ready to move in with it. :)
 
that mic access is fake...
 
@MetaEd Who is working out how to self-police? It struck me that I mainly came up with a way not to.
 
It works the same way regardless of microphone access ;)
 
Thanks, folks.
 
But, as others said, waiting a few hours is probably as good solution as any.
 
It's been on my window for at least 12 hours.
 
//help
 
2:58 PM
###################### Help ######################

==================== Commands
//about        | Let me tell you a little about myself...
//alive        | Used to check if the bot is working
//appul        | Apples.
//ban          | Bans a user from using the bot. Only usable by hardcoded bot admins
//ban-room     | Blacklists a room
//blame        | No description was supplied for this command
//declare      | Changes a commands status. Only commands available on the site can be edited
//doge         | Such doge. Much command.
 
It's the first time I saw this bot in this room.
 
@MikeMiller I mean the room as a whole. If the community's solution is to delegate to specific users, that's still the room policing itself.
 
This time it’s set to run until April 3 UTC because April Fools itself falls on a Sunday this year. This might change once Monday actually rolls around, but at the moment that’s the plan. — Adam Lear ♦ yesterday
 
Ah, it's an April Fools thing? I honestly didn't get that.
 
Zee
//wake
 
3:01 PM
@Zee You have to tell me who to wake up!
 
Zee
//shrug
 
¯\_(ツ)_/¯
 
//appul
 
@ThomasAndrews I LUV APPULS!
 
@ThomasAndrews Try explaining to it in detail how it is supposed to work.
 
Zee
3:05 PM
//blame metaed
 
@Zee blames Perturbative for metaed
 
Zee
//location
 
@Zee OliviaZoe/Supernova (16286dc85e6)
 
Zee
//help
//about
 
@Zee Hiya! I'm Alisha, a chatbot designed by Olivia. I'm open-source and the code is available on Github. Running version 1.3
 
Zee
3:07 PM
//shutdown
 
@Zee I'm afraid I can't let you do that, User.
 
Zee
//hope
 
Zee
//help
 
3:09 PM
###################### Help ######################

==================== Commands
//about        | Let me tell you a little about myself...
//alive        | Used to check if the bot is working
//appul        | Apples.
//ban          | Bans a user from using the bot. Only usable by hardcoded bot admins
//ban-room     | Blacklists a room
//blame        | No description was supplied for this command
//declare      | Changes a commands status. Only commands available on the site can be edited
//doge         | Such doge. Much command.
 
why is Alisha frequently gone into this room, did @Princessluna's code gone wrong again?
 
Zee
//kill secret
 
Zee
//learn stealing
 
@Zee Not enough arguments
 
Zee
3:13 PM
//logs
 
@Zee You need rank 5 or higher to view crash logs
 
30 mins ago, by Vogel612
while I agree that 10k flags are a crappy solution attempt to the problem, not flagging isn't an acceptable solution either
Forgive me for harping, but "flag" and "not flag" aren't the only options. Words work, too.
 
Did the robots kill Secret
 
@BalarkaSen thanks for the cool-headed leadership a bit ago.
 
I cannot be killed, I am not a human being
:P
 
3:17 PM
The robots have replaced Secret
 
Hi,
 
Hi Datti
 
hmm. pmatrix does a matrix with parens, bmatrix with square brackets, vmatrix with vertical bars
 
@chatbot : I confirmed a genie is an algorithm
 
is there one for curly brackets?
 
3:18 PM
@Lozanski : how are you ?
 
Zee
//ban zee
 
@Zee You can't change the rank of users with the same or higher rank as yourself
 
@Semiclassical $\begin{Bmatrix}blah & blah \\ blah & blah\end{Bmatrix}$
 
ahah, nice
 
@Semiclassical Vmatrix? TIL
$\begin{vmatrix}
a & b \\
c & d
\end{vmatrix}
\quad
\begin{Vmatrix}
a & b \\
c & d
\end{Vmatrix}$
 
Zee
3:20 PM
//declare zee as god
 
@Zee I'm afraid I can't let you do that, User
 
@Dattier I'm fine thanks, preparing for my Fourier final on Wednesday. You?
 
//open the pod bay doors
 
@AkivaWeinberger Maybe you should consider looking up the manual
 
I m fine too @Lozansky
 
3:20 PM
@AkivaWeinberger nah it's not a+b mod n, just a+b
 
Zee
//lick akiva
 
@Zee Licks akiva. Tastes like a cow!
 
@Lozansky do you know the TFF
?
 
@Dattier What's that?
 
@Alisha O.O
 
3:21 PM
@AkivaWeinberger Why are you going to be a little?
 
So if we're doing $\mathcal{H}_5$, you just need the sum to be less than 5
 
theorem of fundamental fysics
 
$\begin{Pmatrix}a&b\\c&d\end{Pmatrix}$
 
Zee
//give zee money
 
gives money to zee
 
3:22 PM
@Lozansky multiplication quickly with Fourier discret transformation
 
Hm so matrix, bmatrix, Bmatrix, vmatrix, Vmatrix, pmatrix?
 
Zee
//doge zee
 
         so zee
 
@Lozansky Do you study, the science computer ?
 
Zee
3:23 PM
//echo semiclassical
 
@Zee semiclassical
 
@Dattier No, engineering physics
 
$\begin{smallmatrix}3&4\\5&6\end{smallmatrix}$
 
We didn't really cover too much discrete Fourier
 
Zee
Alright , am gonna go cry in my bed , goodbye
 
3:23 PM
@LeakyNun Other than idempotents, what else will satisfy $f(x+y)=f(x)+f(y) \land f(0)\neq 0$?
 
Ok @Lozansky
I will propose this to aops
 
@Daminark So I need to color the integers from $1$ to $n$ such that the set $\{a,b,a+b\}$ always has more than one color, whenever $a\ne b$ and $a+b\le n$?
 
@Dattier Did you figure out the connection between Bonnet's and Rodrigues' formula?
 
Since you said the answer is $O(\log n)$, I'm guessing binary might be relevant…
@Daminark In other words, whenever $a$ and $b$ have the same color, $a+b$ has a different color
@Daminark One possible coloring, I think, is: $\{1\},\{2,3\},\{4,5,6,7\},$$\{8,9,10,11,12,13,14,15\},\dots$
where I'm partitioning according to color
I can actually do better since $a$ need not be a different color from $2a$, right?
But not much better; just shift all the braces one to the left
$\{1,2\},\{3,4,5,6\},\{7,\dots,14\},\dots$
So this is clearly $O(\log n)$. So I guess I need to show that I can't do better.
 
Well you don't need to show that, not even sure if you can show better than that
 
3:32 PM
Oh, right, $O$, not $\Theta$
 
But yeah you have the right idea, that's what I did. A few of my friends thought of coloring odd numbers, then 2 mod 4, etc
 
@Daminark Mm
That makes sense yeah
Is $\Theta$ the right word? Where it's not much more than $\log n$, but it's not much less than $\log n$ either
("Word". Symbol.)
("Theta" is a word)
(Why is $O$ italicized but $\Theta$ isn't? It's just an $O$ with a dash in it)
 
and then there's $\mathcal{O}$
 
When you mess up using a compass
 
contains spherical cows
 
3:38 PM
That feeling when you try to draw a curve of constant curvature and it doesn't close, so you wonder if your paper is secretly non-Euclidean
Test: $\scr O$
Oh no that's too much
 
3:55 PM
ATTTACK: 71
 
@AkivaWeinberger There is $\varTheta$ too.
 
@dave Oh, cool, never knew that
 
I want to prove that the non-zero roots of characteric polynomial of a matrix product $AB$ are the same as $BA$. I'm not given that the matrices are square, but presumably I can pad the matrices with $0s$ to get something like $[A | 0] [\frac B 0 ] \cong AB$. Can I also make a density argument by making a sequence of inv'ble matrices tending to $A$, or is that a contradiction to padding it with zeros?
 
4:12 PM
Banned for 90 minutes for saying “wtf”. Who approves a flag like that?
 
Can someone tell me what the linear function of the line would be in the example of this question math.stackexchange.com/a/2709715/200711?
Basically I'm taking $\phi$, making a linear function out of it and using it as $M$, but I'm not sure how to do that since $M$ isn't in exactly the same form as $y=mx+b$.
 
Is there a way to get notifications from the questions if we want to? Like if a new answer posted to the question, we would get notified by that
That would be great and time saver.
 
There are chrome extensions that can do that
 
Which one?
I mean I get notifications if someone mentions my name. But I especially want to know if the same thing happens in the case of new answers or comments
@MikeMiller
 
4:46 PM
Approximately 37% of the chat's users will believe this statistic
 
I buy that.
 
5:04 PM
@0celo7 idfk
 
hey @MikeMiller
I was wondering if we can think of differential forms as kinda of distortion of volumes
I mean the differential 1 forms really records the derivative as linear map.
and then higher differential forms is really determinants of submatrix of the original matrix.
I was wondering if there is a geoemetric way to see this ?
It is like distortion of volumes ?
 
5:20 PM
My social life in a nutshell, and why I am so pessmistic about socialising beyond 2020
The Predators, vicious pretentious entities, will devour me and my weirdness, turning me into a normal human being and thus eat my soul, dreams, and I will then become a lifeless cog of the society
2
 
@nitsua60 No problem, I just felt like vocalizing this because this kind of pointless flagging spree has interfered with constructive conversations in the chat (about math, say), which I participate in. Wasn't particularly trying to "lead", except perhaps ironically
 
Rip
well whoever deleted it did it for your own good. someone was prolly still flagging it
at least I guess so
 
@BalarkaSen I got 90 minutes for it
 
Hello!

Knowing the base sides and the slant heights, do we calculate the height of the pyramid by the formula $h^2=h_b^2-\left (\frac{a}{2}\right )^2$, no matter what shape of base the pyramid has, i.e. square, rectangular, right angles triangle?
 
5:28 PM
Oh
Just saw in disc
 
Here's part of the proof of Lebesgue' theorem: "The set $E$ of points at which either $\{\psi_n(x)\}$ or $\{\phi_n(x)\}$ fail to converge to $f(x)$ has measure $0$. Let $E_0$ be the union of $E$ and the set of all the partition points in the $P_n$'s....We claim that $f$ is continuous at each point in $E-E_0$." My question: Isn't $E-E_0$ empty, since $E-E_0 = E - (E \cup \bigcup_{n=1}^\infty P_n) = \emptyset$?
Or am I misunderstanding something?
 
5:44 PM
Can a continuous $\Bbb R^2$ paths with finite length have uncountable many loops?
 
@Adeek Differential forms are meant to encode area of k-planes. The derivative spits out something that encodes area of (k+1)-planes, by taking the derivative of what it does to the k-planes in the "extra direction"
I don't know that you get anything useful out of this picture tho
 
6:07 PM
@BalarkaSen Yeah--it's been my experience that if the annoying behavior gets slapped immediately, rather than a flood of "outsiders" coming in, it actually dies down pretty quickly. But I know nobody comes to hang out each day thinking "hey, maybe I can call someone out correctly and get yelled at today!"
So thanks =D
 
I think the outside intervention just makes it worse 90% of the time, just like US foreign policty
 
6:52 PM
How do you propose to do A)? What would the result be? In addition, this having a closed form sounds doubtful to me — Yuriy S 1 hour ago
Sorry
0
Q: Closed form for $\frac{\int_0^1 Ei(x)^5 \ln(x) dx}{\int_0^1 Ei(x)^3\ln(x) dx}$?

mick Consider the expression $$\frac{\int_0^1 Ei(x)^5 \ln(x) dx}{\int_0^1 Ei(x)^3 \ln(x) dx} $$ A) Can we rewrite this with a single integral sign? B) Do we have a closed form for this expression in terms of hypergeometric functions? C) Is there a closed form without hypergeome...

Any ideas ??
 
ooo looks like I'm gonna get my Erdos number to 6
👏
not counting ATLAS publications lol
 
@MatheinBoulomenos hey mathein :D pls text me when you see this :D
 

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