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00:00
@Chris'ssis Congratulations, that's a straw man
3
lol, I star you too for the speed (although I wouldn't say that at all)
:-)
@Chris'ssis So you were an undergraduate student in your third last year of highschool?
@Committingtoachallenge do you proceed in the same way in the real life? Do you stalk people as you read my 12000 messages?
@Chris'ssis In debating environments at uni, yes. "Do you stalk people as you read my 12000 mesaages?"(Editted in), no.
00:03
@Committingtoachallenge I mean it doesn't sound nice to do that. I suppose you're not a happy person too often.
@Chris'ssis Why don't you answer my question? It has a (yes/no) because it is true or false. Why don't you see that?
@Committingtoachallenge This obession (or how to call it?) it's not good, seriously speaking.
I hope you can improve that in the future. :-)
2 mins ago, by Committing to a challenge
@Chris'ssis So you were an undergraduate student in your third last year of highschool?
Oh, now I see ...
@Committingtoachallenge I let you unreveal the mysteries alone. I think this is the best way. ;)
@Chris'ssis I have revealed your false history already, and I am enjoying you avoiding answering to it
00:06
who cares
@Committingtoachallenge lol, you reveal nothing. People do not come here for the comments that are not related to mathematics.
@Chris'ssis Then why build such a massive history and run multiple accounts?
@Committingtoachallenge My history doesn't matter here you know. Who cares my comments history here excepting you? As I told you, you do not seem interested in mathematics.
00:08
It is not like this is going to make or break your mathematics career
@Chris'ssis Jasper Loy?
@Chris'ssis Venus(you claim not to be you)
@Chris'ssis Aren't you solely interested in series, limits and integrals? I am interested in many more areas than you?
@Committingtoachallenge Well, I do it for you. I mean it's OK to ask some questions, but not to be obsessed. Look, if I asked someone a personal question and that person wouldn't tell me the truth here, that would be OK. It's about anonymity!
@Chris'ssis Wouldn't tell me the truth, meaning to not respond, or to lie?
@Committingtoachallenge well, it depends on the situation. Some would say nothing, some would say another thing. It depends on the person.
@Chris'ssis Anyway I have to go, study group for next semester meeting up for first time
@Chris'ssis Was an eye opening talk ;) Thank you
00:12
@Committingtoachallenge lol, OK :-)
Cool. Let's talk math!
@Committingtoachallenge Remember, we're people not computers. ;)
@Chris'ssis can you link to the question regarding the integral you posted earlier?
@Bitrex That one is an integral that is going to appear in my book.
00:14
Ah
Can you post it again? I'd like to F around with it
Or if it's a secret....:(
OK, but don't post it on main
Roger that.
Thnx
@Bitrex Welcome. The answer is really unexpected! :-)
Hello!!!!
Can anyone help with toplogy?
00:16
oh it's a little different than I thought I thought it was sin(x_1)sin(x_1 + x_2)...etc
ok
@JulianRachman dunno, can we?
@anon I believe you can...
basis is still confusing me but I am getting closer to understanding
@Bitrex Yeap. Do you have in mind an approaching way?
@Chris'ssis I'm not that quick! :)
@Bitrex hehe, no hurry with that.
00:21
I'm just an electronics person...
not a SUPER MATH PERSON
@JulianRachman so do you have a question?
Is there a query I can run for MSE for number of questions with 0 votes and 0 answers?
@Bitrex It's not an easy question, one needs some experience for dealing with it. So, no worry with that.
00:26
@anon not in particular. I just want an in-person-for-"first"-grader explanation of a basis which leads me to the definition and a very concrete example.
were you the one I was talking with about top bases the other day?
i believe so.
a collection of subsets is a basis if every open set is expressible as a union of said subsets
which is equivalent to the conditions (1) and (2) given in whatever reference you gave
Ya. So say I had $X=\{a,b,c\}$ and had a topology $\tau=\{\emptyset,\{a\},\{b,c\},\{c\},X\}$ on $X$. Then what would be the basis of this topology?
I thought it would be the set of all singleton subsets of $X$ but that is only for discrete topologies.
@anon
@JulianRachman that's not a topology
00:34
@anon Oops. I meant $\tau=\{\emptyset,\{a,b\},\{b\},\{b,c\},X\}$
why are you putting the word the in front of the word basis? "the basis"?
Sorry. Is "a" the right word to replace it?
yes. a space can have many bases.
sorry. my terminology issues. :(
if you thought spaces had unique bases, that would be a conceptual issue not a terminological one
anyway the bases for that space are pretty trivial
00:38
no. Like I typed it without taking the difference between "a" and "the" into account
there's {{a,b},{b},{b,c}}, and the only other three are obtained by adjoining either {} or X or both
do you have a question?
how does that apply to finding a basis for that specific topology I had defined?
@DisplayName I've asked one of my SQL dude friends if he can whip something up
00:41
@JulianRachman You first asked "what would be [a] basis for this topology" [before correcting your definition of the topology]. I answered that by giving you every possible base.
I take it your follow-up question is to ask how I obtained it? Use your words!
Sorry.......... Yes, that is my follow up question.
hold on need to reboot my browser. start thinking about it. use logical reasoning.
k back
00:44
♫ welcome back ♫
since {b} is an open set, it must be a union of sets in whatever base you want. the only way that's possible is if {b} is in the base.
can you use logical reasoning to deduce {a,b} must be in any base?
@MikeMiller I just learned the zeta-regularized cardinality of a compact p-adic Lie group is zero
explain
$\sum(\dim V)^2=|G|$ for finite groups, so just zeta-regularize the sum for G in which there are only polynomially many irreps of dim below a given bound
(I wasn't looking for p-adic Lie groups G at all but that's the kind of group the literature seems to be focused on)
can you be explicit about what you mean there
zeta regularization is not, like, a thing i've ever thought abuot
oh, you analytically continue $\sum (\dim V)^{-s}$ as a function of complex $s$ in order to evaluate at $s=-2$
00:49
ah, i see
cannot say I see why one would care that this ends up evaluating to zero other than idle curiosity
it was just idle curiosity
great!
i love idle curiosity
although something like $\sum (\dim V)\chi_V(g)$ seems to be a "Dirac delta function" on $G$, and I think works like a Green function for the heat kernel. in particular for finite $G$ if we call if $\delta(g)$ then $\int_G \delta(g)f(g)dg=1$ (normalized counting measure). and a formal reason to believe it should function similarly for compact in general came up when I was trying to prove matrix coefficients densely span L^2(G).
@anon I can say that it must be a union of sets within any base of the topology. But other than that, I do not know.
neat.
not sure how that only snuck in.
00:52
@JulianRachman can any of those sets that {a,b} is a union of contain c?
Done with my proof. Out for some sleep.
(err that should be $\int_G\delta(g)f(g)dg=f(e)$ in my comment above)
@JulianRachman can any of those sets that {a,b} is a union of contain a?
i guessed, @anon
00:54
@JulianRachman can {a} be one of those sets?
Of the union?
yes
then yes?
is {a} an open set?
00:55
waits for Julian to go back and check
21 mins ago, by Julian Rachman
@anon Oops. I meant $\tau=\{\emptyset,\{a,b\},\{b\},\{b,c\},X\}$
Because it is not an open set of the topology
yep
I figured.
Bangs head on wall
so can {a} be one of the sets we are unioning to get {a,b}?
00:57
correct
is it possible for none of the sets we are unioning (to get {a,b}) to contain a?
so one of the sets we are unioning must contain a, and also must contain something other than a, but can't contain c
therefore _____ is one of the basis sets
correct. to get {a,b}
one of the sets we are unioning must have been {a,b} itself
symmetrical reasoning applies for {b,c}
thus a base necessarily must contain {a,b},{b}, and {b,c}
next you can prove that is sufficient: {{a,b},{b},{b,c}} is a base
Oh. So if we were to formally write what THE bases of the topology are, how would we formally write them in terms of basis elements $B$ and a collection $\mathcal{B}$
?
01:02
24 mins ago, by anon
there's {{a,b},{b},{b,c}}, and the only other three are obtained by adjoining either {} or X or both
So {{a,b},{b},{b,c}},
{{a,b},{b},{b,c},{}},
{{a,b},{b},{b,c},X},
{{a,b},{b},{b,c},{},X}
are the four bases yes
So then how would we show that these basis generate the topology?
let's pick {{a,b},{b},{b,c}}. show that it's a base
@Bitrex Very cool. Thanks
01:10
@anon of what topology?
@JulianRachman the topology you put on X........................................
If you take the union of the given base, you get {a,b,c} which is equivalent to the set X.
Just an "educated" guess....
Is that supposed to be a full proof or have you only just started writing out a proof?
I dont know how to prove it
and I didnt know I had to prove it
you asked how we would show these are in fact bases, that these collections of subsets generate the topology
I am making you do it for {{a,b},{b},{b,c}}
01:15
Yes. ANd I dont know... :(
There are certain definitions in mathematics that tell you how to prove if something is a blah or not. In this case, a collection of open subsets is called a base if every open set in the topology can be written as a union of subsets in this collection. That tells you what to do!
So if we took a union of subsets of each open set of the topology I had defined, I can see that the result is the base I had originally wanted to prove?
huh?
is {} a union of elements of {{a,b},{b},{b,c}}?
is {a,b} a union of elements of {{a,b},{b},{b,c}}?
is {b} a union of elements of {{a,b},{b},{b,c}}?
is {b,c} a union of elements of {{a,b},{b},{b,c}}?
is {a,b,c} a union of elements of {{a,b},{b},{b,c}}?
Wait. If I took the intersection...
I took the intersection of all possible bases and got the topology I defined
(I still feel like I am doing it wrong...)
@anon
why are you intersecting different putative bases?
01:33
Idk......................................
I told you to prove {{a,b},{b},{b,c}} is a base. go and do it.
see my 5 "is ..." questions?
do you understand why answering those 5 questions is how you determine whether or not {{a,b},{b},{b,c}} is a base?
Because those are the elements of the topology.
the topology also includes {} and {a,b,c}. I think you are getting confused because the base and the topology itself have nearly the same sets. maybe you should pick a bigger topological space so you don't make yourself dizzy.
or by "those" were you referring to the sets at the beginning of my "is..." questions?
Yes. My head is a little dizzy but I can bear it. (For math!)
in any case your study might be more fruitful if you picked more meaningful topological spaces
for instance, you're aware every open set in R^n can be written as a union of balls, or a union of boxes?
01:38
Yesw
I don't see why you would need any more examples than those. Those perfectly illustrate the point of bases.
@DisplayName I have a query script for you, just tidying it up a little bit
@anon I just wanted to develop an example for future reference.
@Bitrex That was fast!
@DisplayName I think the script may also return questions that are in the negative and have no answers and aren't closed, getting rid of those may take a little more work but there don't seem to be too many of them
01:44
@Bitrex Yeah that's fine. negative with no answer questions are autodeleted
@DisplayName please try this: data.stackexchange.com/math/query/272758/…
2
Looks good! 16216 questions with these qualities
@DisplayName ya lol
Crap, ones at bottom of list have answers
01:47
Oh wait nvm
It works
The ones at the bottom are ones that were just put up and the system doesn't know yet that they are answered
Cool!
Enjoy!
@Bitrex Thank you!
:D
@DisplayName (made possible by Xenos in #cobol on synirc.net)
Good to know :)
does anyone know how to solve this with a computer?
0
Q: How many such families exist? (Placing pigs into pens)

Modded BearConsider the set $[n]$ and a positive integer $k$. Now consider the set $F$ of families of subsets of $[n]$ exist such that: There are exactly $k$ elements in $F$ Subsets can appear more than once Each subset has an odd number of elements Two intersecting subsets $A$ and $B$ satisfy $A\subsete...

02:32
@ModdedBear having some trouble understanding that
great, someone actually tried.
what part is unclear?
let's start with bullet point 2, subsets of what appearing in what?
subsets of $[n]$
$[n]$ is the set $\{1,2,3,4\dot n\}$
yes
so every element of F is a multiset of subsets of [n]?
no, $F$ is a multi-family of subsets of $[n]$
02:36
multi-family is not a word
or are you yanking my chain?
ok, $F$ is a family which contains subsets of $[n]$, but each subset can appear more than once
so for example $F$ could be $\{1,\},\{1\},\{2\},\{3\}$ when $n=3$ and $k=4$.
you said "the set F of families of subsets of [n]" which implies every element of F is a "family of subsets of [n]," although the word "family" should be amended to "multiset" because multisets indicate the possibility of multiple membership whereas families do not
Oh dang, then what you said at the beginning is correct
yeah, $F$ is the set of all such multisets of subsets of $[n]$
@Modded you seem to be going back and forth describing two different things. Lets take a small example, let $n=2$. Is $F=\{~\{\{1,2\},\{1,2\}\},~\{\{1,2\},\{1,2\}\}~\}$ allowed?
(ignoring the condition that there must be an odd number of pigs)
this is insane, maybe you should describe the problem in terms of pigs and pens first
then I'll try to figure out how I'd express the problem without reference to them
02:41
I think it is ok now anon
srry for confusion
ah good I was going to ask about "F" in your first bullet point later
but you've fixed it so I can read on
you should fix it in your second bullet point too
"for example F can contain..."
@JMoravitz If you give $n$ and $k$ $F$ should be automatically defined.
the elements of $F$ are going to be the multisets $M$ satisfying the properties in the bullets
Yea, I wasn't looking at the question at the time, just trying to help sort through if it was a multiset of multisets of subsets of [n] or if it was a set of multisets of subsets of [n]
03:08
Hello everyone
Is anyone online?
I need some help with probability
0
Q: Expected Value - Probability - COVARIANCE

JuanI need some help about calculating a Covariance having the density function (I hope this names are OK, I'm a Spanish speaker). The density function is: $$f_{X,Y}(x,y)=\frac{1}{x}.exp(-\frac{4x^2+y}{2x}).I{x>0, y>0}$$ I need to calculate $E[X.Y]$ and I don't know how. I know how to calculate $E...

03:21
What are some good resources on $L_1$ approximation?
ugh. trying to do reason correctly re: contour integrals with branch cuts is tricky when your brain refuses to remember obvious things
03:53
Is there a notation for all finite conjugations of truth expressions in a set?
04:17
hi
Do you think that in doing mathematics definitions are more important then theorems?.

I feel that definitions are the chief reason why these theorems exist in the first place and the inherent beauty of the subject lies in capturing hidden mathematical ideas through carefully crafted definitions. In a more ethereal sense the definitions already exist whereas the theorems come into existence when one is convinced of the justification provided by the proof. Hence definitions preempt theorems and should occupy the center stage of mathematics. (When I talk of definitions I also mean the motivat
that would seem to imply that (for example) while the concept of integers and primes would exist from the moment they were defined, the infinitude of the primes would not come into existence until someone were to prove it.
so to separate the theorems of an axiomatic system from the axioms themselves seems a bit strange to me
(were i better versed in the subject, now would probably be the right moment to raise the specter of Godel's incompleteness theorem. but i'll leave that to someone with better expertise)
Definitions are like theorems that have no predecessors.
what about a scenario wherein there are multiple but equivalent ways to state the axioms of a system? say, Euclidean geometry with the parallel postulate replaced by something which is expressed differently but is logically equivalent (like playfair's axiom, if i remember right)
then one would seem to be in the situation of saying that each possible 'grounding' of Euclidean geometry, in that fashion, would possess a different set of basic axioms. but any statement that's true in one such formulation would be true in any other
not sure that's insensible, just a bit strange to my brain
04:36
if you fiddle with the things you just said just a bit, you've stumbled on the idea of model theory and elementarily equivalent models, I think
heh, neat.
@MikeMiller Do you know if notation questions are appropriate on Math.SE?
i've read stuff on godel in the past, so i'm probably a bit conditioned to be able to talk in that spirit (though with no pretenses at rigor!)
I think so, @Axoren.
i'd put it under the terminology tag
04:38
@MikeMiller @Semiclassical Thanks
@Semiclassical When you say read stuff, do you mean actual mathematical writing, or more pop-sci writing?
closer to the latter than i'd like to admit
The latter, sadly, does a terrible terrible job of explaining things, and it's easy for it to lead one astray.
mostly Rachel Goldstein's biography, though, which i thought did a good enough job
(in the same way that I want to read some physics... eventually) you should try to read a mathematical logic book sometime if you enjoyed thinking about Godel's
usually at the introductory level it's all quite simple, simple enough that I could grasp it as a sophomore even though I was dumb as bricks then
04:40
heh, maybe. i'm decidedly a dilettante at such things
i'm trying to remember, though, what a relatively concrete example of model theory would be. does ZF set theory + axiom of choice versus ZF+ negation of choice count?
no, no, a model is like, a concrete realization of an axiom system
and model theory, then, is the study of models
right. hmm
05:14
For you gamers :-)
05:35
The problem with Minecraft being the "go to" for creativity is that everyone always makes 100% symmetrical dirt dildos half the time
There are probably far more creative games that are twice as fun, but less popular.
06:20
For you thinkers :D
06:50
@Axoren 100% symmetrical dirt dildos? Is this a thing you have seen built?
First post on the the Mathematics chat with the total chat message count over 20,000,000(He got 20,000,068) goes tooooooooo:
yesterday, by Julian Rachman
Hey. I had a quick question: If you had a topology $\tau$ on set $X=(0,1)$, does that mean that we can form a basis with all singleton sets of $(0,1)$? Moreover, can you do that with all other topologies and take the collection of singleton sets as a basis?
hell, and it's even a math question!
@MikeMiller Happy days :)
For the record, the one who actually got it...:
Greetings
@Chris'ssis How are you :)?
@Committingtoachallenge Great! Ready for some work.
07:00
@Chris'ssis That is wonderful to hear!
Not before taking some milk and cocoa. (brb)
@Chris'ssis I need coffee myself, be back
@Committingtoachallenge OK
07:16
Morning, @Huy.
Huy
Huy
It's high time you went to bed, @MikeMiller.
No, it's only 11.
Huy
Huy
Ok.
I have a cold.
I hate it.
On the plus side, the power saving light bulbs I got for free from IKEA are really good, so far.
@MikeMiller: How are you progressing with your work?
07:49
hmmm, I've just developed a new kind of integral ...
@infinitesimal Does it sound better now?
@Committingtoachallenge Yes. All the time.
Sometimes, they put in the effort to use Pink Wool instead. Creative Multiplayer is the worse thing possible.
I completely forgot to submit a peer review I've been writing for a month and a half, only to remember that I reformatted the laptop I was writing it on.
It's due today.
@Chris'ssis Greetings.
@infinitesimal Greetings :D
07:55
How are you @Chris'ssis?
@infinitesimal Great these days, very creative! I feel I'm going to publish a very good book. :-) You?
@Chris'ssis fine thanks.
That's fine!
08:12
@Axoren wtf Holy crap man that doesn't sound good at all
@Committingtoachallenge It all started when I tried to install xubuntu-desktop. Then, when I tried to remove it.
It never left and everything broke.
Logging in was no longer an option, because logging in would just being me to xubuntu's login screen
Which was no longer installed
08:39
@Axoren So what are you going to do about the due date?
@Committingtoachallenge Writing it from memory right now.
To the best of my ability.
@Axoren That's crazy!
It's due today, which according to my watch, it is only 3:40am right now
I'm almost done.
@Axoren Are you the guy who made the coffee tex tool I was testing?
Nope. Why would I be that guy?
08:41
You must have a good memory.
Oh sorry that was Kasper
@infinitesimal Only for things I've written or things I will write.
I once memorized the constants file in my compiler's course, years ago.
Gone now, but I knew the actual integer values of every constant.
It's not hard, it's like photographic memory, but much easier.
Because it's just text.
@Axoren What was the first thing we talked about :P
That was a while ago. I think it was about "iwriteonbanana's" name.
I only remember things that are locally important temporally, I guess I'd say.
08:46
@Axoren Fair enough
local temporally?
I don't even know how I'd combine those words.
To mean what I mean
@Axoren What time do you normally go to sleep?
Lol
Let's just say that distribution has no defined expected value.
Temporally important.
Your talking on chat graph seems suggestive :P
08:48
@infinitesimal But only local time.
Like recent within some neighborhood.
Or timehood
A Timeberhood.
@Axoren You seem to sleep about now for the next 7 hours
That's just when I get off chat.
And hop on my laptop and write stories in bed.
@Axoren But you talk at every other point in the day
That's just when I have things to say.
Or when people are here.
@Axoren In the most part our times on are opposite
08:50
If I had to describe a subset of when I fall asleep, it's usually at ~9:00pm
That's when I'm not working on anything during the week.
Otherwise, it's sporadic and all over the place.
@Chris'ssis Out of curiosity, how is your integration method new?
@Committingtoachallenge I said a new kind of integral, not a new integration method. There is a difference between them.
@Chris'ssis What does that mean still?

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