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00:00 - 15:0015:00 - 00:00

00:02
Think about this. Can it happen that $A\cap B=\emptyset$ but not the other stuff?
00:19
My first blog entry
Actually new link:
You have to enter in the title first for the link to be auto-populated with it
@geocalc33
Arturo Magidin was like dude you should have a blog :>
It's actually for me to store my notes mostly
01:24
@EnjoysMath
@geocalc33
I think it's getting to that point where I should start a blog too
@enjoys how's topos theory going?
@geocalc33 I could help you get your blogger account working with LaTeX
I quit topos theory, it's too far from application
seems hackish etc
ah I see
I guess all math is done relatively. Even if you have the power of topos theory it's out of reach of my mind, so it's useless
01:30
@enjoys that would be great if you could help with that
K, log into a blogger.com account
Using google or w/e
01:48
comfortable here?
02:02
@geocalc33 I left a test comment on your $\int a$ test page
@EnjoysMath okay
@geocalc33 I would advise you to make short & sweet posts
not long ones
I was working on this question for math HW. Does this question make sense? I am confused as I think the question itself is a contradiction.
You can tie together long lines of reasoning using links
@geocalc33 forgot to mention the "tag system" for your post can be accessed on the right of the edit page. They're called "Labels"
See one of my posts:
It helps search engines / people find your page
And helps you organize your site
02:10
How are the values for O(X+Y) obtained from the chart on top?
Can you conclude something from two contradictory assumptions?
Well, since anything can follow from a false premise...
But was that a reply to my question?
No sorry it was a separate question
 
1 hour later…
03:25
@AfronPie No, it's definitely not. But if you assume $A$ and $B$ are independent, then you do get a contradiction. That's not saying the question is a contradiction.
03:45
@TedShifrin hey ted!
 
3 hours later…
Anonymous
06:53
Is there any easy way to see that $V$ is the commutator subgroup of $A_4$?
07:04
@AfronPie the question is fine. If $A$ and $B$ are independent, $P(A\cap B)=P(A)P(B)$.
07:25
@AdamL $\min(A)$ and $\max(A)$ are supposed to be elements of $A$. For example $(0,1)$ has no min or max the same as $\{\}$. Now $\inf(\{\})=\infty$ and $\sup(\{\})=-\infty$.
0
Q: For any $k \gt 3$, if $n!+k$ is a perfect power then does there exist any $n\gt k$?

MathphileA while ago, I asked a similar question For any $k \gt 1$, if $n!+k$ is a square then will $n \le k$ always be true? where users mathworker21 and WE Tutorial School proved that for non-square $k$, $n\le k$ is always true when $n!+k$ is sqaure. Recently I got the idea to check if the property is...

Anyone interested in a bounty?
08:01
do anyone know dirichlet function?
does
I will construct a sequence of functions on closed interval [a,b]. Let's say there is a countable infinity of rational numbers in this interval so there is a sequence in [a,b],which we denote by $x_1,x_2,...x_n$
Which contains them all
@TedShifrin You've never read The Hobbit? I'm sorry for you.
On closed interval [a,b] we define function f_n by f_n(x)=1 when x=x_1,x_2,...x_n and 0 otherwise
can you evaluate $|f_n(x_{n+1})-f_n(x_{n+1})|$
Which is funny question
but can you show if this is uniform?
I know it is sup{f_n(x)-0} since taking limit I guess f(x) is 0
@robjohn that's fine it's just the first time I
f(x) is pointwise limit function
have needed to invoke the statement in order for something I am doing to maintain logical and functional consistency
08:10
I think sup{f_n(x)}=1 since max it gets is 1 and f(x)=0 because it is limit when it approach infinity it exceeds x_n which is 0
So Am I right?
@robjohn what do you think?
@RealDumbfoggybrain $|f_n(x_{n+1})-f_n(x_{n+1})|=0$
what is the actual question?
@robjohn lol I mean prove it uniform convergent
@robjohn My answer is 1 so I confirm it is not uniform wut u think about my logic?
@robjohn Well to prove it is uniform convergent or not.
@RealDumbfoggybrain what is converging uniformly? the sequence $f_1, f_2, \dots$?
@robjohn yep
@robjohn the sequence of function u may remember when taking real analysis
@RealDumbfoggybrain what are the $\{x_n\}$? is it an infinite sequence?
08:20
@robjohn how can it be infinite since I said it is in interval [a,b]
😂😂😂
Notice that $f_{n+1}(x_{n+1})-f_n(x_{n+1})=1$ so the convergence cannot be uniform
@RealDumbfoggybrain what? there are many infinite sequences in [0,1]
@robjohn whattttttt............
@robjohn wait sorry I mistakenly said it is finite lol
@robjohn Oh sorry I misunderstood lmao
@robjohn it is not processing in latex
Do you have the bookmarklet installed?
@robjohn tell me then what is the pointwise limit of the sequence
I mean the sequence of function I defined there
@RealDumbfoggybrain the pointwise limit is $f(x)=1$ if $x\in\{x_1,x_2,x_3,\dots\}$ and $f(x)=0$ otherwise.
08:25
is it 0?
@robjohn wait so we can't confirm that it is uniform convergent?
@RealDumbfoggybrain I looked back at your definition of $f_n$ and that is the limit
@robjohn then we have two answer which is 0 and 1 😂😂 which says it is both uniform convergent and not
@RealDumbfoggybrain No. If it were uniformly convergent, we would be able to find some $n_0$ so that for $n\ge n_0$, $|f_n(x)-f(x)|\lt\frac12$
But $f(x_{n+1})-f_n(x_{n+1})=1$
@robjohn now my brain did another another calculation and says it is not uniform convergent
That is correct
08:31
@robjohn simply because it wants sup which is max so there is difference of 1 max
Well conversation is best way to get misunderstanding out
I think it was trivial
@RealDumbfoggybrain most things are trivial in retrospect
@robjohn yep
@robjohn do you think the function is integrable?
@RealDumbfoggybrain yes. Any countable set (such as $\{x_1,x_2,x_3,\dots\}$) is a null set, and whether you are using Riemann or Lebesgue integrals, the integral will be $0$.
That is, $f(x)=0$ except on a null set, so the integral is $0$.
I use Reimann integral for now
@RealDumbfoggybrain doesn't matter. Same result.
08:37
@robjohn Wait I think I haven't heard this theorem or may forgotten
I have alternative answer
It just comes from step function
You may know it
@RealDumbfoggybrain For a countable set, consider the partition $\bigcup\limits_{k=1}^\infty\left(x_k-\frac\epsilon{2^k},x_k+\frac\epsilon{2^k}\right)$
@robjohn again I understand wut u were saying 😂😂😂
@robjohn omg how do I see latex
@robjohn I just see unprocessed latex
I mean uncompiled
21 mins ago, by robjohn
Do you have the bookmarklet installed?
bookmarklet?
So is it available on android os?
click the link and try, pal :-)
08:49
@skullpatrol I will try it. When I get home. 😀
@skullpatrol Hey Pal! I want to talk to you about some topic, can you move me to some private chat (I know every chat is public but something like my room “Let’s do...” or yours “Corona update” )
?
@Knight Sounds interesting. Are u undercover mathematician lol like u work for government?
@Knight Second John Nash of this century
This is the Covid century
Covid is interesting virus.
@skullpatrol r u doing stimulation of covid-19?
08:55
@RealDumbfoggybrain Nah! I just want to talk
@Knight I think we can talk about it here
@Knight just start with your theorem that u come up with
from observing this virus
I can only gain info from news
@RealDumbfoggybrain Are you an Indian?
Nah I am not Indian lmao
@Knight wut make u think I am indian 😂😂😂 my bad grammar?
I am sloppy writer
@RealDumbfoggybrain No! Your way of joking (LOL)
And I’m darn sure you’re an Indian
@Knight what u have observe this days with virus?
@Knight I swear I am not Indian
I heard Indian guys only joke bout Bob's and vagene
Or may be I use too much lol and lmao
May be I should use sticker
😂😂😂
09:00
@RealDumbfoggybrain People are more dangerous than virus itlsef
@Knight well sure...... wut bout mosquito
@RealDumbfoggybrain You see mosquitos are found mostly in Asia, you must be Asian ?
@Knight lemme see
@Knight not only in asia
@Knight I am thinking about how can we spread corona faster than preventing it
With restriction
Alternative way of spreading corona
Without human interaction
@RealDumbfoggybrain Just an advice as a friend, some people here don’t like excessive joking (I do like jokes, just like you) so if you’re saying about spreading CORONA they might flag you
@Knight You don't have proof that I am asian
@Knight Not joking but anyway let's stop about corona topic
@Knight r u hacker?
anyway My mom is Asian but not Indian 😂😂😂 see ya
 
1 hour later…
10:23
Random philosophical mathematics question
What is an integer without reference to notions of fractions nor natural numbers?
@Secret I didn't understand it.
it is the free group on one generator
right, that should work
@Secret r u asking about number or definition of integer
an element of the initial object in $\textbf{Ring}$
10:28
definition of integer that is not in terms of the words "fraction", "natural numbers"
Guys do people employ self taught mathematician?
Well without term natural number the definition itself is gonna be 0
null will be the definition
My maximum knowledge in Mathematics is real analysis for now so may be I can't answer that.
@Secret is my answer dumb 😂😂😂
@Secret So wut u think what would it be
Thorgott and Leaky have answered my question
a unitary preserving thing basically or elements generated by one element
@Secret what is answer
it is a discrete subgroup of $\Bbb R$
@Secret So where was it taught? Elements generated by one element
I mean which subject in math
If without fraction I can use addition
but addition needs natural numbers
So I don't think elements generated by one element
Is answer
since it is being generated then how will it be generated
how will u generate something without properties of order field ?
10:39
foggy brain: Depends on what level of metaphysics you are asking: An answer is a statement that address the needs of a question
I am not sure if you can have integers without binary operators like addition, or more generally, an operation at all. Might think about such minimal notion of integers later although I currently don't need such deep metaphysical territory yet
Leaky: That works too
@Secret and What it means by unitary preserving thing basically?
Everything stemmed or is grounded by one element, if you want a highly metaphysical answer
In maths, it is an initial object, meaning there is a unique map that go from it to any other element
ordered fields have nothing to do with Leaky's answer
I don't need to blow up order fields just yet
I am not asking for the most minimal definition of an integer
I am asking for a definition of integer without reference to other number types, so Thorgott and Leaky have provided me the answers that address my question
@Secret may be I am not capable to understand the language of math or philosophy of you level yet
I am just 17
10:45
leaky's answer is in the context of group theory, and Thorgott's answer is in the context of ring and category theory
both are learned at least in year 2 mathematics in university
@Secret I haven't even touch group theory Just real analysis and am high school student
But my next course is group theory
😱
Group theory is very cool, and a very powerful way to understand mathematics. learn it well when it comes
Will it begin from intutive language? Or it will just hit hard like you guys hit me hard with question
@Secret can u solve cube with group theory? There is cube on my book cover.
Rubik's Cube
yup, rubik's cube employ group theory principles
I am not a rubiks speedrunner though, thus I cannot give you the exact algorithm on how to solve a given rubiks cube configuration
I tried to solve rubix cube by induction
10:51
But the basic theory is: For any solvable rubik cube configuration, it is done by applying a sequence of rotations and antirotations from the solved state to the current scrambled state. Since everything is invertible in a group, it guarentees there exists sequence of moves to solve it
@Secret have you ever solve cube without learning advance math?
only the easy ones, and then I just give up
too many backtrackings
@Secret I have thought about thinking cube in term of what u state when I was 14.
Well I think I am not gonna give up solving cube since it makes me think I am not original. Should I not learn group theory.
@Secret So wut u mean by easy ones precisely?
those where it differ from the solved state by only 3 turns
but even then I sometimes messed up
@Secret But group theory is learned in yr 1 in my course list
my course is kinda different
quantstart.com/articles/… I follow this course
I am self taught because It is impossible for me to go university because I have very bad situation
So I must finish yr 3 to 4 course before 18.
Literally need some advice form u guys since I don't have professor who is gonna teach me unlike u guys.
11:01
Hmm... so you are following a more applied path to group theory. I don't know quantitative analysis well to comment, other than yes, there are some pretty high dimensional groups involved for complicated hedge fund portfolios
But I don't follow it fully. Ex I took yr 2 real analysis too.
You might get reasonably deep at the level of pure maths on group theory, but you will probably need other books on group theory as well
@Secret No it more applied I think yr 3 and 4 is kinda applied
@Secret I want to be pure mathematician.
So how I choose which books to read
Should I look further reading listed on my books for more deep knowledge.
books is something I am not good it, will wait for other users to provide you some head start
And I want to study field of math which is hardest and where only few people study it.
11:04
I think the main has a question on recommended group theory text
11
Q: What is a good book for a second "course" in group theory?

Andrew DHaving studied some group theory in my last term at university, I've found it to be quite interesting, although it's also something I want to improve on (mainly when it comes to proving statements), so I figured that it might be worth doing some group theory slightly beyond what I need for this y...

@Secret but there are first and second yr course on group theory
and third year is ring theory
looks like the website I mentioned covers all the undergraduate stuff taught in standard math department
yr 4 is full of applied course
@Secret what do u think which is hardest field to study in Mathematics?
I mean master pevel
level
I think it depends on what problems is researched, more than which field of study it is in
no such thing
I think I want to learn number theory.
Study number theory.
I think mathematician are not rare nowadays. Lots of people are studying in this field that are smarter than me. So it make me think I shall give up on math.
But why are some problems still remained unsolved?
This is my question.
I am sure there are millions of mathematician with phd but still why no one has been able to solve Reimann hypothesis? There are people who is learning math for their entire life.
or may be not ,millions
11:44
Because no one has found ways to solve them, and usual stuff doesn't work
We're not even sure there is a way to solve them
11:56
@Astyx but there are so many super genius who is godlike intellect.
Are there ?
@Astyx I can't believe there are problems which is unsolvable and remain 100+ yr unsolved.
Or am I having dunning Kruger effect?
But think about people with photographic memory. And IQ of 170+.
And people have spend billions of dollars on research. I don't think This 6 problems survive bring unsolved for decades.
7+ billion of people.
And we have website where we discuss math.Where we can have thousand of brain work together.
I think the problems are already solved but people are hiding stuffs.
Look there are people who accidentally solved unsolved problems which remained fo decades for Homework lol
and some asian dude who solved in a day
There are ~7 billion humans, yes
Now let's slough from that statistic the amount of non-mathematical people
From that, let's slough off the number of people who are actually in the domain of such-and-such field where that unsolved problem is studied
https://mathoverflow.net/q/359060/25104
@RealDumbfoggybrain
But that's still lots of people who remain.
12:12
Are there?
remains 50k people according to me.
Click on the picture in the question to zoom in. @RealDumbfoggybrain
@RealDumbfoggybrain =IF(OR(ROW()=1, COLUMN()=1), 1, IF(ROW()>=COLUMN(),-SUM(INDIRECT(ADDRESS(ROW()-COLUMN()+1,COLUMN(), 4)&":"&ADDRESS(ROW()-1, COLUMN(), 4), 4)),-SUM(INDIRECT(ADDRESS(COLUMN()-ROW()+1,ROW(), 4)&":"&ADDRESS(COLUMN()-1, ROW(), 4), 4))))
(Excel)
A more pertinent thing for my issues, anyway...
How is the O(X+Y) gotten from the chart on top?
12:16
@MatsGranvik u mean u solved Reimann hypothesis?
@RealDumbfoggybrain No I have not. Just trying to maximize certain linear programming problems, tangentially related to it.
@MatsGranvik well good luck
@JohnnyApplesauce Is that a system of equations?
Since I have not enough knowledge in math for now so still long way to learn to understand what Reimann hypothesis is sayin
It is a probability distribution function
@MatsGranvik
12:19
I just think something is being hidden. Or I am living in simulation.
https://oeis.org/A003418
"An assertion equivalent to the Riemann hypothesis is: | log(a(n)) - n | < sqrt(n) * log(n)^2. - Lekraj Beedassy, Aug 27 2006. " (due to Schoenfeld)
a(n) = A003418(n)
$\displaystyle \sum_{n \leq x} \Lambda(n) = x + O( x^{1/2+\epsilon} )$
@RealDumbfoggybrain
$\boxed{\Lambda(n)=\lim\limits_{s \rightarrow 1} \zeta(s)\sum\limits_{d|n} \frac{\mu(d)}{d^{(s-1)}}}$
Well I can't read latex lol
It is not compiled
Android version is not working
@MatsGranvik how do u stay motivated for math
Don't you think too many people are smarter than you
@RealDumbfoggybrain It is the other way around. I try to quit math.
12:29
And continuing development seems dumb when there are smart people who can handle this
Math was my dream until I was 15 and start studying university level math and found too much people are smart thus I feel dumb to even tough math. But I kinda got addicted to it.
touch not tough
sorry I come here just to mostly talk less math
Comment-ce qu'on decrit un espace topologique sature? Une example c'est $T_1$ je suppose.. D'Autre examples?
@RealDumbfoggybrain what kind of math do you like most?
C'estq uoi un espace topologique saturé ?
Anyone here familiar with stochastic approximation theory and, in particular, stochastic gradient descent?
@geocalc33 Every kind of math. I am curious but depressed all the time. It feels like There will not be alot of change with my existence or without my existence.
12:48
@Astyx c'est vraiment "le set sature," desole. Le set c'est sature si le set c'est un intersection des sub-sets ouvert de X pour un espace topologuique $(X,\tau)$
set = ensemble en français
oh thanks
Où est-ce que tu lis ça ?
@RealDumb wow you're curious but depressed? What specifically are you curious about in one area of math?
@geocalc33 Number theory. Too much people learning it.
The reason I am depressed because I heard of too many child prodigy news who is pursuing math career and they are lucky.
I mean they are rich and their parents give them freedom to learn it.
I save money not eating food and buy books.
And teach myself math.
And corona is slowing my learning pace since I can't buy books anymore.
12:55
Je lis un essaie par un mathematician qui est francais
Don't get discouraged by stories of child prodigies. A lot of it is just there to catch media attention
And I can't even get good grades because my parents transfer to a school where I don't have language familiarity.
@JohnnyApplesauce Just a guess but the middle value O(X+Y) = 0.37 =0.51-0.09-0.05
Learn maths at your own rhythm, there's no hurry and it's ok to take time to assimilate stuff
@Astyx There is hurry since If I don't learn it fast and deeply then I am gonna be doomed forever. I must join university which is impossible because of my bad grade or just go get a job.
Must solve some open problems in math to get professor's attention lol.
13:01
no
and bad grade is due to language problems I am facing.
@RealDumb you should only try to solve an open problem if you are a professor and have tenure
@geocalc33 I am just 17 lol.
so don't try to overextend yourself
that's probably why you feel the way you do
be patient!
And Also since I am learning CS, Physics and Math at same time learning undergraduate stuff so pace is extremely slow.
I got only 1 yr to learn 3 yr worth of math undergraduate course lol.
13:05
what are you learning about in CS at the moment?
Trying to master all programming language at this moment
I finished 1 books by bjarne stroy
you realize that if you try to master everything, you will master nothing right?
@geocalc33 I have mastered c++ but not fully at very very advance level
book for physics undergraduate
and also got optics
how could you apply c++ to a physics/math problem?
@geocalc33 I learn CS to live I mean get money but I do have interest in CS.
13:13
nice
The more I learn The more dumb I feel.This is my experience.
At least I got this website to ask dumb question 😂😂😂. I feel dumb looking at question I asked. It was just recognizing patterns.
well math is very much a recognition game
@geocalc33 yep.
Also I love art. I have done courses in art. I can also do 3d modeling.
I have join competition on cg boost.
nice
I have a 3d printed model of the boundary (fibrated) of 8 intersecting 2-spheres at my house
I knew a mathematician will do stuff like that.
13:26
@JohnnyApplesauce
0.09 == 0.09
0.16 + 0.15 == 0.31
0.05 + 0.25 + 0.06 == 0.36
0.1 + 0.1 == 0.2
0.04 == 0.04
So how old are you guys btw.
Well it's a pleasure to chat with you guys. Wish you good luck at your journey in Mathematics.
5
@MatsGranvik So the study guide is simply incorrect?
13:55
fj;ksd ghg khg ;jghskjgfj;k fshf jhFfjzdsjgdg
testing
Can others see my message?
please reply
Hello?
@JohnnyApplesauce Could be if your numbers are the anti-diagonal sums.
14:47
Hi @MatsGranvik
Hey @JohnnyApplesauce ! I think I know your brother Johnny Appleseed
@abhas_RewCie Yep
$$\lim_{n\to \infty} \frac{x}{n}\left[ ln(1+ x^2/n^2) +ln(1+4x^2/n^2) + ... ln( 1+ n^2x^2/n^2) \right]$$
Can I write the above limit as the integral $$\int_{1}^{x+1} ln(x) dx$$
?
I think I cannot because we have something like this $$\lim_{n\to \infty} \frac{x}{n} \sum_{i=1}^{n} ln (1 +( \frac{ix}{n} )^2 ) $$
But limit form of the integral should be of the form $$ \lim_{n\to \infty} \frac{b-a}{n} \sum_{i=1}^{n} f ( a + \left( \frac{b-a}{n} \right)i) $$
00:00 - 15:0015:00 - 00:00

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