« first day (2398 days earlier)      last day (2614 days later) » 

12:04 AM
@Daminark Lol
 
12:25 AM
@ForeverMozart What?
 
hey @Akiva
:?
 
1:07 AM
:[
parents won't believe it's free even though they said they would only pay if it's free
what a bunch of mother fuckers
idk ill pay for it once i get a fucking job
 
Calm down pal.
 
idk, i'm just really really tired
and stressed
 
Get some sleep.
 
uhh alright
 
:-)
Cya later.
 
1:14 AM
bye
 
1:45 AM
Hi all
0
Q: Beyond Bernstein functions ? Sign of the derivatives question.

mickConsider functions $f(x)$ defined and real-analytic for $x>0$ , such that for all real $x,y > 0$ and integer $n > 0$ : $$ sign (\frac{d^n }{d^n x} f(x) ) = sign (\frac{d^n}{d^n x} f(x+y) ) $$ In other words ; the signs of the derivatives do not change over the positive reals. Some trivial exa...

Looking for elementairy examples
 
Interesting question!
 
took a nap
i have a question: @skullpetrol = @skillpatrol?
 
2:01 AM
of course, and I'm mick
 
Is $T:F^2\to R^2$ a linear map?
From Wikipedia, a linear map (also called a linear mapping, linear transformation or, in some contexts, linear function) is a mapping V → W between two modules (including vector spaces) that preserves (in the sense defined below) the operations of addition and scalar multiplication.
 
@TedShifrin What prompted that question?
@Simple What are F and R
 
@AkivaWeinberger parents refuse to believe that financial aid will cover it
even though they said they'd only do it if it was free
 
F is complex vector space and R is real vector space
 
en.m.wikipedia.org/wiki/List_of_large_cardinal_properties Why they have such crazy names. Seriously "ethereal"...?
 
2:16 AM
@ZachHauk Have them email them directly
 
2:27 AM
@skullpetrol you have another name, too, don't you? Other than skillpatrol
Or not. I could be hallucinating.
 
3:05 AM
TeX is easy and fun
$$lim_r\to 1 {2^-rx-1}/{r cos(x)}$$
 
please god no
 
cries
 
easy as lim_r\to 1 {2^-rx-1}/{r cos(x)}
VIOLA
 
please go sit in the corner and think about what you've done.
 
@Brody The world is not ready for this monstrosity
 
3:09 AM
i'm proud of all the progress i made so far in $^lA_TeX$. i should of learned more earlier, but im still defiantly exited to use more! XD
 
W I L L T H I S M A D N E S S E V E R E N D ? ? ?
 
lol still? I just blocked him early
 
I must save him from causing even more damage to the world
 
I didn't see the viola or the mutilated $\LaTeX$, nope. Not me. Haha. Didn't see those at all. Hahaha. Hahaha.
 
Few more posts and we're done
 
3:14 AM
wrong, $L^AT_EX$
 
$\mathbb{EVEN MOCKING IT IS LETHAL}$
 
Hey if we're getting away with this, then I can shamelessly promote gift the community with my question right??
1
Q: Factors of integers of the form $p-2^\lambda n$.

MickLHHere $p$ is an odd prime, $n$ is uniform on $[0, 2^\lambda]$, and $\lambda$ is a constant. We define distribution $\mathcal{D}$ by: $$x \xleftarrow{\$} p-2^\lambda n$$ Assume $p \approx 2^{4\lambda}$, $\lambda \in \{128, 256\}$, and $0 \leq k \leq \log_2 \lambda$. Do a non-negligible fraction of...

 
hi @Daminark
 
Hey @Zach
 
whats going on
 
3:20 AM
Not much, how about with you?
 
meh
I'm going to watch a broadway show tomorrow.
 
Cool!
And what's wrong? Is it about the summer program?
 
no i'm just so tired and i have so much school work
 
*voila ^_^
 
i guess the summer program is disappointing
but i can't wallow in sadness
i'll just get a summer job when i turn 14
 
3:25 AM
 
Yeah, you can do it Zach!
And yeah being tired/busy is pretty rough, just power through, I'm sure you'll be fine
 
@ZachHauk imho you should keep pursuing an intellectual excursion for the summer. but job cash is nice too
 
0
Q: Maximal & Maximal Normal Subgroups

ALannisterI have to answer the following two questions: Using Zorn's Lemma, one could try to give a "proof" of the following statement: Every subgroup $H$ of a group $G$ such that $H \neq G$ is contained in a maximal subgroup of $G$. Explain why this argument does not work. Is it true that any group has ...

 
@Brody what, trying to get into that camp specifically?
or just anything
 
3:44 AM
I think he means it in general
It's good to get some money but make sure to stay active
 
@ZachHauk Both? Anything similar that piques your interest or might be fun. Granted, money is a typical barrier that one must scale unfortunately, at least for immersive programs like that.
 
i'll just self study
idc :/
 
self study is great, nobody to spoon feed you means nobody to slow you down either
5
 
That's fine. It's not so much about some itinerary's content as it is a learning activity to dedicate oneself to.
 
Do you have any particular ideas in mind with regard to what you want to study?
 
3:56 AM
im studying non-euclidean geometries right now
 
I would be taking a summer class trip to Mainland China or even a student exchange, if those didn't cost thousands of dollars after scholarships, ha
 
then i'll be studying some algebra, since well that's a pretty mandatory thing in math
from Artin's specifically, because I'm interested in AG
 
Huh, I didn't realize Artin had AG content
Or at least, stuff with an eye toward AG
 
let me see
 
Right now I still need to go ahead with my "Power through group theory as quickly as possible" plan
 
3:58 AM
i've read a bit of literature about group theory
 
Which means Herstein + some supplements
Though I've decided that I'm going to sit in on Laci's group algorithms class
 
like about group actions and cosets and lagrange's and all that other stuff
yeah in Artin's there's literally a section dedicated to AG
 
Ah, yeah my paper last summer was on group actions, the Sylow theorems, and some applications (smallest non-cyclic simple group is $A_5$, etc)
Oh nice
 
Does Ted's book do anything AG-ish?
 
not really
I haven't read any of it except for the non-euclidean geometries section
 
4:04 AM
ah
that's Abstract Algebra: A Geometric Approach, right?
 
yep
 
speaking of... I need a solid algebra text. I was supposed to start analysis+algebra last fall, now I'm almost a year behind because of unnecessary pre-reqs and other crap :/
 
So, my school's regular algebra class uses Fraleigh
Honors uses Dummit and Foote
I tried self-studying from the latter but it's so slow
 
wait regular doesnt allso use D & F?
i had no idea
 
Nope, Fraleigh
 
4:09 AM
we never reference D & F in my section
 
Dummit and Foote has mixed reception?
 
I hate that book anyway.
 
@Brody Really, i hear Artin's was good
it's not totally aimed towards AG
 
Lol Rozenblyum sticks just about religiously to DF
But yeah, Herstein lacks a bit (I'll need to find something else for Jordan-Holder)
But it's pretty good
 
I heard Rozenblyum sucks and everybody gets their instruction from Claudio
 
4:10 AM
Claudio is good, I was in the barn when he was lecturing and it was nice
But after a quarter of Calegari and then Rozenblyum, that section will get Emerton who's apparently real good
So there's that
 
he's an awesome dude, he's helping me out with the Farb thing I'm doing
 
Nice
 
$\text{乘}$
 
what year are you both?
 
2nd years
 
4:13 AM
@MikeMiller are you a phd student?
 
yes
 
thats cool
 
Nice, what do you work in?
Oh @Eric Webster is finally teaching complex using a book that isn't Lang!
 
what is he using?
 
Stein-Shakarchi
 
4:23 AM
Ohhh at least the class has that going for it.
 
Yeah
 
I love the SS books
 
Webster + Lang = :(
Marianna isn't assigning us any books, it seems
 
yeah as usual
"The material of this course is not entirely covered by any existing books."
 
LOL
That's exciting
Actually one of my classmates checked the bookstore which said that Neves is using Lee, even though he did say he'd be using G&P
Which is weird
 
4:26 AM
maybe both?
 
Possible
 
like I told you earlier, G&P is not very formal in a subject where having technical fluency is pretty important.
 
Yeah, might be a good idea to have Lee around anyway
Especially if he ever starts talking about Lee groups
Sorry I just had to
 
No.
 
i think 2/3 of my analysis class just withdrew with the first exam grades having been released
it's funny in a twisted way, but :/
 
4:33 AM
Yikes
 
it was a rather easy exam too and the majority are math majors according to the professor. by all means, it makes no sense!
 
huh.
What all did it cover?
 
*majority are math majors among the total in the class. perhaps the more diligent math majors are the ones who stayed
mm lemme check
the material is nominally the first chapter of Stoll's introductory RA
prove $p\text{ odd}\;\Leftrightarrow\; p^2\text{ odd}$; prove (by induction) sum of first $n$ positive odd integers is $n^2$; show $[1,3]$ and $[5,8]$ are equivalent by finding a specific bijection; show the set of all positive odd integers is countable by bijecting it with N
 
Heya
 
hi Jessy
 
4:44 AM
Sup, son of Bob?
 
what are supremum/infimum of $\{\frac{n+1}{n}\,|\, n\text{ positive integer}\}$? prove or offer counterexample for a) A, B uncountable then A union B uncountable; b) A, B uncountable then A intersect B uncountable; c) x,y irrational then x+y irrational; d) x irrational, y nonzero rational, then xy irrational
 
i'm just tired
 
Me too. And I've got a sink full of dishes to wash.
 
and two more problems but they're really no less simple
 
Are those people who dropped gonna try again next time or...?
 
4:46 AM
I hope so. If they don't change majors, they'll have since it's of course a requirement for the bachelor's
*have to
 
This is making me nervous.
 
But I suppose many don't want to risk the 0 or 1 grade point score on their cumulative. perhaps they didn't like the prof's style
but I'm certain these are pretty simple problems (hell, I can do them) and it's concerning more than half the class got a D or lower
 
shrugs
 
Just want to make sure, function $T:C\to C$ is a linear map, does it imply $T: C^2\to C^2(R^2)$ a linear map?
 
I don't think that's the right way to write $T$ acting entrywise on $C^2$.
 
4:56 AM
$T: C^2\to C^2$?
 
Yeah.
(Though I think it's a common enough abuse of notation.)
 
I guess you can say $T\times T : \mathbb{C}^2 \to \mathbb{C}^2$?
 
Does $T: C^2\to C^2$ is $C$ linear or $R$ linear, I confuse these two concepts
@Daminark yeah
 
So, you're saying, if $T:\Bbb C\to\Bbb C$ is linear, is $(x,y)\mapsto (Tx,Ty)$ a linear map $\Bbb C^2\to \Bbb C^2$?
 
I would write this as $T \oplus T: \mathbb{C}^{2} \to \mathbb{C}^{2}$ personally
 
5:04 AM
Indeed.
You never said whether we're assuming $T:\Bbb C\to\Bbb C$ is $\Bbb C$-linear or $\Bbb R$-linear, but in either case the conclusion is true.
In fact, if $V_1,V_2,W_1,W_2$ are vector spaces and $f_1:V_1\to W_1$ and $f_2:V_2\to W_2$ are linear maps, then $V_1\oplus V_2\to W_1\oplus W_2$ defined by $(v_1,v_2)\mapsto (f_1(v_1),f_2(v_2))$ will also be linear (and is usually called $f_1\oplus f_2$).
verifying it is straightforward
 
Lol we just got an attachment from Schlag discussing the "method of the gliding hump"
 
omg classic
good memories.
 
gu'n Tag alles
 
Hey @DHMO
But yeah, we've now started Hilbert spaces
Just gave a definition, and stated a theorem that we'd prove next class. I forget offhand exactly what
 
Did he prove the finite dimensional version of the spectral theorem in the first class?
 
5:16 AM
Yeah
 
In common, I should write $T\oplus T$
 
he finishes the class off with proving it for self-adjoint compact operators on Hilbert spaces
it's a beautiful book end.
 
We did it with Lagrange multipliers the first time. He said this is vital because he'd use weak compactness of the unit ball to get the infinite dimensional case
Nice
 
meh, the professor said he couldn't lower the bar any further so perhaps the sieving is better for the remaining students who want a bit more depth
 
@Daminark sprichst du Deutsch?
 
5:17 AM
But yeah, the theorem I think was that if a set $A$ has a couple conditions that include convexity, then $d(x,A)$ is always achieved
 
and I say that at the risk of sounding even more pretentious
Hola @DHMO
 
@Brody hola
estudias topologia?
 
@DHMO Nein, aber ich (want to learn)
 
@Daminark aber ich will lernen
@BalarkaSen greetings
 
cómo estás?
 
5:19 AM
@DHMO Need some help! Why is $$(\vec{a}+\vec{b}+\vec{c})^2\ge 0$$ in this answer math.stackexchange.com/a/1520406/404484 ?
 
@Brody estoy ocupado como usualmente
@anonymous can a magnitude be negative?
 
@anonymous It's the magnitude...
 
@DHMO Isn't it the dot product ?
 
@anonymous ${\vec v} ^2 := \vec v \cdot \vec v = |\vec v|^2$
 
5:20 AM
Hey @Balarka!
And ah
 
Hi @Daminark, @DHMO
 
@DHMO Oh oh, I missed that. Thanks.
 
@BalarkaSen do you have anything interesting / any exercice regarding point-set topology?
 
'ello @Balarka
 
(and I don't even know that it's called point-set topology until yesterday)
@anonymous @BalarkaSen i'm just curious; can you two communicate?
 
5:21 AM
@DHMO Have you ever heard of pointless topology?
 
@Daminark it's pointless
 
@DHMO Eh, what?
 
@DHMO Point-set topology? Hmm.
 
@anonymous I mean, in a language other than English
 
There is one thing confuse me, I have a system of ode, $x'=y, y'=-9x$, why I can not write the transformation matrix as $\begin{pmatrix}3i & -3i\\-1 & 1\end{pmatrix}$
 
5:22 AM
@DHMO Yeah, probably in hindi...why ?
 
@anonymous I think you two are from different regions?
so hindi is everywhere the same?
 
I'm ok at Hindi. I mostly speak Bengali.
 
@DHMO a. bueno yo estoy aburrido
 
@Simple because it is A' = (0 1;-9 0) A?
 
@DHMO Almost. I was brought up in India...so I guess I know how most of them speak!
It isn't much different in Kuwait
 
5:24 AM
 
@anonymous heh? why did you go there?
 
Lol
 
Intuitively it feels like you have a real line except that every singletons are actually intervals
 
@DHMO Father got a better job here.....(He is a researcher in oil and mining technology)
And we all shifted
 
@Secret lexicographic order topology of $\omega_1 \times [0,1[$
@anonymous I see
 
5:25 AM
Well, gonna go play Werewolf with the haus so see you guys around.

And lol I heard Munkres uses the long line as one of its 3 counterexamples to like, everything
 
@Secret I don't think $\omega_1$ and $\Bbb R$ have the same intuition
namely, the former is well-ordered and the latter is not
@anonymous so you speak arabic?
 
@DHMO (0 1;-9 0) has eigenvalue $\pm3i$, so the eigenvectors are $[i/3;1],[-i/3,1]$
 
@Daminark what are the other two?
@Simple and then?
 
I can write the transformation matrix $T$ has column of eigenvectors, right?
 
@DHMO A little. I never officially learned Arabic. And in school we use mostly English (and some Hindi as it is an Indian school).
 
5:27 AM
I guess I'll have to leave that to someone who knows that transformation matrix means @Simple
@Secret and should we continue yesterday's discussion?
 
Ok
 
@DHMO hmm, since $\omega_1$ is well ordered but has cardinality continuum, perhaps something like a continuum of singletons except there are gaps between thus unlike the reals where it is dense (because $\omega_1$ is well ordered, we are able to always find the next element)?
 
@Secret cardinality is quite different from "ordinality"
(order-type)
two order topologies can be based on the same cardinality
but different methods of ordering can give completely different topologies
 
@DHMO yes I know, but when I built intuition on infinite things, often the first step is I worry about the size first, then consider the ordering and the topology next
 
@Secret alright
in that case
 
5:31 AM
@Secret I wanted to make sure that you are aware that a room with no messages of 14 days gets frozen. I am mentioning this in connection with Zero-term algebra chat room. Of course, if a frozen room is needed again, you can ask a moderator to unfreeze it.
 
the long line has actually the same cardinality as $\Bbb R$
so intuitively it's like the real line.
according to your logic.
 
@DanielFischer Just for clarification, are you saying that perhaps $$\lim_{N \to \infty} \int_{-y}^{y}\frac{\pi J_{1}(a(N+1/2+it)) \cot(\pi(N+1/2+it)) }{N+1/2+it} \, i \, dt $$ vanishes for $a=1$, but not for, say, $a=7$? That would seem a bit strange.
 
Ok I need to sketch the graph of $$\sqrt{x}+\sqrt{y}=1$$. Any ideas anyone? On squaring it twice I'm getting the equation of a rotated parabola. I need to remove the $xy$ term and find all the details of the parabola if I square it. Is it possible to roughly sketch it without doing all the rotation and stuff (directly from the first equation)? @DHMO @BalarkaSen
 
@anonymous $y=(1-\sqrt x)^2$
$y=x+1-2\sqrt x$
 
@DHMO yeah. If my intuition is correct, then by cardinal arithmetic, we get $\mathfrak{c}\mathfrak{c}=\mathfrak{c}$ (viewed as a line, there are continuumly many singletons, but each singleton has cardinality continuum), thus giving the excepted and that it is as large as the reals
 
5:35 AM
@Secret yes
and it's also the order topology
just that the order is different
 
@DHMO Umm, how do you sketch that? That isn't any standard equation...
Just by plotting points?
 
@anonymous $y=\sqrt x$ is standard
$y=x+1$ is also standard
and I have confidence that you can manage linear combinations
 
Ok just adding the graph pointwise
I see
 
I have asked a question on the main site on calculus,it seems really tough question,Wolfram alpha fails at this question even with pro time .If anybody is interested then please answer it ...Link -->http://math.stackexchange.com/questions/2161846/just-another-problem-on-integr‌​ation
 
Need to try
 
5:36 AM
1
Q: Just another problem on Integration:-

satyatech What I tried was I took $$\tan^{-1}(x) =t $$ ,but I got terms like $$\cos(\tan(t))$$ which I don't know what to do with,,, So please guide me into solving this..

 
@MartinSleziak Thanks, I will let the mods know when I need that unfrozen cause it will be a while before I can return to it as the next phase in the investigation will be non associative algebras that are not lie algebras, which I am still learning about them
 
$\displaystyle \int \frac {\sin^3 x} {(\cos^4 x + 3\cos^2 x + 1) \tan^{-1} u (\sec u + \cos u)} \mathrm du$
 
That arctan makes it difficult
Interesting
 
@anonymous On the unit square it's clearly like $x + y = 1$, but concave down because $y'' = -1/2 \cdot x^{-3/2} < 0$.
Also, the graph only exists on the interval $[0, 1]$ :P
 
@anonymous and I don't like multivariables.
and I don't like trigonometric unctions.
 
5:39 AM
@BalarkaSen aha! That's a better way of approaching it :) Cool!
 
$u$?
 
The calculus way :)
 
oh I see
 
@Brody yes
 
@anonymous It might also be reasonable to try something like $x=u+v$, $y=u-v$ (which is basically rotation by angle $\pi/4$, if you add also factor $1/\sqrt2$ because of symmetry.
 
5:39 AM
it's univariate
 
It tells you what it roughly looks like anyway.
 
@anonymous my approach: $x^2+y^2=1$ is a circle
$|x|+|y|=1$ is a diamond
so $\sqrt x + \sqrt y = 1$ is a shuriken
 
@MartinSleziak Thank you. I just wanted to avoid rotation as it makes it lengthy sometimes. However, I will keep that in mind!
 
Right ^
 
@anonymous And you can also try whether you find some posts about this curve on the main site. For example, this post is among the search results: Parabola $\sqrt {x}+\sqrt {y}=1 $.
 
5:41 AM
@DHMO As long as it's extended by symmetry!
 
@BalarkaSen indeed
 
But good description. I like it.
 
@MartinSleziak Thank you. Yes, I saw that :)
 
I apologize to other user with username anonymous for pinging him at the same time.
 
@BalarkaSen I guess my message got ignored
 
5:42 AM
anonymous is a common name nowadays :P Oh the irony!
 
@MartinSleziak why can two users have the same name?
 
@DHMO It didn't, but I don't remember a good point-set topology problem off the top of my head. Do you know about homotopies/homotopy equivalences?
 
not at all
 
@DHMO That is useful to remember. I'll keep it in mind!
 
@BalarkaSen if confining the topic would make you remember: lower-limit topology
 
5:43 AM
Shuriken...lol XD
 
How about I tell you what those are and then I give you problems?
@DHMO I never bothered about lower limit topology until yesterday
 
@BalarkaSen what about the discrete topology on $\Bbb R$? this seems interesting
 
That's a stupid topology
 
@MartinSleziak the top answer is wrong
 
5:44 AM
@DHMO What can I say to that other than "because Stack Exchange decided to allow duplicate usernames"? (And you could ask the same question basically any experienced SE user who is around. Like DHMO.)
 
@MartinSleziak was the last sentence a typo?
@BalarkaSen consider the compact sets of the topology
 
@DHMO I have read up about finite subcovers in physics forums. I think I have resolved my [0,1] compact question for now. Otherwise we can continue on discuss about point set topology. In particular I really need to figure out how I can do limit points better in topology
 
Discrete topology is the finest topology you can have on a set... every set is open.
 
I see 3.2 k reputation. That can be called at least relatively experienced.
 
@DHMO Clearly only finite sets are compact!
 
5:46 AM
O and guys, I am currently on mobile. Expect slow typing from me
 
@BalarkaSen how do we define fine?
@BalarkaSen which is interesting
 
It's darn boring man I tell you
 
@BalarkaSen give me an interesting topology on $\Bbb R$
 
The Euclidean topology :D Very interesting
 
@Secret so what is your answer?
@BalarkaSen it's the standard topology...
 
5:48 AM
It's still very interesting! Ok, here's a problem. Prove that every closed subset of $\Bbb R$ is zero locus of a continuous function.
In the Euclidean topology.
 
@Secret give me a pair of disjoint open set and closed set that form (a) a closed set and (b) an open set, under the standard topology. And don't give me the empty set
 
@DHMO If you have two topologies and the open sets of one are all open in the latter, then the latter is finer.
 
@BalarkaSen and what is a zero locus
 
Preimage of zero.
 
@MartinSleziak None of those answers are helpful tbh :(
 
5:49 AM
Once you're done make that smooth.
And prove that same thing.
 
what the hell @BalarkaSen
 
x = x'cos(θ) - y'sin(θ)

y = x'sin(θ) + y'cos(θ)

x' = x cos(θ) + y sin(θ)

y' = - x sin(θ) + y cos(θ) How do you guys remember this set of axis rotation equations ?
I get confused with the signs!
 
@anonymous use matrix
 
@anonymous By the matrix
 
@DHMO How?
 
5:50 AM
@anonymous memorize the rotation matrix
back-transformation is negative of transformation
 
@Secret If you do not mind if I correct you s;s;ogjt;u, it would be more precise to say that the cardinality of real line is $\aleph_1\mathfrak c=\mathfrak c$. But you are right that we get that from $\mathfrak c \le \aleph_1\mathfrak c \le \mathfrak c \mathfrak c = \mathfrak c$.
 
[cos, -sin; sin, cos]
 
I tend to remember the $x',y'$ ones.
Simply because I've used them so much.
 
@Brody Well, in that case that's the oportunity for you to post another one.
 
@MartinSleziak why $\aleph_1$?
wait
$\omega_1$ is the order type of $\aleph_1$?
oh, I got confused
 
5:52 AM
@DHMO Yes. And it has cardinality $\aleph_1$.
 
@BalarkaSen Ah, interesting. The first row is the derivative of the second.
I think that will make it easier
 
@MartinSleziak didn't mean to be snarky. two of the four appear wrong. the others do not answer the question. makes you appreciate SE
 
Anyway, it's easy to derive on your head. If (x, y) rotates to (x', y') by angle theta counterclockwise, then the x-component of x' is x cos(theta) [just do it mentally] and the y-component is y sin(theta).
@DHMO Garbage. Cantor set.
 
@BalarkaSen I have no idea
 
Well, you wanted a problem, there you have it.
 
5:54 AM
I see this topology word thrown around a lot
 
@BalarkaSen oh. {0} is closed.
 
So you proved that zero set of a function is always closed. Doesn't mean every closed set is zero set of some function!
 
indeed
If $|\Bbb R| = \aleph_2$, can a closed set have cardinality $\aleph_1$?
 
Cardinality of R is N_1, right?
 
@BalarkaSen I don't even know how to construct continuous functions
@BalarkaSen no, that's the CH
 
5:58 AM
@DHMO Do I remember correctly that every infinite Borel set has cardinality either $\aleph_0$ or $\mathfrak c$?
 
Ok. I dunno
 
@MartinSleziak I don't know
can you give me a Borel set that has cardinality $\aleph_0$?
 

« first day (2398 days earlier)      last day (2614 days later) »