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00:15
@Daminark complex geometry has funny names in it
flabby sheaves fine sheaves etc
I mean who is in charge of such naming convention lol
@Cryin yeah, the idea is that you know by continuity that the rank doesn't decrease, but the way you know the rank doesn't increase is that it's already capped out
@Daminark ah, yeah I see, you're right I didn't think about it getting bigger. Cool thanks again for the help!
@Adeek lel, that's... Interesting
00:39
@Adeek Hey what's up
00:59
Hmm..., suppose we take the set of reals and remove a countable dense set, is it possible to shift the remaining elements in an order preserving manner so that all the holes are filled in?
01:43
Hello @Ted!
rehi Demonark
I'm still stuck on a question on main. I guess I really am stooopider.
Sometimes main's got tough questions. Which?
Really it's a PDE question. Where's @EricSilva when I need him?
Ah, rip
Hmm, so one of the problems in functional analysis defines the $C^k$ norm of $f:[0,1]\to\mathbb{R}$ to be $\sum \max |f^{(j)}(t)|$
And asks to show that $C^1([0,1])$ is dense in $C^0([0,1])$
Yup, Demonark, standard exercise.
01:50
Do you think just saying "Stone-Weierstrass" would do it or is that likely overpowered?
That's overkill, but valid.
The "correct" technique is one you should figure out, nevertheless.
Probably convolution? When doing S-W that was described as a sort of "smoothing" process
That would be good.
That or bump functions
Well, what if you want $C^\ell$ dense in $C^k$ for $\ell>k$?
Hard to control derivatives of bump functions.
01:56
Ah good point
So you want to find some kernels $\phi_n$ such that that $\phi_n * u$ is always smooth and converges uniformly to $u$
yes, but you need to worry about in which norm.
Hmm, would we want some sort of thing where the derivative of $\phi_n * u$ is gonna be $\phi_{n-1}*u$? Not sure if that's feasible but if so, I think that might be a worthwhile wishlist?
Or maybe not exactly that but sorta one where it'd be of the same form
It'd be a convolution with a similar kernel so that it still converges uniformly
heya @Antonios
how's it going, ted?
@Secret my paper seems to have bothered a few people so lets not discuss it anymore, alright?
thabks
doing just fine, @Antonios ... haven't heard from you in ... ages!
02:19
Yo @Antonios!
yeah, well. Just grinding away here at no small number of things.
Hi @Daminark.
well, it's keeping you warm so far, Antonios
It's actually ridiculous.
Our house is freezing. The cold comes straight through the windows.
Yikes ... New England is supposed to know how to build houses, unlike the south.
You'd think so, but all of our windows are single-paned, rather than double.
02:21
We had good insulation and double-pane windows ..
Oh. Ooops.
Which is miserably bad in terms of efficiency.
Among other things, yes.
So, I've put on the fire place and am working as close to it as I can, nearly.
fireplace*
You could just get in.
Want to make sure min = inf.
Might as well at this point.
min = inf? sounds like some sort of compactness argument lol
02:24
Well, get into the fireplace and test it out.
hehe, in I go.
Actually working on some Algebraic Geometry stuff right now.
I'm not sure whether I should run or stay in place
well, I know the going up and going down theorems ... they sound illicit, but maybe they'd help.
I see "algebraic" and am happy but I also see "geometry" and want to run away in fear
@Typhon I see no one bothered in the transcript. Where are these people?
02:26
Yeah, the name "going down theorem" has cracked me up a few times at the wrong moment.
Bad boy.
There are some quite absurdly named theorems in math.
Well, those names make sense. You just have to keep your dirty mind(s) out of it.
Maybe so, but Exercise 56 in Lang's chapter on group theory is legendary.
Well, I suppose that depends on which edition.
On the other hand, it's Serge.
02:30
I might need to send a picture of this.
Oh... wow
I just looked it up and... wow
Oh, geez ... Tits is a French mathematician, guys.
So we've got that, we've got the exercise where he says to find a book on homological algebra and do every single problem (I want to see a professor assign that)
02:32
What other Lang problems will go down in history?
I know I know, but there's no way that's a coincidence.
I dunno, @Antonios. It's pretty sure Lang was gay. :)
Is that so?
To be fair, from all accounts I've heard, it's 100% certain he was a troll.
Speaking of trolls it's @BalarkaSen.
Sometimes, yes.
hi/bye @Balarka.
What is up dramalernation
Balarka is all chem-ed up, I'm sure.
Taken a fancy to chemistry, have we?
I am proud of this meme
Only for professional reasons
Anyhow, I'm outta here. Maybe Eric will help me with my PDE question.
02:35
goodnight @TedShifrin
@Ted Bye.
I need to figure out why ripples work
Maybe it's because they wiggle
I suspect the proof is the following ASCII art: "---- ~~~ /\/\/"
Yes, that is indeed the right approach
Submit that to Arxiv
02:56
Amazing
See picture 2
|~~/
I've been told that you can define (topological) closure with category theory
@BalarkaSen @Daminark do you know of that?
no and i have no wish to know
Lel
I don't know of it, if it's interesting enough go ahead
Though I will say, someone must have been trying really hard to do that, whatever it is
well we're supposed to consider P(X) the powerset of X as a poset with inclusion
03:04
check kuratowski closure operator it might help you
Ok I have to do some chemistry now
@Leaky I don't think a categorical interpretation could even be valid
@Daminark wut the hell
It's gold it really is
vixra gems :)
03:14
@Daminark yesss
7.8/10 insufficient "whomst"
:P
i give it a NOT GOOD/10
i would switch panel 4 and 3 lol.
guys just a sanity check
i have a random variable that represents the year a house was built , is it meaningfull to check it's mean , variance , sd and such stuff ?
03:24
@Daminark shit joke at your 6
well im just plain confused
@BalarkaSen ?
Topology is fun
@Daminark washington
how is it that Real analysis can be so utterly shit but topology can be so intresting?
03:34
A relative of mine gave me an old Deutsche Mark he collected back in the time he was in Germany. It's good to see chubby old Gauss smiling in there
otoh it angers me that such a great mathematician should be associated with the dirt of capitalism
absolutely disgracefuk
not even going to edit that typo
03:52
lmao
Quick notation question (I have to ask because google isn't terribly helpful when you try and describe notation). Is my interpretation of the provided picture correct, in that, for jr to be assigned to the first item in the bracket stack, vr must be zero and mvr dot t_hat <= js or is it an or operation?
or am I just plain lost (gotta cover all the cases here)?
04:14
its and
though i have nfi what the context is
i normally think of it as as a list of requirments
@Faust context is page 56 of this pdf (marked as 44) drive.google.com/file/d/…
one of the biggest hints if it was or then its not a function when $v_r =0 $ as it is assigned two values so it must be and.
@Faust unless the last to values are or.
the problem is in the context, that math is making non sense, so I, to check everything, I'm going to make sure my assumptions about the notation are correct. That bit came into doubt because it was really weird that it was -jst for any case when the velocity is not 0
I don't follow your logic @Faust. You're saying that it is and. So we must have that $v_r = 0$ and $mv_r \cdot t \leq j_s$... But then $mv_r \cdot t = 0$ so one could just substitute $0 \leq j_s$
Hey guys, could I throw a really soft question at you all?
It's not math, but is definitely within the purview of a math-related chat
04:24
But then or doesn't make sense either to me so idk...
no it seems to makes sense in context @GiantCowFilms there are two diffrent coefficients of friction when the friction force is not great enough to make the velocity 0 the $f_f $ is $-j_d \vec{t}$
Actually nvm this is probably better suited for academia.se
tell us anyway
i still think its and...
@Faust but that still doesn't add up if its and
because if there is any velocity, regardless of whether or not, the static friction force is suffcient to negate it, it defaults to dynamic friction, hence the issue.
04:28
the first line is alittle wierd
i suspect there is a typo...
Great.
I'm definitely screwed if my source material is broken.
@GiantCowFilms Negative progress is still progress
of the negative variety
And the award for tautology goes to @Dair
@Dair My entire life has only been negative progress :P
negative progress needs positive progress... something about balancing the force I presume..... uh....
But anyway, can we confirm its broken?
I rarely trust myself... I would rely on someone else to make that confirmation.
04:35
if you look at 2.67 $f_s$ is in a specific direction different than the direction of the velocity
i think thats significant
I'm not following?
I think everything makes sense in 2.67 but im not sure about 2.69 after the integration
i dont understand how the impulse can exceed the resistive force and the velocity can be zero but or doesn't make any sense eithier
exactly why it is confusing me
and hence why I though it might be an or condition, vr = 0 or mvr dot t < js
(apologies for my lack of Latex skills)
the only thing i can think of is that the velocity $v_r$ is somehow pointed in a non tangential fashion to the surface like only of a portion of the velocity is resisting the friction the rest is pushing against the surface
vr could very easily be non tagential
04:44
so energy is being lost in a way not through friction
and from my understanding of $v_r$ that may be possible but im not sure
the fact that gives you a diffrent friction coefficient may not be surprising
but im not sure im not a physicist
I'm not either :(
Random Off-topic but fun to read question:
50
Q: How to properly dispose of sensitive documents without a shredding machine?

user7230Turns out that the office never had a shredder due to noise concerns and we seldom have work documents that demand such treatment. But one day the unexpected happened, and we had to literally burn the stuff up in the toilet (with care, of course). How do others deal with such a situation?

burn 'em
04:57
I'm surprised the much more sensible solution of eating the documents wasn't mentioned.
2
i really hope im not invested in that company
if the best idea they could come up with is goto the bathroom and set it on fire
shred it, then eat it
it seems like shredding should be the first step regardless of what else you choose to do tbh
easier to burn, bleach away, etc
i guess you put it a big bucket of water...
and stir it up...
seems safer than setting it on fire inside of the office...
yeah
and again, easier to do that once it's shredded
lol
05:04
how else are you supposed to heat the stew without a fire though?
i will never understand the average person i swear
heh, that's another: fuel for your next bonfire
is a metric just a way of measuring distance?
i think ive studies other metrics and never knew thats what they were actually called...
at least if im understanding the definition of a metric
nvm i found the actual definition of metric
@Faust yes
hows leaky?
enjoying skool?
05:16
sure
first semester almost over?
Hi @MikeM
it's over two weeks ago
second semester starting soon
kool
whatcha taking this semester?
It's too cold
I am become frozen
4
05:18
analysis
mechanics
algebra
calculus
user131753
05:46
in General topology, 1 min ago, by user 170039
Let $(X,\tau)$ be an ordered topological space. Then it is true that any interval of $(X,\tau)$ is connected?
@user170039 $\Bbb Q$ isn't connected
in fact it is totally disconnected
user131753
@LeakyNun I think I should have stated the question a bit more precisely. I wanted to mean: "Let $(X,\tau)$ be an ordered topological space. Let $r\in X$. Then is it true that every continuous function $f:[-\infty,r]\to\{\pm 1\}$ is constant?"
@user170039 same answer applies
consider $X = \Bbb Q$, $r = 2$, $f : x \mapsto \operatorname{sgn}(x-\sqrt2)$
user131753
@LeakyNun Thanks.
06:07
oi leaky
can you give an example of a set X and a
collection of subsets of X, T , which is not a topology on X, but satisfies the
first two conditions for a topology and the third, for all countable index sets
I.
basicallys it fails for an uncountable union but is fine with a countable union
take $X$ to be $\Bbb R$ and $\tau$ to be all countable and cocountable subsets of $\Bbb R$
whats a cocountable subset
a subset whose complement relative to $X$ is countable
also $\Bbb R $ would have to be in T?
$\Bbb R$ is cocountable
06:11
what does compliment realitive to X mean?
oh
the complement of $A$ relative to $X$ is $X \setminus A$
whats the set that isnt in T?
that can be made form unions in T?
$[0,\infty)$, for example
$\displaystyle [0,\infty) = \bigcup_{x \in [0,\infty)} \{x\}$
oh frak
very clever
not really
06:16
Thanks ^^
06:42
@ACuriousMind I was talking to some old friends on irc and they said that I should be ashamed of myself to have written something so offensive and that they were disgusted with my "racist attitudes". Once again, I apologize if I offended anyone on here.
07:22
[Random]
To be expanded later in rambles:
In some sense it seems natural that infinite sets should not change size as we take elements away from it. Consider this:
10+1
100+1
1000+1
10000+1
...
As one can see, as the sequence goes on, the difference becomes more and more negligible. Now imagine what happens if it is indeed negligible:
$\aleph_0 + 1 = \aleph_0$
so we have a limiting case where there is a number so large that adding and taking stuff away from it no longer matters.
Now, we can continue this trend, and envision an even larger number $\aleph_1$ such that $\aleph_1 + \aleph_0 = \aleph_1$
So far so good and we we end up with the cardinals in ZFC.
But now, let's take a step aside and think about proportions:
$\aleph_0$ is the first number such that when you take away or adding finite number of things, the ratio before and after is 1
Now can we find some $K > \aleph_0$ such that $\aleph_1 + K$ vs $\aleph_1$ has some ratio $\frac{a}{b}$ where $a,b \in \Bbb{N}$
Perhaps, the essence of infinity is its inexhaustibility, but this is to be investigated in more detail later
 
2 hours later…
09:54
Compute the limit: $$\lim_{x \to \infty} x \left( 1 + \frac 1 x \right)^x - ex$$
10:11
If I have length of 4 sides given to me, How do I determine if its a rectangle or not?
example 5 5 6 6 is rectangle but I am saying this because it have 2 equal sides.. What other properties do I require ?
@Monte it doesn't have to be a rectangle
Ok.. but What if I want it to be a rectangle.. What other properties do I need to check?
except those diagonals and angles
with just 4 sides given to me
only two pairs of same length is required
Fine that is what I'v been trying to do.. I want to create an algorithm that checks if the entered 4 points form a rectangle or not
so I am just checking if the count of entered 4 numbers are 2 or not
also if all sides are equal than it is a rectangle
But I want this algorithm to be foolproof
Hence I want to know all the possible values of side that my algorithm will fail
oh wait!
@Monte sorry, I made a stupid mistake
two pairs of equal lengths just mean parallelogram
you need a right angle to have rectangle
10:22
yes you are right
Hence, for example 5 5 6 6, How do I say if this is a rectangle?
I mean apart from the fact that I have 2 equal sides, How do I play around with these 4 numbers and claim this to be a rectangle?
10:43
@Monte it does not need to be a rectangle, as I have said
but for 4 numbers to form a rectangle, they must be pairs of equal numbers
@LeakyNun but then I am comparing the equal I am just checking if the numbers form a parallelogram and not a rectangle. I want to know if there are other things that I need to check for the given 4 numbers such that it is confirmed to be a rectangle?
@Monte are you checking whether 4 numbers can form a rectangle, or that they must form a rectangle?
I've heard conflicting things from you
@LeakyNun Yeah my mistake.. It must form a rectangle.
you are given 4 points right
check for 4 right angles rather than the lengths. that should be more efficient
yes.. integer length of 4 sides
10:54
1 min ago, by Leaky Nun
you are given 4 points right
1 min ago, by Leaky Nun
check for 4 right angles rather than the lengths. that should be more efficient
do you have an example of your data?
The example are basically any random 4 whole numbers. Like 5 5 5 5 or 4 4 5 5 or 1 2 3 4 etc
then there is no way to check it.
a rectangle and a parallelogram can have the same side lengths
So are you saying if I am given a,b,c,d as length then I must apply Pythagoras theorem?
I never said that
where does your problem come from?
You said check for 4 right angles rather than lengths so I thought of Pythagoras theorem
10:59
how is your link relevant?
@Monte that was when you said you are given 4 points

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