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00:13
@robjohn ah okay i didnt know that
do these chatrooms have latex capatibility?
You’re confusing the $t$ intervals and the $x$ intervals. You still need $g$ on $(0,\infty)$.
I definitely have confused those two intervals on and off, although I don't see how that is the issue right now.
@ClydeKertzer In the room description (upper right corner of the page) there is a link to $\LaTeX$ in chat
You can install ChatJax from that page
"start ChatJax" is the one you probably want
I will share my work (if I am posting too much, then just delete, I guess)
I've just been playing around with graphing software, and it looks like my bounding functions are bounded by $y = 1$, although it's not clear to me why this is necessary, or even if this is what my professor is asking me for.
I understand if nobody wants to read three pages. I'll send a message to my professor. I guess it's obvious that my bounding functions are bounded by $y = 1$, since they're all $x/(1+x)$ times e^[negative number].
01:08
Does any body know how to use ChatJax for rendering LaTeX equation in Chat? I tried to follow the instructions in the link to $\LaTeX$ in chat but to no avail.
I think you make the "start ChatJax" link a bookmark, and then whenever you load the chat page, click the bookmark and it should work.
@Novice: OK, I just bookmarked the start ChatJax page (is that what you meant?) No i ma going to type an equation...
$e^{-i\pi/2}+1=0$
The constant function $1$ is not integrable, Novice, right?
@Novice: dod not work... Oh well, will try something else ...
@OliverDíaz Sorry, I have it working on Windows 10 and Mac OS. I just do what I said. Not sure what other advice to offer.
@TedShifrin It's not integrable, but I don't see where this is required. I am using the definition of a uniformly bounded family of functions from Wikipedia. Maybe he means that the integrals need to be uniformly bounded, in which case I'm probably toast, because the integral of my $g_m$ is $m + 1$.
01:22
Reread your theorem 2.
We’re on $(0,\infty)$.
Not $[a,b]$.
Yes, well, I thought I needed to make the theorem apply over $(0, \infty)$, which is why I considered all those intervals and functions. There must be something very obvious I'm missing, because I have no idea what's going on.
Fixing $t$ in a closed interval is fine, but not $x$.
Sounds like you need to talk with your prof.
@TedShifrin You mean because there's something basic I'm not getting?
01:44
@Novice: I got it to work on MacOS under Chrome, did not work with SAfari.
Weird, it works on Safari for me. Anyway, happy it works for you.
Mine works fine on both OS and iOS on Safari.
@Novice: with regards to your problem (differtiability of $t\mapsto \int^\infty_0\frac{e^{-tx}}{1+x}\,dx$, choose an interval $[a,b]\subset(0,\infty)$ for $t$ and the result in your notes. That way you get differentiability in the interval $(a,b)$.
But it was tricky setting it up, and I forget.
You need a $g$ that’s integrable on $(0,\infty)$ and bounds the partial ….
@TedShifrin: I will just use Chrome while on Chat. Otherwise I'll spend many hours trying to get tot he bottom of this and will end up not sleeping...
01:50
I’ve been there numerous times!
@Novice: $\frac{|e^{-tx}-e^{-t_0x}|}{|t-t_0|}\leq |x|e^{-\xi x}\leq|x|e^{-cx}$ for all $t$ in some interval $[a,b]\subset(0,\infty)$ that contains say, $t_0$.
Then dominated convergence.
@OliverDíaz Thanks, but I have to think more about this. I've been going back and forth with my professor over email, and chatting here, and I don't understand anything anybody is trying to tell me.
I may be mistaken, but my professor seems to think that I can use a single bounding function $g$, which doesn't seem possible, unless I've overlooked something terribly obvious.
02:05
@Novice: I don't think there is anything more to it. since you are dominating the expression $\frac{|e^{-tx}-e^{-t_0x}|}{|t-t_0|}$ by a function $g(x)=xe^{-cx}\in L_1(dx/(1+x))$. Recall that differntiability is a local thing, so to check differntiability at any point $t_0$, you only need to control what happens near $t_0$. Of course, there may not be a "uniform" dominating function $g$ that works for all $t$'s, but that is not what one needs for differntiation here.
02:44
@OliverDíaz I don't use Safari on my Mac (I use Firefox), but it works in Safari on my iPhone.
02:57
@Novice A single bounding $g$ that works for all $t\in [a,b]$, not all $t$.
@TedShifrin That is what I was taking about. A bound for each bounded closed interval. That will do what @Novice needs... (but of course you se that)...
@robjohn: I just got it to work with Safari on my new M1-processor computer. I just have to drag it to the favorites bar (maybe bar is to the name but I think you know what I mean).
@OliverDíaz Yes, that is what works for most browsers.
Glad you got it working. It makes things much easier.
03:18
@robjohn: yes it does, I can discuss maths here now...
 
5 hours later…
08:14
Let $X\sim_\alpha Y$ when $\alpha X \cong \alpha Y$ and $X\sim_\beta Y$ when $\beta X \cong \beta Y$ where $\alpha$ is one-point compactification and $\beta$ is Stone-Čech compactification
Can we say something about those equivalence relations
Never mind
 
2 hours later…
09:54
Does $\mathbb{R}^4$ embedd into a compact topological group?
Does $\mathbb{R}^n$ embedd into $SO(n+1)$?
 
2 hours later…
12:15
If $G$ is a group such that $p\mid |G|$ where $p$ is a prime then the number of order $p$ subgroup $\equiv 1\bmod p$. Any idea for this?
12:49
Think of the identity element
I don't get it
13:31
Is there a special name for First-Order Logic with all terms restricted to variables (i.e no function terms)? Is it simpler to decide satisfiability in this case?
 
2 hours later…
15:31
@onepotatotwopotato Take a look at this answer.
15:53
@robjohn Thanks. Proof of Cauchy theorem never gets old
I'm an analyst, so I usually think of complex integration when I hear Cauchy theorem, and I wondered how that applied ;-)
@Jakobian doesn't the stereographic projection do that?
16:18
Including the point of projection gives the one-point compactification
@robjohn S^n is a subset of SO(n+1)?
No, but it can be embedded with the stereographic projection.
S^n can? How
wait, I am thinking of $S^n$ in $\mathbb{R}^{n+1}$
Oh, no, I wanted to go the other way
I've managed to embedd $\mathbb{R}^n$ into $(S^1)^n\subseteq U(n)$
Which is good enough I guess
17:14
bphbhtpbhtbht
Olivia at the keyboard …
Hi Olivia.
in the puzzling chat we have identified a five-tuple of words that solves over 95% of wordles, i.e. you can play the same five words every day and be guaranteed to win on the sixth guess, with that high probability. if your dignity can take the hit of averaging 6 guesses.
my own average has dipped just below 4.
it's SHALE/POINT/CURVY/GAMED/BEEFY.
olivia came into my office a minute ago meowing. she exercised her claws on my chair and rubbed my leg and then left for my daughter's room. i don't know what she wants in there.
now she's meowing at a lizard outside.
17:43
I use the same first word every time. But I change up the second word according to the letters I have right in the first. My average is almost exactly 3.75.
I play in "hard mode" almost exclusively, so I have to reuse correct letters. I think I've broken that rule only once.
my best friend does the same. she doesn't enable it in the app, so it's enforced by her willpower alone.
we all know my feelings about it.
My French average was beating my English. I guess I should calculate that too.
I have never played wordle. Long ago, I told myself I needed to stay away from online games so that I didn't fall into a black hole.
join us, robjohn.
Nope. French now worse. 4.1 + one unsolved.
You're almost at the black hole time of your life, @robjohn.
17:49
@leslietownes evil!
i keep it limited. my best friend can spend 20 minutes on it. i don't think it through. i react. it's 60 seconds out of my day, max.
if that means the occasional loss and 4+ average, so be it.
I don't think I manage 60 seconds every day, but it's close. Occasionally a few minutes.
I tried anti-wordle a bunch of times and I can't get good at that, so I've quit.
yeah, i tried that three or four times, and no.
i do play quordle every day, also around 60 seconds per play. octordle sometimes.
ok, and i did write a program that solves wordles and can test lists of starting words. it's something of a gateway drug.
robjohn might have had the right idea about this.
hey, kiddies, come play my game. It's free (for now)
why is complex analysis considered the good twin and real analysis considered the evil twin? [even though my intuition tells me that jumping from ℝ to ℂ was supposed to make things harder?]
17:58
many of the hypotheses that appear in the beginnings of complex analysis books have far-reaching consequences that make the world of stuff satisfying those hypotheses tractable.
many of the hypotheses that appear in the beginnings of real analysis books do not.
'analytic' functions solve the cauchy riemann equations which are a special case of, well, solutions of differential equations
Where else does one derivative buy you infinitely many and, in fact, analyticity?
@leslietownes That seems interesting.
Robjohn will pipe in with elliptic regularity :)
18:26
The complex derivative puts such a structure on the functions that good things follow. The real derivative does not impose this same structure and as a result there are many real differentiable functions that can behave badly.
Of course, essential singularities are the black holes of complex analysis.
There's nothing wrong with an infinite Laurent series :)
No, but as you fall into the singularity, you see universes pass you by.
and there is no event horizon to protect the rest of the complex plane!
complex analysis seems way too beautiful for me.
It is quite beautiful
i love it. my favorite classes in grad school were on complex analysis
18:34
And some of us love the interplay with differential geometry ...
The Schwarz lemma, Ahlfors figured out, is about hyperbolic geometry.
i had a prof who tried to put me on to all of that. no thanks.
some of the nevanlinna theory is that way too, although i wouldn't know. i cut out my eyes.
It's your usual narrow-mindedness.
You operator theorists basically just like linear algebra.
for any result in finite dimensional linear algebra, there are a zillion proofs, and two of them push the symbols in just the right way so that they generalize. and you just go and find those proofs.
if you can draw a picture of what the argument is trying to do, that's a sign it won't work in infinite dimensions.
I see you're not disputing my claim.
i found my happy home.
not at all.
18:38
Using inner product to do projection works in any dimensions ... despite my drawing pictures.
there's a piece of those arguments that doesn't work. when you try to find something nonzero and orthogonal to a set that you only know isn't everything. that set could be dense, and still not be everything.
other than that, yes.
i didn't phrase that well. but sometimes your hypotheses that give you enough room in finite dimensions don't give you enough room in infinite dimensions.
Well, the fact that subspaces can fail to be closed isn't my fault!
it's a good thing. it gave me a job for a few years.
it didn't pay very well, which is why i went into suing people, but, that's another story.
ted: my daughter reacted to a touchy moment this morning by accusing her mother of being a bad mom. "you're a BAD MOM." she said this several times. it was in response to not being allowed to watch the garbage truck pick up our garbage. how would you handle?
the problem is that by my own existence i have established a precedent of talking s--t basically all the time.
so it's hard to single this out as noteworthy.
Encouraging lack of respect for the parental units is bound to lead to trouble. Mom should have put her out in the garbage.
P.S. You certainly shouldn’t think I know anything about parenting.
it's weird that you say that, because last night, our daughter threatened to put her mother out in the garbage.
i'm just curious what a normal person outside of this crazy household would do.
18:53
Ah, role reversal.
I think it may be past time to rein in her insolent mouth.
the problem is that she's me. she's a three year old version of me. i can't police it
Your wife may divorce you both!
this is entirely possible
 
1 hour later…
20:16
Anyone wants to factor this number ?
 
1 hour later…
21:33
@Peter No.
2
21:53
My professor released my final grade, so I suppose he's not going to reply to me anymore. I suppose that's the end of my saga. Still don't see what was wrong with the answer I submitted.
Anyway, thanks to people for trying to help.
 
1 hour later…
23:10
How do I go about showing $b_n \geq 2 \times 5^{n-1}$

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