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Beautiful
 
3:04 AM
The imaginary part of the sum of all primes is 2. Still figuring out the real part.
 
 
3 hours later…
5:54 AM
Let a > 0, how can I show -a+sqrt(a^2-4) is always negative?
 
2
Q: Minimize sum of guesses to win lottery

ABStkokesTen boxes are given with $a_1,a_2,a_3,a_4,a_5 ......a_{10}$ number of balls in them respectively .These boxes are randomly ordered but $a_1,a_2 .....a_{10}$ is told.We can arbitrary select a box and guess number of balls in it.If our guess is greater or equal to number of balls in it then we win ...

 
6:18 AM
Here be fractal dragons
 
 
3 hours later…
9:26 AM
When does it become important/useful to use a degenerate bilinear form in linear algebra
 
10:02 AM
@bolbteppa Not sure how important it is to "use" one. Knowing whether it is degenerate is quite important though.
 
The Killing metric (non LA) is the only place I can remember having to face up to them
 
olleH
I'd like to make an approximation just like equation 6 from this paper
Basically it's an interpolation between two limits
I'd like to do something similar for another function
The authors give no background info so I'm a bit stumped how they did that, and with such accuracy
And I'm quite sure it's not just made up out of thin air
 
11:04 AM
@MatheinBoulomenos why write $\Gamma(U,A)$ when you can write $A(U)$?
 
12:04 PM
@MikeMiller I asked the question on mathoverflow and seem to have gotten two conflicting answers:
https://mathoverflow.net/questions/336073/possible-isometry-groups-of-open-manifolds
although it appears the one providing a counter example is correct
 
 
1 hour later…
1:07 PM
Problem: If $g$ is strictly monotone on $\Bbb{R}$, and $f$ is a measurable function on the measurable set $E \subseteq \Bbb{R}$, then $g \circ f$ is measurable.
Proof: Since $g$ is strictly monotone, there is a set $D \subseteq \Bbb{R}$ set of measure $0$ such that $g$ is continuous on $\Bbb{R} \setminus D$ (WLOG, assume that $D \subseteq E$). Since $m(D)=0$, $g \circ f$ is measurable on $D$. Now restrict the functions to $E \setminus D$. Let $U \subseteq \Bbb{R}$ be open. Then $g^{-1}(U)$ is open in $E \setminus D$, since $g$ is continuous on $E \setminus D$.
Hence, $(g \circ f)^{-1}(U) = f^{-1}(g^{-1}(U)$ is measurable, because $f$ is measurable by assumption and $g^{-1}(U)$ is an open set (in $E \setminus D$). Hence, $g \circ f$ is measurable on $E \setminus D$, so it is measurable on $(E \setminus D) \cup D = E$.
How does this sound?
 
@LeakyNun makes it clearer that this is a functor
 
1:25 PM
@user193319 I didn't read that very closely, but this should mimic the proof that the composition of continuous functions is continuous.
 
@RyanUnger I'm not sure I follow. I'm taking the composition of a continuous function with a measurable function.
 
@user193319 Actually you don't need to worry about the discontinuities. Recall that for measurability it suffices to check if $f^{-1}((a,\infty])$ is measurable for all $a\ge -\infty$. But for a monotone (increasing) function, $f^{-1}((a,\infty])$ is always an interval.
So the preimage by $g$ gives an interval, then use the measurability of $f$...
 
Ah, nice. Two different solutions. Thanks!
 
2:11 PM
@RyanUnger what's this about Princeton admin asking applicants about their criminal record?
 
@skullpetrol what
pretty sure every application asked me if I had a felony
 
yeah, I read it on twitter
 
it's a standard question for employers to ask...
 
if you are a student you they arent your employer tho
 
They're paying me...
 
2:13 PM
grad students are often employed (both in the US and Europe)
 
I think they got the question removed from grad schools...
 
UT Austin said they'd require a full background check, actually
 
what's next? Drug testing :P
 
I have a license for my medical cocaine
 
@skullpetrol Yes, if you don't test positive for caffeine, they won't admit you.
 
2:18 PM
:-D
 
I don't even think if my security clearance required me to answer questions about criminal record. But probably there was something in it about allowing them to check that themselves.
 
This is surely not a U.S. TS clearance...for those they come and interview your neighbors, family, etc.
 
top secret
stupid name but that's the official designation
 
you mean Cosmic Top Secret? Or some other level of security?
(or maybe the US has a less stupid naming convention)
 
2:22 PM
Lol, cosmic is a NATO thing, right?
A security clearance is a status granted to individuals allowing them access to classified information (state or organizational secrets) or to restricted areas, after completion of a thorough background check. The term "security clearance" is also sometimes used in private organizations that have a formal process to vet employees for access to sensitive information. A clearance by itself is normally not sufficient to gain access; the organization must also determine that the cleared individual needs to know specific information. No one is supposed to be granted automatic access to classifi...
TS is above "Secret"
the next level is CTS, compartmentalized top secret
that's technically the highest level but it's stratified from within (indicated by compartmentalized)
 
@RyanUnger Probably. The level below it is called NATO secret (I think I have that clearance. At least I applied for it, and they have now given me access to the systems I needed it for, so presumably the clearance went through)
 
CTS is absolutely brutal to get. Lots of interviews, background checks, interviewing acquaintances, lie detector tests
And you have to submit a report on any foreign nationals you come into contact with
 
Well, the lie detector tests would only be in the US
no other nation takes those seriously
 
But the questions they ask are crazy too
They ask about medical history, personal life, habits
 
Internet use?
 
2:28 PM
Well they catch people trying to cheat the lie detector test
So why stop using it
 
for NATO secret it was not that bad. But it did require a full list of all current debt, all stays abroad the past 5 years (not counting short vacations) and past 10 years of employment history, including all periods without work
@RyanUnger Because lie detectors have been scientifically proven to not work properly and be beatable
 
No one actually thinks they're foolproof
 
as far as I recall, they are illegal to use in most countries for anything but entertainment purposes
 
The point isn't to have a foolproof system, the point is to just add one more layer of security
What is the purpose of making them illegal?
 
But if that layer potentially says nothing at all, and you have no way of knowing how much it says, it is useless
 
2:31 PM
The word potentially is pretty key there
In some instances it is helpful
 
@RyanUnger In which instances?
 
I'm not in the counterintelligence business and even if I were, I wouldn't be able to answer that question
 
Police use them in interrogations, no?
 
I highly doubt that. It would be a violation of the 5th amendment.
 
I prefer the old school lie detector test
Keep pouring boiling water on their face until they crack
:3
or something idk
what times they were, the middle ages
 
2:37 PM
the good cop, bad cop routine always works on me :P
@RyanUnger ya, you're in the counterexample business :-)
in The h Bar, Jul 23 '17 at 3:40, by The Raiders of Las Vegas
Bad idea #271: Dropping into the half-pipe on a Segway.
 
3:07 PM
@s.harp Yes, Misha's answer is correct. Peter Michor was trying the approach I suggested yesterday, and it doesn't work for reasons I explained then about needing closed orbits.
Misha's answer is very nice.
 
@RyanUnger they do in fact use them sometimes, they legally can’t force you to undergo it, but police do things to subtly violate people’s rights during investigations literally constantly
 
3:59 PM
Hi and hello CHAT
???
So silence
OK bye
 
so silence, much quiet, wow
 
@ÉricoMeloSilva ok doing my CV
which email are we supposed to put
seems really weird to be doing this before the semester starts and we have any of this info
 
@RyanUnger im putting my princeton email
 
@ÉricoMeloSilva we don't have the math.princeton.edu email yet
 
isn’t that one just supposed to redirect to the ones we already got tho anyway
also yeah when do we get those even
 
4:07 PM
we get them during orientation
I guess it just redirects...
 
ok i see
 
there's the grad school orientation and then a math dept orientation
 
what's your netid
I got runger
absolutely based email
 
easilva
 
4:09 PM
runger lol
 
whats the a
 
my middle name is alexander
 
cool
@BalarkaSen I had runger2 at tennessee
the OG runger is a pediatrician in knoxville
@ÉricoMeloSilva is the title "PhD student" and when (if?) we pass the generals, it becomes "PhD candidate"?
 
honestly i have 0 clue but that sounds right
based on what ik of other schools
do u know other ppl in our cohort
 
I only met one other person who got into Princeton at the other schools I visited...not sure if he decided to go there
I know lots of current students
 
4:14 PM
lol all the prospies i remember from the open house aren’t coming to pton
 
it's the best place in the world for GA so it wasn't really a choice...
 
for the open house they gave us a final list of admits w our chosen fields for the ppl who’d gotten in at that point and only me and 1 other person had GA as their field so there aren’t many of our kind
literally everyone i met at all my open houses was a number theorist
 
LOL blame the fields medals
GA had a rough year, there was also only one NSF award for us
Princeton has a really good number theory program though, doesn't it?
@MatheinBoulomenos do you know
 
doesnt stanford too or smth
 
Princeton/IAS has two fields medalists in number theory
plus Langlands, Sarnak
 
4:20 PM
presumably also ppl didn’t wanna live in princeton
@RyanUnger my grfp app got such good reviews and i didn’t get it and it was sad
not too sad but sad
 
I had really good reviews too...
 
the one person who got it at uchi is way smarter than my dumb ass so it’s ok
 
someone at UTK math got it :P not me
for mathematical biology
 
well there u go
bio is a magic spell, the key to unlocking the treasure vault
i think the uchi math person to get t was a number theorist
she’s really very good tho so i get it
 
the guy I met at Austin who also got into Princeton was a PDE guy
Navier Stokes
Will
 
4:25 PM
GA?
 
i remember his face but idt i talked to him
@AlessandroCodenotti stands for Good Ass math
 
@AlessandroCodenotti georgia or geometric analysis depending on context
 
Evening all
 
@ÉricoMeloSilva Ah, I didn't know you applied as a set theorist
Hi @ÍgjøgnumMeg
 
4:26 PM
LOL @Alessandro
 
Hey :)
 
@AlessandroCodenotti u got me there bud
 
GPA is probably not needed right
just put summa
 
nah fuck gpa
just put ur latin honors
 
4:27 PM
summa cum laude
 
we don’t get those at chi
 
wot
bah I need to scrap this format
 
chi has no latin honors for some reason
just to seem cool
 
avantgarde
 
4:30 PM
When's the start date?
 
what is chi
 
september...9?
 
oh chicago
 
@BalarkaSen Greek letter
 
@BalarkaSen no one calls it that i just didn’t want to type
 
4:32 PM
lol
>some quote
 
“i got 99 problems”
 
LOL
 
I could cite Thom like Hirsch does
that's always impressive
 
"Singularity, bitches" - Rene Thom
 
if the quotes not in french what’s the point
 
4:34 PM
user image
2
 
i was always destined for greatness
 
@Ryan what is it with you and i.gyazo
why always that site
 
what else am I supposed to use
 
imgur???
idk fam
 
it captures images and uploads them
automatically
does imgur do that
 
4:35 PM
i guess not
 
yeah I take a screenshot and it gives me the link
 
That's cool
 
@BalarkaSen IAS is doing a special year on h-principles
2021-2022
 
OH
Shit cool
 
you'd better come
 
4:37 PM
@BalarkaSen come hang out w us
 
you can apply for funding...normally its only post docs I think but you'll be famous
 
Can I like apply or whatever
 
Tristan Buckmaster is an organizer I think
I think the special years include standard conferences
you can apply for funding for those
there's also year-long funding but that's for researchers
 
idk ill see. seems unlikely i can fund my trip but anyway you two can write notes for me @Eric @Ryan
 
Well Tristan is faculty at Princeton and I aim to learn something about this convex integration business
So I'll be talking to him
 
4:41 PM
Nice! I'll have to learn that as well.
You can teach me maybe
 
what is convex integration
 
He solved a big conjecture in fluid mechanics using convex integration
No clue Eric but it was all the rage at the ICM
 
oh word
that sounds cool
 
De Lellis has also been working on it recently
 
ooo sick he’s cool
excited for his gmt class to fill the holes in my brain that not doing much math for a year has left
 
4:45 PM
@ÉricoMeloSilva It's an h-principle for ample differential relations. I can give you an example which is like the only thing I know
Let me finish my cigarette first lol
 
@BalarkaSen you smoke?
why are the CV templates on overleaf made by indians
 
immense brain drain is the basic answer i suspect
 
this is the most Indian thing I have ever seen
 
LOL
@RyanUnger Yeah I do
 
I'm extremely surprised Balarka
Aren't you like 13
 
4:48 PM
@RyanUnger You should watch a bollywood movie
 
Seriously, idk how old you are
@AlessandroCodenotti I have
But putting your JEE percentile on a CV...wow
 
smoking is cool and sexy and anyone who says otherwise is a cop nobody @ me for this
 
it's actually a nice template
 
this is the template i use actually
 
@ÉricoMeloSilva So look at any smooth path $\gamma : I \to \Bbb R^2$ which is short, in the sense $\|\gamma'\| < 1$. I imagine this as a non-vertical path in $\Bbb R^3$ with it's tangent vector lying inside a fixed cone field along the path
You can also say it's the trajectory of a particle through spacetime idk
 
4:51 PM
@BalarkaSen IAS
Murphy and Eliashberg will be there
hot damn
 
Every such path can be $C^0$-approximated by arclength-parametrized paths, which satisfy $\|\gamma'\| = 1$.
These are always tangent to the boundary of the cone field
A trajectory of a photon maybe
 
Balarka talking about spacetime
 
talk physics to me bb
 
Roughly speaking this happens because $\|\gamma'\| < 1$ is a convex differential relation (cones are convex). Gromov proved every ample differential relation satisfies the h-principle; every solution which lies in the differential relation can be approximated by solutions which are tangential to the differential relation (goes along the boundary, of which it's the convex hull of)
 
ugh I forgot how classes work in tex
 
4:55 PM
I think this whole circle of ideas is proved using convex integration but this is where my knowledge stops
 
can I put the .cls in the same folder as the .tex
 
@BalarkaSen what does ample mean?
 
@RyanUnger 19. Oh, actually, I graduate undergrad on 2021.
 
i love how this man is 3 years younger than me and 300 times smarter than me
 
@BalarkaSen ok so you'll be an Eliashberg or Gromov student already
you won't need our help
 
4:58 PM
 

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