The h Bar

0celo7

2:00 PM

@ACuriousMind (Lee)

Yashas Samaga

@JohnRennie how old are you?

John Rennie

@YashasSamaga on the flip side, I'm not being nagged (apart from by Cortana)

Anyway, I'm off out into storm Doris. Wish me luck!

Yashas Samaga

Good luck. It is choking hot here. 110F

0celo7

jesus

maybe JEE is a side-effect of mind-melting heat

Yashas Samaga

lol

It is hot because it rained yesterday

ACuriousMind

2:04 PM

@0celo7 I think you can look at the n-th homology of $M-\{x\}$ to show what you want to show.

0celo7

@ACuriousMind Is $M-\{x\}$ contractible or something?

Yashas Samaga

@0celo7 no idea about the physics but the day which comes after a rainy day always has extreme temperatures

ACuriousMind

@0celo7 Uh...not for arbitrary $M$, no

but the difference between the homology of $M-\{x\}$ and $M$ is different when $x$ is an interior point and when it is a boundary point

0celo7

@ACuriousMind So you want me to use the MV sequence or something?

@ACuriousMind Why is that?

ACuriousMind

@0celo7 Yes, I think so. Consider taking the neighborhood of $x$ homeomorphic to one of the two things and the rest of $M$ slightly overlapping with it as the two open sets

0celo7

2:08 PM

@ACuriousMind You'd first have to show that that doesn't depend on the particular chart, once you have picked one.

(i.e. that two interior charts compute the same homology, and the same with two boundary charts)

ACuriousMind

I have no idea what that means

I'm not picking any chart

0celo7

You're picking a neighborhood, no?

ACuriousMind

Yes

0celo7

Chart domain if you wish

ACuriousMind

What's the problem with picking a neighborhood

Mayer-Vietoris works for each pair of open sets you can pick, there's no requirement to show anything

0celo7

2:09 PM

Let me reread the statement of MV :P

Hmm. Now I remember why I dislike algebraic topology.

@ACuriousMind Thanks.

@ACuriousMind I'm supposed to do perturbation theory on Na, but there's 11 electrons. Which one am I supposed to look at?

The single valence one, I assume.

ACuriousMind

@0celo7 You dislike algebraic topology because you don't need to check annoying independent-from-choice requirements? :P

@0celo7 Uh, the outer one, I guess?

0celo7

@ACuriousMind No, because of long exact sequences.

@ACuriousMind So that would be an $n=3$ state?

ACuriousMind

LES are love, LES are life

0celo7

Or at least, I should approximate it as a Hydrogen $n=3$ state?

ACuriousMind

@0celo7 yeah

0celo7

2:14 PM

@ACuriousMind Then I will never love

Balarka Sen

Are you done with our previous discussion

0celo7

Yes

Balarka Sen

good

0celo7

Now it's time for...geodesics

Balarka Sen

@ACuriousMind meh, exact sequences are just a fancy way to put beautiful pictures into obscure pictures.

0celo7

2:20 PM

ACM is an algebraist

he says strange things like that

ACuriousMind

@BalarkaSen I was not entirely serious :P

Balarka Sen

@0celo7 Have you gotten to Voyeur of Utter Destruction in the album? 's one of my favorites from there

0celo7

@BalarkaSen truth be told I stopped after 3 songs

I'm currently thinking

Balarka Sen

aw

but yeah, these are just the sort of things that's criminal to force other people into liking if they don't. but oh well.

0celo7

@BalarkaSen I can't think. Consider the 2-sphere, and let $S$ be the south pole. Are you familiar with the Riemannian distance function $d_S$?

For the sphere, it just assigns to $p\in S^2$ the length of the great circle connecting $p$ and $S$.

Balarka Sen

2:29 PM

Ya. In general it's the infimum of the arclengths of all the paths from $p$ to $q$, yeah?

That's what $d(p, q)$ is I mean

0celo7

Right.

Balarka Sen

OK

0celo7

So it's not hard to show that $d_S$ is smooth on $S^2-N$.

Balarka Sen

Right

0celo7

(use normal coordinates)

But you have a problem at the north pole

I want to show that it is not even differentiable there

Balarka Sen

2:30 PM

Hm

0celo7

Well...maybe it's differentiable.

But certainly not $C^1$.

So the derivative should be discontinuous there.

Balarka Sen

Suppose you move along one single great circle. If you come down from $N$ to $S$ along that great circle $d_S$ gives you a function on that great circle. Now revolving it around any great circle is $d_S$ on a small neighborhood of $N$

Because it doesn't matter from which great circle you are in as long as you're on the same lattitude

0celo7

Sure

Balarka Sen

So $d_S$ sends a point $(\theta, \phi)$ to $r(\theta + \pi/2)$ right

$\theta$ is the lattitude

0celo7

$r$?

Balarka Sen

2:36 PM

radius of the sphere

you can extract that from the curvature if you want to be intrinsic; which is $1/r^2$

0celo7

Hmm. Why wouldn't it just be $r\theta$?

Wait, how does one measure lattitude?

Is it $-\pi/2$ to $\pi/2$?

Yeah

Ok, then I agree.

$0$ at the equator

Yeah.

2:42 PM

So it's linear on each great half-circle and radially symmetric. The graph of that should look like $z^2 = x^2 + y^2$ (a cone) then

And $N$ is the cone point

That's not differentiable at $N$

0celo7

@BalarkaSen Agreed.

Now how about this: general manifold, $p$ fixed. Suppose $x\in M$ has two minimal geodesics connecting $p$ and $x$. Is $d_p$ $C^1$ at $x$?

I think not, because the gradient of $d_p$ should "point along" the two geodesics.

And they should be pointing in different directions at $x$.

Balarka Sen

What's a minimal geodesic again?

0celo7

@BalarkaSen Geodesic whose arc length equals the distance between its end points.

Balarka Sen

Ah, ok

I guess it should have been obvious that not every geodesic satisfies that (bit of the great circle in S^2 which is big)

0celo7

Which is big?

Balarka Sen

2:47 PM

I mean you cut off the great circle in two pieces; one big and one small. Both are geodesics, but only the small one equals the Riemannian distance

I was just talking to myself

0celo7

Oh, oh. That not all geodesics are minimal.

Balarka Sen

Yeah

0celo7

Yeah, that's something that physics books get wrong all the time.

Geodesics are critical points of the length functional, but no one said they had to be minima.

Balarka Sen

True

Good summary

@0celo7 That sounds about right

You can slide a little bit from $x$ along both the geodesics connecting $x$ and $p$ and you get "two tangents" at $x$.

0celo7

Yeah.

Balarka Sen

2:50 PM

OK, so we're all happy

0celo7

You can use existence and uniqueness of ODE to show that the tangents are different.

(otherwise, run time backwards and your two geodesics must coincide)

Balarka Sen

Right, agreed

0celo7

@BalarkaSen ok, cool

Mostafa

Hey

Take this test and tell me your score

at least 40 guesses

snarxiv.org/vs-arxiv

0celo7

@BalarkaSen Suppose I have a continuous function $f:S^{n-1}\to\Bbb R$. We can consider the graph $\Gamma(f)=\{(s,r):s\in S^{n-1},r=f(s)\}\subset\Bbb R^n$. Does this have measure zero in $\Bbb R^n$?

Mostafa

2:57 PM

You should tell which one is a real HEP-theory paper.

0celo7

"9th year grad student"

Mostafa

xD I'm a "physics major"

Balarka Sen

@0celo7 I think so. For smooth function I guess that's obvious because the graph is a codimension 1 submanifold

0celo7

"String/M Theory"

Balarka Sen

and you use that locally it's measure zero

0celo7

3:00 PM

Yes, for smooth functions it's clear

Balarka Sen

Also the graph lives in $S^{n-1} \times \Bbb R$ not $\Bbb R^n$.

0celo7

@BalarkaSen Well...I think I want to homeomorph it to $\Bbb R^n-\{0\}$.

Balarka Sen

oic

0celo7

but that might screw up the measure

more thinking is required

Mostafa

@ACuriousMind I'm curious, can a high energy theorist score better than a monkey? :p

ACuriousMind

3:05 PM

Mar 24 '15 at 15:52, by ACuriousMind

@JamalS Nah, I'm consistently around 40%

0celo7

lol

ACuriousMind

Hm, that's from almost two years ago, though

0celo7

"String/M Theory"

Mostafa

That time you were not a legitimate high energy theorist

(btw, how do you find these old messages?)

0celo7

he's an AI

Mostafa

3:10 PM

this chat is indexed by Google but you need to know the (somewhat) exact phrase to look for:/

and the transcript won't help much

ACuriousMind

@Mostafa Yep, just good memory for specific phrases

Also, come on snarXiv, "(0,2) string compactifications" vs. "nonzero central charges" is impossible to get right by something other than guessing :P

Mostafa

@ACuriousMind Also, I read your recent paper. Nice one!

Sir Cumference

@Mostafa ...why does that paper say "ACuriousMind"?

ACuriousMind

@SirCumference Because scigen lets you input any author name you want :P

Yashas Samaga

:|

Sir Cumference

3:16 PM

Huh...

neat

Yashas Samaga

scientists who read ACM's papers are going to freak out

Secret

Acuriousmind's snarxiv's paper, if one attempt to ignore all the gibberish, will give you an impression it is some kind of machine learning algorithm paper

Mostafa

sighhh ...I coudn't surprise ACM today :/

ACuriousMind

@Mostafa Got 72% over 50 attempts this time around

Secret

My crazy (and at times worrying) ability is I can often somehow get sense from gibberish, nonsense and word salads for reasons that I am still trying to understood

It seems I have seen too many weird ideas...

Mostafa

3:20 PM

@ACuriousMind Towards the "Nobel Prize Winner"....

Giskard42

Anyone know how the rate of air cooling goes vs atmospheric pressure? The only data I can find is from a high-school paper with (by their own admission) a flawed experimental setup

Mostafa

Have you seen the rankings?

Giskard42

@Secret Perhaps that's due to the word chaining method the generator uses? The source material for the generator probably made sense, so perhaps it's leaving a notion of sensibility in the markov chaining?

Sort of like how /r/subredditsimulator works

Secret

That could be a possibility. I once got a snarxiv paper on some kind of maths function. By deleting all instance of division by zero ln(0) and other singularities in the paper, it seemed to be some kind of analysis paper

Mostafa

Lubos Motl is ranked 54th.

ACuriousMind

3:25 PM

@Mostafa Well...someone who typed in that name, anyway. Also, since one can simply cheat by looking the titles up on the arXiv, these rankings don't tell you anything

Secret

Meanwhille, I have a certain bad reading habit in that I tend to automatically ignore stuff that is nonsense in the article and sometimes, I have to focus on that to be aware I am ignoring something

A side effect of this is that I sometimes miss typos because they are autocorrected as I read, thus it will seems there is nothing wrong in the text unless I pay attention

Giskard42

@Secret I get the exact same thing

Sort of like the Dan Gilbert thing

In the middle of a centence he put the word anchovy in

And only later, after he's pointed it out, do you see the word anchovy

Your brain only sees what it wants

Secret

Indeed, and it is extremely annoying when it comes to proofreading theses

Giskard42

I could imagine

Mostafa

@ACuriousMind I don't know why but I feel he's the real Lubos Motl...

skullpetrol

3:41 PM

(removed)

Giskard42

@Mostafa Holy crap, that guy

Rationalwiki is often scathing, but reading this page is something else

skullpetrol

Link please.

John Rennie

@skullpetrol rationalwiki.org/wiki/Lubo%C5%A1_Motl

ACuriousMind

@skullpetrol ...can you seriously not figure out yourself what you should google to get to the link? :P

skullpetrol

Thank you @JohnRennie

Giskard42

3:55 PM

I thought the technocracy concept might be workable, but now I'm having some serious second thoughts

skullpetrol

@ACuriousMind :P

John Rennie

@Giskard42 rule by high energy physicists? Really? Have you met any high energy physicists? :-)

Giskard42

@JohnRennie Not rule by physicists but basically the top few in each field

each position would be held by the people best educated to handle that position

But if that's the best String Theory can give us then I'll take gorram trump

Sir Cumference

Goddammit obe

It's been weeks

John Rennie

@Giskard42 I've met lots of eminent scientists over the years and I generally wouldn't trust them to rule a straight line.

0celo7

4:10 PM

People who have messenger bags are psychopaths

Mostafa

@JohnRennie Would you vote for Trump or Lubos?

0celo7

@SirCumference what?

Giskard42

@Mostafa Oh crap I kicked the politics hornet's nest

Sir Cumference

@0celo7 I've been asking him to follow up on sending me the logo he made for Astro SE

Giskard42

ABANDON THREAD

Sir Cumference

4:10 PM

So I can make an ad

John Rennie

@Mostafa can I have stick a red hot knitting needle through both my testicles as a third option?

4

Sir Cumference

It's been over a month

Mostafa

@JohnRennie Or discuss the homework policy option....

Giskard42

@JohnRennie Hey, that's not that bad, free vasectomy!

Balarka Sen

You're gonna regret that third option

Emilio Pisanty

4:12 PM

9

Q: Funding opportunities for an independent researcher

In one of my questions I asked about the career paths to become a professional astronomer. Now let's consider the next logical step. What if a person has gained his/her PhD in Astronomy and had an opportunity to do a couple of postdoc positions. The time comes for independent work but where can ...

^ should be closed, really

Sir Cumference

@D17 Dude, come on

It's been a month

Giskard42

Unfortunately politics appears to be unchanged by the state of anyone's anatomy

(except of course the father of trump)

ACuriousMind

@JohnRennie You bring up that image rather often.

0celo7

@ACuriousMind why is that allowed?

Isn't it violent

skullpetrol

But it's self inflicted.

ACuriousMind

4:16 PM

It's a somewhat unpleasant image, but it is not rude or demeaning towards anyone. Why should it not be allowed?

John Rennie

@ACuriousMind it has always struck me as so ludicrous that it is amusing. You may choose to interpret this as evidence for a warped sense of humour.

Giskard42

@0celo7 It is consentual...

0celo7

@ACuriousMind fine

Everything I do is wrog

ACuriousMind

@JohnRennie Pray tell, What's your humour's warp factor?

John Rennie

I suppose people laugh at about 10% of what I think is funny. Warp factor 10?

Giskard42

4:18 PM

TARS, what's your humor setting?

anonymous

@YashasSamaga I don't even understand how that matters. In raw egg the yolk is in liquid state. In any liquid if you spin it at a high rate you will see most of liquid particles gather near the walls. Even the pressure near the walls will be higher. It is not unlike pressure increasing with depth under liquid. Take this video for example (youtube.com/watch?v=DvwB87s-RMo). Now probably the only thing that matters is what is your axis of rotation ?

Rotating water with oil - Centrifugal force for each liquid

►

John Rennie

@anonymous do you mind! We are discussing testicles here!

skullpetrol

Not everything @0celo7

ACuriousMind

@JohnRennie Wasn't warp factor 10 "infinite speed" on the Trek scale?

skullpetrol

10c

ACuriousMind

4:20 PM

I recall a terrible episode of Voyager about that

John Rennie

@ACuriousMind oh no, I've stepped into the morass that is Star Trek canon! :-)

anonymous

@JohnRennie The physics of eggs and testicles isn't much different :P A testicle is comparable to a boiled chicken egg :'D

(If you find our conversation distracting you can click the ignore button)

ACuriousMind

"A testicle is comparable to a boiled chicken egg" - I think I'm done with the internet for today :P

2

John Rennie

@anonymous eggs are liquid. Testicles are not. Well, I can only speak for myself of course.

anonymous

@JohnRennie Ever heard of "hydrocele" ?

John Rennie

4:23 PM

Also, it doesn't hurt when you crack eggs into a frying pan.

@anonymous this is where we post the now notorious photos of elaphantiasis victimes. Yes?

anonymous

@JohnRennie It also doesn't hurt you if you crack someone else's testicles into a frying pan . Okay, lets stop here :P

Enough for today :'D

John Rennie

Well, not unless you burn your fingers on the pan.

anonymous

I wonder what would happen if I chose to be a doctor :'D

skullpetrol

Have you tried the MCAT?

anonymous

Nah. Its better I stay far far away from being a doctor, lest I start experimenting with people's testes. @skullpetrol

John Rennie

4:28 PM

@anonymous I'm a doctor! You can trust me :-)

skullpetrol

Do you use "Dr."?

John Rennie

No.

0celo7

@JohnRennie hey if I disscolve 1kg of Pu239 in nitric acid, what happens

Ive heard it goes critical

John Rennie

Isn't that what they do at Sellafield?

@0celo7 Wow, it does!

Cecil Kelley criticality accident

A criticality accident occurred on December 30, 1958, at the Los Alamos National Laboratory in Los Alamos, New Mexico, in the United States. It is one of only ten such events to occur outside of a nuclear reactor, though it was the third such event to take place in 1958 after events on 16 June at the Y-12 Plant in Oak Ridge, Tennessee, and on 15 October at the Vinča Nuclear Institute in Vinča, Yugoslavia. The accident involved plutonium compounds dissolved in liquid chemical reagents, and it killed one man, Cecil Kelley, a chemical operator, by severe radiation poisoning, within 35 hours. ��2...

Cor, the things you learn in the physics chat.

Yashas Samaga

@0celo7 You'd go to jail.

0celo7

4:35 PM

@JohnRennie I heard because we're supposedly getting a license for 3kg metallic plutonium in our new building

Yashas Samaga

o0

0celo7

@YashasSamaga my university runs the largest nuclear security research group in the country (world?)

Yashas Samaga

@0celo7 where do you study/work?

John Rennie

@0celo7 have you ever seen the Nukees comic strip?

0celo7

@JohnRennie newp

AccidentalFourierTransform

4:37 PM

@0celo7 ok but can you explain uranium!?

John Rennie

Nukees = nuclear engineers

0celo7

@AccidentalFourierTransform we're getting 20kg enriched

AccidentalFourierTransform

Trump Explains Uranium

►

5

0celo7

@AccidentalFourierTransform The general sentiment in the department is that he's "not even wrong."

It is pretty cringey :P

AccidentalFourierTransform

... and other things..., like lots of... things...

anonymous

4:39 PM

@AccidentalFourierTransform I hope I won't forget all science after playing that video :D

Stijn

Hi, sorry for disturbing but we have someone named Fawad over at Tavern on the Meta. I understand they got suspended for admitting to having a second account, and then also creating an account named "ACM is a bad guy", correct? We've advised him to just wait out the suspension and not attempt to discuss it with the involved parties.

anonymous

@Stijn Yes. What happened?

Stijn

@anonymous nothing bad, he asked some questions about suspension and then asked why he couldn't invite people over to a chat room on the MSE chat server.

AccidentalFourierTransform

wait wat

skullpetrol

Good advice @Stijn

ACuriousMind

4:41 PM

@Stijn thanks for the information

Stijn

Thank you too for the info :)

Yashas Samaga

@anonymous you are misinterpreting everything I am telling

@anonymous the unsymmetrical thing was just an example

@anonymous I can list countless factors which could affect the race

anonymous

@YashasSamaga Lets stop this discussion. I showed you a video and gave my reasons. I don't know what will convince you if you keep talking about abnormal eggs.

There are countless videos on youtube regarding the experiment.

0celo7

@ACuriousMind are you going to hunt him down?

2

Koolman

This how can we say it is common emitter

Yashas Samaga

4:51 PM

$V_{BB}$ and $V_{CC}$ have the emitter in common

anonymous

@Koolman The emitter is connected to both Vcc and Vbb.

Koolman

Oh got it

0celo7

@JohnRennie I must say, I do not understand it

skullpetrol

They have that on JEE?

Yashas Samaga

Yup

Koolman

4:53 PM

Jee Mains

Yashas Samaga

My Open School Physics textbook has 10x more content on semiconductors

0celo7

JEE is third year engineering in America

Yashas Samaga

rectifiers, square law device, adders, etc.

@0celo7 I am not surprised.

Koolman

@YashasSamaga from which state you are

Yashas Samaga

1 out of every 15 students from India get 2400/2400 on SAT subject testsl 1 out of every 5 get 800 on math;

0celo7

4:54 PM

@JohnRennie it's not very funny

Yashas Samaga

@Koolman Karnataka

Not to mention that the AP syllabus is our regular high school syllabus.

JEE is harder than USAPO and USACO

Koolman

Great

John Rennie

@0celo7 I thought it was quite amusing, but started reading at the first strip and they have started running out of ideas now.

0celo7

@JohnRennie I read the first strip and I thought it was stupid

I've never received that reaction

John Rennie

Perfect entertainment for me then :-)

0celo7

4:56 PM

Most people are endlessly fascinated

Then I try to steer the conversation towards balls and they get weirded out

anonymous

@YashasSamaga That is a bit of over-exaggeration.

Yashas Samaga

@anonymous I am not kidding

anonymous

Do you have statistics to back your claim?

0celo7

@YashasSamaga SAT is all about taking the test, not the material

Yashas Samaga

@anonymous yes

0celo7

4:58 PM

I'm a decent mathematician for my age and I probably could not get above a 700

anonymous

@YashasSamaga Show it

Koolman

@anonymous i think @YashasSamaga is correct

0celo7

Given enough time, sure

Yashas Samaga

oops

the percentiles are missing

1min

Mostafa

@YashasSamaga One out of three young graduates unemployed in India

Koolman

4:59 PM

How output characterstics are controlled by input characterstics ?

Yashas Samaga

Because the competition is too high.

Koolman

@Mostafa population

Yashas Samaga

Mathematics Level 2
Mathematics Level 2 description
800
out of a range of
200 to
800
My Score Range: 770-800
80th
Your National Percentile

Your percentile indicates the percentage of test takers in the prior year’s cohort taking this test who had scores below your score.

80th percentile = 1 out of every 5 students get an 800 on math

Transcript for