The h Bar - 2017-08-23 (page 2 of 3)

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2:00 PM

@0celóñe7 Why are these random dumb shit topologies named after people

@Secret sounds almost fun

I'm wondering what I can read at work that looks technical enough to not get questions asked, as right now there's lilttle work to do

@BalarkaSen It should be read as "topology of a Schwarzschild blackhole", not as "Schwarzschild topology" meaning the actual topology is named after Schwarzschild.

@ACuriousMind Ahh. Well, I was guessing it has something to do with topology near a singularity of the spacetime (whatever that means!).

I was making a semi-humorous comment. It's just that I have seen this in the context of moduli spaces too: I waited in a talk for a few hours for them to define a clever topology on the Teichmuller space of genus $g \geq 2$ surfaces and it turned out to be $\Bbb R^{6g - 6}$. Boo.

@BalarkaSen In this case, the singularity is a pp curvature singularity

snek or not, it's prevneting me from enjoying my PhD, grrr

2:03 PM

$R^{\mu\nu\rho\sigma}R_{\mu\nu\rho\sigma}\to\infty$ somehow

@0celóñe7 What does R over superscript mean?

I need to make the font of this poster smaller

there's no room

Uh

@BalarkaSen what

Ok no I am having trouble interpreting that index notation

Sorry for being silly

2:05 PM

@BalarkaSen That's the Riemann tensor and I've raised/lowered all indices

@Secret perhaps it is time to put the chat room on the back burner?

a pp curvature singularity is when a polynomial in the Riemann tensor blows up

Ah, alright. Makes sense.

heheheh

pp

Thought it's hard to interpret "blows up" because the point where it "blows up" isn't in the manifold

how many random people at a college science fair are gonna understand this

user image

2:06 PM

2/10

AccidentalFourierTransform

>$G=1$

will not understand

That is called a scalar singularity

I don't know what a college science fair is.

AccidentalFourierTransform

$4\pi G=1$ pls

2:07 PM

@ACuriousMind people presenting posters on summer research

@0celóñe7 Yeah, that...doesn't mean much to me :P

@ACuriousMind Me neither, hence why I am asking

@rob my advisor is completely unhelpful, is there a time I can call you about this

Open to the public?

@skullpatrol yeah

Tough call.

2:09 PM

@ACuriousMind 90% of these research projects are on stuff like psychology, biology, bioengineering, etc., where the basic concepts can be understood without too much difficulty

I don't think anyone there will understand what a fixed point theorem is

does it matter?

@BalarkaSen yes

why

are you going to be executed if nobody understands your poster

because I want to get more money from these people

then make it fun

use buzz words

make it flash

2:11 PM

put a picture of neil degrasse tyson in your poster

as background

@djsmiley2k Quantum black hole cohomology

and put on the title "IS MATH RELATED TO SCIENCE?"

absolute banger 10/10

Sadly I submitted an abstract

this would be much easier if I just did an elliptic regularity poster

no one would even bother asking questions

I do have buzzwords like "albert einstein" "black holes" etc.

@ACuriousMind @Slereah did you read the thingie above? I appreciate thoughts

@0celóñe7 I think it will be almost completely arcane to someone not studying math or physics.

@ACuriousMind Do you agree that there is likely no way to make it un-arcane?

2:14 PM

@0celóñe7 Well, I don't know exactly what your project was about, but yes, I think it is likely you cannot make a layperson understand what you did in the space of a poster.

@ACuriousMind the project is about existence/uniqueness theorems for static, spherically symmetric stellar models in the presense of a cosmological constant

also various inequalities and qualitative behavior of polytropes

Yeah, I think you won't be able to make the average person understand more "There's this equation that matters for stars and I looked at its solutions" :P

Do you have any pictures you could put on there?

@ACuriousMind Working on those

trying to generate lots of graphs with Matlab

I can plot density/pressure vs. radius

I think it might be a good idea to take a few pictures you think look nice and then focus the poster on trying to explain what's visible in the picture and why it matters

@ACuriousMind the pictures are a part of the project

maybe I should put the picture from JD's avatar

2:18 PM

@0celóñe7 Sure

I don't really have that much space though

I just thought that instead of trying to explain the project from beginning to end, you might start just explaining one specific result

I.e. don't start with "GR works like this:", but "Here's a picture of my results, and what it shows is that:"

@ACuriousMind yeah

Show them The Evidence

@skullpatrol Y'know, that joke is getting pretty old :P

And you already made it at least once with respect to this same poster.

2:23 PM

Rule 1 of dank memes: Don't beat a dead meme to further layers of death.

@BalarkaSen one of my new profs has some basic memes

user image

the only thing that confuses me is the notation for the eigenspace

What does the $V^{m_i}_{w_i}$ mean

Shankar is good

Is $m_i$ the dimensionality?

@Phase probably

2:26 PM

RIP

Is it not? I can't tell

It seems reasonable

so it's V, of dimensionality $m_i$ with eigenvalues of the form $\omega_i$? What does he mean when he writes the identity between $/omega_i$ and $i$

I really don't think JD should have been suspended from chat.

He was ok here.

@Phase The three dashes mean it's a definition, i.e. it's not an identity so much as declaring that both of these notations refer to the same space.

So he just means an eigenspace with a number of eigenvalues equal to it's dimensionality?

2:30 PM

Yes

I guess I assumed that holds true for all eigenspaces

are there cases where it doesnt?

@Phase I think $m_i$ is the dimension of the eigenspace, and he's saying that you can index the eigenspace either by it's actual eigenvalue $\omega_i$ or just by $i$ (i.e. saying "the space with eigenvalue $\omega_i$" is the same as "the space with the $i$-th eigenvalue")

Eigenspaces only span degenerate eigenvectors right?

If you have 1 non-degenerate value and a degenerate value that applies to 3 eigenvectors

do you just have $V^3$?

whoops wrote 4 instead of 3

I don't understand the question

An eigenspace is the space spanned by all eigenvectors of the same eigenvalue

E.g. if there are 3 eigenvectors with eigenvalue $\omega_2$, you'd write $V^3_{\omega_2}$ for their eigenspace in this notation

Right, even if it was a 4x4 matrix with 1 non-degenerate value

Thanks, : )

2:36 PM

Can we get back to my question?

Why did JD get such a long chat room ban?

Who's JD?

Yeah idk either

AccidentalFourierTransform

Jul 19 at 12:14, by AccidentalFourierTransform

JD Salinger

Anonymous

@BalarkaSen I'm studying now. Can we do it at around 11:30 pm?

@skullpatrol it was g o h s who banned him

Don't poke the hornet nest

2:40 PM

Thnx

I didn't know.

g o h s?

Is this some kind of SE deity?

Don't ask.

It is. Now, pretend you never saw that

^

you can't just say that and then "dont ask"

AccidentalFourierTransform

2:41 PM

does he have some kind of script that notifies him whenever someone mentions his name?

@skullpatrol Because he was a continual disruptive influence. Please drop the topic, we will not further discuss users here where they cannot respond themselves.

He is like voldemort, just be quiet

._.

@Phase Shog9, one of the SE Community Managers.

AccidentalFourierTransform

shog shog SHOG shog SHOG sHoG shog Shog SHoG shog shog SHOG shog SHOG sHoG shog Shog SHoG shog shog SHOG shog SHOG sHoG shog Shog SHoG

2:42 PM

:O

RIP @AccidentalFourierTransform

Some people seem very paranoid about drawing his attention. Draw conclusions from that as you will.

AccidentalFourierTransform

why

@Blue Sure!

Huh

@rob How good or bad is Python?

2:43 PM

Jesus Christ

In comparison to, say, Javascript or C++?

So I guess this Shog dude is fairly strict as a moderator?

how often do people in this chat get penalised directly by external moderators?

AccidentalFourierTransform

on a daily basis

Me? Almost daily.

I have seen shog9 #rekt some people and some chats.

AccidentalFourierTransform

2:44 PM

@ACuriousMind projective representations?

He deleted a chat once

For no good reason

Yeah (to the first sentence)

@Phase All moderators are chat moderators. Please do not think of moderators from other sites as "external moderators".

@AccidentalFourierTransform Hmmm?

Anonymous

@BalarkaSen Okay :)

@BalarkaSen there was a good reason?

AccidentalFourierTransform

2:45 PM

@ACuriousMind well, projective representations or not?

@AccidentalFourierTransform Yes.

AccidentalFourierTransform

thanks

@ACuriousMind what?

@ACuriousMind Moderators from other groups then I suppose. How are they aware when stuff 'needs' to be addressed? Do all Moderators get flagged when something in a chat is reported?

If you are thinking about the SiFi chat, yes. It is folly to think moderators, especially community moderators, especially one of the bigshot community moderators like Shog9, would act without any reason.

But let us not discuss this here. What CM's do to chats is of no business to me as long as it doesn't hurt me. Ignorance is bliss. :P

2:47 PM

Why is everyone so secretive about moderation

The SE culture is very strange

Please stop now guys.

AccidentalFourierTransform

Club penguin was also secretive about moderation

@Phase and 10k+ users of the site, I think

AccidentalFourierTransform

look what happened

The moderator community is the Global Elite reptiles that Alex warned us about

^pls dont ban

2:47 PM

SE is worse than 4chan

It can get worse.

AFT please don't joke about Club Penguin

@Phase A rude/offensive flag is visible to all users with more than 10k total rep (and this is one of the reasons why response to such flags has a high variance), flags for moderator attention are visible to all moderators.

I'll ask almighty mod gods to ban u

Are Mod notification boxes just constantly spammed with flags then?

AccidentalFourierTransform

@ACuriousMind I need to know what happens in the mod chat

2:49 PM

Whenever I talk to Indians, yes.

AccidentalFourierTransform

you guys share the best memes, dont you

@skullpatrol Look, starting this discussion and now asking to stop is pretty inconsistent. Why did you ask the question if this was not the result you expected? (I agree it would be better to drop it, but what was your intention here?)

13 mins ago, by skullpatrol

Can we get back to my question?

What is Club Penguin?

Sad Violin - Air Horn Sound Effect (MLG)

2:49 PM

What is club penguin

@Phase No, chat flags are actually pretty rare.

@ACuriousMind can a mod dismiss a flag on one of their comments?

AccidentalFourierTransform

> What is Club Penguin?

The last bastion of freedom

It got shut down

AccidentalFourierTransform

ಠ_ಠ

2:50 PM

Club Penguin was rare in that the speedrunning community was singlemindedly devoted to getting banned

Exhibit A

Remnants of a dead society

@0celóñe7 Oh, come on. You talk to Balarka, to me and I can say for myself, I have never flagged anyone's posts..

AccidentalFourierTransform

user image

Fug, YT really needs to auto mute

@Sid Are you the fish guy? I got a billion flags from that

@BalarkaSen is a meme lord, we are on the same wavelength

and I didn't flag it. Apparently I was somehow insulted without me even realizing it

If someone said "I'm insulted, pleas stop" I would. That never happens.

3rd parties just flag everything and get a hit from the flag lottery.

2:54 PM

Hey @0celóñe7 are you feeling optimistic or [reasonably] hopeless regarding this abomination

@Phase im blue, ill beat off a guy, ill beat off a guy, ill beat off a guy...

sorry I couldn't resist humming the tune

so good

@BalarkaSen b&

Can you get banned from SE or the SE chat for bringing up Pseudoscience constantly?

Yes

honestly, is there like an online Mod Handbook for this site? I'd be interested to see what it entails

Ask on meta

2:56 PM

@Phase You do not get banned for specific content unless that content inherently runs afoul of Be Nice.

Make sure to Be Nice to carp.

Duck salmon though

Trout?

Those are sacred too

I've never had deboned trout

don't say "sex" either

I'm as much of a fan of Trout as the next guy but I wish they'd stop waving their sexuality around in my face

2:58 PM

Guys, I have a question. The range of a force is inversely proportional to the mass of the force carrier, right? But gluons which are force carriers of the Strong force are massless and still the range of strong force is so small. why?

something something colour singlet

My question @ACuriousMind was answered by 0celóñe7

@QuamosM87 What do you mean by "the range of strong force is so small"?

What is true is that we have confinement, a quantum phenomenon that prevents there being free objects charged under the strong force.

So you can't really talk about the classical "range" of the strong force, since there are no free charges it could act on to begin with

the strong force is bound to the nucleus right? so it acts upto a short distance. for em force the photons are massless, so the range is infinite

wait let me give to the link

hyperphysics.phy-astr.gsu.edu/hbase/Forces/funfor.html

I should make doublebig poster that explains all of GR

3:04 PM

@QuamosM87 Ah, that is the residual strong force (also "nuclear force") that is modelled by being mediated by massive pions, not gluons.

@ACuriousMind We need new avatars

Put a picture of Hawking on it.

He's not pretty

He's an attention grabber.

0

Q: Why you can use mathjax in this website?

I have just noticed that you can use mathjax in this website, i.e. in Physics meta, but why? Here for example: $E=mc^2$ But mathjax is used only when you ask serious question in physics or mathematics and etc..., but serious question in physics should not be asked here on meta, but on physics ...

discussion mathjax tex meta

0

Q: Can I get banned in this website?

Can I get banned in this website? Shall the system ban me if I am asking too many bad questions here?

3:07 PM

oh okay now i get it. thanks @ACuriousMind

put a picture of feynman :-P

@QuamosM87 Also, since I just read it on that page: The range of a force is not limited "by the uncertainty principle". That's a misuse of the uncertainty principle. The proper way to derive the force associated to a certain mediating particle is to do the calculation I outline in this post, which yields that the force of a particle with mass $m$ goes as $\exp(-mr)/r^2$.

How old were you when you learned the HUP? @ACuriousMind

Anonymous

@skullpatrol Of course he knew it since birth.

Anonymous

AI's are usually pre-programmed. :P

He's does seem unusually comfortable with it.

3:22 PM

@skullpatrol Uh...in its proper form (and not just the handwavy $\delta x \delta p \geq \hbar$ without derivation), 19, I guess.

Anonymous

I learnt the proof using Cauchy Schwarz few days back. Tbh it's a bit confusing. I need to revise it a few times.

@Blue also it's wrong :) or at least not completely correct

Anonymous

@0celóñe7 Huh. It seems everything is wrong in Physics

I will tell you details in a few years when you are learning Functional Analysis

Anonymous

Thanks. Will be waiting :P

Anonymous

3:32 PM

@0celóñe7 You gonna go for a PhD after your undergrad?

@ACuriousMind you helped me earlier. I was wondering if you could help again! In the last example here (tcm.phy.cam.ac.uk/~bds10/aqp/handout_spin.pdf), I understand how to get |0,0>=A{- |1,0>|1,0> + |1,1>|1,-1> + |1,-1>|1,1>} but I can't see how to get an equation to solve for A (1/sqrt(3) in this case).

Of course

Currently in a PDE lecture, so I should probably pay attention :P

Anonymous

@0celóñe7 That's great. Good luck :D

@EdinburghDruid It's just normalization - with that value of $A$ the state has a norm of 1.

Thanks! Spent way too long looking at it

3:38 PM

This may very well be Legit for all I know but this gets the award for "sounds most like pseudoscience"

Pritt Balagopal

4:24 PM

Hello everyone

0

Q: Is it possible to receive reputation points on meta?

Is it possible to receive reputation points on meta? I have asked 1 question, which got upvoted, but before asking it I had 101 reputations. After the upvote I still see 101 reputations. I know that every upvote gives you another 5 reputations, so I should have 106 reputations, but not 101. Is t...

discussion reputation meta

Pritt Balagopal

I need some help.

Prathyush Poduval

@PrittBalagopal What ails you? :P

Pritt Balagopal

I'm looking for good videos that can explain the circular fringes (Newton's rings) due to interference of light.

Prathyush Poduval

No idea, Have you tried youtube?

Pritt Balagopal

4:25 PM

I just joined college, and already they're killing me with an experiment to which I have not the vaguest idea about it.

Prathyush Poduval

@PrittBalagopal What is the experiment?

Pritt Balagopal

@PrathyushPoduval Yes I did, but most of them are indian. Although I am an Indian too, I find Indian videos to be too "bookish" and hard to learn the actual concept.

@PrathyushPoduval The Newton's rings one.

Prathyush Poduval

Sorry, I don't know of any good source

Anonymous

@PrittBalagopal Did you look at Physics Galaxy ? They did explain the concept well. You might be confused by interference of reflected light and transmitted light at first. Farcher on Physics Stack Exchange (main site) helped me a lot regarding that.

Anonymous

Newton's rings is a phenomenon in which an interference pattern is created by the reflection of light between two surfaces—a spherical surface and an adjacent touching flat surface. It is named for Isaac Newton, who first studied the effect in 1717. When viewed with monochromatic light, Newton's rings appear as a series of concentric, alternating bright and dark rings centered at the point of contact between the two surfaces. When viewed with white light, it forms a concentric ring pattern of rainbow colors, because the different wavelengths of light interfere at different thicknesses of the air...

Anonymous

4:32 PM

Wikipedia and the links given therein are also helpful.

Pritt Balagopal

Great thanks @Blue, I'll check those out

@PrittBalagopal May I ask why you are looking for videos specifically and not texts?

Anonymous

It's a pity that Farcher and Floris don't visit the chat :/

Anonymous

@PrittBalagopal Let me know if you have any confusion after watching those videos.

Pritt Balagopal

@ACuriousMind I'd like texts too, but I have a practical tomorrow (curse my institute for not explaining the concept), and I need to see a practical view of what's happening.

@Blue Physics Galaxy doesn't sound so good. It's basically just text translated into a video. I need an actual setup of the experiment, to see the phenomenon in it's true form.

Prathyush Poduval

4:38 PM

@PrittBalagopal youtube.com/watch?v=FGiicuHs0zA?

I didn't watch it entirely

Anonymous

@PrittBalagopal If you understand what's happening then setting up the experiment isn't difficult at all. I'm sure that you didn't watch the full playlist. You need to watch the videos in order to understand.

Anonymous

Tbh these things should be taught in high school. Perhaps that is why your institute didn't explain it to you.

Anonymous

If you don't have time then watch from video 39

Anonymous

user image

Anonymous

The setup is trivial.

4:43 PM

Hi, everybody.

Anonymous

Hi @DanielSank

Pritt Balagopal

Yeah, they explained Young's double slit to us, but they didn't do this one.

Anonymous

If you understood YDSE then you'll get this too. :) It's just interference!

AccidentalFourierTransform

> Yime-dependent Schrödinger equation

:-P

Anonymous

@AccidentalFourierTransform urbandictionary.com/define.php?term=yime

Anonymous

4:51 PM

:P

AccidentalFourierTransform

TIL

Anonymous

"a weirdo stalker with greasy sunglasses." XD

@0celóñe7 That's no trouble at all

@rob if you follow my discussion with ACM, I'm trying to explain the GR background on the poster, but it seems completely untenable

Some weird path integral-ish thingy in math chat

in Mathematics, 1 hour ago, by Kanishk

$$f(x)= \lim_{n\to \infty}\int_0^{f(x_0)} \tan\int_1^{f(x_1)} \tan \int_2^{f(x_2)}tan \int_3^{f(x_3)}\dots\int_n^{f(x_n)}\tan(f(x_n))\,dx_n\,dx_{n-1}\dots dx_0$$

4:55 PM

@Secret ew, why?

No idea, probably this user is doing some kind of real analysis thingy

It seemed to be some kind of countably infinite interated tan of an integral

@PrittBalagopal You can look up interference due to division of amplitude

What even is the Frechet derivative of this thing

@0celóñe7 I think that what you have so far looks reasonable.

Can anyone refer a book for computational physics in Python language? I found the book by Mark Newman quite useful. So is there a similar kind of book? Actually, I used Newman PDF and it only contains 4 chapters. So I'm looking for another book which is similar to it

5:13 PM

-1

Q: Thanks for the feedback! Votes cast by those with less than 125 reputation are recorded, but do not change the publicly displayed post score

Yeah but you can't get reputations in this website at all, so as a result I always have 101 reputations and 101 < 125, so I won't ever be able to downvote, but no way I see that others do this so what's going on?

5:27 PM

@rob sitting in an Efremenko class. You know him?

5:43 PM

@0celóñe7 I do. A nice guy.

AccidentalFourierTransform

6:24 PM

-2

Q: Why on Physics meta you neither receive nor lose reputations but on meta stack exchange you do?

Why on Physics meta you neither receive nor lose reputations but on meta stack exchange you do? On Physics meta: When someone either upvotes or downvotes one of your questions or answers then your number of reputations is unaffected. But on meta stack exchange: When someone upvotes one of you...

dude is obsessed

@rob I have to at least decrease the font, this is getting cluttered

AccidentalFourierTransform

new avatar? I dont like it

-2

Q: What shall I do if I am both question and answer banned and all my bad questions in physics stack exchange can't be improved?

What shall I do if I am both question and answer banned and all my bad questions in physics stack exchange can't be improved?

discussion questions answers suspensions quality

-2

Q: Why on Physics meta you neither receive nor lose reputations but on meta stack exchange you do?

Why on Physics meta you neither receive nor lose reputations but on meta stack exchange you do? On Physics meta: When someone either upvotes or downvotes one of your questions or answers then your number of reputations is unaffected. But on meta stack exchange: When someone upvotes one of you...

@AccidentalFourierTransform did you like the previous one?

AccidentalFourierTransform

no

6:33 PM

@JohnRennie does this seem reasonable? i.gyazo.com/72c2f2dd1533b14fe769057f76f37ade.png

AccidentalFourierTransform

$M$ is both the manifold and the mass

use $\mathcal M$ for the former

or $m_B$ for the latter

Don Thomas Reyes

Hello can i ask some assignment question here?

or exercises

AccidentalFourierTransform

also, you can remove the (classically written as $\mathrm ds^2$)

it is kinda superfluous

and you can save one line

@DonThomasReyes sure

@AccidentalFourierTransform I thought I did remove that

Oops

@AccidentalFourierTransform good point, thanks

I'll use mathscr for manifolds

Don Thomas Reyes

Oh ok thank you.

AccidentalFourierTransform

6:41 PM

$\mathcal M\ge \mathscr M$

the first one is classy

the second one is drunk

Drunk on good Kentucky bourbon.

AccidentalFourierTransform

go home manifold, you can hardly stay on your feet

Don Thomas Reyes

A 0.3 kg mass hangs at the end of a string. A second string hangs from the bottom of that mass and supports a 0.9 kg mas. (a) Find the tension in each string when the masses are accelerating upward at 0.700 m/s^2. (b) Find the tension in each string when the acceleration is 0.700 m/s^2 downward.

I tried to solve (a) for first box my formula is T=m1(a) + W ; wherein W=(m1+m2)g ? Did i did it correctly?

7:33 PM

@AccidentalFourierTransform mathfrak

7:44 PM

$(\mathfrak M,g)$

AccidentalFourierTransform

oh_no_god_no.gif

Hi, everybody.

Someone give me an interesting physics question.

I wanna feel useful.

Maybe a noise related question?

Ok

Or even something quantum.

Can you explain to me the God particle?

It's also called the Shog

7:55 PM

No.

if that helps

I wouldn't touch that with a ten foot pole.

Shog and 7SidedDie scare me.

Poor Shog :(

@DanielSank how would I model the elastic collision of two point particles in full GR

7SidedDie?

7:55 PM

@0celóñe7 Not a clue. Next.

Another name I haven't heard of

@Phase another evil

likely here already

AccidentalFourierTransform

so, are you gonna upload the hangout to youtube or not? ;-P

Btw

Why did you change your name to that mess of accents @0celóñe7

@AccidentalFourierTransform Calmate.

7:58 PM

@Phase a bet

jeez

@AccidentalFourierTransform it's already uploaded to Google Drive.

I'm listening to it. There's an echo :-)

AccidentalFourierTransform

for a second there I was wondering whether "calmate" was actually an English word

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