The h Bar

0celo7

5:00 AM

ok I have to go to bed, cheerio

user218912

@0celo7 this??

user228700

@0celo7 Again with this -__-

Obliv

@0celo7 SEE? NO one who is actually easily offended says that they are easily offended..

good night weakling. I will stay up until I see the sun rise then set again.

user116211

Hi @rob; all the best for the election.

user218912

@Obliv wow we have a badass over here.

0celo7

5:01 AM

So maybe I am a weakling, or maybe I'm just smarter.

I think I know which it is.

rob

@MAFIA36790 Thanks!

user116211

Tell me @0celo7; I've some great collection of Bourbaki groupie. You can use them as your gravatar.

0celo7

link?

Obliv

@0celo7 well I'm managing my time properly too. If I study until the exam starting today I can probably get at least a C

loose definition of proper.

user116211

@Obliv You are trolling yourself.

user116211

5:04 AM

Hey Hey @orthocresol.

user218912

@Obliv C is not good.

user116211

._.

user116211

This looks great:

user116211

Apr 30 at 7:19, by Slereah

Obliv

C is better than D which is better than F

user218912

5:05 AM

how dafuq did 0celo7 get banned for saying that?

user218912

lol

Obliv

@IceLord huh?

user116211

OMG; the banning monster is in loose; I'm getting out.

user218912

@Obliv he got banned for replying to you.

user116211

@Obliv: Go to bed.

Obliv

5:06 AM

How do you know? I didn't see a message removed

user218912

@Obliv scroll up.

Obliv

@mafia that's academic suicide

user116211

:(

Obliv

@iceL I'm dumb and can't find it

user116211

@Obliv chat.stackexchange.com/transcript/message/32704245#32704245

user218912

5:08 AM

@Obliv you mean you're blind.

user218912

xD

Sir Cumference

I'm back.

Obliv

@mafia can you tell me which post it was after?

Sir Cumference

Anyone care?

Obliv

I seriously can't find it.

Sir Cumference

5:09 AM

Wait did 0celo actually get banned?

user116211

@SirCumference Good morning.

Sir Cumference

@MAFIA36790 Well it is 1:09am here...

But yeah did 0celo get banned?

user218912

0celo7 banned 4 realz

user116211

@SirCumference damn; I thought you got a nap.

Sir Cumference

Huh... :3

user218912

5:10 AM

I have no idea how he got banned.

Obliv

David Z is not going to be happy with stupid flags again :[

user218912

he didn't say anything bad.

Sir Cumference

@IceLord The system makes no sense.

user116211

@IceLord I have no idea too; I didn't see any of his comments offensive.

Sir Cumference

It should take more than one flag to ban someone.

user116211

5:11 AM

4 mins ago, by MAFIA36790

OMG; the banning monster is in loose; I'm getting out.

Sir Cumference

@0celo7 Really?

user218912

10k users decide whether to ban right?

Obliv

whatever he said he was going to sleep anyway.

user116211

@IceLord Court of Owls

user116211

@Obliv But suspension is suspension :(

Sir Cumference

5:12 AM

@MAFIA36790 How do ya quote messages?

user116211

@SirCumference Just paste the permalink.

Sir Cumference

Okay

Sep 29 at 9:47, by David Z

Don't use chat flags except for seriously inappropriate messages. We've had a problem with inappropriate chat flagging for a while, and more so recently.

Obliv

@mafia it's not like he's going to run for mod anytime soon so what difference does it make? I don't think he cares.

user116211

@Obliv Just wait for when he comes.

Sir Cumference

Well anyway

@0celo7 Studies show there are physical and chemical differences in the brain...

Do some research. You'll offend someone.

user218912

5:14 AM

I need to sleep.

user116211

@IceLord Go to bed.

Sir Cumference

@IceLord Same...

user116211

@SirCumference Take some pills.

Sir Cumference

@MAFIA36790 No.

user116211

@SirCumference They won't kill you, for sure ;P

Sir Cumference

5:15 AM

@MAFIA36790 Melatonin screws with male reproductive organs

That's not pleasant either...

user116211

Or take a walk; you would feel drowsy.

user116211

@SirCumference WTF

Sir Cumference

@MAFIA36790 Look it up.

user116211

My doctor is prescribing melatonin for over six months T__T

Sir Cumference

Probably something you should know, if ya want children some day :P

You're probably not in trouble, just don't use them regularly.

Obliv

5:17 AM

If you get chat banned can you join a different chat room

I didn't try this when I got banned

Sir Cumference

@MAFIA36790 Melatonin isn't regulated by the FDA since it's considered a vitamin rather than a drug, so it's almost always overdosed.

Not a good thing.

user116211

@SirCumference I've not used a single one; my eyes generally get heavy after 3 am generally.

user116211

@SirCumference Damn; I'm suing my doc.

Sir Cumference

@MAFIA36790 Well nothing happened to you so you really don't have much to complain about :P

user116211

But he was planning for destroying my organs ;P

rob

5:19 AM

@SirCumference Can you link to a source for the melatonin side effects?

Sir Cumference

@rob Just look up "melatonin side effects"

rob

@Obliv That sounds like a recipe for moderators to play whack-a-mole with troublesome chat users.

Obliv

@rob yeah I guess the same rules apply to all chat rooms. was worth a try

Also, the video you linked on your profile is hilarious @rob

rob

@SirCumference In the first ten links I find one sentence fragment that mentions possible interference with hormones during adolescence. What do you find?

@Obliv Best film ever made

Sir Cumference

@rob lmgtfy.com/?q=melatonin+male+reproductive+system

Obliv

5:26 AM

Haven't seen it but now I want to. I love old films with rich humor

user116211

5 mins to go for 0celo

Sir Cumference

@MAFIA36790 3 mins...

Obliv

@mafia for a standing wave $y(x,t) = 2y_m \sin(kx)\cos(\omega t)$ what is the purpose of the $\cos$ term? Afaict time is irrelevant if the standing wave doesn't move

user116211

@Obliv What do you think $\omega$ is doing here?

Obliv

it's there so that $\cos(\omega t)$ provides a way for the wave to repeat with respect to another parameter

$\omega = \frac{2\pi}{T}$

so when $t = T$ it repeats

Sir Cumference

5:35 AM

0celo's back.

user116211

@Obliv The position of, say a bead, in the string changes over the course of time, even in standing waves.

user228700

I've a quick question; if the coefficients of a quadratic equation are unreal, is it **untrue** that unreal roots occur in conjugate pairs?

user116211

Hey @0celo7; why did you go?

user116211

._.

Obliv

@mafia oh but I thought the wave form is static throughout

so the bead stays in place

only the amplitudes at each position $x$?

user116211

5:37 AM

@Obliv Okay, say it's in $x$ but its $y$ position changes over the course of time.

user116211

Its $x$ position doesn't change though.

Obliv

youre' right i glossed over that

@kaumudi what are conjugate pairs?

user228700

@Obliv Two complex numbers that are conjugates of each other.

user228700

If @JohnRennie isn't back by tomorrow, I will positively start freaking out.

Obliv

@Kaumudi I would think no, it isn't untrue.

John Rennie

5:41 AM

Fortunately John is here :-)

Obliv

Eyyy @johnR

Sir Cumference

Howdy @JohnRennie

user228700

@JohnRennie Ah, you're finally back! Good morning sir :-)

Sir Cumference

I wonder where Chris White is...

John Rennie

I'm visiting relatives all this week so my attendance here will be a bit erratic.

user116211

5:42 AM

@SirCumference NOOO!!!!

Sir Cumference

As far as I know he hasn't been on since he got his PhD

John Rennie

I'm typing this from my Mum's kitchen

Sir Cumference

@MAFIA36790 Huh?

user228700

@JohnRennie Ah, OK...

user116211

@SirCumference He left SE.

Sir Cumference

5:43 AM

@MAFIA36790 Wait what?

user116211

@SirCumference Didn't you hear about that; it's a month old news.

user228700

@JohnRennie Oh :-P I was just wondering about ur prolonged absence. No questions for u; Orthocresol helped me out :-)

Sir Cumference

@MAFIA36790 Uh, no?

Catch me up to speed please

user116211

Let's not discuss about him; that wouldn't make him return, @sirC.

Sir Cumference

Wait are you trolling me?

user116211

5:44 AM

@SirCumference wait... lemme link the transcripts.

user116211

@SirCumference I never troll anyone.

John Rennie

@Kaumudi Cool. I imagine he knows a lot more chemistry than me anyway since that's his speciality :-)

Obliv

@sirC IIRC he got chat banned for something then he asked to have his account deleted or something

yea riperoni

Sir Cumference

@Obliv Wait whaaaat?

user228700

@JohnRennie I'm a bit surprised by ur use of pronoun; I've been imagining Orthocresol to be female :-P

John Rennie

5:47 AM

Sadly, the assumption that everyone on a science web site is male is generally reliable.

Sir Cumference

@JohnRennie Huh...

That's kind of sad, I can't think of one woman here...

user228700

@SirCumference Uh, I'm female :/

John Rennie

Well I can think of one woman here :-)

Sir Cumference

@Kaumudi Oh, uh...hi...

Sorry :/

user228700

@SirCumference Lol :-P

Sir Cumference

5:49 AM

@Kaumudi Well your profile pic has some guy on it

So I kinda assumed

John Rennie

Pizza John T shirt I think

user228700

@SirCumference I changed it yesterday because one user kept inviting me into a chat room for no reason.

Sir Cumference

@Kaumudi That's a bit creepy

user228700

@JohnRennie Yeees! U know about that?

Sir Cumference

@Kaumudi You didn't just ignore him?

(I mean literally press the ignore button)

@MAFIA36790 Any luck?

John Rennie

5:50 AM

@Kaumudi I used Google to do an image search. I have to confess I have zero knowledge of Pizza John or what the significance on the image is.

user228700

@SirCumference No, I wasn't aware of the existence of that button :/ I'll keep this in mind. It's better that I don't have my face on this website anyway.

user116211

@SirCumference I'm burying a dead phone, wait...

Sir Cumference

@Kaumudi True.

@MAFIA36790 Um, k?

user228700

@JohnRennie Oh :-( For a moment there, I was kinda excited.

Sir Cumference

@JohnRennie Oh my God

I just realized

Congrats on getting 200k rep...if you recently got that.

user116211

5:51 AM

Sep 19 at 13:56, by ACuriousMind

@EmilioPisanty I'm pretty sure it's a (over?)-reaction to him getting banned on chat.

Sir Cumference

That's some serious dedication

user116211

@SirCumference Why are you late, dude T__T

John Rennie

Thanks. These things happen :-)

Sir Cumference

@MAFIA36790 ;-;

user116211

Sep 19 at 13:57, by Emilio Pisanty

I think his entire SE profile is gone, too

user116211

5:52 AM

Sep 19 at 13:56, by ACuriousMind

Because right after that happened, his profile text was changed to "delete me" and he never returned.

user116211

That's pretty much sufficient; if not dig the transcripts @SirC.

user228700

Martin, one of the CSE mods knew about the shirt! Maybe I'll attract more Nerdfighters with this image now! :-D

Sir Cumference

@MAFIA36790 Look at the first and last messages

That's how slow I am

user116211

@SirCumference WTH O.o

Sir Cumference

Yep...

user116211

5:54 AM

Anyways, @sirc, I'm re-iterating: Let's just don't discuss about Chris; it wouldn't make him come back...

Sir Cumference

I can't keep up...

@MAFIA36790 I'm not asking for him to come back

Just what happened?

user116211

@SirCumference No need of speculations; he is just gone. An over-reaction for sure.

Sir Cumference

Like Tildal?

user116211

@SirCumference No idea.

user116211

4 mins ago, by MAFIA36790

Sep 19 at 13:56, by ACuriousMind

@EmilioPisanty I'm pretty sure it's a (over?)-reaction to him getting banned on chat.

Sir Cumference

5:56 AM

@JohnRennie Uh, you're active here, right?

What happened to Chris White?

user116211

@SirCumference We can never know the reason of suspension.

Sir Cumference

Dang.

That's a shame...

Obliv

@mafia For a longitudinal wave, can one create a wave form that is analogous to a cosine wave in say a string (transverse)? Like, instead of displacing the element in ,say air, both forwards and backwards in the direction of the wave velocity, it only displaces the element in the direction of the wave speed then returns to equilibrium?

also does anyone know how/why differences in pressure of a medium (due to a longitudinal wave) cause an element of the medium to be displaced back and forth?

Nvm I figured it out.

user116211

6:26 AM

@Obliv Why not?

Obliv

Yeah I thought so. @mafia hey since i've run out of coffee I need music to keep me up. You know anything particularly good at that/enjoyable?

user116211

@Obliv Wait...

user116211

Survivor - Eye Of The Tiger

►

user116211

Rocky Classic

user116211

Michael Jackson - They Don't Care About Us

►

user116211

6:34 AM

Old but insanely ear-soothing

Obliv

hmm not quite what I was looking for but thanks regardless

user116211

@Obliv Eye of the Tiger is awe-inspiring!!

Obliv

6:59 AM

hmm would the bulk modulus $B = \frac{-\Delta P}{\frac{\Delta V}{V}}$ be defined for a single element of the medium?

'where P is pressure and V is volume

this is the elastic property of a fluid through which a longitudinal wave travels $v = \sqrt{\frac{B}{\rho}}$ where $\rho$ is the volume density of the fluid

uhh yeah nvm that's quite obviously the case.

DanielSank

7:19 AM

@Kaumudi I can't tell if they were teasing you...

user116211

@DanielSank o/

DanielSank

\o

user116211

WTH! Goldstein is $1.5!!

user116211

What a deal, lord!!!

Obliv

7:36 AM

@mafia link?

user116211

@Obliv amazon.in/Classical-Mechanics-Herbert-Goldstein/dp/…

user228700

@DanielSank Who? JR and SC? I didn't feel like they were :/ Why do u think so?

Obliv

dude $1.5 ~= $15

crap

1.5 dollars ~= 15 dollars

user116211

The price is increased!! It's now $2.2 ;/

user116211

@Obliv What?

user116211

7:39 AM

I'm using Google conversion to get the dollar equivalent.

Obliv

Oh

wtf why is it more expensive here?

Emilio Pisanty

0

Q: Solid State physics

let us say we have the 2D graph of E(k1,k2) for two atom nn hopping hamiltonian and somehow we find that there are zero gap at the corners of Brillouin zone(which i don't really see how they are related),Now the question asks how could this be, how could we have zero gaps at the corners of the Br...

^ could use a helping hand

user116211

@Obliv Here it is student-friendly ;))

Obliv

:[

user116211

Any help @Emilio?

Emilio Pisanty

7:41 AM

@MAFIA36790 I'm on my phone

user116211

What do you want to do?

Emilio Pisanty

The question could use some improvement

user116211

Okay, first I would change the title.... lemme see.

user116211

Okay, check @Emilio, if the edited version of the post is better than the first one.

Obliv

oh my god my brain is melting. how does puu.sh/rxdaU/166b850bbd.jpg puu.sh/rxdc3/22473a8b84.png (in the second image) there exist a change in volume in the displaced element?

first image is context.

Isn't the whole element $\Delta x$ moving along with the longitudinal wave ?

user116211

7:52 AM

Are you reading Resnick?

Obliv

yes

I don't see how the two faces differing in displacement lead to a change in volume.

user116211

That is a messy explanation.

Obliv

I don't find much of what's in this textbook to be rigorous enough so I have to keep picking up bits and pieces elsewhere to fill the gaps honestly.

It's pretty annoying

user116211

Check French; there is a rigorous derivation in it.

user116211

I have to see Crawford; I remember it has also a discussion on it too. But am not sure.

Obliv

8:01 AM

I don't have either of those texts (can't really search for one by a guy named french since it's not exactly a specific search term) I think I can reason this out with some good ol' original thinking maybe..

user116211

amazon.com/Vibrations-Waves-P-French/dp/8123909144

Obliv

Just need to relate $\frac{\Delta{V}}{V}$ to the change in displacement over the change in position of the fluid element..

user116211

amazon.com/Waves-Berkeley-Physics-Course-Vol/dp/0070048606

user116211

@Obliv yes.

user116211

@0celo7, you need to sleep.

Obliv

8:04 AM

What the hell @0celo7 LOL why are you back

Like, it makes sense in that image that when the fluid element passes the wave pulse, the front facing end gets displaced before the rear end. This results in a change in volume due to the difference in displacement. But, when the entire element is in the wave then there is no change in volume.

oh duh what the heck is wrong with me

in the case where the entire element is in the wave pulse there wouldn't be a change in pressure anyway for me to derive

user116211

I don't know why the review gets completed by just one looks okay; I thought we needed 3 looks okay to get the post out of the review.

DanielSank

2 hours ago, by Sir Cumference

That's kind of sad, I can't think of one woman here...

user116211

user228700

8:29 AM

@DanielSank Well, he did explain it afterward; my avatar has the face of a grown man wearing a fancy moustache and all :-P

user228700

That is John Green, not some rando BTW.

innisfree

@EmilioPisanty what's up? I thought the edit fixed a problem with the snippet of Mathematica code?

Obliv

Okay.. I think that's it for tonight. Going to be back at it in like ~8 hours probably. Thanks for the help @mafia

user116211

@Obliv Good night.

Obliv

I can probably go for another hour but I don't think it'd be as productive as sleeping and studying tomorrow

user116211

8:35 AM

@Obliv yes, it won't be productive; better sleep.

user228700

@DanielSank: "John Michael Green is an American author, vlogger, director, writer, producer, cinematographer, editor, stunt performer and actor." Astonishing as it might seem, all of those things are true.

user228700

@MAFIA36790 How come u visit this room almost as often as me(who is sitting at home, all day, everyday)? Don't u have classes at college?

user116211

@Kaumudi We are having holidays.

user228700

@MAFIA36790 For what?

user116211

@Kaumudi So, you don't know about Durga Puja?

user228700

8:42 AM

@MAFIA36790 Ah. I do know about the festival, of course, but Malayalees celebrate only two festivals; Onam and Vishu. Do schools get a holiday for Onam there?

user116211

Even if we have classes, it's for 2 hrs only. I have to go out at 9:30 am; generally reach home at 1 pm.

user116211

@Kaumudi No.

user228700

@MAFIA36790 Oh, wow, I see.

user116211

Practicals are excluded.

user228700

@MAFIA36790 Hm, OK. Does it make sense to say "Happy Durga Puja"? How is it that one wishes?

user116211

8:43 AM

@Kaumudi Sure it is ;)

user228700

OK then, happy Durga Puja :-)

user116211

We can have some extra classes if we want; then it takes another hour or so.

user116211

@Kaumudi Thanks.

user228700

I see. You still won't reveal which college u attend :-P

user116211

Recently there was students election or all of that sort; so yeh; we got extra holidays too.

user116211

8:46 AM

@Kaumudi By then, you should have guessed ;)

user228700

I guessed before and all my guesses have been wrong. Now that Ik that you live in Calcutta, I have some more options, but since you don't want to reveal the name of the institute, I decided not to push it.

user228700

Did u write WBJEE? Since it's conducted only in WB, I decided not to write it this year :/ Probably won't write it next year either.

user116211

@Kaumudi No.

user116211

@Kaumudi Good :) I like to maintain anonymity.

user116211

@Kaumudi It's for engineering only. I've no interest in it.

user116211

8:50 AM

@Kaumudi I think any one can take the exam; it has also examination centers in other states too; may be north eastern states.

user228700

@MAFIA36790 But from what I heard, it's conducted only there :/

user228700

Say, have u heard of BIT, Mesra?

user116211

@Kaumudi Maybe, no idea.

user116211

@Kaumudi Yes, heard the name; but absolutely having no idea.

user228700

@MAFIA36790 Oh, OK. I had gotten selection there too, this year, for an integrated degree in Physics but the university doesn't have a good reputation and besides, it's pretty easy to get into it; they consider only the board marks, so it's not very meritocratic.

user116211

8:53 AM

@Kaumudi I thought JEE marks was mandatory for every college/university.

user228700

@MAFIA36790 Yeah, that's what made us suspicious of the college; ONLY board marks were being considered :/

user116211

@Kaumudi No; it's a valid college; no doubt though.

user228700

@MAFIA36790 Yes, it's definitely valid and all, but it's not the best...

user116211

@Kaumudi Many state Govt. run universities consider solely the board marks.

user116211

@Kaumudi ohh.

user228700

8:55 AM

One more question, before I get back to my studies; u gave the CBSE board exams this year?

user116211

@Kaumudi I was in State Board.

user228700

(Well, that's the first part of the last question :-P)

user228700

@MAFIA36790 Ohh, okay. I was going to ask if the controversial Math paper was tough there as well.

user116211

@Kaumudi Was it? I did check some CBSE question papers; but have no idea of 2016.

user228700

@MAFIA36790 Well, yeah! It was too damn tough in most states. The pattern used to be-20% H.O.T.S, 60% Avg. and 20% Tough so that even the average students would pass.

user116211

8:58 AM

ohh.

user228700

For the past two years(including 2016), however, the pattern changed (without prior notification regarding this change) to 60% H.O.T.S, 20% Tough and 20% avg.

user228700

It created a huge uproar! Do u know that it was discussed in the effing Parliament? XD

user116211

OMG.

user228700

@MAFIA36790 How the hell did u not know about this? Okay, maybe it wasn't this tough in those parts. The Southern region had it tough though. After the exam, almost everybody was crying. And then at night, news channels began to discuss it. It came in the front page in the newspaper the next day...

user116211

WTH; we follow Aajkal; don't think it published such thing AFAIR.

user228700

9:04 AM

Many of my intelligent friends scored badly :-( They shouldn't have brought this change out of the blue like this.

user228700

@MAFIA36790 Oh, okay. I'm pretty sure it would've been published *somewhere*(if not in the front page) in the WB edition of Times Of India...

user116211

I generally don't follow ToI.

user228700

I dunno how this happened but a girl who scored close to 200 in MAINS scored 7 in the Math paper. SEVEN. This news came from a very credible source but it's still very hard to believe :o There were protests outside the CBSE office in Delhi or wherever their office is...

user116211

Okay, can't digest.

user116211

It takes sufficient efforts to get failed, no matter how difficult the paper is, though ;P

user228700

9:08 AM

There is an online complaint forum for CBSE. For days after the fateful day of the Math exam, it was flooded with suicide threats if they didn't concede to give grace marks.

user228700

@MAFIA36790 Haha, that's very true.

user116211

Although I should mention that performance in board exams in not at all correlated with performance in entrance exams like JEE.

user228700

It was a very interesting paper for me. I used to score horribly in Math at school because of shortage of time and silly mistakes but I was able to redeem myself in the final exam. Now that I have said so much about the exam, you may be wondering how much I got and I'm so glad to say that due to God's grace, I managed to get 95.

user228700

@MAFIA36790 Yes, yes, but all the students who perform well in JEE at least pass in boards!

user116211

@Kaumudi Well, as I said, no matter how horridly one performs, they get somehow passed as far as I seen. Failing needs lot of efforts ;)

user228700

9:12 AM

@MAFIA36790 Yes, especially when every teacher who is correcting the paper wants you to pass.

user228700

Anyway, I have to get back to my studies. I'll come back with some questions in a short while, I'm sure :-P

user116211

@Kaumudi Yes, that's the very fact; there is an implied effort to make you pass. I should mention though, there is a severe dearth of competent teachers for checking the exam both for a state as well as CBSE.

user116211

@Kaumudi Sure.

user228700

9:55 AM

For all the procrastinators:

user228700

waitbutwhy.com/2015/03/procrastination-matrix.html

Farcher

11:45 AM

@Qmechanic I hope this is the correct place to contact you? No problems about deleting my reply regarding the duplicate of physics.stackexchange.com/questions/283889/very-basic-question However I wrote my answer because the other two answers did not spot an error that the OP had written. I have a copy but cannot post it because the question is on hold. Is there a way of you posting my copy?

heather

@Farcher, can't you comment?

Qmechanic

12:17 PM

@Farcher : I temporarily reopened it. Let me know when you have added your answer.

0celo7

@Kaumudi what?

@Obliv @MAFIA36790 I don't know what happened, but I was asleep all night. I don't know why my phone logged me back in.

Farcher

12:47 PM

@Qmechanic Done. Very many thanks for you effort.

s.harp

Hello, I have recently read the statement that symmetry breaking does not occur in quantum systems. The argument went as follows:

Consider a realisation of a Hamiltonian $H=p^2/2 + U(x)$ in $L^2(\mathbb R^n)$. Any symmetry group $G$ of the potential also acts on the Hilbert space. Thus, symmetry breaking does not occur.

So... why does the fact that the symmetry group will act on the Hilbert space imply that symmetry breaking does not occur? that doesn't make much sense to me