The h Bar

Anonymous

05:00

@Yashas Can you explain me the sodium spectrum . Those two yellow lines are from which transition?

vzn

@0celouvsky yeah that sentiment goes very far in todays world doesnt it? you should call up the whitehouse and express those ideas, theres a new admin that might be willing to listen :P

Anonymous

And does sodium also have several ranges of transition like hydrogen has?

user228700

@JohnRennie Truth be told, I don't care about what he's trying to do; in any case, it's coming out as if he's insulting us and I can only go so long before I start to feel annoyed.

0celouvsky

I think it's because the sigma matrices generate the Lie algebra of the spin group?

Yashas

@blue Sodium is not a unielectron atom

Koolman

05:00

@0celouvsky we have enough time to explore after jee exam

0celouvsky

@Kaumudi.H Then you can feel annoyed, you already said you ignore everything I say.

@JohnRennie Are we allowed to call people nasty things now?

Anonymous

@Yashas Right. I know that. But do you have any data about how many series sodium produces?

John Rennie

@Kaumudi.H I sympathise, and I'd be annoyed in your place, but viewed clinically the only criticism Ryan is making of you students is that you shouldn't be going along with a broken system.

Yashas

@blue It is becaz of a transition but it isn't in our syllabus. We study only unielectron atoms and in MOT, we have homonuclear molecules and heteronuclear molecules of NO, CO, etc. only

0celouvsky

And that they should keep it out of this room.

Especially considering 95% of the discussion is chemisty.

John Rennie

05:02

@Kaumudi.H That's annoying because it's not as if you have any choice assuming you want to eat once you've left home. But it isn't a personal criticism.

Anonymous

@0celouvsky First prove that statement.

Anonymous

Otherwise no one will listen.

0celouvsky

@blue Self evident.

Anonymous

@0celouvsky It isn't

vzn

DOWN WITH THE ESTABLISHMENT!

John Rennie

05:03

@Kaumudi.H My point is that the argument is helping no-one.

0celouvsky

Oh like you're going to listen either way.

You're talking about chemistry right now

Anonymous

@0celouvsky Nope.

Anonymous

It is physics

John Rennie

→ 1 message moved to Trash

No personal comments please.

vzn

lol guess the ambiguous "hybrid feline troll" ref was not taken as a term of endearment. :P

0celouvsky

05:04

@Slereah It says on page 544 that $\Sigma^\alpha_\beta$ form a basis of $\mathfrak{so}(1,3)$

Anonymous

@Yashas Right. So what all do we need to remember about Na spectrum? Only the wavelengths of the two yellow lines?

0celouvsky

Ah, you remember the curvature expansion $F=F^aT^a$ from gauge theory?

Slereah

what is $\Sigma$

0celouvsky

I think this is a similar thing

@Slereah some combination of Pauli matrices

user228700

@0celouvsky: Get this: We don't have any other choice in this matter. Our education system is effed up and there is nothing to be gained by one or two of us boycotting it. Hundreds of students are driven to suicide due to the immense pressure put on them in the 2-3 years of high school so it is not OK when you go on and complain about all this when you aren't even affected by any of this in any significant way other than "wah wah, they're littering the h bar with JEE crap".

3

Anonymous

05:06

0celouvsky

Oh please

Yashas

@blue You don't need to remember any numbers for JEE Advanced.

0celouvsky

I have nothing against the JEE

I have something against the JEE here

vzn

@0celouvsky dude, females are scarce around here & think you could do more )( to avoid scaring em away. still miss sofia :(

0celouvsky

@vzn No passes here. What a weak thing to say.

Anonymous

05:07

@Kaumudi.H I would advice you not to waste time explaining it to someone who doesn't wish to listen.

vzn

@#$& hothead. bye

Anonymous

@Yashas I'm sorta confused. The spectral diagram in Wikipedia has way more than two yellow lines...

Anonymous

Did you see it?

Anonymous

0celouvsky

@Slereah Too many indices

Yashas

05:08

@blue There is also Zeeman splitting for unielectron atoms

We ignore them.

Slereah

@0celouvsky that's what happens with spinor GR

Twice the indices

user228700

@0celouvsky I'm sorry, man. This has been discussed before and most agree that it is OK for us to discuss questions from JEE here. It would be a decent thing of you to do if you could stop complaining about a problem that's not even yours to begin with but I've touched on that before and I have nothing else to add to this discussion.

John Rennie

→ 1 message moved to Trash

0celouvsky

You people are making the problem mine. Why am I the one who has to be "decent"

Anonymous

@Yashas Zeeman splitting can't cause spectral lines in red and blue regions. Can it?

user228700

05:10

@0celouvsky I have been as decent as I possibly can in this conversation. No evidence suggests otherwise.

John Rennie

Please don't start with the flags. Let's just cool down and start being polite or I will freeze this room. You have been warned.

0celouvsky

@Kaumudi.H You're not even the one i have the problem with

@JohnRennie people are flagging?

Yashas

@blue that was just an example

@blue You even get different spectral lines for different isotopes.

John Rennie

@0celouvsky That's not helpful.

Yashas

because the reduced mass of the nucleus changes

0celouvsky

05:11

@JohnRennie My goal is not to be helpful, I'm sorry.

user228700

@JohnRennie I can assure you that I'm not doing any flagging.

John Rennie

→ 1 message moved to Trash

0celouvsky

@Kaumudi.H Look, I have the issue with those other two.

Your discussions with JR are much better than their trivia games

@JohnRennie What are you doing that for?

Anonymous

@Yashas I see. So the spectral lines in the other color regions are due to sodium isotopes? Interesting.

Yashas

no

I don't know about that

but you are worrying about little details

it isn't even there in the olympiad syllabus

Anonymous

05:13

Okay, I will leave it for the moment then

John Rennie

@0celouvsky To stop you being suspended, but the next time you say something inflammatory I will let the flaggers have their way.

Yashas

it is definitely out of the JEE syllabus

0celouvsky

People flagged "weaklings?"

Jesus Christ. These people won't give up.

This is what JEE does to people. Sad.

Anonymous

@0celouvsky I flagged them. Please behave yourself.

0celouvsky

@Kaumudi.H I am sorry for this system, I truly am.

I'm afraid your comrades cannot be saved :(

Anonymous

05:15

@Yashas Right. Thanks a lot :-)

0celouvsky

@Slereah Check page 78 of Kobayashi-Nomizu Vol 1

There they expand the curvature in terms of a basis of the Lie group

I think that's what's going on here

Slereah

could b

I mean, in usual GR, the Riemann tensor is $R_{abcd} \partial^a ...$

0celouvsky

have you gotten to (9.25)?

Slereah

I guess it's just the basis

0celouvsky

@Slereah this isn't the Riemann tensor. It's the curvature of the spin bundle

Slereah

05:18

same shit

0celouvsky

@Slereah that's different

the curvature form on a bundle is a lie algebra valued 2-form

Slereah

close enough

IIRC there's a link between the two

0celouvsky

yeah it's via associated bundles and the frame bundle

nasty stuff

John Rennie

@Kaumudi.H you have mail

0celouvsky

I like how he writes the EFE: $$-\frac{1}{4}\eta_{\alpha\beta\lambda}\wedge \Omega^{\alpha\beta}=4\pi *T_\lambda$$

Slereah

05:20

Yeah, it's one of Those

Rovelli has a whole bouquet of weird EFEs

0celouvsky

Although this is pretty confusing. This is the same $\Omega$?

So...the curvature of the spin bundle is indeed the Riemann curvature?

Slereah

Pretty much?

up to some transformation to get it in non-shit n-forms format

0celouvsky

Strange. I'll have to investigate that

I'm sure it's in Wald

But not from this very abstract PoV

Slereah

My usual guy for weird spinor GR things is Poplawski

Though i'm not sure he does forms

arxiv.org/abs/0911.0334

0celouvsky

$\mathrm{Vol}_\Sigma=-\star\theta^0$

ok now he's just making things up

Why on Earth a negative?

Slereah

05:24

Rovelli has the EFE as $$\epsilon_{IJKL}(e^I \wedge R^{JK} - \frac{2}{3} \lambda e^I \wedge e^J \wedge e^K) = 0$$

(for the vacuum)

user228700

@JohnR: I've replied but what's with this:

Slereah

He also has the self dual formalism

user228700

When did u become a PR for AVG? :-P

Slereah

$$P_{iIJ} e^I \wedge (F^i - \frac{2}{3} \lambda P^i_{KL} e^K \wedge e^L) = 0$$

And he has the Plebanski formalism where the Hilbert action is $$\frac{-i}{16 \pi G} \int (\Sigma_i \wedge F^i + \frac{1}{3} \lambda \Sigma_j \wedge \Sigma^k)$$

John Rennie

05:27

@Kaumudi.H I use AVG anti-virus on my PC, and it checks e-mails as well as downloads etc. I didn't realise it was adding a note to my e-mails though. There will be a setting somewhere to turn that off - thanks for letting me know :-)

0celouvsky

an i in the EH action?

it has pleb in the name lol

Slereah

He is terribly plebeian

0celouvsky

Maybe I should compute $\star\theta^0$ and see what I get

Slereah

Isn't that just the volume form, indeed

0celouvsky

He's saying I need a negative

Slereah

05:31

$\bigwedge_{i} \theta^i$ or somesuch

Well could be I guess?

Koolman

1

Q: $\int ^{\infty}_0 \frac{\ln x}{x^2 + 2x+ 4}dx$

We have to find the integration of $$\int ^{\infty}_0 \frac{\ln x}{x^2 + 2x+ 4}dx$$ In this I tried to do substitution of $x=e^t$ After that got stuck .

does anyone know a better method

I mean for a high school student

Slereah

Hm

0celouvsky

@Slereah you think this tetrad is orthonormal?

Slereah

@0celouvsky aren't they supposed to be?

0celouvsky

Because then I'd have to compute $-\star\theta^0(\theta^1,\theta^2,\theta^3)$

@Slereah Yeah I think so

Slereah

05:36

Krasnikov says that the curve of a spaceship taking turns depending on the result of a random experiment is "non-analytic but smooth"

0celouvsky

so it might also be because of a stupid sign in the definition of $\star$

Slereah

what

0celouvsky

I'll work that out later

@Slereah what's wrong with that?

Slereah

Is that accurate?

0celouvsky

I have no idea

You're the one into crazy things like that

Slereah

05:38

"Namely, the spaceship is described now by a body whose evolution is not fixed uniquely by the initial data (in other words, its trajectory (non-analytic, though smooth) is no longer a solution of any “good” differential equation)."

Seems like an abuse of terminology to me

Anonymous

@Koolman Break it up from 0 to 1 and 1 to infinity

Anonymous

Then substitute y=1/x for the second part

Yashas

@Koolman Was that a JEE question?

0celouvsky

agreed

Koolman

@Yashas mock test

Allen

Anonymous

05:41

Then it should be easy

Anonymous

The first step would be to break it up

Anonymous

From 0 to 1

Anonymous

and 1 to infty

Anonymous

Simplify as much as possible

user228700

@JohnRennie Ah, I see. No problem :-) (Sorry for the late response; mum was screaming for me to have some breakfast already)

Anonymous

05:43

Ah! Then apply integration by parts

Anonymous

@Koolman

Yashas

@blue It isn't so simple.

I tried parts and you get monster integrands

Koolman

I am trying

John Rennie

@Kaumudi.H Breakfast at 11 a.m.?

user228700

@JohnRennie .__. Don't start.

user228700

05:45

Sheesh and today is Vishu and all!

Koolman

@blue for which part

Balarka Sen

i take breakfast at 1, i think?

Joshua Lin

you can do by parts then if you get divergences no worries just put the parts back together again probs fine

John Rennie

@Kaumudi.H No, I was being envious :-)

user228700

Oh, what? OK :-P

Balarka Sen

05:48

it's kind of amusing to see the craze of solving horrendous integrals by standard tricks and stuff whereas it can be done easily enough by "standard" complex analytic procedures

I mean, I understand that's what the exams want from you but that was the whole point of residue theorem.

To standardize horrendous integration, to some extent.

John Rennie

@Kaumudi.H The festival is notable for its solemnity and the general lack of pomp and show that characterize other Hindu festivals of Kerala such as Onam.

Slereah

the definition of a faster than light metric is fairly horrendous

0celouvsky

@Slereah So it would seem Witten's whole proof rests on the ability for us to find asymptotically constant solutions of $\sigma^a\nabla_a\phi=0$.

John Rennie

Hmm, so no getting drunk, painting yourself and running around screaming then? :-)

user228700

@JohnRennie Exactly. Even in Kerala it's quite boring so imagine what it's like in Chennai!

Saturnus

05:52

@JohnRennie that actually sounds like great fun to do at a conference

Slereah

@0celouvsky sounds reasonably doable

0celouvsky

@Slereah Straumann quotes three papers for that

John Rennie

I suppose you could get drunk, paint your self and run around screaming. I guess you'd probably get locked up though :-)

0celouvsky

seems to be nontrivial

Slereah

FTL metrics seem to only be defined with respect to another metric, though

user228700

05:53

The only upside is that we get money from our elders but...only my mom is home so I received money only from here.

0celouvsky

what's an FTL metric?

John Rennie

@Saturnus The Church of England doesnt go in for stuff like that. But then we have the Glastonbury Festival :-)

Slereah

A metric such that u can travel between points in a shorter time than you should

user228700

@JohnRennie Oh, most certainly :-P

Slereah

Such as the Alcubierre or Krasnikov metric

Saturnus

05:54

@JohnRennie hmmm imagine a group of physicists at the festival doing all that

John Rennie

Thanks, I have just imagined a group of drunk, painted, naked, screaming physicists and I feel ill now.

Saturnus

@JohnRennie you're welcome

John Rennie

:-)

Saturnus

admit it, you want to join in

user228700

@JohnRennie x'D

0celouvsky

05:56

@JohnRennie did you hear that I'm quite likely going to be doing my bachelor's thesis on GR?

Balarka Sen

@JohnRennie "I saw the best minds of my generation destroyed by madness, starving hysterical naked, dragging themselves through the negro streets at dawn looking for an angry fix..."

John Rennie

Burroughs?

Balarka Sen

Ginsberg

close but no cigar for you

0celouvsky

Ruth Bader?

Or the one of Landau-Ginsberg fame?

Or is that Ginsburg

John Rennie

@BalarkaSen Oh well, given that I read nothing but science fiction I was lucky to get that close :-)

Balarka Sen

05:58

haha, fair enough

John Rennie

@0celouvsky Hairy American Beat Generation

@0celouvsky: the thesis sounds fun, though aren't you supposed to be blowing yourself up with improbably reactive metals instead?

0celouvsky

@JohnRennie I am a double major

Balarka Sen

aren't you a nuclear engineer

Slereah

He is majoring in both physics and african american studies

0celouvsky

I am currently trying to work out some high frequency noise in the spectrometer

John Rennie

06:01

The US double major system has always seemed a bit odd to me. You just end up working twice as hard.

0celouvsky

not blowing myself up

Slereah

well you're not required to double major

0celouvsky

@JohnRennie I wouldn't do any work if I didn't study other things and have a research job

John Rennie

I suppose it's a way of maintaining a foot in the jobs market while also doing what you really enjoy.

0celouvsky

I'm not sure that I enjoy math

I don't think it's very fulfilling

Balarka Sen

06:03

traitor

Slereah

then why do you talk about it all the time

0celouvsky

There's always a "so what" at the end of every proof

John Rennie

I was wondering that

Anonymous

@Yashas Integration by parts has to be applied twice. You get a term like $$\frac{1}{x}\tan^{-1}(\frac{x+1}{\sqrt{3}})$$

Anonymous

I can't see any easier way

0celouvsky

06:04

$\mathscr P$$\mathcal P$

Slereah

$\mathscr{Poo}$

0celouvsky

mathscr works for lower case???

Slereah

I don't think it does

Balarka Sen

yes but it's dumb

0celouvsky

$\mathscr{abcdefghijklmnopqrstuvwxyz}$

Slereah

06:05

$\mathscr{abcd}$

it's just basic letters

John Rennie

Ooh, Frank Carter & The Rattlesnakes is on the radio!

0celouvsky

I'm off

cheers

John Rennie

@Kaumudi.H: BTW I failed spectacularly at trying to eat moderately yesterday. However I plan to do better today. So far I have eaten nothing but my breakfast cereal, but then I have only been up for an hour and a half :-)

user228700

@JohnRennie Oh :-( An hour and a half and only cereal is commendable and I'm not even being sarcastic!

John Rennie

The trouble is that my Mum has made two carrot cakes. Two! Right now they are smiling at me seductively.

user228700

06:17

There's talk of semiya payasam for lunch here!

John Rennie

Hmm, kind of rice pudding but made with vermicelli.

user228700

@JohnRennie Two?! For the both of you? My my, I don't know how you're going to resist that!

user228700

@JohnRennie Dunno what rice pudding tastes like...

John Rennie

I don't know how you're going to resist that - I'm probably not going to resist it for long :-)

Rice pudding

Balarka Sen

chug some water. easiest breakfast

John Rennie

06:20

@BalarkaSen Low calorie too :-)

user228700

^ :-P When there's nothing to eat, I drink about a whole litre of water to keep hunger at bay but then the sodium levels in my blood begin to drop and I start feeling dizzy :-|

Balarka Sen

exactly right. very recommendable

John Rennie

@Kaumudi.H I find coffee works well for keeping hunger at bay.

user228700

But caffeine is said to increase hunger pangs! :-o

John Rennie

Stimulants tend to have that effect. Amphetamines are used as appetite suppressants.

@Kaumudi.H is it?

user228700

06:23

Well, yes, that's what I've heard anyway!

user228700

Huh. I've Googled it and no, caffeine has the opposite effect, it seems.

user228700

Shouldn't have believed my cousin when he told me that he drinks coke while eating pizza so that he can eat as many slices as possible, without wanting to throw up :-|

John Rennie

> so that he can eat as many slices as possible, without wanting to throw up

A noble aim for a young man!

user228700

:-) Indeed!

Slereah

EC stacks, baby

Ephedrine and caffeine

John Rennie

06:27

Duke University says:
Caffeine can also be used to mask hunger and fatigue due to poor eating or sleeping habits. It is not unusual for caffeine to be used to provide extra energy when lacking sleep or food. Temporarily, this is normal, and certainly provides relief. However, use of caffeine to replace food and/or sleep on an on-going basis is not appropriate and can be detrimental. Many studies have shown the negative impact of sleep deprivation on judgment, acuity and physical well-being. Continually using caffeine as a means to address hunger and avoid food can be an early sign of disord…

link

user228700

.___. Jeez, OK.

John Rennie

Disordered eating eh? That pretty much describes me :-)

Or possibly disorderly eating

Slereah

Isn't all of England disorderly eating

with your awful food

John Rennie

Food is pretty good in the UK these days. Cooking has become fashionable.

user228700

@JohnRennie Yes :-P Without my mum to keep me in check, I dunno what I'd do because I have a habit of going the whole day without eating if not reminded; I stop feeling hungry after half an hour of the actual time in which I'm supposed to eat because of acid reflux.

John Rennie

06:29

The TV schedules are stuffed with programmes about cooking.

In fact I was watching Masterchef last night.

Kind of like pornography, but edible.

user228700

I haven't watched Masterchef UK yet; only Masterchef US & Aus.

user228700

...and it's great!

John Rennie

Sometimes it's good. I find a lot of the food unnecessarily fussy ...

user228700

Lol, "unnecessarily fussy" is the whole premise of the show! :-P

John Rennie

Last night one of the contestants prepared parkin as a dessert. Parkin is a traditional English cake, and it looked absolutely fabulous. Not fussy - just delicious!

Balarka Sen

06:34

let's face it, the only food is milk-float

John Rennie

The judges liked it too, and he got through to th next round.

@BalarkaSen milk float?

Balarka Sen

coke taken down with milk

user228700

One of my favorite T.V shows growing up was Wallace & Gromit. Absolutely charming :-)

John Rennie

@Kaumudi.H Very British :-)

user228700

Very! :-)

Slereah

06:36

@BalarkaSen poor idea

milk and acid do not go well together

I had to learn it the hard way

Vodka, milk and redbull do not mix

John Rennie

@BalarkaSen Cocaine and milk? Isn't snorting milk a bit messy?

Slereah

not powdered milk

John Rennie

Balls, balls, balls, balls, balls - a disk failed in one of my servers last night, right at the start of a four day holiday! Oh well, the engineers are going to love me! :-)

user228700

Oh, man, that sucks! :-/

John Rennie

@Kaumudi.H It's OK. It's not me has to go out and fix it on a holiday weekend :-)

Anonymous

06:47

4 day holiday for what? Any festival?

Koolman

3

A: $\int ^{\infty}_0 \frac{\ln x}{x^2 + 2x+ 4}dx$

May be this will be a more elementary solution. Let us start with a the substitution $x=2y$. Then \begin{gather*} I = \int_{0}^{\infty}\dfrac{\ln(x)}{x^2+2x+4}\, dx = \int_{0}^{\infty}2\dfrac{\ln(2y)}{4y^2+4y+4}\, dy =\\[2ex] \dfrac{1}{2}\int_{0}^{\infty}\dfrac{\ln(2)}{y^2+y+1}\, dy + \dfrac{1}{...

@blue @Yashas

John Rennie

@blue Easter. Today is Good Friday.

Koolman

fantastic answer

Anonymous

@Koolman That is great. But is that a standard trick?

Anonymous

I haven't come across it before

Anonymous

06:50

x=2y

Anonymous

Doesn't seem standard to me

Koolman

@blue no

this is done to make the coefficient of denominator same

Anonymous

@Koolman Oh yes

Anonymous

That is a great way

Anonymous

@JohnRennie Oh. Nice :-) Today is a working day here

Koolman

06:53

@blue not for everyone

Anonymous

@Koolman Ah, it depends on where you stay, perhaps

Anonymous

And where you work

Koolman

yeah

Yashas

$I_2$ is zero

wth

it is not obvious at all

even if you look at the graph

Anonymous

@Yashas Break it up from 0 to 1. I2 is standard once you get that first step

Koolman

06:55

I2 = -I2

Anonymous

Yes^

Yashas

Yea I know

Koolman

then I2 will always 0

Yashas

I know that $I_2$ is zero

but it isn't obvious in the graph

Anonymous

Why draw the graph?

Koolman

06:55

where is graph

Yashas

Anonymous

@Yashas That is unecessary...

Anonymous

And yep, it is not obvious

Koolman

we cannot comment through this graph

Yashas

I won't graph it in the exam but I get curious to see how the function looks

becaz I will remember it

I would have honestly concluded that $I_2$ isn't zero from the graph

Anonymous

06:58

@Yashas Actually that kind of graph is very common. The area from 0 to 1 cancels the area from 1 to infinity

Yashas

-_-

Anonymous

So you should'nt be so sure

Anonymous

That it won't be 0

Yashas

I know that the area from 0 to 1 must cancel area from 1 to infnity but it isn't obvious from the graph.

@blue I have never got fooled by a graph this bad before.

Anonymous

@Yashas But it is obvious that that it "can" be 0

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