The h Bar

Simply Beautiful Art

13:00

O.O

AccidentalFourierTransform

$\Huge{O.O}$

@Yashas yes

Simply Beautiful Art

$$\huge\sigma.\sigma$$

AccidentalFourierTransform

something in the upper well can decay into the lower well

0celouvsky

@AccidentalFourierTransform show off

AccidentalFourierTransform

but not the other way around

Yashas

13:01

It won't decay to a lower well if I don't give it some energy.

but there will be a net release in energy if it makes it all the way down to a lower well

hmm

AccidentalFourierTransform

stability is about what happens when you allow systems to move a little

something in an unstable position will stay there forever

unless you wiggle it a bit

Yashas

I can wiggle something just a little bit when it is in a well and it needn't necessarily go to a lower well

Simply Beautiful Art

@AccidentalFourierTransform Reminds of butterfly effect and chaos theory

Slereah

@0celouvsky by the way

amazon.com/Einstein-Equations-Behavior-Gravitational-Fields/dp/…

another book to buy

AccidentalFourierTransform

@Yashas exactly. thus, wells are stable

the lower one is more stable

but they are both stable

Yashas

13:05

I dono why a lower well is told to be more stable than a higher well.

I still don't have the intution :(

I am pretty sure that few months later, that thing is going to be an obvious stuff.

AccidentalFourierTransform

because if you wiggle the upper one strongly enough, it will leave the well into the lower one

Yashas

idk how human brain works but complicated stuff become silly things as time passes

AccidentalFourierTransform

but the opposite will never happen

Slereah

One physicist is literally called "Abuzer"

Someone call the police

Yashas

I can give a case where the system prefers the opposite

Fawad

13:07

@AccidentalFourierTransform $\Huge\text{O.O}$

AccidentalFourierTransform

that breaks the physics o.O

@Fawad mine is bigger ;-)

Slereah

$$\huge{\Theta \omega \Theta}$$

AccidentalFourierTransform

oh no, not again

Yashas

@AccidentalFourierTransform

If you give some energy, the ball will land at E before you can reach A.

Simply Beautiful Art

$$\huge\hat\Theta\omega\hat\Theta$$

AccidentalFourierTransform

13:08

@Yashas not necessarily

Yashas

Hmm, I already see a flaw in my argument.

Yea

Slereah

$$\huge{\widetilde\Theta \omega \widetilde\Theta}$$

AccidentalFourierTransform

$$\huge \overbrace{\left. \overbrace\iiiint\vphantom{\cfrac12}\stackrel\curvearrowright\varepsilon-\overli‌ne{\boxed{\hat\sigma}} \underbrace{\underline{ \ \supset}} \overline{\boxed{\hat \sigma}}\right)}$$

0celouvsky

@Slereah do you want a PDF?

Slereah

Of what

Simply Beautiful Art

13:10

@AccidentalFourierTransform HEY! THAT'S MINE!!!

Slereah

The book?

I can prolly get it

AccidentalFourierTransform

@SimplyBeautifulArt yeah, but apparently I broke it :-(

Simply Beautiful Art

$$\huge \overbrace{\left. \overbrace\iiiint\vphantom{ \cfrac12}\stackrel\curvearrowright\varepsilon -\overline{\boxed{\hat\sigma}} \underbrace{ \underline{ \ \supset}} \overline{\boxed{\hat \sigma}}\right)}$$

Fawad

fail

Simply Beautiful Art

@AccidentalFourierTransform I'm better at it

0celouvsky

13:10

@Slereah it's a mycopy book

Slereah

Sorry, no japanese characters allowed

Simply Beautiful Art

lol @Fawad

Yashas

The right side looks like a face. What's the left side?

0celouvsky

Unless it answers all my problems I won't get a hardback

Simply Beautiful Art

@Yashas Hair and an ear

Slereah

13:11

Oh wait

I think you just didn't escape the characters

AccidentalFourierTransform

the rest of the face lol

Slereah

$$\huge{ (\^ム\^) }$$

Yashas

@SimplyBeautifulArt Oh lol, it is seriously out of proportion.

Slereah

Dang

Simply Beautiful Art

xD

Slereah

13:11

what's ^ in latex

ACuriousMind

@AccidentalFourierTransform Chat inserts spaces between many continuous characters without spaces, you need to put some spaces in between the MathJax commands to avoid it inserting such a space in the middle of a command

AccidentalFourierTransform

$\newcommand{\Huge}{\text{get rekd}}$

Slereah

$$\huge{ (\text{^} ム\text{^}) }$$

not the best

there we go

AccidentalFourierTransform

@ACuriousMind Ill totally forget that next time this happens, but thanks

lol

Simply Beautiful Art

@Slereah AW MAN! Such hacks

AccidentalFourierTransform

13:13

$\newcommand{\huge}{\text{get rekd}}$

Simply Beautiful Art

@AccidentalFourierTransform ?

Balarka Sen

maybe i came in the wrong time to chat

Slereah

Can we get the mathjax people to include the halloween package for Tex

I really want some equation ghosts

Yashas

29 secs ago, by AccidentalFourierTransform

$\newcommand{\huge}{\text{get rekd}}$

It is really an empty message lol

ACuriousMind

Sigh, is it "let's break MathJax" time again? :P

Simply Beautiful Art

13:13

oh no

Slereah

Oh well

Simply Beautiful Art

No, please don't break the MathJax

Slereah

if you want to discuss math

AccidentalFourierTransform

$\bar c\partial^2c$

Yashas

$\space$

Simply Beautiful Art

13:14

xD

Slereah

I have a question

ACuriousMind

@Yashas It's not, turn off rendering MathJax

Slereah

Does the fact that vector fields and derivatives of scalar field are related hinge on the partition of unity?

AccidentalFourierTransform

or use the permalink

Simply Beautiful Art

@Yashas It is a dark and evil magic trick... please do not use in public

Slereah

13:14

I have seen it implied on MSE

Yashas

\newcommand{\huge}{\text{get rekd}} :D

Balarka Sen

@Slereah What's a scalar field

Slereah

Oh

Simply Beautiful Art

The Story of Large Numbers, a dive into the unknown

Apr 1 at 0:14, 9 minutes total – 2 messages, 1 user, 0 stars

Bookmarked Apr 1 at 0:24 by Simply Beautiful Art

The Story of Large Numbers, a dive into the unknown: 2nd chapter

yesterday, 5 minutes total – 2 messages, 1 user, 0 stars

Bookmarked yesterday by Simply Beautiful Art

Slereah

i mean a real valued function

Simply Beautiful Art

13:15

Math for anyone who wants to read btw

Slereah

$f : M \to \Bbb R$

Fawad

$$\huge\text{(^ム^)}$$

I didn't wrote "get rekd" :O

AccidentalFourierTransform

but you did, in fact, get rekd

Balarka Sen

@Slereah I see. Well if you have a Riemannian metric on the manifold you can define the gradient vector field of $f$.

Simply Beautiful Art

$$\large\text{NEVER!!!}$$

Slereah

13:17

@BalarkaSen Let's not get the metric involved yet :p

Balarka Sen

That's how I'd imagine you'd get the partition of unity involved (construction of Riemannian metric requires use of partition of unity).

Slereah

Vector fields are often defined as derivatives $V : C^\infty(M) \to C^\infty(M)$

Balarka Sen

I don't know what else you want.

Slereah

Well according to a fellow, part of the problem of defining integration on a non-Hausdorff manifold is that for branching points, this is not true

10

Q: Stokes' theorem etc., for non-Hausdorff manifolds

This question is prompted by another one. I want to motivate the definition of a scheme for people who know about manifolds(smooth, or complex analytic). So I define a manifold in the following way. Defn: A smooth $n$-manifold is a pair $(X, \mathcal{O}_X)$, where $X$ is a topological space an...

cf here

Simply Beautiful Art

Say, how does the MathJax fix itself?

Slereah

13:21

Which I suspect is the reason why Hicks' argument for the pseudometric fails

The integral may not be properly defined for a non-Hausdorff manifold

well, possibly

Still not quite sure

I should work through the proof of Stoke's theorem on manifolds

AccidentalFourierTransform

Simply Beautiful Art

.......

AccidentalFourierTransform

it doesnt work for Australians though

0celouvsky

13:38

@Slereah Do you want a reference?

Slereah

would be nice

Doesn't seem to be in O'neill

It's in Carroll but I don't think it's that rigorous in there

0celouvsky

The obvious reference is Lee Smooth Manifolds.

Guillemin & Pollack have it too

As does Bott & Tu

Slereah

Let's go with Lee

Lee seems to contain a bunch of proof I need

0celouvsky

@Slereah this gr book you sent me seems to be very interesting

Slereah

You mean the Amazon link?

0celouvsky

13:42

I might have to get it

Yeah

I'd get the $25 springer mycopy though

Slereah

Yeah it seems nice

i know it 'cause I got one of the chapter in it

0celouvsky

I need some spinor analysis books

Slereah

The one on non-globally hyperbolic Cauchy problems

0celouvsky

too much stuff

oooo

Are static spacetimes diffeo to $\Bbb R^4$ globally hyperbolic?

Slereah

Well yes, as I have myself proven!

The Lereah theorem, if u will

0celouvsky

13:44

Proof?

I will credit you

Slereah

Diagonalize the metric as $-\alpha(x) dt^2 + g_{ij} dx^i dx^j$

0celouvsky

That is a very nice book indedd

Slereah

Take any closed curve in it

By Rolle's theorem, every component of the tangent vector will have to be $0$ at some point of the curve

Meaning that $U_t$ will be $0$ at some point $p$

Take the norm of the tangent vector at $p$

$g(U,U) = g_{ij} U^i U^j$

The metric of the spacelike hypersurface is Riemannian, so it is $> 0$ if $U \neq 0$

0celouvsky

How does the cylinder not disprove this?

It's not diffeo to $\Bbb R^4$, sure

Slereah

Gotta do it all on a single chart

0celouvsky

13:49

Ah, ok

Slereah

You have to work with the coordinate expressions

0celouvsky

You're proving it's causal

Not globally hyperbolic

Slereah

hm

That's a tougher one

Wait, I don't think it is

Just take Minkowski space on some simply connected subset of $\Bbb R^4$

You might be able to make some singularities appear along curves

0celouvsky

I think I want my manifold to split along time

Slereah

It's causal but not guaranteed globally hyperbolic

0celouvsky

13:51

So you can't have a space that's too crazy

@Slereah Hmm

Slereah

I think I did one before, even?

The Lorentz square

0celouvsky

@ACuriousMind :(

Slereah

Fairly static, but not globally hyperbolic

0celouvsky

ah

you're right

Slereah

I think if you want global hyperbolicity by hand, you'll have to just declare it

0celouvsky

13:53

the diamonds are not always compact

they run into issues near the boundary because it's "open"

Slereah

It's not causally convex, as the term goes

One of the PhD thesis regarding CTCs in my files is from the university of Bozeman, Montana

You may recall it as being the place where Zefram Cochrane launched the first warp ship

Very suspiscious

paracetamol

How about some QM, gentlemen?

Slereah

Shoot

paracetamol

1

Q: What is the basis for naming the orbitals as $p_x$, $p_y$ and $p_z$?

There are 3 p-orbitals per subshell, which are $p_x$, $p_y$ and $p_z$. As well as there are 5 d-orbitals, which are $d_{xy}$, $d_{yz}$, $d_{zx}$, $d_{x^2+y^2}$, and $d_{z^2}$. My Question: What is the basis for choosing the axes as $x$, $y$, and $z$? Can we rearrange the axes, suppose lets repla...

quantum-chemistry orbitals

What d'ya make of the answer I put up there? I know it's (kinda) over-simplified, but do you think it'll do the trick?

Slereah

it is arbitrary, yes

I think $z$ is slightly different here because usually, the Pauli matrix $\sigma_z$ is the diagonal one

but of course you could rename it anything

or even pick a basis where no matrix is diagonal

paracetamol

14:04

@Slereah Whoa...that's pretty... arbitrary :D

Slereah

yes, but of course, having a diagonal matrix makes things easier

that way, you can decide that the spinor $(1,0)$ has orientation $\uparrow$ while $(0,1)$ has orientation $\downarrow$ on the $z$ axis

Instead of the weird eigenvectors $x$ and $y$ have

Fawad

@Slereah what matrix you talking?

paracetamol

Additionally, @Slereah ever heard of a certain "Max-Möller diagram"? I've come across a "Mö ller diagram" when I studied the Aufbau principle though ._.

Slereah

@Fawad The pauli matrices

@paracetamol I have not

paracetamol

^^^ @0celo I've got an umlaut "o". I bet you're jealous :3

Fawad

14:08

@Slereah got

paracetamol

@Slereah Good, I suspect the "Max" bit was an unnecessary add-on :P

Danu

35

Q: Can the Mods please stop overeagerly move comments to the chat?

I recently asked a question. I got some valuable comments, but the commenters and I disagreed on a few things. After like 5 comments we reached agreement. Then @ACuriousMind stepped in and moved almost all comments to the chat. I didn't knew it at the time, but it seems that comments that are m...

discussion comments

This tilts me so hard

All these people who be like hurr durr progress of science hurr durr censorship,

The wording of the post makes it clear that it's essentially just a personal rant

ACuriousMind

::shrugs:: Most users don't get that comments are not where they can chatter away as one does in forums or in, well, chat. Meta.SE is full of these posts, now we have another.

Danu

The large number of votes on it in some sense shows it should not be taken seriously :P

rob

Yeah, I'm confused by the voting patterns on that post.

Danu

14:19

The number of people who casually visit and are like: NO THIS IS HOW IT SHOULD BE vastly outnumbers the people with >1 year of experience

ACuriousMind

@Danu Oh, I take it seriously (and I'm not sure why you wouldn't). Many users are attached to their comments and get upset when they are deleted, the upvotes just show that that's a feeling many share. But since I don't really hear a argument for not deleting comments that is compatible with the Q&A mission of SE, taking it seriously doesn't mean I'm going to change anything.

Danu

And even among those there are many who love shouting HURR DURR MODERATORS CENSORSHIP

Fawad

@ACuriousMind you got notified when someone write (@ACuriousMind) in his question or answer?

Danu

@ACuriousMind What I mean is that posts like this, where someone sorta says "you moderators suck", are always going to attract a lot of upvotes from random dissatisfied people.

Even among those regularly visiting chat there are several that I suspect would upvote just because they like thinking/saying you guys do a bad job.

Slereah

Waiiit a moment

That article has "M. Lubo" as an author

ACuriousMind

14:21

@Danu Eh, I think that's making it a bit to easy. Posts that are just really random rants usually do get downvoted into oblivion

paracetamol

Hands @Slereah a curry-wurst

Slereah

Oh, it's Luboš

Danu

@ACuriousMind I don't have so much trust in the PSE community, I guess :p

Slereah

I guess it's not our Luboš Motl

rob

One of the few disadvantages to living in a world where censorship is rare is that people interpret removal of any speech as censorship.

paracetamol

14:22

Luboš

Luboš - is a Slavic male given name meaning love or wolf and used mostly in the Czech Republic and Slovakia. In Slovakia with spelling Ľuboš. The name is a short form of names like: Luboslav, Lubomir. == Notable bearers == Luboš Bartoň, Czech professional basketball player Luboš Fišer, Czech composer Luboš Kohoutek, Czech astronomer Luboš Kubík, Czech former professional footballer and manager Ľuboš Micheľ - a former top-level Slovak football referee Luboš Motl (born 1973), Czech theoretical physicist == External links == http://www.behindthename.com/name/lubos18...

ACuriousMind

@Danu The upvotes show that comment deletion is something that users feel strongly about. Sure, some may vote like you say, but I do believe that votes on meta tell us more than that.

rob

"You've erased my graffiti, this is worse than Fahrenheit 451"

Danu

@ACuriousMind I'm mostly just happy that I don't actually have to deal with it :-)

Jaime Gallego

@heather Did you go to the March for Science?

ACuriousMind

And, I mean, I get why they feel strongly about it. In most other places, having your comment deleted would imply your contribution was somehow "bad", while on SE, it just means that it was not the sort of thing that belongs in a comment

Slereah

14:23

Indian fellows

ACuriousMind

I think maybe calling these things "comments" was not the best idea since comments are such a free-for-all on many other sites

Slereah

One author is called "Aditi Sen(De)"

What is the (De) thing

is that part of the name

Danu

@ACuriousMind I don't really know any other sites

@ACuriousMind Not even that... I flag for "obsolete" all the time.

Fawad

@Slereah who? What are U talking about?

rob

@ACuriousMind Do you have a suggestion for a better name?

Slereah

14:25

Some paper I'm putting in JabRef

It has a bunch of indian authors

paracetamol

@Slereah As far as I know...nope ^_^

Slereah

One of them has a name listed as "Sen(De)"

which seems like an odd name

ACuriousMind

@Danu I wasn't thinking about other physics sites, just internet sites in general (think of YouTube comments, or the comment sections of many newspapers, for instance)

paracetamol

@Slereah Her name is probably just Aditi Sen ._. and yeah...a very Indian name

ACuriousMind

@rob If I had I would link to my eloquently reasoned feature request on meta at this point ;)

rob

14:26

@Slereah Any hint of nationality? Could be something that doesn't transliterate well.

Fawad

@paracetamol de short form of "desi" :P

paracetamol

._.

Unlikely...

Slereah

@rob From Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019, India

rob

@Slereah The only thing I know about Indian languages and names is that there are lots of them and some are complicated.

heather

@JaimeGallego unfortunately no, my parents didn't want to go.

paracetamol

14:29

@rob Only "some"? ;)

rob

I would put it in my bibliographical tool exactly as it's published.

Slereah

That's why I like the chinese physicists

They have short names

Fawad

@Slereah example? I never came across Chinese physicists..

rob

@Slereah You should read the editorial that appeared when the US APS journals began printing Chinese names in Chinese.

Slereah

Li-Xin Li, Jian-Mei Xu, Liao Liu

all short and to the point

Of course that might be another story if they used chinese transliteration with tones

Jaime Gallego

14:32

@heather I would have gone yesterday, but completely forgot about it until today :P

paracetamol

Disapproves of @Slereah's Communist inclinations

:3

Jaime Gallego

(There's a satellite event at Madrid)

rob

journals.aps.org/prab/pdf/10.1103/PhysRevSTAB.10.120001

> For example, the eight Chinese names 王伟, 王薇, 王维, 王蔚, 汪卫, 汪玮, 汪威, and 汪巍 all transliterate as Wei Wang.

Slereah

My communist inclinations are more when I have papers from the Journal of Experimental and Theoretical Physics

2

which is a soviet journal

paracetamol

@Slereah :D

Slereah

14:33

The Журнал Экспериментальной и Теоретической Физики

rob

Oops, chat thinks I wanted that Chinese text to display vertically. Sorry. (fixed)

Slereah

To give its real name

paracetamol

@Slereah No Russianing in chat ಠ_ಠ

Slereah

fine

The Zhurnal Éksperimental’noĭ i Teoreticheskoĭ Fiziki

paracetamol

...

Skeptical look

ACuriousMind

14:34

@paracetamol You might need to fight @DanielSank, then :P

paracetamol

Fine...I'll take your word for it ;)

Fawad

15 mins ago, by Fawad

@ACuriousMind you got notified when someone write (@ACuriousMind) in his question or answer?

paracetamol

@ACuriousMind I'm not looking for fights here 0:)

ACuriousMind

@Fawad No.

rob

@Fawad Pings work in chat and comments, but not in questions and answers.

Fawad

14:35

rob

All of these assumptions are wrong. Try to make less of them next time you write a system which touches names.

paracetamol

Waves a curry-wurst under @Slereah's nose

:3

ACuriousMind

@paracetamol What?

@rob You like linking that, don't you ;)

Slereah

How did people even do research before the internet

The average journal of physics is 2000 pages long

Imagine having to haul a bunch of those

rob

@ACuriousMind Is that twice this year?

paracetamol

14:43

Apr 19 at 14:29, by Slereah

also I have some photographic evidence of him eating a curry wurst

ACuriousMind

@rob Oh...I think I might have confused you with Emilio

Anyway, I'd like that article more if it gave examples for these cases, I'm always left wondering what sort of circumstances or culture leads to these names after reading it

@paracetamol I don't follow...he said currywurst once so now you ping him with messages about currywursts?

paracetamol

@ACuriousMind Is it offensive? ._.

ACuriousMind

No, just non-sensical :P

paracetamol

i.e- should I stop?

@ACuriousMind Oh...

Heaves a sigh of relief

heather

is there an automatic calculator for someone's g or h index (not mine, obviously) that is free?

rob

14:46

@ACuriousMind My last time was in November, and we discussed one example.

Maxwell

@yashas, is it true that we can derive Newton's first and second law from third law?

Slereah

We can't.

rob

@heather Sure there is. You get a list of their publications from their CV, find citation counts for the first ten, then make up a number because no one actually cares about the $h$-index.

Yashas

@Maxwell That makes no sense.

ACuriousMind

@Maxwell Try searching the site for such questions: physics.stackexchange.com/q/66057/50583

Yashas

14:48

If 1st and 2nd law could be derived from 3rd law, then we wouldn't have named the 1st and the 2nd to be a law.

Maxwell

@yashas, then none can be derived from either?

Yashas

yes

the first law defines inertia

heather

@rob i don't have their cv

Yashas

the second law defines force

the third law, hmm, doesn't define anything but is a cool one

rob

@heather CVs are usually publically available.

What problem are you actually trying to solve?

AccidentalFourierTransform

14:50

world peace

heather

lol, no

i'm editing on wikipedia and i'm trying to find the h-index of an amateur astronomer who's coauthored a few papers.

rob

@heather That's "original research." Don't put it on wikipedia. Problem solved.

heather

finding the h-index of a researcher isn't original research, i don't think. eh, whatever, i'll just leave it.

AccidentalFourierTransform

does W. typically include the h-index of researchers?

rob

@heather Computing it is.

Maxwell

14:55

@yashas, @ACuriousMind, this question was asked in a competitive exam as follow:

Q. In Newton's three laws, one can derive

A). First and second from third

B). First and third from second

C). Second and third from first

D). None can be derived.

And they say that option A is correct!

heather

@AccidentalFourierTransform, i don't know, honestly. I was looking around and it seems like a possible way to show notability. I guess I don't even know how to find citation counts for papers, so.

rob

@Maxwell The first law (velocity is constant absent force) is a special case of the second (acceleration is proportional to force).

@Maxwell You could "derive" the third law (equal and opposite forces) from the first two by thinking about the difference between "open" and "closed" systems.

But the third law doesn't say anything about mass, so I don't see how you could start there and discover the second law.

ACuriousMind

@rob Ah, we're in murky territory there. I'd say that the first law establishes the existence of inertial frames (in which the implication that zero net force means zero acceleration holds) and the second law then gives a way to compute acceleration in such a frame.

The Story of Large Numbers, a dive into the unknown

The Story of Large Numbers, a dive into the unknown: 2nd chapter

Transcript for