The h Bar

John Rennie

4:02 PM

@Kaumudi.H: good job I checked - it's a full size HDMI connector so you need a standard HDMI to HDMI cable.

user228700

Wokay! It's nighttime anyway. I'll do it in the morning :-)

user228700

Thanks you!

0celouvskyopoulo7

@ACuriousMind 1-form or one-form?

ACuriousMind

1-form

Slereah

une-forme

0celouvskyopoulo7

4:09 PM

How do I do a remark in latex

Slereah

remark?

0celouvskyopoulo7

I want a "Remark. By Gauss-Bonnet, the sphere does not admit a metric of constant negative curvature."

How does one style that?

Sha Vuklia

Guys, is there also a different way to explain why there can’t be an electric field inside the cavity of a conductor (if no charge in the cavity is present), where we don’t use field lines? Is it possible to just talk about the vector field itself? I see that for every possible $\int E\cdot dl$ you could think of from a point on the inner surface of the conductor through the cavity to another point on the inner surface, this must yield zero.

However, how does this guarantee that we indeed have $E=0$ on each point in the cavity? For all we know the $E\cdot dl$ simply cancel eventually in the integral as you travel trough some arbitrary path inside of the cavity.

Secret

(Meanwhile in worldbuilding chat, we are discussing about pure magic and how to write a fictional setting where research is done with a magical mindset and no science)

pure as in the sense of: pure maths vs applied maths, fine arts vs applied arts

that is, we basically throw away all that RPG pew pew stuff and discuss about magic as itself

Slereah

"In view of this definition, globally hyperbolic spacetimes are clearly time orientable"

Bernardo Meurer

4:17 PM

@JohnRennie Are you around?

Something truly bizarre is going on

Slereah

you know I have no idea what maximum class of causality a non-time orientable spacetime could have

John Rennie

@BernardoMeurer I am!

Slereah

IIRC you can have causal ones

Bernardo Meurer

@JohnRennie Sweet, let me push the new code :)

John Rennie

@BernardoMeurer I'm resampling video on my MOFO NEW Precision 6700!!!

Bernardo Meurer

4:18 PM

I made my own strsep() now so you should only need change the asprintf() and strptime() lines

John Rennie

@BernardoMeurer I keep forgetting the URL ...

Bernardo Meurer

github.com/bemeurer/prog

@JohnRennie Fancy!!

John Rennie

@BernardoMeurer Some CPU as yours - it's resampling video at 800% CPU! :-)

Bernardo Meurer

Sweet :)

Slereah

How does one denote the set of open sets of a manifold

Bernardo Meurer

4:19 PM

This CPU does really well on compilation

John Rennie

Let me know when to download ...

Bernardo Meurer

@Slereah It's called the manopticon

@JohnRennie Just pushed :)

0celouvskyopoulo7

@ACuriousMind For a diffeo, $f_*=(f^{-1})^*$, right?

ACuriousMind

@0celouvskyopoulo7 Yup

John Rennie

@BernardoMeurer got it. It'll be a few minutes while I make the changes to get it to compile on Windows ...

Jaime Gallego

4:23 PM

@EmilioPisanty Thanks :) I don't really know much of it though. I'll certainly ask you peeps for teaching when summer comes.

That and linear algebra

Bernardo Meurer

@JohnRennie I gotta walk home, here's the steps:
1. Verify that `trip_n` and `station_n` are the same structure with a different payload
2. Verify that the implementations of `trip_n.tailInsert()` and `station_n.tailInsert()` are the same
3. Verify that the parsers for both operate very similarly, and that they work.
4. In `main.c` run the `t_head->print(&t_head);` line, verify that the list is printed in order
5. Now in main run the `s_head->print(&s_head);` verify that it only prints the tail.

Be back in 15-20 minutes

@JohnRennie In fact, I see the logic in it only printing the tail, the real issue is why does trips_n print correctly at all

John Rennie

@BernardoMeurer what arguments do I need to give it?

Ok never mind I've got it.

Balarka Sen

@yuggib Nah, those are honest to god branches of topology.

Slereah

I think the microlocal spectrum condition might be the same thing as the hadamard condition

But people are very coy about it so I'm not sure

Balarka Sen

Also there do exist people working on point-set topology.

But "topology" in the modern sense does not really have any connection to point-set.

user228700

4:33 PM

Jesus Christ. I was looking into the facilities at my (most probably) to-be college. They have a link for "Men's Hostel". When I clicked on that, I was taken to this website Wtf...

Balarka Sen

That's what's it's going to feel like

user228700

:-/ And what is that?

Slereah

"Thus, the two-point function(al) of a Hadamard state has a wave front set resembling the spectral condition, i.e. positivity of the energy, of quantum field theory on Minkowski space in a microlocal fashion, which justifies the name microlocal spectrum condition"

There we go

@BalarkaSen What does the jet bundle do

Balarka Sen

hell if i know

0celo should

Slereah

I ask everyone and nobody seems to really know

@0celouvskyopoulo7 thinks it's bullshit

Balarka Sen

4:36 PM

tell me something i don't know

(i guess you did; "jet bundles")

user228700

@JohnR: I'm thinking of just going to bed. Can we continue this tomorrow..?

Balarka Sen

what a wasteful way to spend postexam day

i guess my constructivity is limited to mucking up my sleep schedule beyond human recognition

user228700

@BalarkaSen Hey! I had an excellent lunch, got my hair cut and even cycled to the library!

Balarka Sen

bleh

user228700

What would you have done?

Balarka Sen

4:39 PM

melt my mind

and sleep schedule

user228700

What sleep schedule?

Balarka Sen

force myself to go to sleep tomorrow mornin at 9 by going on a mindmelting trip with a lynch/cronenberg double bill and reading joyce. at least, that's what i want to do now

user228700

Yeah, no, thanks.

Balarka Sen

oh well

Sir Cumference

Could anyone tell me if this is useful?

user228700

4:42 PM

I guess I'll stay up for some more time to finish a few more chaps... (@JohnR)

Sir Cumference

0

Q: Regional 12-hour timestamps

This script is a modification of Kip's "Display absolute timestamps (in local time)"; I have his permission to post this. Most of the credit for the script goes to him. About This script displays timestamps based on your timezone in 12-hour format. This is pretty convenient for anyone who doesn...

John Rennie

@Kaumudi.H those other two files are ready now if you want them.

0celouvskyopoulo7

@Slereah The only places I've seen jets used unironically is Hirsch (scary), Kolar et al (very scary), and Michor (impossibly scary)

user228700

OK OK! :-) Do send!

0celouvskyopoulo7

It's just not something people really use

ACuriousMind

4:43 PM

@0celouvskyopoulo7 ...where have you seen jets used ironically?

Balarka Sen

What's the book by Kolar?

John Rennie

@Kaumudi.H Download from the same web site as before.

0celouvskyopoulo7

@BalarkaSen The categeory theory book I try to read every so often and fail

"Natural Operations in Differential Geometry"

Natural jet functors on Weil algebras

Shit like that

user228700

Jesus Christ. 1 day left.

Slereah

user228700

4:44 PM

Better move to the router again...

0celouvskyopoulo7

hahaha

Balarka Sen

@0celo Oh yeah i remember

@Slereah ....

......

i mean

John Rennie

@Kaumudi.H it'll speed up

Slereah

I'm not sure it's a very complex integral really

It just looks like gaussians

I think it's supposed to be path integrals

0celouvskyopoulo7

@ACuriousMind I consider most of physics to be ironic.

John Rennie

4:48 PM

@Kaumudi.H: I copied the wrong files - ABORT THE DOWNLOAD!!

Sir Cumference

Howdy @AccidentalFourierTransform

user228700

@JohnRennie x'D Done.

AccidentalFourierTransform

sup

John Rennie

@Kaumudi.H OK, look again now.

Sir Cumference

@AccidentalFourierTransform I'm looking for help from someone of any of these countries:

I don't suppose you fall into those?

0celouvskyopoulo7

4:51 PM

@SirCumference ...

I'm in America

AccidentalFourierTransform

the red ones or the green ones?

Sir Cumference

@0celouvskyopoulo7 Oh, right

0celouvskyopoulo7

wtf

Sir Cumference

@AccidentalFourierTransform The orange ones...

@0celouvskyopoulo7 Care to test out a script I wrote?

AccidentalFourierTransform

then nope

0celouvskyopoulo7

4:51 PM

what does it do

Sir Cumference

It converts timestamps on posts and comments to your regional time, in 12 hour format

Like

John Rennie

@bernardo you divot! You've got the stations in reverse order so head->next points to nothing. You need head->prev to walk back up the list of stations.

Sir Cumference

@0celouvskyopoulo7 So?

Bernardo Meurer

@JohnRennie I'm back

John Rennie

1 min ago, by John Rennie

@bernardo you divot! You've got the stations in reverse order so head->next points to nothing. You need head->prev to walk back up the list of stations.

Bernardo Meurer

4:54 PM

I did what? :P

I don't see how there's any difference between what I do for trips and stations

Emilio Pisanty

@0celouvskyopoulo7 not specific enough

there's both orange and gray countries in America

(in that map)

0celouvskyopoulo7

@EmilioPisanty Huh? America is one country.

John Rennie

@BernardoMeurer I can't do the trip import because I don't have an implementation for that time function so I just remmed it out. But trying to run the code with the line remmed out causes a crash.

0celouvskyopoulo7

Has been since we acquired Hawaii in 1898

Sir Cumference

@EmilioPisanty "America" can refer to the continent or to the US

Bernardo Meurer

4:57 PM

@JohnRennie Just take the function off and return an empty string and so on

the data doesn't matter

Sir Cumference

In this case 0celo's referring to the US

0celouvskyopoulo7

@SirCumference what kind of script is this

Bernardo Meurer

@JohnRennie cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/time/…

0celouvskyopoulo7

the kind that can break my computer?

Sir Cumference

@0celouvskyopoulo7 'Course not

0celouvskyopoulo7

4:57 PM

steal my bank information

I don't trust you

Emilio Pisanty

@0celouvskyopoulo7 in the Simón Bolívar panamerican spirit, I guess, yes, much of Latin America is one nation, but no, America is a continent

Sir Cumference

It requires Tampermonkey tho

Bernardo Meurer

Just paste the function there actually

It will work

0celouvskyopoulo7

@EmilioPisanty Maybe for you

But not for Americans

Sir Cumference

@EmilioPisanty Not according to US citizens

Or as we say here, "Americans"

0celouvskyopoulo7

4:58 PM

If I am referring to the continent, I will say so.

The people who assume "America" (without further qualifications) refers to the continent are anti-American insurgents.

Emilio Pisanty

@SirCumference you mean "this small subset of Americans has decided that the rest of the continent does not matter, so we're just going to grab the name for ourselves regardless of what anyone else thinks"?

Sir Cumference

We often say "America" to refer to the US and "North America" to refer to the continent

ArtOfCode

@0celouvskyopoulo7 that... ain't true

Emilio Pisanty

Then yeah, if you're OK with doing that kind of a dick move, I guess there's nothing anyone else can say

Sir Cumference

@EmilioPisanty I didn't decide how our language works. Blame etymology.

American English just decided that over the years.

Emilio Pisanty

4:59 PM

@SirCumference you mean US English

Sir Cumference

...

ArtOfCode

and is bordering on the offensive - maybe one to stay away from

Sir Cumference

@EmilioPisanty American is the adjective of the US

Bernardo Meurer

@ArtOfCode Go collect coconuts

Sir Cumference

Just as "Britain" is the adjective for the UK

ArtOfCode

5:00 PM

@BernardoMeurer I've already got a bunch, actually

@SirCumference that it can't

Emilio Pisanty

@SirCumference no, the phrase you're looking for is US American

you're not in the US, you're in an international environment

Sir Cumference

@ArtOfCode Then what's the adjective?

@EmilioPisanty Chill

ArtOfCode

@SirCumference as in "I am a _____"?

Emilio Pisanty

@SirCumference use correct geographical terms

Sir Cumference

@ArtOfCode More like, "a British idea"

There's no substitute if I'm referring to the UK

@EmilioPisanty Try convincing 300 million people who grew up speaking that way

ArtOfCode

5:02 PM

@SirCumference a British idea is an idea that comes from somewhere within Britain, whether that's Scotland, Wales, England or Northern Ireland

Emilio Pisanty

@SirCumference You're not talking to them. You're in an international environment.

ArtOfCode

If you knew more specifically, you could say it's a Scottish idea, or a Welsh idea.

Sir Cumference

@ArtOfCode Great Britain doesn't contain Northern Ireland...

Emilio Pisanty

All it takes is saying US American

Sir Cumference

The UK does

ArtOfCode

5:02 PM

@SirCumference no, but as you say, "Britain" as an adjective does - because you can't say "UKian"

John Rennie

@BernardoMeurer I'm getting crashes in asprintf now. I copied and pasted an implementation and I guess it's buggy. This is going to take too long to get running. Bloody POSIX! :-)

Bernardo Meurer

@JohnRennie :P

John Rennie

But, in your print function for the stations head->next is definitely null and head->prev isn't

rob

Hi all. I'm trying to figure out why everyone has their underpants in a knot and I can't make heads or tails of it. Could we talk about the moderation question in the other room and let hbar get back to physics?

0celouvskyopoulo7

5:18 PM

I don't claim anyone knows what the hell weighted Sobolev spaces are though

Sir Cumference

Ugh god, just stop

Bernardo Meurer

@AccidentalFourierTransform So

AccidentalFourierTransform

So

Sir Cumference

So, as I was saying...

@0celouvskyopoulo7 You willing to download Tampermonkey?

rob

No, we're done arguing now.

ArtOfCode

5:23 PM

→ 15 messages moved to Physics Meta

0celouvskyopoulo7

What the hell

ArtOfCode

take it over there or drop it

this conversation is over

0celouvskyopoulo7

I thought the conversation was ridiculous from the start

@SirCumference I'd rather not

Sir Cumference

@0celouvskyopoulo7 :(

AccidentalFourierTransform

why was my picture removed :-(

0celouvskyopoulo7

5:24 PM

I once tried to dl it and Chrome said it could access all my browser history and whatnot.

So nothanks

Slereah

How do I write the identity of a QFT algebra

$1$, $I$, $\text{Id}$, $\mathbb{1}$??? Do I put a hat on it, or a $_\mathfrak{A}$???

AccidentalFourierTransform

use $|0\rangle$ for the identity

$|0\rangle T=T$

Slereah

You monster

Sir Cumference

@0celouvskyopoulo7 That's only if you manually download sketchy scripts

The Meta chat is hell

user228700

@JohnR: DONE YAYYY! :-D

user228700

5:31 PM

And yep, everything works just fine! Thanks ever so much!!

John Rennie

@Kaumudi.H all three films play when you open them?

If so I'll delete them off my server.

user228700

Haven't checked the 2nd one yet, hang on...

user228700

Yep, that one works as well.

user228700

@JohnRennie OK! THANKS SO MUCH!! :-D

John Rennie

All part of the service :-)

user228700

5:34 PM

What "the service"? :-P

user228700

Ah, that's actually a saying huh.

John Rennie

Phew. I'm going to call it a day and go back to my book - Children of Time by Adrian Tchaikovsky.

100 pages to go ...

@Kaumudi.H a very English saying :-)

user228700

@JohnRennie Oh, you should be able to finish that in a heartbeat!

John Rennie

I'll certainly finish it tonight.

user228700

It's been a long day for me as well and now I'm going to shut down the laptop, my phone, everything and get back to this book which is actually nice and funny.

user228700

5:36 PM

Again, thanks so so much! :-) Goodnight!

John Rennie

I've just got a copy of Natasha Pulley's new book, and her last book, The Watchmaker of Filigree Street, was absolutely amazing!

Goodnight

ArtOfCode

guess which one of us is blue

Slereah

that gravitational wave answer I did is already my most popular answer of all time

slightly odd

rob

→ 5 messages moved to Physics Meta

0celouvskyopoulo7

For the love of Christ

I'M COLOR BLIND

Slereah

5:44 PM

@0celouvskyopoulo7 Just check which one has the highest frequency

It's not rocket science

ACuriousMind

@0celouvskyopoulo7 Actually...that would be a good point would I not expect you to recognize AFT regardless of color ;)

AccidentalFourierTransform

thank you for seeing beyond my color

all colors are beautiful

I see users, not colors

Slereah

@ACuriousMind So if I understand roughly the GNS construction, basically

You take a state and wiggle it around, thanks to the cyclicity of states

and bam

You get the Hilbert space

Is that correct

nbro

An astonishing result in quantum physics is the fact that a superposition is actually a linear combination (using complex numbers) of different states... why a linear combination? Possibly quantum physics is also just a simplification of what actually is going on under the hood...

Slereah

Because the linear combination is what we observe

The simplest example of this being the double slit experiment

The probability amplitude is the sum of each state for each slit

0celouvskyopoulo7

5:54 PM

@Slereah I have a book on Spinors arriving today :)

Slereah

which

0celouvskyopoulo7

"Dirac Operators in Riemannian Geometry"

Got it uber cheap

Slereah

Do they mean Riemannian or pseudo Riemannian

0celouvskyopoulo7

It's a central reference in my a thesis I'm building off of

@Slereah Riemannian

nbro

Scientific educational graffiti!

AccidentalFourierTransform

5:58 PM

what is $\omega(AB(i\beta))=\omega(B(0)A)$?

0celouvskyopoulo7

looks like GDP

AccidentalFourierTransform

ew, gross

ACuriousMind

@Slereah It's so vague that I can interpret it to be correct, yes :D

Slereah

what part of "wiggle it" doesn't sound good

0celouvskyopoulo7

homotopy?

homotopy $\cong$ wiggle

Slereah

6:03 PM

Nah

It's more the cyclic thing

Apply members of the algebra on the original state to make it into other vectors

and in that way produce the entire Hilbert space

I think that's the ruse

ACuriousMind

@Slereah That's...not really how the GNS construction works

Slereah

I'd better read on then!

isites.harvard.edu/fs/docs/icb.topic1466080.files/GNS.pdf

ACuriousMind

But maybe you're calling something else "the GNS construction"

Slereah

Seems pretty good on the topic

plus it's from our old friend Jaffe

ACuriousMind

To me, the GNS construction is what turns an abstract state of a $C^\ast$-algebra into an associated representation, where the state is represented by a cyclic vector.

Sha Vuklia

6:10 PM

Guys, could someone explain why we have $K=\sigma v$? I would think that $dI=\sigma\cdot\text{area}$, so we have
$$
K=\frac{\sigma\cdot\text{area}}{dl_\perp}.
$$
However, how to incorporate $v$? It seems like we should have $v=\text{area}/dl_\perp$, but that isn't right from a dimensional perspective. So could someone help me out?

John Doe

6:21 PM

@ACuriousMind Does this revised working make sense: $e^{i \theta L_z}| \hat{z} \rangle =
|\hat{z} \rangle \implies \frac{d}{d \theta}[e^{i \theta L_z}| \hat{z} \rangle] = (\frac{d }{d \theta}e^{i \theta L_z} )| \hat{z} \rangle + e^{i \theta L_z} \frac{d | \hat{z} \rangle}{d \theta} = i L_z e^{i \theta L_z}| \hat{z} \rangle = iL_z| \hat{z} \rangle = 0 \implies L_z| \hat{z} \rangle = 0$

AccidentalFourierTransform

$\mathrm e^{i\theta L_z}|z\rangle=\mathrm e^{i0}|z\rangle\ \Longrightarrow \ L_z|z\rangle=0$

Sha Vuklia

Oh I see where I made a mistake. I thought that $[\sigma]=[Q]/[L^2\cdot T]$, because we're talking about the mobile surface charge density, but we don't have to divide by time.

AccidentalFourierTransform

your mistake was choosing to study physics

physics is the worst

god I hate physics

Sir Cumference

@AccidentalFourierTransform You sound like @0celo

Sha Vuklia

@Accidental I hate it too at times, but honestly, it's good to do physics besides math. Math is too perfect, and I learned to turn off my intuition thanks to math. Now I'm back at more "realistic" and intuitive thinking :P

@Sir lol, at first I thought 0celo responded, but then I checked the user name :P

hey @Mithrandir

Mithrandir24601

6:31 PM

Rytsas @ShaVuklia

Sha Vuklia

wut:d I guess that's just a hello in some foreign language google translate can't detect

ArtOfCode

have we not had enough drama for one day

Mithrandir24601

It's high valyrian version of 'hello' - I think it's wishing you good health or something like that

Sha Vuklia

oh right. I did not watch GoT

Mithrandir24601

It's really good, but it took me until about season 4 to really start enjoying it - the books are also good, but occasionally feel like they've got a lot of unnecessary details, although lots of people disagree

Sha Vuklia

6:35 PM

haha, I couldn't even finish the first half of the first episode :P I don't think I would have continued until season 4

Mithrandir24601

Yeah, season 2 was... A bit of a struggle at times, to be honest

0celouvskyopoulo7

@ArtOfCode there are some people who simply cannot act in accordance with the chat rules

Uh, what?

When have I been banned

I am a model citizen

Bernardo Meurer

Lol

ACuriousMind

@Mithrandir24601 I actually think the later seasons are not as good as the first ones

Sha Vuklia

:P

Slereah

6:43 PM

well there was that time you were banned for like 3 months

Bernardo Meurer

@0celouvskyopoulo7 For some neighborhood of model maybe

0celouvskyopoulo7

It's still not clear to me why I was banned for three months. Likely an oversight.

Mithrandir24601

@ACuriousMind Really? Fair enough I suppose, but I'm going to disagree

ACuriousMind

@Mithrandir24601 When they started diverging from the books, I feel the storylines started to be less coherent.

Mithrandir24601

Hmm... I'd say that it's the books' storylines that aren't coherent. I suppose that's part of what makes it good though

Also, I believe there are things that GRRM said he would change in the books

ACuriousMind

6:47 PM

The recent storyline in the North, for instance, doesn't make a whole lot of sense to me, and Ramsey started to feel waaay too much like an author's pet with plot armor.

Mithrandir24601

I do agree with you about Ramsey

ACuriousMind

Which wouldn't be so bad if not one of the quirks of GoT were that most protagonists don't have plot armor and are just unceremoniously killed.

Mithrandir24601

Sort of agree about the whole north plot

yeah, exactly

well, almost

It's beginning to feel like there are a couple of characters with plot armour, but I don't want to think that as GRRM will then just kill them off. He does need some main characters for the Grand Finale though

ACuriousMind

I think Arya has plot armor because GRRM promised someone (his wife? I don't remember) he wouldn't kill her

Mithrandir24601

Ooh, never heard that before, but I'm not surprised

I mean, it would just be weird if he gave her an entire subplot just to herself lasting at least half the novels, only to kill her off before she actually does anything that affects the main storyline

ACuriousMind

7:05 PM

@Mithrandir24601 I'm really curious how/whether they'll manage to satisfactorily resolve the whole plot without pulling some sort of deus ex machina

Although I guess Rhllor is a deus-in-waiting :P

Mithrandir24601

True... My solution would just be to get Brandon Sanderson in and have the whole thing finished in about three years, yet again

heather

hello =)

Mithrandir24601

Rytsas @heather

heather

@Mithrandir24601 "rytsas"?

Mithrandir24601

High Valyrian meaning, I think, something along the lines of 'good health' and used as their greeting

(actually, me explaining this is the very reason there's a conversation about aSoIaF just above)

ACuriousMind

7:12 PM

@Mithrandir24601 Sanderson <3

heather

@Mithrandir24601 well thank you =)

@ACuriousMind new profile pic I see

ACuriousMind

@heather Yup, I got tired of Fall-from-Grace

It's now the sage Lantry from Tyranny.

Moses

@ACuriousMind Have you seen the position operator in spherical basis given by $r_{\pm} = \mp \frac{r}{\sqrt{2}} \sin \theta e^{\pm i \phi}$ and $r_0 = r \cos \theta$?

ACuriousMind

@Moses I, uh, have no idea what I'm looking at, I'm afraid

Moses

@ACuriousMind Okay no prob I will post a question. Because I'm not sure about this at all.

@ACuriousMind It also states that the position operator as spherical harmonics is given by $r_{1} = r \sqrt{\frac{4 \pi}{3}}Y^{q}_{1}(\theta, \phi)$, does that make any sense?

ACuriousMind

7:28 PM

The l.h.s. appears to be a wavefunction, not an operator

Moses

@ACuriousMind Yeah it appears to be. It's very confusing. But okay thanks.

ACuriousMind

From what you're telling me I'd be confused too ;) What are you reading?

Moses

@ACuriousMind It's either a book or a set of notes on Quantum and Atomic Optics, it's like 1000 pages but I'm only planning to read like 10 or so...

Probably a book...or a very long course...

Slereah

7:43 PM