The h Bar

Emilio Pisanty

17:01

@JohnRennie it's the worst option except for all the others

John Rennie

:-)

Emilio Pisanty

That said, pushing auxiliary files to a separate folder isn't a huge problem either

Just not as trivial as you'd hope

John Rennie

Are auxilliary files temporary files created during the compilation?

Emilio Pisanty

Depends what you mean by temporary

0celo7

@ACuriousMind Did you unban me?

John Rennie

17:04

As in, if they get deleted does it matter?

@0celo7 You're back! :-)

Emilio Pisanty

There's a .aux file that's essential if you want to compile correctly

0celo7

@EmilioPisanty Are you certain?

If I just load the .tex and run it, it always works

Doesn't matter if there's a .aux or .log or whatever else

Emilio Pisanty

@0celo7 yes and no

It won't get references right, for instance

0celo7

Ah, yeah

For this I had the references as footnotes

Er, I actually need to still put them in

Emilio Pisanty

That's all in the .aux file

0celo7

17:06

But there's no real bib file

John Rennie

@EmilioPisanty is this the notorious compile it repeatedly until it works feature of TeX?

Emilio Pisanty

But that doesn't mean you need to add the aux file to git

@JohnRennie that's what it is, yes

John Rennie

Ah, but once you've got the final pdf (or whatever) it's then safe to delete the .aux files as well as the .log files?

ACuriousMind

@0celo7 Yes, because you didn't do anything wrong this time. For the flagger (and the record), excessive profanity is fine to flag, but a single instance of "fuck" not directed at anyone (i.e. not used as an insult) is not flag-worthy.

Emilio Pisanty

@JohnRennie yes

Balarka Sen

17:08

flippety flip

@ACuriousMind Is this okay?

0celo7

@ACuriousMind implying I do anything wrong sometimes?

Emilio Pisanty

@ACuriousMind are we the SE chat room that spends the most time on metachat discussions?

0celo7

thank you, in any case

ACuriousMind

@BalarkaSen I don't see anything flipping wrong with that :P

Balarka Sen

clap... clap clap

John Rennie

17:10

I got suspended once for saying faggots

They were very nice faggots as well

0celo7

That's offensive @j

Emilio Pisanty

@JohnRennie halp

John Rennie

In fact I had six faggots for lunch yesterday

Balarka Sen

lol

John Rennie

@EmilioPisanty Yes?

0celo7

17:12

@JohnRennie is that a euphemism?

John Rennie

@BalarkaSen they were very good actually. I mashed them and put them on bed of mashed potato.

ACuriousMind

@EmilioPisanty We certainly spend more than average on that, yes :P

Emilio Pisanty

@JohnRennie win 10 is stuck with a blue screen and circling dots with a "restarting" sign

John Rennie

Has it just updated?

Emilio Pisanty

Has been for over an hour

@JohnRennie I don't think so?

John Rennie

17:14

I ask because MS release Windows updates on the second Tuesdau of the month i.e. the day before yesterday, and PCs tend to pick up the update over the next few days.

Emilio Pisanty

It was sluggish and the power menu had "update and restart" so I clicked on that, and this was the very first thing it went to

0celo7

@JohnRennie is that alluding to some irishmen?

I knew you Englanders were hard core anti-irish but that's a bit much

John Rennie

Aha! "update and restart". It's installing updates.

I'm afraid you'll just have to wait. It can take a remarkably long time. An hour isn't unusual.

Emilio Pisanty

Goddammit

dmckee

^ That. And I'vbe heard several horror stories about unreasonably long up[date cycles (hour+)

Balarka Sen

17:16

I hate updates

Emilio Pisanty

Normally it shows some kind of progress

John Rennie

Go have dinner, drink a couple of bottles of wine, and if after that the update hasn't finished throw the PC out of the top floor window.

Emilio Pisanty

Our at least it explicitly says it's updating

dmckee

One thing I like about how Apple updates macs is it sets most of them up before the re-boot with the machine still usable.

Emilio Pisanty

@JohnRennie I just sent and cooked dinner and ate it and washed up and it's still doing it

John Rennie

17:17

@0celo7 :-) I really did have pork liver faggots for lunch yesterday.

dmckee

Though some kernel updates seem to violate that general rule.

Balarka Sen

@0celo7 lmao

I just got the reference

John Rennie

@BalarkaSen hmm, I haven't got it yet ...

@EmilioPisanty does the computer have a disk activity light? Is it flickering?

0celo7

What do the Irish eat

Balarka Sen

There's this really bad gag about potatoes and Ireland which I think is vaguely tied to the Great Famine

John Rennie

17:21

Well, yes, the Irish were notorious for eating potatoes back in the Victorian period. But that seemed a tenuous link.

0celo7

And you are what you eat

So a mashed potato is an Irishman in a bad situation

John Rennie

Ah, OK ...

0celo7

In this case, there's an orgy happening above him. With livers!

John Rennie

Either someone has slipped acid into my coffee or this conversation is getting weird :-)

0celo7

You're the one who brought it up

John Rennie

17:24

I just said I'd eaten faggots with mashed potato for lunch yesterday, which is true and they were very nice.

Well, not everyone considers pig offal a delicacy :-)

In fact that was the meal

bolbteppa

So now they refer to side dishes as twigs/branches? :p

0celo7

@JohnRennie that's NSFW

@JohnRennie you're incapable of eating green stuff

John Rennie

It does kind of look like it's already been through a digestive system :-)

Emilio Pisanty

17:57

@JohnRennie no, there's no light

It's an ssd if I remember correctly

It's still going

The wifi wasn't picking up when I told it to restart

Is it safe to try a hard reboot?

Seriously, it's going on two hours with no visible change

Physics Meta

18:34

0

Q: Red indicator in the review queues

New top bar is live, and I loath it. Creature of habit I guess. Anyway, see the screenshot: What is this red indicator doing there? What is it supposed to mean? The queue is clear; is this a bug? I keep refreshing and it just stays there, staring at me.

Abcd

What does momentum *imparted to floor* mean? It doesn't make any sense to me because velocity of floor is always zero and hence $M. \vec{v}= 0$.

Context: A ball bounces repeatedly on a floor. Find the momentum imparted to the floor. $e$ is given. I just want to understand the "momentum imparted to the floor" part of the question. I will solve it myself then.

imparted to floor*

John Rennie

@EmilioPisanty I'd drink some wine and go to bed. If it's still hung tomorrow morning press and hold the power button till the computer turns off, then hope it turns on again.

@Abcd presumably it means the change in momentum of the ball

Abcd

@JohnRennie Oh, why did they mention "floor" then?

Is it the same thing, if yes, how? How can momentum be imparted to floor?

John Rennie

@Abcd the point is that the total momentum can't change so the momentum imparted to the floor must be equal to the momentum change of the ball.

But I agree it's a poorly worded question

Abcd

@JohnRennie Yes, but we can apply momentum conservation only when net external force is zero. However, here there's gravitational force in vertical direction.

@JohnRennie AT the same time, it's a famous question.

If anyone knows the reason for momentum conservation in vertical direction despite the presence of gravity, please let me know.

ACuriousMind

18:55

@Abcd You're not applying momentum conversation to the system "ball". You're applying momentum conversation to the system "ball and earth", on which the external force is zero.

Abcd

@ACuriousMind Oh, yes! Exactly! I wish I had thought of it this way. Anyway, Thanks a lot :).

0celo7

20:31

@BalarkaSen I need help with bundles

Balarka Sen

?

0celo7

@BalarkaSen $M$ and $N$ are manifolds. Consider the bundle $E=\mathrm{Hom}(TM,TN)$. Let $\pi:E\to M$ be the projection. What is the interpretation of $\pi^*\Lambda^nM$?

Balarka Sen

Hm, so that's a bundle over $E$...

... such that sections over $U \subset E$ are coming from sections over $\pi(U)$ by composing with $\pi$

sections over $\pi(U)$ are just $n$-forms

0celo7

so it's hom-valued n-forms?

or n-form-valued homs?

Balarka Sen

Wait, let's think about $E$ as just $TM \otimes T^* N$, for Christ's sake

Now, hm, hm, hm

The projection map $\pi$ is just collapsing the $T^*N$ factor and mapping $TM$ to $M$ by standard tangent bundle proj, right?

0celo7

20:39

Yes

Balarka Sen

So what is pullback of the n-form bundle along the tangent bundle projection?

It's that tensor $T^*N $

0celo7

I think a point in that pullback is an element of $\Lambda^n_xM$ attached to an element of $L(T_xM,T_yN)$, for some $y$?

where does $N$ come into this picture

Balarka Sen

I think it's just $\Lambda^n M \otimes TM \otimes T^*N$

0celo7

over what base

Balarka Sen

Wait, I'm getting all confuzed.

@0celo7 Ok, answer me this simple question. What is pullback of $\Lambda^n M$ along $TM \to M$?

0celo7

20:47

@BalarkaSen It's the bundle over $TM$ with fibers $\Lambda^n_xM$

where $x=\pi(v), v\in TM$

Balarka Sen

Which is kind of weird to me

0celo7

but a bundle over a bundle is a bundle over the lowest space

@BalarkaSen Pullback bundles have always confused me

I need to draw some pictures when I get hom

freudian slip lol

Balarka Sen

@0celo7 But anyway, your thing is that tensored with $T^*N$.

0celo7

@BalarkaSen In a tensor product do you product the bases?

@BalarkaSen Ugh

the usual hom bundle construction is for bundles over the same base

Balarka Sen

Yeah I was confused

0celo7

20:51

I have no idea what Hom(TM,TN) is actually supposed to be

Balarka Sen

lol you tricked me

0celo7

sorry

Balarka Sen

Maybe it's a bundle over $M \times N$

Or maybe not

0celo7

yeah it is

where is @ACuriousMind when you need her

Balarka Sen

Right, over each $(m, n)$ associate the vector space $\hom(T_m M, T_n N)$

Slereah

20:53

Is @ACuriousMind a lady now

Balarka Sen

lmao

ACuriousMind

@Slereah I think my female avatar confuses some people :P

0celo7

@ACuriousMind are you saying I'm too stupid to remember your gender?

ACuriousMind

@Slereah Why are you proving things about worms?

Slereah

mister lefty worm is equal to mister righty worm

0celo7

20:56

@BalarkaSen soooo $\pi^*\Lambda^nM$ is a bundle over $M\times N$

that makes more sense

Balarka Sen

Well, is it

ACuriousMind

@0celo7 No, I'm saying my avatar confuses some people (such as here) :P

Balarka Sen

Oh $\pi^*$

sure

ACuriousMind

When I had Triss I actually got a comment on the main site that started with "Hey beautiful"...

0celo7

Lmao

Balarka Sen

20:59

@ACuriousMind You need to be more A E S T H E T I C C about your avatar

I suggest this

ACuriousMind

21:12

@BalarkaSen No, video RPG characters are my jam, as you like to say

Balarka Sen

slowed down 80's elevator music are my jam

and should be yours too, unless you are a normie

ACuriousMind

@BalarkaSen Got no problem with being a "normie"

DanielSank

21:27

I just had the response function of my ear measured.

I have a 20dB dip at 1KHz.

Balarka Sen

@ACuriousMind Seriously, man, learn the musical memes.

Emilio Pisanty

22:21

@rob is there a multiple-comment-upvote feature hidden somewhere on the site?

As to "Physics is a subject which you can do with equations, there's nothing else" --- there are textbooks and study guides that may give you that impression, but that's basically nothing like being a physicist. — rob ♦ 22 hours ago

3

↑ 'cuz, y'know, a thousand times that

@JohnRennie computer finally came back to life, btw

0celo7

23:41

@BalarkaSen ACM must live a sad life

No memes, no magic

He's just not a very hip hop person

@JohnRennie idk what's going on

it refuses to let me me commit changes if I change the .tex

@BalarkaSen so that pullback dude is a bundle over the hom bundle

Dunno why I thought it should be an M-bundle

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