The h Bar

Huy

20:00

no

I remember the exercise with the arctan

our TA only had this terrible formula for the nth derivative of arctan

and I thought about partial fractioning $1/(1+x^2)$

0celo7

what are you babbling about

Huy

and got a nicer formula

so he's the troll

just listen to the story kids

this is the story of how I met your mother

0celo7

what the heck is 1/(1+x^2)

Huy

the derivative of arctan(x)

0celo7

what

Huy

20:02

even my students know that

why are you trolling me

0celo7

because I can't factor $s^2-2s+5$

Huy

maybe you made some mistakes again

0celo7

can I just give up

oh fine you tell me what the characteristic equation of $y''-2y'+5y=0$ is

Huy

only after 20 minutes

fukin LoL

0celo7

oh are they complex or something

Huy

20:04

well yea

you'll get some fancy sin and cosine

0celo7

how do you know

Huy

do you know the joke with the sin and cosine

0celo7

indeed

Huy

and e^x

I think the joke only works in German

0celo7

they're all cousins in an incestuous relationship

Huy

20:05

so I won't tell it after all

0celo7

sag es auf Deutsch, dann

Huy

nein danke

0celo7

bitteeeeeeeeee

bittebittebitte

Huy

no I'm not in a joking mood

maths is a serious thing

0celo7

you're the troll around here

Huy

20:06

no

0celo7

oh! complete the square! I'm an idiot!

Huy

more like square the circle

if you know what I mean

0celo7

not really, no

Huy

:(

0celo7

It's easy to square the circle

Huy

20:07

lies

0celo7

just draw a box with side $\pi$, right?

Huy

do you even TeX

ACuriousMind

@0celo7 You and quadratic equations are not becoming friends, are you? :P

0celo7

I don't see the issue

@ACuriousMind MIDDLE SCHOOL

Huy

well by Galois you can't construct rationals so it's impossible to draw a box with side $22/7$

0celo7

20:08

@ACuriousMind dude I can't even complete the square :D

@Huy uh lol of course I can

ACuriousMind

@0celo7 How the hell did you pass math in high school, then? :P

0celo7

@ACuriousMind skin of my teeth!

ACuriousMind

No idea what that means.

0celo7

German alert

it's a saying

Huy

deine Mutter

is a saying too

0celo7

20:10

The literal translation...makes absolutely no sense. It means "just barely"

Huy

but in German

0celo7

My mother isn't German

Huy

but a saying ?

0celo7

for the love of crap how do you complete the square

Huy

lol

0celo7

20:10

is it $b^2/2$ that you add?

or $(b/2)^2$?

Huy

so physicists really do only recall formulas and plug numbers in

0celo7

I'M NOT A PHYSICIST

4

ACuriousMind

^that

0celo7

what are the physicists working in the nuclear engineering department?

what are the engineers who do plasma physics?

isn't "physicist" the name/descpription of the job?

I figured out how to complete the square!

Huy

good for you

now you can finally derive the formula for solving quadratic equations all by yourself

0celo7

20:14

what :o

I thought you needed to be a grad student at least to do that

Huy

we did that in 3rd grade

0celo7

alright I'm calling bullshit on that one

Huy

call my teacher

0celo7

I went to German school for 6 years

2-8

Huy

I never went to a German school

0celo7

20:15

never saw the quadratic equation

Huy

we didn't even just see the teacher derive it

0celo7

I don't even believe that you proved anything

Huy

we derived it ourselves

0celo7

I must be literally retarded

Huy

our teacher had a very nice exercise sheet for it

which made the quadratic equation a little bit harder every time

0celo7

20:15

I think I have a mental handicap

I didn't see the quadratic equation in a math class until 10th grade

@ACuriousMind did you star those things

Huy

10th grade

rly?

0celo7

yes

Huy

that's a bit late

did you never multiply something by itself before

0celo7

what?

ACuriousMind

I seem to recall it was 8th grade when we treated it systematically.

0celo7

20:17

Well I took 8th grade math in Germany, and I didn't see it

ACuriousMind

@0celo7 If I answer that, THE ASTRONOMER will punish me.

0celo7

it's telling that I was a C student in math in Germany

...why am I a math double major? what's the point, I'm not good at it

Huy

u can become

study functional analysis

would be a good start

0celo7

I've tried becoming good

I asked a TA about that, and the book he said was a light intro is too hard

Huy

I have a headache

0celo7

20:19

telling me to study functional analysis is a troll meme at this point

Huy

you're the troll at this point

0celo7

I bet you feel real proud about that one

Huy

very much so

0celo7

@ACuriousMind well don't say his name so loud, goof!

Huy

I printed it out and am laminating it

0celo7

20:22

random factor of $5$ floating around

more sign errors

an odd number of them!

@Huy oh I'm sure

just know that if you're not actually doing that, you're just trolling :)

Huy

I know

0celo7

pic?

Huy

I don't send my pics to strangers on the internet

0celo7

you sent me pics of your room!

omg I bet it wasn't even yours

Huy

maybe that wasn't my room

0celo7

20:26

@ACuriousMind Seriously, are "physicists" only people who have degrees in physics?

ACuriousMind

I would say that that is the defining characteristic of a professional physicist, yes.

0celo7

Is Dyson an exception?

So what you're telling me is that you could talk to a professional but not be able to say that he is a physicist without looking at the diploma?

ACuriousMind

Yes, because that's how I chose to define "professional physicist" in the sentence above :P

0celo7

seems like you're trying to bar me from kinship :'(

ACuriousMind

19 mins ago, by 0celo7

I'M NOT A PHYSICIST

You did that yourself.

0celo7

20:31

I'm not anything.

I have a high school diploma.

Huy

laminated?

0celo7

probably not

Huy

then it's worth nothing

0celo7

lol @ 3rd order ODE

so much writing

Danu

hullo

Huy

20:33

hi danu whats up

Danu

not much

agar.io

0celo7

what?

Danu

a stupid online game

that I play when I'm braindead

I proved some stuff about the "topologist' sine curve"

which was pretty great

0celo7

@ACuriousMind Do you have Hitman: Absolution?

Huy

that it's not path connected but connected?

or is there something else I must know about it

Danu

20:35

are the games after blood money good?

yes

ACuriousMind

@0celo7 No. I've not heard good things about it, either

0celo7

@Danu dunno, just started and I'm pretty terrible at it

@ACuriousMind Too "mainstream"?

Danu

@0celo7 Those games are pretty hard

(I know them up to part 4)

Young me was unable to "properly" complete most levels.

0celo7

for one I just shoved the guy down a steam vent and stabbed everyone while making my escape

I intend to replay that one :D

ACuriousMind

@0celo7 No, it just has bad writing/story and not excellent enough gameplay to gloss over that

0celo7

20:37

the story is incredibly confusing

I have no clue what's going on

I'm about an hour in.

er, anyone know how to inverse Laplace transform an reciprocal cubic?

Huy

................................................................................‌.............................

0celo7

what's that for?

Danu

Have you played the old Hitman games though, @ACuriousMind?

ACuriousMind

@Danu No, heard good things about them, though

0celo7

I got Silent Assassin for a buck and change

Danu

20:42

@ACuriousMind Pretty friggin' awesome.

Most epic games I think I played as a kid

@0celo7 Oh man... That first mission...

I spent so many hours lurking in the outside hills hahaha

0celo7

I feel like you just have to wait a lot

Danu

I was way too young to be really good

@0celo7 Guess what real hitmen* do

0celo7

for a hole to open in the guard patters, etc

@Danu nice edit :D

Danu

@0celo7 brainfart :D

0celo7

Real hitmen = Sam Fisher

Danu

20:44

haha

0celo7

yes, I have a mancrush on him

Danu

Keep on dreaming

0celo7

Sam Fisher is real!

You're telling me real hitmen don't clear a room while hanging upside down from a pipe on the ceiling?

pls

Danu

Just rewatching the first mission of Hitman 2 is giving me mad nostalgia :D

0celo7

you can't just say Sam Fisher is a joke and not explain

he will cut you up

Danu

20:50

As Leeb likes to say: "Proof: Clear"

0celo7

Leeb can go f*ck his proofs

Agent 47 vs. Sam Fisher vs. Solid Snake

@ACuriousMind How does one factor a cubic polynomial?

ACuriousMind

With math

0celo7

For example $3x^3+5x^2+x-1$

ACuriousMind

Seriously, that's not hard to figure out

0celo7

@ACuriousMind why do you troll me

@ACuriousMind what?

I've never been taught how to do it

is there a way to find one zero and divide it out?

Danu

20:56

Wikipedia

Huy

-1 is an obvious one

my students love doing this kind of stuff

0celo7

ok, we get it, you have smart students

Huy

no

0celo7

but that doesn't help me one bit

Huy

I'm just trying to emphasize your middle school maturity

Danu

20:57

@Huy hehehe

0celo7

rational root theorem? what is this madness

Huy

wow

0celo7

Wolfram knows what level I'm at

Huy

I never know when to use "evaluate" or "compute" or "find"

0celo7

@Huy I didn't see it

Huy

21:03

usually you start by checking 1, and afterwards comes -1

0celo7

never would have guessed

Huy

yes because the measure of a singleton is 0

0celo7

huh?

Danu

Calculate?

0celo7

oh I remember that

ahhhh

yes, it's coming back

Huy

21:05

measure

probability

anything ?

0celo7

you really are a troll, you know

Huy

:(

0celo7

you guys are so mean you'd probably just laugh if I asked how to factor a quadratic

Huy

ask in the maths chat

we're used to trolls there

0celo7

dude I seriously can't factor $3s^2+2s-1$

the best I can do is see $-1$ is a root and long divide

user685252

21:10

Use the quadratic formula

Huy

u can factor -1 even twice

and then you're done

0celo7

I used to be able to just write it down

Danu

I've never learned long division

Lel

ACuriousMind

@Danu wat

0celo7

@Huy what

Huy

21:11

means u can divide by $(x+1)^2$

Danu

@ACuriousMind Never needed it, either

Huy

and not just by $x+1$

0celo7

the cubic, yes

but not the quadratic

Huy

lol

hint

$(x+1)^2 = (x+1) (x+1)$

0celo7

stop trolling

Huy

21:12

I don't understand your confusion

0celo7

how do you factor that quadratic

ACuriousMind

@0celo7 I do not see what you find so difficult about this. Just compute its roots!

0celo7

@ACuriousMind I can do that

There's a trick for just writing it down, but I've forgotten

Huy

zweiklammeransatz?

0celo7

what?

Huy

21:14

idk what trick u mean

0celo7

I'll give you two parentheses

ACuriousMind

Computing the roots is not hard. I don't see why a "trick" would be needed

0celo7

because it's hard for other people

Huy

what other people are you talking about

ACuriousMind

You are not "other people", are you? :P

0celo7

21:17

ok I know I told you guys to be meaner, but this isn't what it was supposed to be like :(

@Huy I have to do partial fractions on this now

user685252

If you can't factor it then its prime :P

DanielSank

@Danu I would indeed have answered that question, but now someone else did it with "sandwiches".

I f*$#@%g hate those stupid food analogies.

Danu

I never heard that one

But the bounty is about explaining it without sammiches

DanielSank

@Danu orly?

0celo7

food analogies are the best

a black hole is really a donut shop

you get so fat you never leave

DanielSank

21:20

@0celo7 zomg that hurt.

user685252

Ba dum tss

0celo7

it's funny because rotating black holes have ring singularities

and donuts are products of rings

Huy

wat

0celo7

$\mathrm{donut}=\mathrm{ring}\otimes\mathrm{ring}$

Huy

don't tensor me

ACuriousMind

21:23

::cringes::

DanielSank

^ should I turn on chatjax for that?

Huy

for your own safety don't

0celo7

just some engineering math

ACuriousMind

I see engineers misuse the $\otimes$ even worse than physicists :P

0celo7

Hmm, I think the people of this chat forget that I have two majors

oh well

I doubt it will ever matter, anyway

So I wrote down the problem wrong. That's fun.

Huy

21:25

classic 0celo7

0celo7

I can't do anything right.

@ACuriousMind It's funny that BBS sometimes uses $\times$ and sometimes $\otimes$ for the group product :D

Huy

dear lord

I'll try to cry myself to sleep now

thanks for the nightmares

good night and good luck with your remaining exercises

0celo7

they also make no distinction between algebra and group

Huy

...............................................................

please stop the torture

mercy

0celo7

wonder what else they do

@ACuriousMind You surely have a list of offenses committed by BBS, right?

Huy

21:30

what is bbs anyways

0celo7

amazon.com/String-Theory-M-Theory-Modern-Introduction/dp/…

Huy

bible of bs ?

0celo7

pretty much, although I think GSW/Pol is more standard

Huy

ok

i sleep now

bya bya

bye

0celo7

sweet dreams

Huy

21:31

thx <3

0celo7

$\mathrm{SU}(2)\otimes \mathfrak{so}(5)\times E_8$

Danu

@DanielSank Yush!

DanielSank

@Danu I see. I was confused by the fact that there's already an accepted answer.

Danu

@DanielSank Note that the question is four (!) years old.

ACuriousMind

@DanielSank Note also that the bounty is from dmckee, not the asker.

0celo7

21:38

maybe he is the user

dun dun DUN

DanielSank

@ACuriousMind Indeed.

0celo7

@ACuriousMind what's the biggest abuse of notation in physics?

probably some QM or QFT thing, right?

DanielSank

@0celo7 Actually, one of the worst offenders is the constant conflation of functions and variables.

0celo7

please elaborate

DanielSank

Similarly, there is a very frequent conflation between vectors and representations of vectors in a particular basis. This confusion is made worse by the fact that representations of vectors are themselves vectors!

0celo7

21:49

are you saying like $v^ie_i$ vs. $\{v^i\}$

Danu

But those errors are mostly problematic for beginners, at graduate level that type of stuff doesn't really pose any problems.

DanielSank

@Danu I wouldn't agree with you there.

@Danu Self-consistent notation really helps me understand what I'm doing. This was a huge issue in GR.

0celo7

lol, you'd love wald

abstract index notation is the biggest scam

DanielSank

@0celo7 What? No it's not.

Abstract indices are a very good idea IMHO.

0celo7

dude it's just index notation but the indices aren't indices!

DanielSank

21:52

@0celo7 Right! They're labels on function arguments.

0celo7

and it hurts when he writes partial derivatives or Christoffel symbols in abstract index notation

DanielSank

@0celo7 I wouldn't know about that.

0celo7

as far as I understand it, the abstract indices should only be on tensors

but Christoffel symbols aren't tensors

I think one can make the partial derivatives make sense

Danu

@DanielSank Meh---I think most people seem to get by just fine.

Also, AFAIK the tensors-not-being-their-components is done in most graduate courses.

DanielSank

@0celo7 Yes.

@0celo7 Oh.

Danu

21:57

(neither are partial derivatives)

DanielSank

@Danu True, but most people don't understand what the hell they're doing.

0celo7

@Danu Yeah, I'm trying to think how he defined $\partial_a$

but I don't have the book with me and my iPad is at home, too

Well, now that I think about it, Hawking-Ellis uses the same notation

So neither makes sense.

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