The h Bar - 2015-05-13

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1:25 AM

@0celo7 Did you use your Jack Nicholson voice on that? Did you? Oh! Please tell me that you did.

@0celo7 Oh ... I am so going to steal that!

user54412

1:52 AM

@Icosahedron No no no. The tensor product has nothing to do with the direct product, even though about half of physicists will use the terms interchangeably when not thinking. I've commented on this numerous times because it's such a common misconception.

user54412

The tensor product doesn't even have the same dimension as the direct product, except in the unfortunate case of two spin-1/2 spaces being combined, since 2+2 = 2*2.

@dmckee You bet I did!

Ignore that.

@dmckee Please do! It's how I approach self-studying. However, then I end up starting a problem and two months later I still don't know what to do.

Freaking Wald 10.1

I will take an analysis course just to solve that damn problem

user54412

@0celo7 Are you still losing sleep over the strictness of some offhand inequality in a textbook exercise?

@ChrisWhite YES

I'm losing sleep over the whole thing

I got parts a) and b), why is c) taking months!?!?

user54412

2:07 AM

I think c was supposed to be a 1-liner

I looked it up in Hawking & Ellis because they treat the Cauchy problem, but they just state the result and say "it can be derived"

user54412

lol

user54412

after I spent the better part of a day fretting over one subpart of one question in MTW, only to realize it had a typo in it, I resolved to never spend so much time on a single textbook problem

15 pages of the text is based off of the result of the exercise

I need to take a look at that again.

I shall attempt a solution in calculus tomorrow.

2:30 AM

@0celo7 I don't see what zee did in a step, can you tell me?

I.2 first page, eq 3-4.

I did it though I did not get that answer.

(btw it's dumb) :D

looking

chain rule

yeah...

Multivariable chain rule

though I didn't get 1/2

the velocity is squared

Power rule, then chain rule

2:35 AM

ok got it. thanks

np

2:57 AM

This is a manly ass man.

@ChrisWhite The book literally states they are the same thing. tensor product or direct product...

@Icosahedron Where

My mistake, it says direct tensor product.

Ok, that video is pretty cringe-worthy. That guy has massive cojones.

two ap exams tomorrow... and I did physics all day.

3:02 AM

@Icosahedron WATCH THAT VIDEO

He sticks fishhooks in his arm just to show you how to take them out

how about I don't.

@Icosahedron That's objectively wrong. They're different things.

I forgot everything about stats.

idk if you're serious

I sort of am.

I was supposed to read the book again today.

but instead I started to do my independent study today.

3:05 AM

NSFL

AHHHHHHHHH

HE YANKED IT AND IT DIDNT COME OUT

I don't think I want to click that.

I'm leaving.. it's weird here at this time of day.

This video is freaking awesome

later

bye

::pushes fish hook through skin:: "Guys, this hurts, but it's not that big a deal."

:<

user54412

I'm guessing you're supposed to push the hook through a new hole and clip the end off before pulling it out.

user54412

3:12 AM

That said, I'm not clicking that link.

6

@ChrisWhite Yes. However, he shows that this is not strictly necessary and pulls one out the old-fashioned way.

2 hours later…

4:56 AM

@0celo7 "Yes. However, he shows that this is not strictly necessary and pulls one out the old-fashioned way." let's play: "Fishhooks or physics!" The game where you guess if 0celo7 is talking about a technique in physics or about a video where a guy pulls fishhooks out of his arms!

@ACuriousMind Hahahahahaha

Einstein = Geodude. Confirmed

user54412

Ok, does the makeshift \oiint here look off to anyone else? It only looks right to me if I delete one \! from the source.

user54412

user image

@ACuriousMind $\vec a \times \vec b$ is often called the outer product.

@ChrisWhite Get the integrals closer

user54412

?

Waffle's Crazy Peanut

5:02 AM

Boo!

user54412

I didn't come up with it, I'm just wondering if something's off with my browser fonts

user54412

Since no one here commented on it.

user54412

@Waffle'sCrazyPeanut Hi

Waffle's Crazy Peanut

@ChrisWhite Morning! :)

@ChrisWhite It doesn't have nothing to do with it

Waffle's Crazy Peanut

5:04 AM

What's cookin'? I'm on vacation. So, I'm free for the next two months or something...

(Uh, 47 days actually)

Every bilinear form on $U\times V$ canonically corresponds to a linear form on $U\otimes V$

@ChrisWhite Ah, sorry. I didn't read properly. It looks good to me (better than that)

@Waffle'sCrazyPeanut Great :D

@ChrisWhite Really? I often spend a day or two on a subquestion

Waffle's Crazy Peanut

Hmm... Back after a long time, and I find @ChrisWhite's rep. score mildly amusing. He was rocking till he reached 20k :P

(althought that usually means I'm trying to learn the background math prereqs)

user54412

@Waffle'sCrazyPeanut Yeah. Thesis and all that.

Waffle's Crazy Peanut

I see. What are you doing these days?

user54412

5:09 AM

@Danu You're young. You should. :) Then one day you'll have the same realization that I had -- that life is too short to worry over details. It's enlightening, but it also means you officially become old.

I find that I become more and more worried about the details, the older I get ;)

So far, at least...

user54412

With each year gone by, each coming year represents a larger and larger fraction of your remaining life.

user54412

Wow, I'm depressing tonight.

user54412

@Waffle'sCrazyPeanut Coding. Coding. More coding. Visualizing code output. Then coding some more.

Waffle's Crazy Peanut

@ChrisWhite I'm impressed. That's what I call "being productive" :)

5:13 AM

@Danu it is because you are shifting towards mathematics...in mathematics, the devil is in the details

@ChrisWhite It's okay :D

You'll be more bored of it all too ;)

Waffle's Crazy Peanut

@Danu: What do you do?

waffles understands that people are busy

user54412

@Danu I have to ask:

user54412

A good example would be the study of assymptotic behavior of solutions, which is a truly vital part of much of physics. — Danu 7 hours ago

user54412

Was that misspelling intentional, given the question about analytic solutions?

Waffle's Crazy Peanut

5:22 AM

@ChrisWhite LOL! :D

user54412

@Waffle'sCrazyPeanut :(

user54412

You should hang out here more -- this room's been so... German and mathematical lately

3

user54412

(Danu's studying mathy stuff in Germany. Or so he claims.)

Waffle's Crazy Peanut

@ChrisWhite waffles realizes his mistake now

he also assures that he'll hang out more often in h-bar

5:50 AM

hi

Waffle's Crazy Peanut

Hey!

Hi @phonon

6:14 AM

Its @Waffle'sCrazyPeanut ! Sup dude?

@ChrisWhite I can prove it! :P

Waffle's Crazy Peanut

@StanShunpike Nothing much. Morning... Coding...

(well, it's about noon now)

6:37 AM

@Waffle'sCrazyPeanut what are you coding?

Waffle's Crazy Peanut

@StanShunpike I just got into Mozilla a few days back. I'm trying to understand how a few components work.

Do you work for Mozilla?

Is that the Firefox company?

Waffle's Crazy Peanut

Not exactly. (Like I said), I just got into it. It's a great welcoming community for open-source development.

Anyone can work there :)

Lol true. I forgot about that.

Waffle's Crazy Peanut

@StanShunpike: How are you doing?

1 hour later…

7:49 AM

I have discovered how to conquer the world.

8:19 AM

@DanielSank which one?

1 hour later…

9:40 AM

@yuggib I guess he disappeared from this one

10:03 AM

@Danu yeah it seems so...

4 hours later…

1:50 PM

@Waffle'sCrazyPeanut I'm great! Just finished a new song, schools going well.

Here's the new one

m.soundcloud.com/gotlepton/volo

I wish it were warmer tho!

Its 48 degrees in may here. Wtf

2:25 PM

@ChrisWhite Yes. But then MathJax' rendering of inter-symbol spaces seems to vary a bit between reloads of a page. It makes optimizing spacing frustrating.

3:06 PM

Hello there, can anyone help me with a simple Mathematica problem ? (I'm new to mathematica and I believe it's rather simple, so I'm asking here instead of posting a question on Mathematica SE). How do we use unit vectors in spherical coordinates ? For instance if I want to define $H(\vec{m},\vec{r},)=\vec{m}\cdot\vec{r}$,$\vec{r}=r\cdot\vec{e_r}$ where $\vec{e_r}$ is the first unit vector in spherical coordinates, how would I do this ?

user54412

@Hippalectryon I'm not entirely sure what you're looking to do.

user54412

Spherical coordinates are orthogonal, and if you've defined your basis to be unit vectors, then naive dot products function exactly as you'd hope and replicate a true inner product.

I mean, if we were in Cartesian coordinates, I could just define x={1,0,0} etc. I can't define r an easy way here, can I ?

user54412

So for example if you have $\vec{a} = a^r \vec{e}_r + a^\theta \vec{e}_\theta + a^\phi \vec{e}_\phi$ and similarly for $\vec{b}$, then the inner product of $\vec{a}$ with $\vec{b}$ is just $a^r b^r + a^\theta b^\theta + a^\phi b^\phi$.

Sure, but how would I define $\vec{a},\vec{b}$ in mathematica since $\vec{e_r},\dots$ are not defined by default ?

user54412

3:18 PM

Just as lists of components in your understood basis: if $\vec{a} = 4 \vec{e}_r + 3 \vec{e}_\theta$, then a = {4, 3, 0}

Oh right, then I just use the builtin functions to transpose the coordinates systems when needed. Thanks.

3:52 PM

@DanielSank I approve of your attempts to have people write better titles

2 hours later…

6:11 PM

@Danu Thank you SO much for saying that.

It's a crummy job but for some reason I really care about this :P

@yuggib Is that a many worlds joke?

I'm trying to adimension my equations in Mathematica; I have a function $f(x)$ and I'm doing $x=x_0\cdot x^*$, but I don't have a clue how to do that in Mathematica, has anyone here already done it ?

@NeuroFuzzy Haha! The video showed the merits of old fashioned perturbation theory vs. this newfangled Feynman crap.

I've crawled up to 2k. Darkness has descended on two more review queues now. :)

:D

FWIW, it won't be very frantic reviewing in the early days, a la my FPRs, until I get a hold of what has to be done. :)

When Darkness descends, sheeple rise

4

LOL

6:28 PM

@ACuriousMind Holy crap, what did I ever do to you to deserve this??

@0celo7 lol, but I only taught you about \mathrm, not about kerning. I'm not that cruel.

Hello @ACuriousMind

Ahh it's a rabid fan!

Go away, he's mine!

@user223679 Hi

@0celo7 And you say I have a schoolgirl crush on Urs...

2

I wasn't serious, but I'm not so sure about yourself

I think \mathrm is worse because almost every book I have doesn't use it

Computer modern has decent kerning, right? At least, it hasn't bothered me.

6:36 PM

Whats up @ACuriousMind

@0celo7 I...think so, but I'm not a typographer

@user223679 Just came home from a long university day, now it's mainly the joy of having a long weekend that's up right now.

Great!

What does "overall classification of "very good"" mean? @ACuriousMind

Is that some sort of marking scheme?

@user223679 Yes, "very good" is the highest category in the German marking scheme.

I'm not sure how to translate it into other schemes (and the university doesn't know either, they just say the national scales are incomparable)

You go further in your studies based on that remark? Is there some sort of percentage sort of a thing? @ACuriousMind

@ACuriousMind As a student or as a teacher ?

6:44 PM

@Hippalectryon His/Her profile says Student.

@user223679 Yes, I'm continuing with an MSc, and no, it is not based on percentages. For every course, you receive a mark between 1 and 4 (sometimes with decimals). (Roughly,) If the average weighted by credit points is higher than 1.6, it is called "very good", then follow "good", "satisfactory" and "adequate" in descending order.

@Hippalectryon Student

@ACuriousMind They don't have "excellent" for 4/4 then? :)

@user223679 Well, 1 is the best and 4 is the worst passing grade, so the best is 1.0, and no, it is not called something different than less than perfect scores.

@ACuriousMind I see France isn't the only country with weird/unusual notation habits lol

Thats surely wierd!

6:49 PM

@Hippalectryon Heh, I guess not.

@ACuriousMind What were you? 1.1 or 1.2 :D?

@user223679 1.137

1.4, actually.

Böring number

@0celo7 Whats the grading system at your place?

6:51 PM

@0celo7 They round off to the first decimal place, it doesn't get more interesting, ever

@user223679 A, B, C, etc.

And no marks? @0celo7

I was making a joke about the fine structure constant

@user223679 Yes, 100 pt scale with 10 pt increments

So A is 90+?

Yes

6:54 PM

Do they disclose the pts? Or just present you with your grade?

In France we usually do it out of 20

@user223679 always points

The points from which the 1 to 4 mark are assigned are actually totally random here. I've had tests from anywhere between 16 and 150 total points.

@ACuriousMind Here too, but we normalize to 100

@0celo7 That's, uh, called percent then ;)

6:55 PM

@ACuriousMind Maybe

Percentage points :P

@0celo7 abstrusegoose.com/389

They should grade out of one moles of points :3 You got 25.10^22 ! good !

hah

Hey. I thought one gets the orange review notifications when one crosses 10k. I'm getting it at 2k only! Am I special?

@TheDarkSide No, you're getting the actually useful number of pending suggested edits and the like for yourself, I think

10k users get the totally useless number off all pending reviews, regardless of whether they can act on them or not

The only thing you can do with that number is to shout at the other reviewers to do their jobs when it rises :P

7:00 PM

Ohh.

@ACuriousMind Lol

Shit. I'm not special. :: Heartbroken ::

:D

You're the dark lord

Haha.

BTW. I may not reach 20FPR today, but 18 is the highest I have done in a day since I got the Steward.

(Forget the story, I'm just showing off :P)

@TheDarkSide ...which story?

The story in the sentence, I meant.

18 in a day, 20FPR etc.

@ACuriousMind Lol. Schoolgirl crush on Urs!

@TheDarkSide For a story, I would expect some kind of explanation why you won't reach 20FPR today. Like this it's just a statement :P

7:06 PM

@ACuriousMind Because I not going to stay here for the remaining two more, I guess.

Until they come fast.

On a side note, I noticed a chat room named Bjorn's tongue something!

lol

That one is @0celo7's fault

lol

Did he bite your tongue? :P

is there a way to delete it?

Relevant conversation starts here.

@0celo7 I think it automatically deletes itself if no one uses it for a few weeks.

7:09 PM

@ACuriousMind That explanation isn't as much fun as the one that I suggested :P

@TheDarkSide The truth always pales in comparison to our imagination ;)

@TheDarkSide Your explanation is really gay TBH

Or just creepy

Lol.

And I sign out on that note. Bye guys :)

Cya

@ACuriousMind :) (I waited for it, this time.)

7:12 PM

Funny guy!

@DanielSank with a certain probability it is...

@ACuriousMind Awww, I haven't had a Döner in years...

Nor Schnitzel

:(

@0celo7 That's not Döner, that's Fanta. Oh, and what's that unrelated thing on the right ? :P

@0celo7 Had one just yesterday ;)

I couldn't even order one today because I don't remember the word for cucumber!

7:22 PM

@0celo7 Why would you need that? Don't you like cucumbers?

They're freaking nasty

Gürke

Are you talking about pickles or normal cucumbers?

Shit

Is the word different?

Pickles are awesome, cucumbers are nasty.

Yes and no - pickles are Gewürzgurken, cucumbers are Gurken.

Oh, no umlaut

7:25 PM

Not everything here has an umlaut :D

Hmm, I really want to say it with an ü

I fondly recall walking to Decis Döners down the road from school

Probably no "s" on the Döners there, the plural of Döner is Döner.

The walking was not that great :P

@ACuriousMind You sure

@0celo7 Haha...well, perhaps it made you hungry

@0celo7 Very.

The Turkish guy who ran the place was never able to pronounce my name properly

This was quite common, Ryan is apparently hard to pronounce

7:32 PM

Hm, I'd not said it's particularly difficult, but perhaps I'm also saying it wrong :P

Sigh...I haven't answered a question in days.

I need a Google street view on the place to verify the name

I found the overhead but there's no street view :/

WTF...starting a download kills my entire internet connection except for the download

@0celo7 What town?

@ACuriousMind Ramstein

It's on Bahnhofstrasse

Right across from the train station

Well, if I ever visit Ramstein, I'll look for it ;)

...but I don't think I'll ever visit Ramstein^^

Yeah...not much I miss about it besides my friends and the food

There's a heavy American presence because of the nearby Air Force Base

7:47 PM

I know, it's kinda famous for that

@ACuriousMind Famous or infamous? I've been to the memorial many times.

@0celo7 Hm, famous like "well-known" without any particular positive or negative connotation, I think.

8:46 PM

I don't mean to be a downer, but the vast majority of PhD students in many fields (very much including biology) end up leaving academia, either after the PhD (hopefully) or after many years as a postdoc/junior faculty (more tragically). Be wary of doing drastic things that only pay off if staying in the field. — Chris White 7 hours ago

Interesting comment on an interesting post

@DanielSank I felt you needed (and deserved!!) some encouragement :)

@0celo7 ...missing the potential for 1.337!

@ACuriousMind but everyone calls either Gurke

@0celo7 Lol only possible place for an American, innit

@0celo7 You must familiar with the nice band that named itself after that disaster

@KyleKanos HOW DARE YOU MAKE ME FEEL TERRIBLE! :P

:: continues mathematical physics degree ::

@Danu Yes, and then everyone asks which kind of Gurke you mean :D

Urgh

All the structure in mathematics is so nice

9:07 PM

@Danu What, "urgh"?

Your Gurke comment :P

@Danu What about it?

@ACuriousMind Nothing, really. Just felt like being whiny about it

@Danu Haha, okay. Be whiny about my Gurke all you want.

@ACuriousMind Something's really off about that.

9:26 PM

@Danu I have no idea what you mean :) ::whistles innocently::

9:37 PM

@Danu I didn't consider myself an American when I was over there.

I am fully converted now.

@Danu I'm not into metal, but if I was, I would like them.

@Danu Crap. I never thought of that...

@Danu Can a mathematician or physicist be a symmetrophobe?

Ahhh...how I love comment discussions. Especially when there is a danger people confuse me with CuriousOne, it just adds more delicious confusion.

rinku?

@0celo7 Yes, too much symmetry/structure makes things boring. You need to find that sweet spot where the structure is rigid/symmetric enough to allow strong statements, but flexible enough that interesting stuff can happen.

@0celo7 rinku?

@ACuriousMind Link in Japanese

I have too many weeaboo friends

@0celo7 How the heck was I suppposed to know that? :D

9:48 PM

@ACuriousMind ¯_(ツ)_/¯

Excellent!

@ACuriousMind Well? rinku to convo pls

Look e.g. here

And on the other entanglement post from OP

Honestly, that convo is confusing to me.

Well, I did speak of "delicious confusion" :P

9:56 PM

Well, I have no idea what you're talking about.

I'm confused by all three people.

I don't see where he confused the two of you.

I said "there is a danger", and I think the OP was briefly confused on the other thread

@Qmechanic Is perhaps the notation $OSp(2|1)$ simply a label for the SUSY algebra generated by the NS superstring supercurrent and Virasoro generators and doesn't actually mean anything by itself?

Too many weeaboo friends. HAH!

10:26 PM

rather otaku.

user54412

@ACuriousMind And yet there you go, putting in umlaut next to a D for no reason

i should be reading.

@ChrisWhite :O

can you use dirac notation all the time outide of quantum mechanics?

@Icosahedron Sure.

10:32 PM

I have not see that before.

It's not commonly done.

Doesn't mean it can't be done.

@0celo7 Not all the time, you have to be careful when writing $\langle \psi \rvert A \lvert \phi \rangle$ for a non-Hermitian $A$ - it is not clear whether that is meant to be the inner product of $A\phi$ and $\psi$, or of $A^\dagger\psi$ and $\phi$

@ACuriousMind Minor technicality.

In fact, that even causes confusion within QM.

I was thinking of the general idea.

i.e. |> is a vector, <| a dual, etc.

And, as you said, this is an issue in QM too. I don't see what's wrong with my statement.

10:36 PM

@0celo7 I thought of that only belatedly

But yeah, it doesn't become worse in QM cases, you're right

I think that Dirac's original notation was supposed to avoid that ambiguity.

1 hour later…

11:47 PM

I'm feeling pretty annoyed with what seems like a an unusually high rate of ignorant questions from lay people recently.

Is it just me being stressed or is this a real phenomena?

@dmckee I have a similar impression.

Like that absurd balloon gravity question?

@dmckee is it a few people asking the questions or many?

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