The h Bar - 2015-09-05 (page 1 of 2)

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12:13 AM

0

Q: How is the Routhian of classical mechanics defined?

The Hamiltonian is a function on the cotangent bundle to a configuration manifold $H:T^*M\rightarrow \mathbb R$. The Lagrangian is a function on the tangent bundle to the configuration manifold $\mathscr L:TM\rightarrow \mathbb R$. What is the Routhian function $R$ defined on? My guess is $TM\b...

classical-mechanics differential-geometry

Does this have an answer?

hell if I know

12:28 AM

@ACuriousMind You should have seen Dr. Lang's face when I spoke German to him.

12:52 AM

user image

(an elefino)

@Slereah Reading chat logs. Seems as if an instigator should take his own advice more :p

1:11 AM

hello

I got a new laptop and freaked out when I totally forgot what my email was for this account

and then remembered what it was three days later

but the fact that I freaked out scares me

:p

@FenderLesPaul You had a desktop before right?

@obe it was a laptop too actually

switched over to a mac

my life has been turned upside down

PC is the same.

The only difference is where minimize/close is located on a window.

1:27 AM

no it's quite different

1:39 AM

@FenderLesPaul A desktop-laptop hybrid?!

2:35 AM

@NeuroFuzzy A laptop connected to a monitor with a mouse and keyboard?

2 hours later…

4:53 AM

Back in the late bronze age there was even such a thing as a laptop docking station. Not so common anymore.

NbRCeID 3

nature.com/articles/srep12488

5:33 AM

I'm trying to write a query to rank users by their total answer score divided by the number of answers they've given.

Anyone here understand SQL subqueries?

@Danu Yep. That one.

6:01 AM

@NeuroFuzzy that elefino looks like it would be a poacher's dream lol. I've never seen so much ivory on one animal. Good thing it doesn't exist. Be extinct already.

6:58 AM

Hey, check this out!

data.stackexchange.com/physics/query/360094/…

It's an SQL query which ranks users by their average answer score!

You can configure a minimum required number of answers needed for a user to be included in the query.

(oops, slight typo, use this link)

Our highest rep per answer user of all time is drhodes who has answered one question for 495 upvotes!

Hi Daniel

Requiring a minimum of 100 answers we find Ted Bunn in the lead.

@Danu Hi. What's up?

You do know that "avg answer score" is already a query, eh?

@Danu Did not know.

Just using this for first time.

@DanielSank Oh well ^^

I don't score so well :(

7:03 AM

@Danu When you say "already a query" do you mean it's already a column on the Users table?

Nope, don't see it.

I mean there's already an SQL query that finds avg answer score

@Danu You mean like, ever in the history of the universe?

Not surprising.

@DanielSank I mean like... has been posted in this chat in the last 1.5 years

@Danu Lol, ok.

@Danu Well, mine's better.

'cuz reasons.

^^

7:07 AM

^

wut?

^^^?

Does any of you know what ASMR is?

Yeah

Stands for "Autonomous sensory meridian response".

Duh.

Yay, someone who knows!

or are you kidding? :P

@Danu What do your instincts tell you?

7:09 AM

Cargo cult.

@DanielSank sigh

@Rigor ?

@Danu Actually, reading the article, I have experienced this phenomenon.

@DanielSank Yay! :D

Let me guess, i Ellinika sou?

I have it all the time :P

No, haha

She has no idea what it means/is

7:11 AM

Cargo cult science

Cargo cult science comprises practices that have the semblance of being scientific, but do not in fact follow the scientific method. The term was first used by physicist Richard Feynman during his 1974 commencement address at the California Institute of Technology. Cargo cults—a religious practice that has appeared in many traditional tribal societies in the wake of interaction with technologically advanced cultures—focus on obtaining the material wealth (the "cargo") of the advanced culture through magical means, by building mock aircraft landing strips and the like. == Feynman's speech == The...

I don't think many people really tried to do any serious research into it

It's starting, though. I participated on a study on it recently

@Danu That's not at all what I mean -_-

What's your trigger?

Yeah, not her necessarily, though she can do it by playing with my hair

Many things trigger it for me

@Danu Maybe you ought to lay off the drugs for a while.

Certain voices, crinkling sounds, scratching sounds, scissor sounds

7:15 AM

@Danu grain alcohol, cocaine, E...

@DanielSank It's so funny to see this idea people have about Amsterdam, failing to realize that in fact the lenient drug policies make it way less "cool" to do drugs: Smoking weed is seen as very boring by most.

@DanielSank Never done any of those :P

@Danu You know what's even funnier is Dutch people who can't tell the difference between a tease based on caricature of a trope and what the people doing the teasing actually think.

No, I do know that you're not the one making this mistake; I just wanted to put that statement out there

(because it has come up before :P)

@Danu I figure it's like any other place where a "vice" is legal: the locals couldn't care less but there are probably tourists who go to binge.

yes?

Yush! Although luckily binging on weed doesn't really do so much except making you extremely tired, so the high tourists aren't too bothersome either :)

7:21 AM

@Danu Yeah. That fact is often brought up when people point out how stupid it is that alcohol is legal in the US but marijuana is not.

Which would you rather encounter on the street: 1) Someone high, 2) Someone drunk?

Yeah, and it's a good point

It's such a joy to be going through my diffgeo notes again :D

3 hours later…

10:39 AM

hey

2 hours later…

12:09 PM

@Danu just to be clear, I'm as serious about your drug addiction as you are about my idiocy

@Huy I still don't have a mouse

@0celo7: I have a MacBook Pro now.

@0celo7: Did you look at other mice in the meanwhile?

You said you wanted the air!

@0celo7: I thought so too. Then I found out the 13'' MBA is only 200g lighter than the rMBP 13''.

I thought it was like 500g at least.

>grams

>eu

12:13 PM

In related news, @ACuriousMind, Lang said I should claim German citizenship because it makes traveling abroad easier: certain countries like Germans more than Americans.

Possible. I have German and Swiss citizenship.

@0celo7: Is there some way to use KeePass with Safari on OSX?

I don't use KeePass or Safari.

-.-

You should check out the humble bundle if you like Clancy games.

I have so much stealth entertainment now...

I have looked at other mice.

One thing I find weird is that nowadays, some people say physics is stagnating because all that we expected to be true turns out to be true

It's kind of a weird mentality

12:22 PM

I pretty much asked everyone I know. My roommate plays LoL and RTS games exclusively, he has a Razer Naga. The one PC guy I know back home uses a Razer Deathadder. I've also had the Rat recommended. Steelseries sensei. Some others too that I forgot.

@Slereah And yet people still believe in quantum mechanics.

Just buy any that you like.

I'm not a fan of Razer, so I'd go with a Logitech, Corsair or Steelseries.

What's wrong with Razer

Just never been a fan of the design of their products.

What the stuff looks like is really important to me.

@Slereah Being right is boring, it seems

Quality-wise, not sure whether they're as good as Corsair. They're not bad for sure.

@0celo7: Are their products cheaper than the others?

(cause I doubt that)

12:32 PM

The DeathAdder is cheaper than the Logitech

Yeah, that's like their most popular model I think.

Is it cheaper than the Sensei, for you?

@0celo7 Serge Lang? :P Having conferences with ghosts now?

@ACuriousMind : The 20th century fucked people up

They think unless all physics is wrong we're not making good progress

2

@Danu Yeah he was at the cookout, cool guy

BTW, do you use a dock with your rMBP?

12:35 PM

Well if by dock you mean "USB splitter that has all my crap plugged in"

@0celo7 Dead people like bbq's too! :P

I know two U Heidel people, both seem nice

I think I can conclude all U Heidel people are nice

I'm still trying to figure out where to put my MBP at home. I don't want to just put it on my desk, that's boring. :(

Well I play games on it

What exactly was it again that made you not buy the G502, @0celo7? What problems?

12:37 PM

So it just sits on my desk

I have a desktop for games.

@Huy the videos I watched either complained about the scroll wheel or made it seem really...mushy

Hm.

What about the M65 by Corsair? Is it expensive over there?

Ok, I have to get going. Taking a bus to see my brother in Ohio

I have a 5 hour bus ride, which book should I take

An e-reader :P

12:40 PM

I'm typing on an iPad right now

That was a trick question

I should probably take a school book

take your favorite subject :-)

@DanielSank drops mic

-_-

@NeuroFuzzy average just lost its meaning

1:15 PM

What to do with an answer like this:

58

A: Cooling a cup of coffee with help of a spoon

How to cool a cup of coffee with the help of a spoon. Hmm... Empty the cup using the spoon, discarding the hot coffee. Strike the cup with the spoon, shattering it and forcing it to release the hot coffee. Drink the coffee with the spoon. Use the spoon to carve a cup-shaped hole in a large bloc...

I feel it should probably be deleted, but maybe I'm being a bit too humorless.

@skillpatrol I'm genuinely interested in my psychology text

I remember a similar (as in joke-y) bunch of answers to a question about weighing someone's head

@0celo7 then take it

@skillpatrol yup, packed

cool

1:17 PM

Eating now, have to stop by the gift shop

Gotta get the nephews some hideous orange shirts

:D

why the hell would you want to cool your coffee anyways? That's heresy

Btw, I have been to the fort

the hotter the better

until you burn your tongue and scream

Stale cold black coffee is all there is in life

1:18 PM

#deep

@Danu check your inbox

@skillpatrol I did.

I deleted the room, now that the conversation is over.

...and?

Thanks for your apology? :P

:-)

1:20 PM

@skillpatrol idk what the big deal about the fort is

People are scared to walk around there

it's infested with orcs

@0celo7 They made gold finger in there

I think there's drug dealers or something there

@skillpatrol wait is there an actual fort?

yep

"The fort" is a nbd outside UT

It's where the vodka and weed is

Why do people like vodka anyways

1:23 PM

russians?

@0celo7 It's really the worst of alcoholic beverages

vodka is gross

but so is bud light

and frat bros love bud light

The best, most expensive ones aim at being completely flavorless, which really says it all.

can't question these things

No we had Yuengling the other night

I think everyone realizes bud light sucks

1:25 PM

@FenderLesPaul you're in a frat?

@Danu people will swear up and down vodka is the best liquor

@skillpatrol no I just know a quite a few of them through my A Capella group

@0celo7 Those people are either Russian or have no clue.

@ACuriousMind I agree, and could go for a nice Jameson right now

Whiskey is definitely for the Irish :P

1:29 PM

@skillpatrol Lolwat

Irish whisky, maybe

*Whisky

both spellings are correct

Whiskey = american

Whisky = all other

Still both correct

(not language, but liquor)

1:30 PM

also I should switch to whiskey then

yes, but they're two different things

alcohol is icky

apple juice ftw

@Huy No?

yes

Well, cider is nice.

1:31 PM

Ew cider

apple cider?

mmm apple cider

@SkillPatrol do you like cat stevens?

yep

I've been addicted to "First Cut is the Deepest" lately

such a good song

ya, that one is a cool classic

1:48 PM

I'm not so sure I agree with the meaning...

...the deepest cuts never really heal.

I don't think he ever says they heal

he just says the first cut is the deepest

which is true for a lot of people

Is it really?

certainly true for me

if we're talking about relationship related stuff that is

real cuts can be a bitch no matter what :p

fucking paper cuts

everything heals and leaves a scar

that's life

well sure but that isn't contrary to what the song is saying

so I don't understand which part of it you disagree with?

1:54 PM

the deepest part

well deepest doesn't imply that later cuts don't leave scars

just that they aren't as hard to get over

you get stronger emotionally over time

yes, if it is the deepest you would ge died

can't disagree there :p

like romeo and juliet

or Taylor Swift and John Mayer

1:57 PM

If the first cut is the deepest, I guess I'm in for a shallow cut life

best to go in with a thick skin imo

girls like to test guys that way...

...let's see how tough he is }:-)

that sounds like exercise

it is

runs away

don't look back at the maddussa

2:04 PM

hello darkness my old friiiend

man I wish I could sing as high as Art Garfunkle

having to sing every one of his songs one or two half steps lower sucks

Boston - Don't Look Back

I've come to chat with you agaaaiiin.

welcome

@skillpatrol Thank you. I couldn't resist the chance for a parody.

3:04 PM

@0celo7 No it isn't.

@FenderLesPaul Just learn how to whistle well. I find it to be a lot of fun ^^

@JohnDuffield I know it isn't, as far as we know.

@ACuriousMind What's the quickest way to show that the vev of a time ordered product of $\phi_i\phi_j$ is the Green's function?

@0celo7 I'm...not actually sure how to do that in full generality

@ACuriousMind D:

3:21 PM

@Danu whistling is definitely fun

:)

@HDE226868 hehe

hi

@0celo7 : space is dark, it has its vacuum energy which has a mass equivalence, and there's a lot of it about.

3:35 PM

"Is Karl Popper the pope of science?"

Well pope is in his name

3:45 PM

@JohnDuffield Dark energy is dark matter?

Not even close

What does Einstein and the evidence show?

Einstein and the evidence will be my band name

My band name will be "Genocide by boomerang"

name of first album: c ain't constant y'all

3:51 PM

I need to form my mental image of JD so I can say Einstein and the evidence with the proper tone and inflection

There's a math band called "The Klein Four"

They made some fine math themed songs

Also Tom Lehrer did a lot of nice math songs

for good physics songs, I recommend Arthur Roberts

ww3.haverford.edu/physics/songs/roberts/roberts1947.htm

ww3.haverford.edu/physics/songs/roberts/nice.mp3

ww3.haverford.edu/physics/songs/roberts/cyclo.mp3

Pretty good

sound quality is a bit old tho

I'm never going to listen to a math song

The mere idea gives me violent convulsions

@0celo7 Shaddap, this one is great:

Finite Simple Group (of Order Two)

yeah, that's one of Klein Four

seems to be a hit or a miss with physics songs

4:05 PM

@Danu ::seizes::

God damn it I left my mouse at home

there was one from MIT where the professor did yellow submarine by the beatles but changed the lyrics to "we all believe in relativity"

I could never listen to that beatles song again :(

I can't play splinter cell

have I shown you guys

Well I could but trackpad can't be used for gaems

Bob Waldemort and the order of the expansion?

it's a harry potter parody by people at UChicago

4:07 PM

Windows can't into trackpad

oops

Harry Potter and the Order of the Expansion

4:23 PM

@0celo7 : vacuum energy is a kind of "dark energy", but it isn't the same thing as the dark energy which is said to be responsible for the increasing expansion of space. Some people suggest it is, see this report but IMHO it isn't.

@0celo7 : Einstein and the evidence show that "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". This inhomogeneous spatial energy is dark, and it has a mass equivalence and a gravitational effect. See papers like arxiv.org/abs/1209.0563.

Ahahah

@Slereah How about explaining what is funny instead of just laughing.

Either contribute or don't say anything at all.

Because in general relativity, the energy stemming from the gravitational field is not included in the stress energy tensor

The gravity acting on gravity is expressed in the non-linearity of the equation

Did Einstein say this or is this some cargo cult BS?

Who knows

I haven't actually read much Einstein

He didn't really write the big GR books

But I assume he knew that Duffield was wrong because the dark energy term he added by hand to the EFE

As a lambda term

It is not part of the basic theory

Well it can be if you shift it to the stress energy tensor

But usually it is written on the lhs

Dark matter is also totally unrelated to dark energy

Except for being dark

(not directly detectable)

They have a completely different behaviour

Dark energy being a lambda term while dark matter behaving much like regular matter

Also have some weasels

2

imgur.com/gallery/J6XPwQJ

You can totally write the energy of the gravitational field, but that is rarely done

Because it's usually not that interesting

Except in linearized GR

Still it is unrelated to dark matter

Or dark energy

Although

Fair is fair

Vacuum energy is indeed only one type of possible dark energy

There's quite a long list of what dark energy can be

4:45 PM

I know what it is.

Of course.

The only condition for something being dark energy is that $T \propto g$

(or $p = -\rho$)

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