The h Bar - 2015-08-03 (page 2 of 3)

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7:00 PM

@KyleKanos There are 2 files in the demo, a .sln and .vcxproj.

Hey guys, I've noticed a few times in the last week that a low quality post which was also a pure math post was voted for migration to Math.SE. I don't think we should do this. It seems counterproductive to migrate posts which don't pass muster in other ways. What do others think? Should we migrate first and expect improvement/closure later, or should we focus on the other problems with appropriate close votes here?

4

@KyleKanos Is the job a direct contact? If you're freelancing you should probably set up your own company and as you're probably paying for healthcare and whatnot yourself (not familiar with the system in the US), 60k sounds quite low.

@obe No idea

I'll redo this.

@alarge Yes, I'd need to be there. I don't think I'd be taking it, I didn't like the feel of it when talking to the guy on the phone.

7:05 PM

@DanielSank I suspect it's related to

-6

Q: Migrate Homework to Math.SE instead of close?

Why not migrate the low-level "check my answer" type questions to math.se where they are receptive to them? The "Economics" Stackexchange never made it out of Beta: there were so many beginner's level questions that no experts could stand the place. The "quantitative finance" site however has ...

though the voting would indicate the opposite of what you're talking about.

I say we close so we're not dumping our problems on other people.

I'm pretty sure the answer on Meta.SE is Don't migrate crap

@KyleKanos we're outlaws?

48

A: Why was this question closed as off-topic without being migrated?

What's the golden rule of question migrations? Don't. Migrate. Crap. Guess what I thought that question was? Go on, guess!

There is probably a dilemma for specific questions and too-broad ones. You're told to ask specific questions though, it ends up being too specific and closed as homework, though if you try to make it more general it ends up being closed as too-broad.

@obe you done with Shankar yet?

7:13 PM

@HDE226868 Note, though, that Math.SE does accept HW questions. So what may be "crap" to us may not actually be to them.

2

@0celo7 I'll probably end up finishing the entire book in 30 days, with this delay.

@KyleKanos That's something I hadn't considered.

@obe 1k rep yet?

PSE says: Formulate your homework question in such a way that it doesn't look like a homework question even though in reality it is still a homework question.

@vzn I can't say...he's always watching

7:15 PM

@0celo7 Idk, do I?

@obe You should.

One day.

you can get 1k rep in one day?

you're not John Rennie

one day $\neq$ in one day.

Are you bored?

@obe Why use $\delta,\pi,\sigma$ for constants? Also why are gram, centimeter, etc. not upright?

@obe what?

7:19 PM

@0celo7 Who cares it was a low level answer.

@obe I'm confused...how did you get $\sigma =-1$ from $-3\sigma=3\sigma$...the only solution to that is $\sigma=0$.

oops, whatever.

I'll fix it later.

@obe then write some high-level ones!

@0celo7 I need to finish GR and QM first.

First I'll begin by asking questions.

@0celo7 No one can, rep cap at 200

Unless you manage to answer a +20 voted answer on 5 different sites and were counting those as gaining 1k rep in a day

7:26 PM

. . . with the exceptions of acceptances and bounties (and association bonuses, but you only get one).

there is that

@obe answer all the bounty questions

So you could answer two bountied questions with 500 rep on the line...

There's a total of 500 rep in all eight bounties up at the moment.

I see

@obe you should do that anyway

@ACuriousMind should bounty his QCD code :P

7:28 PM

Carpe diem!

@0celo7 I do plan to spend the entire winter break answering questions, 13 hours a day.

that's a little extreme

I'll be sure to ask a bunch of physics 1 questions

From your E&M class.

that's not until next year

-1

Q: Why does electic charge symbols $+$ and $-$ are the same as the mathematical symbols?

Electron is negatively charged and it is shown by $-$ symbol. Protons are positively charged an it is shown by $+$ symbol. Why does that symbols used for specifying 2 different type of charges? That symbols are used in math for subtraction and addition. Is there any math idea behind charge symbo...

electrons charge history notation proton

Am I crazy to think that should have been closed as unclear?

Why did QMechanic use mod powers?

Perhaps the reasoning was that notation questions are off topic, but you'd have to ask @Qmechanic

@0celo7 as opposed to what?

7:40 PM

@DavidZ Well I thought it was a conceptual question: why are electrical charges positive and negative, not something else?

@HDE226868 I don't understand that comment. I suggested not migrating crap, which is what the votes on the meta indicate as well.

@DavidZ Putting a vote in the queue.

@DanielSank Sorry, which one specifically?

@DavidZ @0celo7 If Physics doesn't want it, HSM might take it.

@0celo7 : I added reason for closure in a comment.

@Qmechanic I see.

7:43 PM

@HDE226868 Ah, don't worry about it :-) I think we all agree on this issue.

What's up with this one? Sounds like non-mainstream, just by the title.

0

Q: Could the Big Bang have occurred over a finitie period of time during which the expansion of the Universe occured?

If energy was added over a finite time period and if massive objects could not form during the time over which energy was added to the Universe, then the Universe could have remained homogenous even though it was expanding. This would explain the homogeneity of the microwave background without r...

general-relativity particle-physics standard-model big-bang

This book...holy crap

Now there's a man-hating woman living off of alimony

0

Q: Can the OP comment highlighting be turned up a bit?

This is a minor quibble but since the site's CSS is in review I thought I'd bring it up. I just found out, via this MSE answer, that if you ask a question and then comment on the answers below it, your username gets a slight background shading. I was surprised to hear this since in three years of...

feature-request design

Grr why are they making me read this

geez, there's a lot of rape in this book

@obe I am bored, this book is really boring

What book?

7:56 PM

that would be free advertising

this book is not worth that

8:11 PM

How could I prove that a complex scalar field has a field operator that is like

~ a e^ikx + b e^ikx

Like, simply

I can see how to do it by doing phi = alpha(x) + i beta(x)

But I don't see how to do it naturally

Just from the quantization of the field

Like what step is different from the scalar case

@Slereah for the love of god use TeX

2

NEVER

φ(x) = α(x) + iβ(x)

so what

$$\varphi(x)=\alpha(x)+i\beta(x)$$

treat each field as a scalar and your field operator is then the linear combination of the two scalar parts

8:14 PM

I can center mine.

>typing varphi

user image

I wish latex had full unicode support

I would love to put in weird characters

Google is making a font to support all of unicode, which is nice

@Slereah I'm not even sure what your question is

If Weinberg taught me one thing, it's how to quantize a scalar field

Well all demonstrations in QFT books are just

Real scalar field

And when it comes to doing the complex one, they just write the solution directly

I am not quite sure how to show that elegantly

because it's the sum of two real fields!!

8:18 PM

Well yes

$\phi=\phi_1+\mathrm{i}\phi_2$

As said I can see it if I decompose it thusly

each $\phi_i$ obeys the EoM

But it feels a bit crass

you're a bit crass

I'll check my sources

8:21 PM

Then again, I suppose that it is also true for the fields directly

Since the EoM are like []phi = 0 and []phi* = 0

(SAY NO TO LATEX)

@Slereah exactly

I don't see the problem tbh

But then I guess the thing is that even in the real case, the solution has two operators that is shown to be the same by the realness

b/c of the hermitianess

But they just never mention that bit

They jump straight to it

and you need two sets of annihilation /creation operators because the field is not hermitian

Zee mentions that explicitly

Oh neat

Let's see if I have it in my PDF folder of totally legal textbooks

I have it on my shelf of no kidding legal textbooks

8:24 PM

Well I have a giant pile of real textbooks, but I'm not made of money

Looking at the folder, I get a large feeling of why we just refer to textbooks by authors

Quantum field theory, J. Norbury

Quantum field theory, L. Brown

if I say Weinberg you have 6 to choose from

Quantum field theory, R. Clarkson

Ah, there's Zee

Good old Zee

do you have 1st or 2nd ed?

I assume he discovered the Zee...man effect?

Because he's a man

2nd ed I found it in sect. 1.8

under "complex scalar field"

8:25 PM

It does not say

Let's check

@Slereah no

well look for the chapter titled "canonical bullshit" or whatever

The exercize?

what

do you have the first or second

I can only find an exercize talking about it

It does not say

I assume first

ok

I can scan my second with my phone

gimme a moment

8:29 PM

It's on gen lib

let's check

so do you need the picture or not

nah I'm good

I am buying it legally as we speak

@Slereah Did you check Weinberg? I'm sure he uses cluster decomposition or some bullshit to explain it.

Let's check

I have it fo' real, too

I'm not too fond of Weinberg because he takes 200 pages to get to Klein Gordon

By that point I am already dead

Zee is downloaded, woo

Hm, it doesn't go into details too much

I think it's a thing where I'll have to redo the SHO by hand to reall y get it

you need to explain what your problem is

What is confusing

8:38 PM

Well I don't get where the operators come from, exactly

In the real case as well?

Read Wald QFTCSBHT for that

Well I know it is by analogy with the SHO and all

But I don't see the step where you go "Oh by the way it is hermitian"

So I think I need to go back through the SHO proof

huh? if you dagger the hermitian expansion you find it's hermitian

Zee's book is terrible---he doesn't do anything difficult in there, I think

if you dagger the nonhermitian one you find it's nonhermitian

8:41 PM

Oh wait

I think I get it

It's just a Fourier expansion thing, sort of

yes

$\sum c_n e^{ik_nx} also ocelot smells$

you're shit at TeX :D

Except if real then n and -n are the same or some shit

@0celo7 what do you mean, putting a vote in the queue? Like the review queues? Those are for posts, not votes

8:42 PM

I don't have the chat tex thing

@DavidZ I mean being 1/5 instead of coming down with mod power.

@Slereah try xelatex or lualatex - less stability but you can use arbitrary Unicode chars, in principle

@Slereah fix the curly brackets

@0celo7 Oh, you mean casting a nonbinding close vote. We don't have the capability to do that. All mod votes are automatically binding.

It is fixed

8:44 PM

@DavidZ I hate this.

@DavidZ Hmm

@Danu don't we all

There've been a few requests on Mother Meta about having non-binding mod reviews, no?

Oh yes, for a very long time

0

Q: Could the Big Bang have occurred over a finitie period of time during which the expansion of the Universe occured?

If energy was added over a finite time period and if massive objects could not form during the time over which energy was added to the Universe, then the Universe could have remained homogenous even though it was expanding. This would explain the homogeneity of the microwave background without r...

general-relativity particle-physics standard-model big-bang

@HDE226868 Did you read all that?

8:47 PM

@0celo7 Not all of it.

@HDE226868 Let's say I have no desire to read any of it. Is it still "ethical" to VTC based on your assessment?

@0celo7 Ethically, I'd say it's a grey area, but I would lean towards reading it all before voting to close.

I was interested up until

> If not, then I believe that the following discussion provides a better explanation of the generation and evolution of the Universe.

Not that I ever thought it had merit.

But it deserves a fair read.

haha this guy comes up with physics questions from Angels and Demons

"How did the laws of the universe conspire to make such a terrible book"

It was not bad

8:52 PM

@HDE226868 I read up until the 2nd paragraph

During one class we saw the LHC bit of that movie

What does "big bang didn't occur instantaneously" even mean

Because of reasons, probably

A summary of the things that are wrong there: He takes the balloon analogy too far in a few different ways, states that the universe is contracting, and says that dark energy and dark matter are nonsense.

What if they are and the cosmologists just want more funding?

And all the deniers get shunned and/or die tragically

8:54 PM

If they are so ruthless, why do they still get paid so poorly

They don't want to draw too much attention

And they are probably not well mentally

@KyleKanos The second paragraph was where I decided to vtc.

9:07 PM

@obe Got it working?

9:43 PM

@alarge No.

@alarge You should ask ACM that question.

Although considering he has not exclaimed from pure joy, I take it his code is still broken.

user54412

Would now be an inappropriate time to mention that MY. CODE. WORKS!!!

@0celo7 I've given up, I think. Deconfinement is a lie.

@ChrisWhite Good for you :)

user54412

And it only took 2 years...

@ACuriousMind You're a good sport.

@ChrisWhite PhD when?

user54412

9:49 PM

@0celo7 My program ends this coming spring or thereabouts, so either I get a PhD then or I leave empty-handed.

You should postdoc at ORNL

Oh man little Mayor is going to get his ass beat...

user54412

I've looked at what projects get allocations on Titan and eventually Summit -- molecular dynamics, plasma, more molecular dynamics, core-collapse supernovae

user54412

There's a sense in the black hole accretion field that supernova people always get whatever time they're willing to give for astrophysics.

@0celo7 Look at this classical mechanics book.

@ACuriousMind I thought your result was contrary to the canonical result, not deconfinement itself?

@obe Interesting, but ain't nobody got time fo that

9:57 PM

@0celo7 The canonical result is seeing a phase transition (the Polyakov loop jumping from zero to non-zero) which is the phase transition between the confining and a deconfining phase for two static quarks.

My loop stays zero, constantly.

@ACuriousMind that's dumb

How long is the code?

Not long: 400 lines

So you printed it out and followed along with a pencil?

Idk how this even works

And it could be 100 lines shorter if I had chosen a somewhat more intelligent way of storing the links

user54412

I kinda want to see this code now

10:00 PM

tl;dr on what this even does

@ChrisWhite dropbox.com/s/76hr06d2avb7b3i/Polyakov.c?dl=0

Is a Polyakov loop different than a Wilson loop?

lol, that's harder than HE

@0celo7 Depends on who you ask ;) In my terminology, a Wilson loop is a loop that does not wrap around the Euclidean time direction, while a Polyakov loop does

@ACuriousMind I have the faintest idea of what you're talking about. QCD is really not my thing.

@0celo7 That's...not how it works, but I have fed test cases to every function to see if it does what I think it does, and they came out right.

I am beginning to think that it is not the code that's wrong, but something in my approach in general

10:04 PM

@ACuriousMind the only programming I've done was simple enough that I could follow along with a calculator

like numerical integration

user54412

@ACuriousMind I know that feeling all too well.

@ACuriousMind Perhaps you have disproven quantum mechanics.

@0celo7 You'd like that, wouldn't you? :P

Jesus Christ if there's teenage sex in this book...I'll throw a fit.

@0celo7 What are you reading?

10:06 PM

@ACuriousMind Required reading for all freshmen.

@ChrisWhite And how often was it the code vs. you that was wrong?

I won't name the title. It's not worthy of advertisement.

Just know it's cruel to force us to read this.

@ACuriousMind I wonder what my nuclear physics classes will look like without quantum mechanics.

@ACuriousMind I don't get this star.

user54412

@ACuriousMind In the end usually the code. But until literally a few minutes ago I still had lingering doubts about my entire thesis approach.

@0celo7 Me neither

@ChrisWhite How do you know it works now?

"works" as in reproduces reality

user54412

10:10 PM

@0celo7 Comparison to a tried-and-true method on a problem that exercises all the physics we can throw at it.

@obe Still trying to get it to work?

@alarge I'm still trying to learn openCL and c++ in general.

@obe Well OpenCL is quite different from C++.

@alarge If you have time you can teach me how to get started with openCL, at least installing it properly.

for Intel.

I actually just installed all the prerequisites for openCL onto my shitty laptop (integrated graphics) earlier this year.

10:13 PM

Can you tell me what to install?

Please.

I use Linux, so that's probably not very useful for you.

I installed the opencl drivers.

and libraries.

Though I can't run demo code.

Why can't you?

Perhaps I'm being dumb.

I downloaded the last one here

@ChrisWhite Huh?

10:15 PM

It's not for intel, though I only wanted the VC++ project in the folder.

If there's something that does what you're trying to do, how can you get a PhD?

@obe I suggest you first try to get a hello world to compile or something similar to make sure your build chain is properly set up.

@alarge Will do.

@0celo7 do the same exact thing but use a bunch of unnecessary and useless pure math to recast it in more complicated terms

@FenderLesPaul #rekt @ChrisWhite :P

10:19 PM

like this paper I saw once called "Hopf Algebras in Particle Physics"

it made me cringe so hard

user54412

@0celo7 All the other GRMHD codes out there use needlessly diffusive Riemann solvers. We have those, but also better ones. So I should get the same answers, only with better shock capturing and such.

I once saw this book called "Quantum Mechanics (totally not a cult)"

it's totally a cult

@ChrisWhite shock capturing?

Riemann solvers?

such?

@ChrisWhite I understood some of that, maybe

@FenderLesPaul I think I know what GR is

Maybe MHD on a good day

You know nothing, ~~Jon Snow~~ @0celo7

user54412

10:22 PM

Didn't you learn about Godunov methods for fluid dynamics on your mother's knee?

I skipped that chapter

@ChrisWhite there were definitely fluids involved

@ACuriousMind that reference is lost on me because I don't have HBO

@ChrisWhite Ok serious question now: how boring can life at Caltech get outside of academics if you don't want to drive to LA all the time? I have to start thinking about what grad schools to apply to soon and I don't want to make the same mistake I made in high school of ignoring aspects of the school outside of academics.

Hi all, hey @ChrisWhite in particular! :D

10:29 PM

Hai

Hi pals

He has been busy I guess.

@0celo7 Have you no internet?

@Danu I don't have HBO Go either.

@FenderLesPaul I agree that this is an important point!

@0celo7 So naive :P

10:30 PM

@Danu I know exactly what you meant.

@0celo7 A'ight

Aight indeed

@DanielSank This is an interesting question (also relevant on "my own" SE site)

@FenderLesPaul You figure out 8.1.1?

no :(

10:33 PM

@ACuriousMind You should explain 8.1.1 to us.

@ACuriousMind yes plz

will provide pastries in return

user54412

@FenderLesPaul Haha. Ithaca not the most active and pleasant place in the world?

Will provide vidya stream in return

@ChrisWhite I have to climb mount doom every day to get to classes I'm surprised I haven't already died

There's a mall within driving distance but apart from that it's basically Shutter Island

Time for some gaming

10:35 PM

@Danu Whatcha playing?

^^

Err... Whatever I have...

@Danu Lucky, I still have 20 pages to go

Probably CoD: MW2 lol

user54412

@FenderLesPaul As for Caltech, my experience is somewhat limited since undergrad and grad school are possibly quite different. But I had lots of fun socially -- it is a very small campus and even off-campus housing is a 10 minute walk at most (on level ground :P).

10:36 PM

I stopped gaming a long time ago...

@Danu People still play that?

@0celo7 Yeah, and I'm still very good at it :)

PC?

(so it's still fun!)

Yea

On Xbox it's completely hacked to shit.

10:36 PM

There are a large number of hackers on PC too

Like... one in every 8 or so lobbies.

It's the only game I've got though, so yeah...

@ChrisWhite I see, thanks I appreciate it! I visited Pasadena once and they had a lot of cool restaurants but it didn't seem like there was much else but the Caltech campus was really pretty.

@ChrisWhite Sounds like Princeton :P

user54412

We didn't often go to LA, and even less often to the beach, mostly because we were too busy. For clubs some people drove to Hollywood, but I didn't often go there either.

yesterday, by ACuriousMind

lol, no idea what's going on there

user54412

Pasadena has way more stuff than Princeton, for the record.

10:38 PM

It was actually David Nichols, who's a post-doc here, that suggested I apply to Caltech for classical GR related stuff

@ACuriousMind Pleeeeeeease

@ACuriousMind missed something, wondering what language its in?

@vzn C

@ChrisWhite I really hated that place, for the month I spent there. Burrito dinner again?! sigh :P

user54412

@FenderLesPaul Pasadena also has lots of nearby mountains for hiking, if you ever find yourself missing that. It's a nice combination, actually -- everything's flat where it should be flat.

10:39 PM

@ACuriousMind does it call a library?

@Danu I seem to remember you telling us that you played Bastion?

@ChrisWhite Ah ok; yeah I wasn't really planning on going to LA too often if I did get into Caltech because I'm not much of a big city person. I do love mountain areas though so that is definitely one thing Pasadena has going for it

@vzn Yeah, gsl for the random number generators

@ACuriousMind so is it like a lot of numerical code mainly? what kind?

@ACuriousMind Yes, yes I did. But I meant online games. I don't feel like playing a single player game right now.

10:40 PM

But easily the best part would be I can longboard without fearing for my life

@FenderLesPaul why would you fear for your life?

user54412

^ I'm guessing the hills that lead to 100-foot drops off cliffs around Ithaca.

@vzn Ithaca has a lot of really steep hills and that lead to even steeper hills and I'm not nearly good enough at longboarding to go downhill around here without holding on to dear life

@vzn Basically, it's just numerical integration by Monte-Carlo method

@FenderLesPaul longboarding = surfing?

10:42 PM

If you want to fear for your life go to Compton.

user54412

@Danu btw why me in particular?

@vzn lol yes he surfs on steep hills

@vzn it's kind of like skateboarding

user54412

^ but more for transportation than tricks is my understanding

but you don't really go for tricks you mostly cruise or try to go downhill-it's easier to balance than a skareboard

10:43 PM

@FenderLesPaul oh ok. there is a type of surfing on "longboards". saw that skateboarding stuff in a movie lately, cool scenes. let me think which one...

@ChrisWhite yeah exactly

@vzn oh I see; yeah I don't know anything about surfing

ah yeah looked it up it was ben stiller in "secret life of walter mitty".

UCSB has a pretty sweet campus too

It looks like a beach resort

except for the ugly buildings

user54412

Yeah -- I spent a month or two at KITP there. I couldn't believe it was actually next to the beach.

@ACuriousMind ah might have done something like that once for exercise. try testing your monte carlo integrator with some other less complex function. did you write the monte carlo integration part?

10:48 PM

@ChrisWhite is KITP as magical as it seems?

@vzn Ah, that's a bit tricky because it's an integral over a matrix group, the function I am evaluating is actually quite simple in that context. Yes I did write the MC part (twice, actally, once with the algorithm I'm supposed to use and once with the Metropolis algorithm to see whether I butchered the algorithm, but both methods yield the same within error margins)

if you go there, ask Zee how to do that once exercise with the anyon thingie

he'll know what that means

@ChrisWhite Cause I don't see you around much

+ you're cool :-)

user54412

@FenderLesPaul In terms of location, definitely. The idea itself is weird (in a good way) -- always hosting week-to-3-month intensive programs.

10:52 PM

@0celo7 Will do!

user54412

@ACuriousMind What are reasonable inputs for your code?

@ChrisWhite where you there for a specific program?

@ChrisWhite The beta somewhere between 1 and 5, the grid can start at 2 and go up to whatever the machine can handle (but e.g. 10 is already "large" in this context), and the MC method should sweep at least 100, but better >1000 times.

user54412

@FenderLesPaul Yes, star formation. At the same time there was a program on wave phenomena and another on baryogenesis.

user54412

@ACuriousMind Ok. And what are the numbers reported in the output?

10:59 PM

@ChrisWhite Man that sounds sweet.

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