The h Bar

obe

12:30 AM

whoah we all logged in at the same time.

0celo7

@obe

problem set

obe

i'm doing it right now.

0celo7

need help

obe

of course.

brb dinner.

I'm writing it in latex btw, because my writing is illegible I realized.

0celo7

12:46 AM

I see

0celo7

12:59 AM

@obe message me on Skype if you need help

if it makes a bing I'll check

David Z

2:04 AM

@Jim seems reasonable to me, at first glance at least

Pretty sure I've seen problems not too different from that in first year classes, even

0celo7

2:57 AM

@ACuriousMind I finally look respectable in this game.

Shing

3:53 AM

hey would anyone be kind enough to explain how dimensional estimates can only be expected to be accurate to an order of magnitude, instead of order of magnitude, say, like 3 or 2?

obe

4:08 AM

@0celo7 here

skill patrol

5:17 AM

@Shing what do you mean by "dimensional estimates"?

Secret

5:36 AM

NbCeID 14
http://www.sciencedaily.com/releases/2015/10/151002082311.htm
Vacuum fluctuations...

Ghost

hello!

Secret

I wish I can touch these cute guys with my bare hands

Ghost

5:51 AM

i am having waaaaay too much fun today

Physics Meta

9:41 AM

0

Q: Make a list of physics meme?

Today I find a physics meme: spherical cow Q: How does a physicist milk a cow? A: Well, first let us consider a spherical cow... With the notorious Schrodinger's cat, I think a list of meme in physics would be fun. What do you think?

discussion

gonenc

11:42 AM

@ACuriousMind weißt du ab wann ich mich für die Übungsgruppen für theo und exppysik 1 anmelden kann?

0celo7

11:53 AM

@gonenc hau ab

gonenc

@0celo7 oi! english only :D

ACuriousMind

@gonenc Usually after the first lecture

gonenc

12:09 PM

@ACuriousMind really? I thought it should be earlier

ACuriousMind

@gonenc Yeah, I'd often have preferred it sooner, too, but the physicists usually wait until after the first lecture. The mathematicians handle this better, generally.

gonenc

@ACuriousMind yeah the groups are already full :D

for maths I mean

ACuriousMind

@gonenc Ah, if they are already full, they will usually ask in the first lecture how many students haven't got a group yet, and add new ones

gonenc

@ACuriousMind I am already in one so there is no problem :D

ACuriousMind

Although I've heard stuff about there being less funding for TAs available this year, so it might be more difficult than usual

gonenc

12:21 PM

@ACuriousMind are the TA's bachelor students or master/phd?

NeuroFuzzy

Good morning!

ACuriousMind

@gonenc Bachelor and master students. PhDs are rare, and usually only occur in the advanced MSc courses as TAs.

@NeuroFuzzy Good afternoon!

gonenc

@ACuriousMind furthermore do you know where inf 228 is? :D

227 is kip but I cant find 228 :D

ACuriousMind

@gonenc 228 is the building directly behind (and connected to) it.

NeuroFuzzy

@ACuriousMind It's 5am here :D

ACuriousMind

12:24 PM

@NeuroFuzzy Well, it's half past 2pm here, so screw your weird timezone! ;D

gonenc

@ACuriousMind indeed :D

@ACuriousMind thanks btw for the info

ACuriousMind

@gonenc No problemo :)

gonenc

@ACuriousMind r going to the kneipentour today?

ACuriousMind

@NeuroFuzzy Why the hell are you awake at 5am, anyway?

0celo7

lots of good reasons for that

ACuriousMind

12:29 PM

@gonenc Yes, I'll be there

gonenc

@ACuriousMind maybe see u there but I don't know if I'll do it again

0celo7

@ACuriousMind let $\phi(x)$ be a free scalar field, how the hell do you show that $(\Box_x+m^2)\langle\phi(x)\phi(y)\rangle=-\mathrm{i}\delta^4(x-y)$

This has been bugging me for ages and now it shows up in obe's problem set

No mode expansion!

@ACuriousMind um aren't those fields not necessarily on shell anyway?

because Zee assumes they are in his proof...he uses a mode expansion, which is only valid on-shell, right?

ACuriousMind

@0celo7 It's a version of the Schwinger-Dyson equation at $J=0$.

0celo7

well I knew that

but the problem says "use only the field equations and the commutation relations"

ACuriousMind

If you don't want to use path integrals, Fourier transform and mode expansion is indeed the way to go

0celo7

12:39 PM

so the fields are on shell

@ACuriousMind no contour integrals either

no path integrals

ACuriousMind

@0celo7 Unless otherwise stated, they are

0celo7

ok...

but

wha

if you write the vev as a path integral, aren't you integrating over all field configs?

ACuriousMind

@0celo7 Yes. So?

0celo7

so the fields are not on shell if you use all fields

ACuriousMind

The expectation values you calculate with the path integral are "on-shell".

0celo7

12:41 PM

@ACuriousMind here is the problem statement i.gyazo.com/ba440d94c6af69a5818c4642e16c6c51.png

no path integrals (hasn't been covered in his class), no contour integrals

ACuriousMind

@0celo7 They are. More specifically, the fields in $\langle \phi(x)\phi(y) \rangle$ are on-shell. That the integration in the path integral is over all field configurations is completely unrelated to that.

0celo7

what

ACuriousMind

@0celo7 So mode expand that thing and commute away! (One can derive the commutation relations for $a,a^\dagger$ from those of $\phi,\pi$)

You need neither path integrals nor contour integrals for that, it's just a tedious calculation

0celo7

But you end up with step functions

I saw that

I don't see how you don't need a contour integral for that

ACuriousMind

@0celo7: You can write $\langle \phi(x)\phi(y) \rangle = \theta(x^0 - y^0) \int \mathrm{d}^3 p \frac{1}{2E_p}\exp(-\mathrm{i}p(x-y)) + \theta(y^0 - x^0) \int \mathrm{d}^3 p \frac{1}{2E_p}\exp(\mathrm{i}p(x-y))$ and apply the differential operator.

0celo7

12:58 PM

I know that

stop saying things I know

but I can't take the derivative :O

not good at calculus

ACuriousMind

@0celo7 Yeah, so that should give $0$ after an ugly calculation :D

0celo7

it should give a delta, no

ACuriousMind

Oops, yes, the delta

0celo7

::cringes::

might as well put LA lecture to good use...

I get a double derivative of the step function

hopefully it cancels

this is horrible

cruel and unusual punishment

ACuriousMind

1:13 PM

You sound like me when I took QFT I :D

0celo7

I see why no book does this

I thought it couldn't be done

no, it's just stpudily long

ACuriousMind

The path integral version is so much nicer

0celo7

there's like 8 terms

and that's just the time derivative

screw this

@ACuriousMind yes

@ACuriousMind how does Weigand do it

ACuriousMind

@0celo7 Contour integral.

0celo7

I think Zee does it both ways?

dunno, his book confuses me

ACuriousMind

1:22 PM

And later on with the path integral.

0celo7

Weinberg uses magic I'm pretty sure

ACuriousMind

It's probably trivial when you apply cluster decomposition

And give everything five indices.

0celo7

I still have no clue what that's about

ACuriousMind

I'm not sure, but I think it is a weird way to state a locality requirement

Why one should state it that way is not clear to me, though

0celo7

prove it

@ACuriousMind got him a Nobel

that's one reason

ACuriousMind

1:25 PM

@0celo7 I think the Nobel was for his work on symmetry breaking and the W- and Z-boson, not the cluster stuff.

0celo7

shhh

there's so many ways of doing QFT

this is nuts :O

just write a book dammit

@ACuriousMind please

think of all the engineers out there who are confused

poor, alone and confused

they need a hero

ACuriousMind

I'm not the hero they need. I'm the hero they deserve.

0celo7

1:41 PM

same thing

Secret

0celo7

just write a book :D

Secret

My attitude on abstract algebra is similar to the attitude when I ask this question here
As long you state the rules, I can work out the whole thing one step at a time

Therefore, you really need something like a word version of the Busy Beaver Function (which is known to be uncomputable) in order to mess up my mind

ACuriousMind

@Secret Why did you post that badly cropped photo instead of the link to the question?

Secret

gah too late

0

Q: Trying to understand the mechanics of the Red queen's country in Through the Looking Glass

An excerpt of the Red Queen Race event in Through the Looking Glass The Queen propped her up against a tree, and said kindly, 'You may rest a little now.' Alice looked round her in great surprise. 'Why, I do believe we've been under this tree the whole time! Everything's just as it was!...

alice-in-wonderland lewis-carroll through-the-looking-glass

ACuriousMind

1:43 PM

@0celo7 One day, I will. Probably.

0celo7

@ACuriousMind HE'S JD

ACuriousMind

Ah, that's the secret.

0celo7

although I think JD just printscreens

Secret

From my experience, the only concepts that don't follow any conceivable rules are:
1. The order of performing an adminstration step
2. Empathy, emotions
3. Romantic love
4. Human corruption in politics and coporates
5. Exeprience itself

These are what I refereed as **nonstructural concepts** and I have a question asked on that some time ago:

http://philosophy.stackexchange.com/questions/26847/what-exactly-is-a-non-analytic-method-of-thinking-any-examples-of-widely-accept

ACuriousMind

@Secret First thing I notice: Why the hell is there a P.S. at the top of the post?!

P.S. means post scriptum, it's something that comes after what you have written.

0celo7

1:49 PM

Should that be A.S.

ante scriptum

ACuriousMind

And you seem to throw a lot of words about just to get to the insight that there are objective and subjective things.

Except you never call them that, but instead talk about "chunks".

Secret

That might be because either I lack of vocabuary (after all I am not a native English speaker) or that I realsie some subjective concepts have some kinds of structure at tleast to that person where he/she can describe clearly to others

@0celo7 I don't know this word exists, let me fix my question with that

0celo7

I don't either

ACuriousMind

@Secret It doesn't exist

0celo7

But PS is inappropriate

@ACuriousMind u wanna fite

ACuriousMind

1:53 PM

It would be the literal analogue to P.S., but it is not used in English (and wasn't in Latin, either)

0celo7

I can make words if I want to

Secret

answers.yahoo.com/question/index?qid=20091105193420AAKkVwO

It exists

0celo7

@ACuriousMind ::teabags::

ACuriousMind

@Secret 1. That's a Yahoo answer. 2. Even that one says it doesn't exist as a phrase.

0celo7

1. Irrelevant 2. It's Yahoo, so it's not definitive

ACuriousMind

1:55 PM

@0celo7 nice :D

Secret

@ACuriousMind

The idea of chunks is that there are key concepts in a field of study that one can use it to describe most of the field. I hae been using this framework for years when I study for exams by condensing lecture notes

One example of a chunk in Electromagnetism is the Maxwell equations, plus the motivations and steps arranged in a logical manner that can prompt me to derive all the electromagneitsm stuff went through in the lecture without much error

A chunk allows one to make power point slides of a field of study by single out the key points that, analogous to how generators in abstract algebra can generate most elements in a set, can be used to derive most of the field of study

This helps me to reduce the amount of stuff I need to memorise

and this is how I tackle biology subjects because the same principle applies there

However, as far my experience (and also chats with my professors in fields from arts to science to business, and also my peers) there seemed to be no obvious structure to the following
1. The order of performing an adminstration step
2. Empathy, emotions
3. Romantic love
4. Human corruption in politics and coporates
5. Exeprience itself

Especially for experience. No two experience are nonunique, as evidenced by the seeing red psychological experiemnt

ACuriousMind

Key concepts are certainly useful for learning, but they are not an epistemologically well-defined concept.

0celo7

this is not a philosophy chat

ACuriousMind

What you can meaningfully talk about are axioms.

0celo7

it is a math and gaming and random life commentary chat

physics sometimes makes a cameo

so stop philosophizing

ACuriousMind

2:04 PM

@Secret One terms the parts of experiences that are essentially incommunicable to other people qualia.

Secret

Nice, looks like I learned a new word to describe what I referred as non chunks

0celo7

::hurts::

ACuriousMind

I recall that abomination. It has been posted here before

And the gall to call that "modern"!

0celo7

Schwartz, Quantum Field Theory and the Standard Model

It's a good QFT book though

Secret

(I am too slow...)
The thing is, I am often said to think and learn like a computer, and that I can handle most structural concepts quickly. People often have a wrong impression I am analytic (because of my habit to classify things), but I am actually disorganised

Having said that, my thinking process is so deeply rooted in structural thinking methods that I felt like the reason why I cannot solve some problems might be because I a using the wrong type of thinking

Therefore that question was a way to query for such type of thinking

---
I had a feeling that trying to understand experience might be harder than unification in physics

While it is known to be hard, it is at least sturctural

ACuriousMind

2:13 PM

@Secret: Pro-tip: Use --- (in a message of its own) as delimiter, the chat will actually make a break then.

Secret

noted

ACuriousMind

Like...you can talk

ACuriousMind

And have this separated

0celo7

what

chat will make a break?

ACuriousMind

Don't you see the white gap between my two messages?

A line break, not a break as in pause.

Secret

2:15 PM

@0celo7 I prefer upper and lower indices, this old convention shwon there is too error prone

0celo7

sure

yeah

it's right there

ACuriousMind

@0celo7 No, not between those two :D

0celo7

oic

ACuriousMind

Between "Like, you can talk" and that.

0celo7

icic

0celo7

2:16 PM

no more philosophy

ACuriousMind

Do you have some kind of bad memories regarding philosophy?

0celo7

no

I need help

I don't know how to read all my stuff

Secret

The answer to that epistemology question suggests me to talk to an art critic.
Now the challenge is how to survive the encounter to learn something without going insane and unable to do physics correctly anymore

(physics coming shortly , in the context of neutrino oscillation)

0celo7

jesus

ACuriousMind

@0celo7 Firmly fix the beginning of the text in your vision. Start moving your field of vision along the letters, combining them into words, and, finally, sentences in your mind while doing so.

@Secret The answer doesn't suggest you talk to an art critic.

0celo7

2:19 PM

too blurry

ACuriousMind

It means to say that your approach to divide art into "chunks" is just not what most people mean when they speak/think of "art".

@0celo7 Well, put your glasses on, then!

Secret

@ACuriousMind
Indeed, I am still trying to learn the thinking of an artist, which might be a hope to get a glimpse of nonstructural thinking styles

0celo7

@ACuriousMind not that kind of blurry

ACuriousMind

@0celo7 What other kind is there?

The blurriness caused by your eyes glossing over because you don't want to read it?

Secret

@ACuriousMind
In the spring school, I and my peers have been introduced briefly about neutrino oscillation. The professors said that the mass eigenstates are in a superposition (and some details I forgot) and because of this as the neutrino propagate in space, the state vectors describing the superposition evolve according to the hamitonian. This causes the superposition of flavor states to change

And then we breifly talked about the seesaw mechanism, which there's a heavier particle that (forgot) that result in the measued mass of the higgs to be lighter than expected (forgot)

0celo7

2:24 PM

@ACuriousMind Partially

Reading QFT is so hard

because I do know a lot of it

but I'm missing some details

so I tend to start skimming

and then I waste a lot of time

Secret

@ACuriousMind I remember there's something called the neutrino mixing angle, but how is that relate to the mass and flavor eigenstates?

ACuriousMind

@Secret The mixing angle is usually used when you have only two types of neutrinos participating, because then the mass matrix is just the rotation matrix associated to that angle. If it is zero, there is no mixing, and the flavor and mass eigenstates are the same. The larger the angle is, the "farther apart" the states are.

@0celo7 Well, that happens.

Secret

I see. So if you have all 3 types of neutrinos participating, you use the mass matrix instead to describe how the states are "distributed" and how the hamitonian evolve the superposition of the mass states as the neutrino propagates?

and that will be described by 3 mixing angles because there are 3 possible pairs of flavort ransformations (e.g. electron to mu, mu to tau, tau to electron)?

ACuriousMind

@Secret Yep. But writing it in terms of the three mixing angles is quite ugly, and usually not done (unless you actually want to calculate something with them, of course)

Secret

I see

What reason is the final neutrino mixing angle (if my memory serves, it is the tau to electron one) took such a long time in history comapred to others to be measured?, or in other words, why is the final mixing angle measured so late

ACuriousMind

2:34 PM

@Secret Probably because the tau is so heavy and thus more difficult to produce, but I'm not versed in the historical and experimental developments.

Secret

ok

Secret

Warning, the next post has pictures (in the form of words)

dmckee

The last neutrino angle nailed down was $\theta_{13}$, and it was hard because it is small. As in $\sin^2\theta_{13} < 0.1$ so doing even a 10% measurement of it required getting 1% precision in a neutrino mixing experiment.

That's simple hard.

But we got it in reactor experiments at the km scale. No tau's involved.

Secret

But why it is small (that is, why is the tau neutrino state "close" to the electron neutrino state?

dmckee

Doing tau neutrinos is hard, too, because of the difficulty of knowing that you've seen one in a many tons detector. That is OPERA's main science goal.

Notice that the mixing angles are subscripted with numbers.

Secret

2:40 PM

so tau neutrinos are rare in general?

dmckee

By convention we compare the mass states, not the flavor states for this purpose.

There is not particular reason to expect large or small value of mixing angle a priori.

But the quark ones are all small, while the neutrino sector has two large and one very small.

Tau neutrinos make an experimental appearance only when you have energies comparable to the tau mass, which lets both fission and fusion sources out.

You need cosmic rays and or particle accelerators.

Secret

Yeah I noticed, I think 1=electron, 2=mu 3=tau?
So it has a small value is basically (as far we understood), just experimental findings and no underlying explanation yet?

Hmm.. there's an interesting asymmetry in the mixing angle in the neutrino sector there, I wonder whether it has any significance...? (P.S. I have not read that lepton sector violation paper yet that you previously posted in the chat)

dmckee

Because of the large mixing angles ($\theta_{12}$ and $\theta_{23}$) there is no close correspondence between the flavor states and mass states the way there is in the quark sector. One of the mass states is about 45% electron, 45% muon and 10% tau.

So, just read these as different classes of bookkeeping and don't think "mass state 1 goes with electron" and the like.

Secret

2:55 PM

For the above mass state, do we expect it to be quite light because of how it is contributed mainly by electron and muon states?

and we know electron and muon are lighter than a tau (roughly by an order of magnitude between two adjacent generations?)

Secret

Chat died again, now I know how 0celo7 and skilpatrol feels

dmckee

It worth saying that the order of the mass states is not known. The normal hierarchy would we 1(lightest), 2, 3(heaviest). But the possibility of the inverted hierarchy (3, 1, 2) is still open. Most people expect normal and the space for inverted is getting steadily whittled down.

ACuriousMind

tumari ---------------aoo le lo john aur horus — Abhi 1 min ago

...*what*?

dmckee

That said, all these masses are very light. They sum to less than 1 eV and we know the heaviest one is at least 1/4 eV.

Beyond that it's mostly guesswork.

0celo7

@ACuriousMind wow you really don't know American culture

Secret

3:08 PM

@dmckee Inverted hierarchy, ah yes, they mentioned about that in class, thanks for reminding

ACuriousMind

@0celo7 You mean that gibberish has meaning to you?

Secret

If that's true it is interesting because it will mean the neutrinos will be the only particles in the standard model to have their mass not correspond to generation numbers

@dmckee Is there an underlying reason why the neutrino sector has two large and one very small angles (because this sounds quite asymmetric), or it is still a work in progress to work out the mechanisms that caused that?

dmckee

@Secret No one knows. As I say, there isn't a strong a priori reason to expect anything. Or at least there isn't one known.

Secret

guess we have to keep searching then...

0celo7

@ACuriousMind yes, it represents the struggle

Secret

3:25 PM

@ACuriousMind @dmckee
In the spring school, I had a chat with a particle physicists on whether the following way to *qualitatively* think about neutrino oscillation is accurate enough, after being recalled about how the hamitonian evolve state vectors of a state (mixed or pure) in time as it changes the distribution of the observables:

*Picture*
Let’s just for simplicity, assume the three mass states (1, 2, 3) “look” black, white and purple respectively.
Now suppose I have a neutrino source, that fires out a neutrino that initially look whitish. As the neutrino propagate freely away from t…

correction:
it might look grey, or dark purple a second later, or greyish purple soem hours later

correction: "mixing" in the end of the paragraph should be "missing"

ACuriousMind

@0celo7 ...what?

0celo7

3:41 PM

Chat won't load on laptop

What's up wit that

Everything else works

works now?

it says "establishing secure connection" on the bottom of the page

@ACuriousMind anything I say now will make me look insane, so I'm not going to say anything

ACuriousMind

@0celo7 I already think you are insane, you have nothing to lose by telling me.

0celo7

I...I thought we were friends

friends don't call friends insane

Huy

damn I missed the K70 RGB feeling

0celo7

try to log into Rockstar Social Club via GTA4

Huy

this is like first time all over again

ACuriousMind

3:48 PM

@Huy Did you make a cup of tea to celebrate? ;)

Huy

no .______.'

I have a glass of water here but out of reach

0celo7

@Huy implying the RGB makes a difference

Huy

so I have to go away from the keyboard to drink it

it's a huuuuge difference !!!!!!!!!!

it's like a whole different keyboard !

:3

0celo7

@Huy are you trying to log in

Huy

no GTA4 doesn't work

get CSGO on the halloween sale

it'll probably be 3$

0celo7

3:49 PM

does it freeze for a bit and then kick you out?

Huy

or something like that

if I try to log in it just gives me the error

0celo7

that's what I mean

yeah it's broken

Huy

and what's your bugfix

ic

0celo7

doesn't work

Huy

yeah just wait until then if you don't want to buy games at full price

I'll practice it until then so I have a chance

0celo7

3:51 PM

BF3 is $20

f that

Huy

lol

0celo7

tfw I have it for Xbox, have Premium, am highest level and have everything unlocked

these SoBs want $20 for the PC version

Huy

EA

0celo7

AMD wants me to update drivers

sigh

Huy

is reddit down?

0celo7

3:52 PM

there are no drivers for my chipset

ACuriousMind

tfw when you go into your bathroom and your window is missing.

0celo7

AMD y u stoopid

Huy

tfw you go into your bathroom and there is no window

0celo7

^^

no one can see me while I'm pooping

stealth poop

hmm, maybe I am insane

Huy

if I leave my bathroom door open I can see the lake through my bedroom's window

while pooping

ACuriousMind

3:53 PM

No, really, we had a window this morning. Now there's just a hole in the wall. There are people renovating the roof, but I was not informed we would be deprived of our window.

Huy

that's sad to hear ACM

0celo7

"I promise the window was there this morning!"

@ACuriousMind time to switch to Linux

Windows is unreliable, not there when you need to poop

ACuriousMind

@0celo7 Aurrrrgh!

0celo7

the hell was that

ACuriousMind

Aug 15 at 20:03, by 0celo7

Can we get a VTC chat option for shitty puns

0celo7

3:55 PM

damn son

I didn't even remember that one

so my book

I need a topic

Huy

wat book

0celo7

I want to write a book

Huy

I already wrote one

0celo7

I don't have any time though

ACuriousMind

@0celo7 Did you just call me son, son?

Huy

3:57 PM

so it would be really redundant

0celo7

of course you did

Huy

yeah over here to graduate high school everyone must do some sort of "project" and I decided I don't want to read books and wiki entries and write a summary so I wrote a book

0celo7

wtf

Huy

some other guy was up many nights to watch the moon closely through a telescope and confirm Kepler or something with it

0celo7

once again, moving further and further left on the bell curve...

ACuriousMind

3:59 PM

@Huy What was the topic of that book?

Huy

@ACuriousMind: a fiction about a kid that's not me

0celo7