The h Bar

user54412

01:54

500 Late Answers to be reviewed. I review 20 of them and am told to come back the next day. The next day the queue has been cleared. :(

user54412

After 3 years on this site, I have 30 Late Answer reviews. At this rate I'll get the Steward badge in... 97 years.

3

Rigor

03:09

@0celo7 perhaps if he wasn't so insistent with "The Evidence" that wouldn't happen as much.

Not to mention the lack of equations.

DanielSank

06:49

@ChrisWhite How the hell did the queue get so long so fast anyway?

ph

John Duffield

07:17

@0celo7 : only I don't. And nor do I get the abusive little troll label either. Because I don't hang around sneering at the people who ask questions. I answer them, with robust references.

@Rigor : user Rigor, member for 3 years 9 months, reputation 103. This user has not answered any questions.

skill patrol

07:42

Lashing out doesn't help the cause Sir.

3

Remember you said you are one of the "good guys."

I've been thinking about your A level Physics statistic over the past 20 years; and it appears that Internet literacy has come at the cost of interest in Science and maths at school @JohnDuffield

0celo7

11:20

@JohnDuffield you're not abusive or little, the third one is spot on though :^)

I just had a nightmare that HE did not define the tangent space rigorously

skill patrol

11:32

Do you think Internet literacy has come at the cost of interest in Science and maths at school? @0celo7

0celo7

No clue

Not really sure what that even means

skill patrol

Did the boom in Internet activity over the last 20 years contribute to the decline in interest in Science and math at school?

ACuriousMind

11:53

I don't see any reason why the internet should be responsible for a "decreasing interest in science and math". I'm not even sure the interest has decreased (falling scores don't mean falling interest).

skill patrol

UK physics A-levels were down 57% in 20 years.

0celo7

Down?

As in the number of tests taken?

@ACuriousMind There goes your theory.

What about other countries?

UK might have other stuff that contributes.

2

Q: Yang and Mills' (and others') justification for local gauge invariance

In most physics textbooks, local gauge invariance is simply postulated---you start with a global symmetry, e.g. the global phase, then allow it to depend on the spacetime point, make the necessary adjustments to the derivative (i.e. introduce the gauge field) in order to preserve the invariance, ...

@ACuriousMind

@dmckee what do you mean by "sudden phase transitions" here?

ACuriousMind

@0celo7 Meh, not a particularly interesting question, unless I misunderstood something.

0celo7

Your answer is not very interesting

ACuriousMind

@0celo7 I don't think there's more to say. :P

0celo7

12:06

I don't get the first quote

We do fix neutrons and protons

What are they trying to say

AngusTheMan

Does anyone have a decent source for learning that absolute FUNDAMENTALS of C ? Literally needs to be more basic that the "for dummies" book, shamefully.

0celo7

$c=1$

that's all you need

ACuriousMind

@0celo7 The quotes all seem a bit muddled to me because they act as if the gauge transformations didn't include the global ones

0celo7

aren't the global ones trivial

ACuriousMind

As for neutrons and protons, they might hail from a time where we speculated that there might be an exact $\mathrm{SU}(2)$ symmetry relating them.

@0celo7 Depends on what you mean by trivial

0celo7

12:09

but it's not exact because mass?

@ACuriousMind you don't need the mechanisms of gauge cov derivatives

ACuriousMind

Yep

@0celo7 Indeed, the global transformations leave the gauge field unchanged

But they're still there

So if a global symmetry meant "action at a distance", that would still be there

Also, there are undoubtedly global, but not local symmetries, like...the Lorentz group?

0celo7

the global ones are just local ones where the parameters are constant, right?

ACuriousMind

@0celo7 Yes.

0celo7

@ACuriousMind er, Lorentz is a local symmetry in GR

ACuriousMind

@0celo7 But not in usual QFT

skill patrol

12:11

@AngusTheMan have you read this?

ACuriousMind

And that's what they're talking about

0celo7

are not all global symmetries also local

or is a local symmetry a symmetry that is not global

AngusTheMan

@skillpatrol A general relativity book?

skill patrol

Both

SR & GR

as he wanted them taught

ACuriousMind

@0celo7 Huh? Local transformations are allowed to vary in spacetime, global ones are not. So, every global transformation is trivially a local one, but a theory which is symmetric under the global transformations need not be invariant under local ones.

@AngusTheMan Is "FUNDAMENTALS of C" a roundabout way of asking for a book on special relativity?

AngusTheMan

12:14

@skillpatrol I'm not sure what you mean, I am after learning about C.

ACuriousMind

Ohhhh

You're asking about the programming language?

AngusTheMan

ah forgive me guys.... I mean the programming language

ACuriousMind

lol

AngusTheMan

haha I was like ... wut!!

skill patrol

:D

The Whiteboard

General Discussion for softwareengineering.stackexchange.com P...

AngusTheMan

12:17

@skillpatrol Thanks :)

skill patrol

np pal

Slereah

Hey

A global symmetry needs not be local, no

free scalar fields have global U(1) symmetry

but not local

John Duffield

12:42

@skillpatrol : I don't think it has actually. IMHO the internet is not to blame for the "dumbing down", and instead counters it. But not enough. It isn't easy to counter popscience lies-to-children garbage that's all over the media.

skill patrol

@JohnDuffield But popsci has become more available with the Internet, no?

John Duffield

@0celo7 : I object to this dishonest abuse : "It's interesting how JD gets the crackpot label everywhere he goes." Can we have a moderator please?

Slereah

It is certainly interesting

also apparently ignoring a fellow on the chat only lasts for so long :p

skill patrol

@JohnDuffield come on, don't be so sensitive :-)

flagging isn't going to change people's opinion.

2

@JohnDuffield use ignore

John Duffield

I can't use ignore to stop some nutjob quack telling porkies about me.

skill patrol

12:51

why not?

this is not a popularity contest

John Duffield

@skillpatrol : I don't think popscience has become more available with the internet. Instead I think there's been an increase in the number of "celebrity physicists" peddling popscience in magazine like New Scientist and on the Discovery Channel.

Somebody said health and safety has contributed to the issue too. Experiments are tame, there's less excitement.

ACuriousMind

@Jim! Long time, no see. How are you?

skill patrol

@JohnDuffield yes, the magazine industry has been transformed by the Internet

TV too

copy right laws are becoming ridiculous

A U.S. federal judge rules that the copyright to "Happy Birthday to You", claimed by Warner/Chappell Music, is invalid.

Slereah

it's on the lyrics though

Not sure what's the status of the music

John Duffield

@skillpatrol : I don't think TV or magazines have been "transformed" by the internet. They've been affected, but not radically. You can't blame the internet for people not being interested in the science and technology that makes the world a better place.

skill patrol

13:01

the Internet is not all good

Slereah

is it not

bad.horse

Jim

@ACuriousMind Good

Sorry I haven't been around much. I really miss you guys

Slereah

Oh Jim

We love you too

Jim

::blush::

skill patrol

:O

Jim?

is that really you??

:D

Jim

13:14

No

I'm an illusion

Slereah

So @Jim, u r a cosmologist

What is universe

Jim

Universe is that which contains all that exists

Slereah

what is existence

Jim

a state of being

skill patrol

Phil 101

Jim

13:17

::sigh:: I miss these random conversations.

Slereah

Hey one thing I was wondering about cosmology

Is the inflation period associated with symmetry breaking because the false vacuums are lambda terms

I seem to recall something to that effect

Jim

Are you asking if the inflaton is a goldstone boson?

Slereah

I do not believe so!

I am no inflation expert, I'm afraid

Also isn't the inflaton like

A f(R) thing

Jim

no

Slereah

Does it occurs in basic GR?

Jim

13:25

yes. Most inflation theory uses basic GR

Slereah

Hm

Thought the inflaton was part of the scalar-tensor thing

I may be thinking of dilaton, perhaps

Jim

the scalar-tensor thing is also a part of basic GR

Slereah

Whaaat

Where does the scalar field enter it

Jim

the stress-energy-momentum tensor

Slereah

Probably should read up on it I suppose

So many things to read ;w;

Jim

13:33

f(R) literally means you are adding some function of the Ricci scalar to the EFEs

it replaces the need for dark energy, etc.

Slereah

Oh wait I may be thinking of another thing

What's the name of the theory where G is a function

Some action $f(\phi) R$

Jim

I don't know. I've never come across it

Slereah

Might just be "scalar tensor theory"

Jim

that would be the most ambiguous name for a theory ever

every theory has scalars and tensors

Slereah

Then don't look at the old names for the weak interaction theory :p

Brans–Dicke theory

In theoretical physics, the Brans–Dicke theory of gravitation (sometimes called the Jordan–Brans–Dicke theory) is a theoretical framework to explain gravitation. It is a competitor of Einstein's theory of general relativity. It is an example of a scalar-tensor theory, a gravitational theory in which the gravitational interaction is mediated by a scalar field as well as the tensor field of general relativity. The gravitational constant G is not presumed to be constant but instead 1/G is replaced by a scalar field which can vary from place to place and with time. The theory was developed in 1961...

That's the one

Jim

13:37

Ohhhhh! Brans-Dicke! Yes, I've heard of it. It's a very useful educational tool

0celo7

Freire (diff eq) made the first exam too easy

10 As

Jim

how many students?

0celo7

21

Jim

could be worse

0celo7

says it was his highest rate of As in an undergrad class

got a perfect score though

Jim

13:38

Be proud of yourself and your peers

skill patrol

Chrome users may find this handy for MathJax.

0celo7

@Jim How're things?

You've been absent lately.

How about a "scalar tensor spinor twistor theory"

skill patrol

Hi @Richard

Richard

@skillpatrol - Urgh. Flagfest

Slereah

What are spin 3/2 objects called, if anything

Richard

13:43

I'll let someone else deal with this

Peace out

Slereah

Rarita Schwinger equation stuff

0celo7

Rarita-Schwingors

ACuriousMind

@Slereah I believe they're called "useless" :P

0celo7

rekt

Um

Slereah

Schwingors

0celo7

13:44

@ACuriousMind

Do you even gravitino

Slereah

Let's make a petition to name them schwingors

2

Jim

@0celo7 That's because I don't have a job

Slereah

There's also pinors and sinors

Jim

No job = No physics.SE for me

0celo7

My anecdotal experience of physicists getting jobs is pretty grim

ACuriousMind

13:45

@Slereah Must sinors repent?

0celo7

@ACuriousMind smh

Jim

@0celo7 don't have to say that again

ACuriousMind

@0celo7 ?

Jim

.... because you wrote it and I can read it as many times as I want

0celo7

@ACuriousMind Bad pun

Slereah

13:46

@ACuriousMind : Yes

arxiv.org/abs/gr-qc/9504048

0celo7

@Jim sorry

lololo

Slereah

(sinors are a variety of pinors)

ACuriousMind

@Slereah lol

Jim

@Slereah sinors go to hell

skill patrol

@Slereah are you advertising JD's avatar :P

0celo7

13:48

@ACuriousMind ignore that

twas a misunderstanding

Slereah

Basically pinors are elements that the cover of $O(n,p)$ act upon

Instead of $SO(n,p)$

The joke is that O is SO without S

So pinors are spinors without s

dohoho

0celo7

I don't read "spinors" as "spinners" but as "speenoars"

I'm gonna fuck that up one day in front of a prof and get shit on

Slereah

(Sinors are for $SO(n,p)$ instead of $SO^+(n,p)$)

0celo7

spinors suck

why did Dirac have to invent them

Slereah

He didn't

that was all Cartan!

Jim

13:50

@0celo7 speenoars? with a hard i? I read it as spinoars

0celo7

fine, Cartan

@Jim er

Slereah

Brent Spinor, of Star Trek fame

0celo7

yeah no hard i

I do that when I think in a British accent

yes, I think in a British accent some times

Jim

@0celo7 Naturally. That's not weird or anything

0celo7

interestingly, I never think in a German accent

skill patrol

13:52

why?

0celo7

dunno

that's why it's interesting

skill patrol

being able to think in both accents is fun

0celo7

$\frac{a}{b}$

hmm

this extension does what exactly

it does not parse while I'm typing

$\int\omega$

lame

disabled

skill patrol

:(

Having the "MathJax" button beside "send" is handy.

Shing

should I start asking a new question, or change the question to quite a large content?

http://physics.stackexchange.com/questions/210078/how-energy-of-a-photon-or-em-wave-has-something-to-do-with-frequency
<----- the "edited" part

0celo7

14:00

did not see that button

$\int$

what does it do

@skillpatrol

skill patrol

click on it

MathJax
Interval:
5000

UpdateDisable
OkCancel

0celo7

I did

what does it do!?

skill patrol

allows you to adjust the milliseconds between refresh and update etc.

I think.

0celo7

who cares?

the render mathjax bookmark works just fine

@Slereah See Weinberg G&C

he has multiple sections on it

@Jim why is it so useful

Slereah

Brans Dicke more like Brans Dick

0celo7

14:15

jesus

what is wrong with you

Jim

@0celo7 It helps introduce more complicated topics in cosmological perturbation theory, non-gaussianity, etc. It's a good toy model to get you accustomed to tools and ideas before starting the really advanced cosmology

0celo7

non-gaussianity?

wtf I don't know anything

Jim

the CMB has a measure of non-gaussianity. That measure tells us quite a bit about the universe

Slereah

The temperature variation thing?

Jim

sort of but no

it deals with the power spectrum, but it's got a lot more complicated math than that

Slereah

14:20

Is it the multipolar moment thing

Jim

no. That isn't it. All of those things are fairly gaussian. The non-gaussianity is small and occurs mainly in higher orders than the 3-point correlation. Actually, it mathematically can't occur in lower orders

But without my notes, I'd never be able to explain it well

Slereah

Oh well

0celo7

damn cosmologists

tell us they know the secrets of the universe but can't elaborate without lecture notes

Jim

Or for a price

Slereah

gives Jim some Cosmo Snacks

Jim

14:32

Rosmo Racks? Roh Boy!

0celo7

::senses reference::

Jim

scooby-doo, I assume

Slereah

yes

I believe it is mostly moon pies and tang

have you done pre-big bang cosmological models in cosmoschool

I am curious to know more about the fractal model that solved Olber's paradox

Jim

Depends how you define the big bang

0celo7

big bang is popsci gabage

Jim

14:34

But I never touched a fractal model, as far as I know

18

Q: Is the Big Bang defined as before or after Inflation?

Is the Big Bang defined as before or after Inflation? Seems like a simple enough question to answer right? And if just yesterday I were to encounter this, I'd have given a definite answer. But I've been doing some reading while writing up my thesis and I'm finding conflicting definitions of the B...

cosmology terminology big-bang cosmological-inflation

0celo7

it's still popsci garbage :^)

peddled by the likes of Hawking and Penrose

Jim

Well, that is who normally peddles such stuff

Slereah

Basically it was a pre-GR model that solved the black night problem by saying that star distribution followed a fractal pattern

Not sure how advanced it got

0celo7

black night?

Slereah

Olber's paradox

0celo7

14:37

which is

someone pls help me buy music

Slereah

If the universe is infinite and eternal, why is the night black

Jim

@Slereah then no, I never touched pre-GR stuff. I went straight to the post GR stuff because that's what works best

Slereah

Well you could have had like

0celo7

@Slereah because observable universe?

Slereah

A science history class

@0celo7 : Well back then the universe was assumed to be eternal

Jim

14:38

science history? Nope. I didn't take a physics undergrad

Slereah

So the observable universe was all the universe :p

Jim

All my physics knowledge is from 3 years of studying

not enough time for classical mechanics, let alone science history

Slereah

Who needs classical mechanics for things moving

Jim

@0celo7 It's supposed to be a non-expanding universe. The Hubble horizon would be infinite

0celo7

people who actually effect GDP

Slereah

14:40

Like Donald Trump

0celo7

why are we bringing the Lord Protector into this

Jim

Oliver Cromwell?

0celo7

DJT you Brit

Jim

What's the J stand for?

0celo7

his middle name

Jim

14:41

that starts with h

0celo7

John

what

this is going to be some stupid joke

Jim

For the record, Who's on first, What's on second, and I Don't Know is on third

skill patrol

his starts with h

Slereah

Slappy Squirrel

►

0celo7

@skillpatrol yup, stupid

skill patrol

14:45

no, stupid starts with s

Jim

@0celo7 Abbott and Costello would disagree

skill patrol

you're right :-)

0celo7

@Jim then they're stupid

Slereah

Hm

I should read Weinberg fully someday

But goddamn

Even the second chapter stretches out into infinity

Secret

Is the number operator $\hat{N}=\hat{a}^\dagger \hat{a}$ always positive definite

I have this question because I remember operators in QM can be represented by matrices, and in linear algebra, there's something called a Gram matrix (which is important in linear regression calculations) that has the form $A^*A$ ?

Slereah

14:53

@Secret : Yes

Secret

ok

Jim

@0celo7 some call it funny

Slereah

$a \approx x + ip$, $a^\dagger \approx x - ip$

Jim

but stupid works equally well

Slereah

So $N \approx x^2 + p^2$

Jim

14:54

I believe the stupidity is what makes it funny

ACuriousMind

@Secret $\langle \psi \vert N \vert \psi \rangle = \lvert\lvert a \lvert \psi \rangle \rvert\rvert^2$

As a norm, the latter is obviously positive-definite.

Secret

I see
I am so glad I took the linear algebra course last sem, I am seeing more and more links like these between the maths and QM

and today I learnt about a bit of QFT and particle physics at the spring school. Currently I am tidying up my notes

Jim

the spring school? But it's autumn

Slereah

Though beware

$N$ only exists in a free theoryyyy

Spooky interacting QFT noises

0celo7

does that even make sense

why can't I count when there's an interaction

silly physicists

Slereah

14:59

Because then there is no Fock space :O

skill patrol

@Jim not in the southern hemisphere :-)

The Whiteboard

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