The h Bar

All the GR books: HE, Wald, BEE, CB, Zee, Weinberg, Carroll, Schutz, Hartle, MTW, Straumann, Penrose, Visser, Sachs-Wu, Kriele, Ringstrom, O'Neil, Chandrasekhar, Poisson, Stewart, Ludyk, Padmanbadan (can't spell that one), Joshi, Stephani, Einstein

Slereah

You forgot Stephaniiii

0celo7

there's another GR solutions book

Slereah

yeah

I also have a book on like

0celo7

12:06 AM

in the same Cambridge series

Slereah

Scalar fields in GR

0celo7

Does Gourgoulhon count?

I'd say it's at least "related"

Slereah

kinda

ACuriousMind

::sigh::...new day, 19 things in the queue...

Slereah

Tho really Stephani isn't only solutions

Like the first 13 chapters are GR shit

0celo7

12:10 AM

I think that's a good starting list

I'll work on the post.

Slereah

I have plenty of GR children books from when I was a kid

0celo7

Like Schutz?

Slereah

Pop science stuff

I also have this book

amazon.com/How-Teach-Relativity-Your-Dog/dp/0465023312

It's funny because he has a light cone of shame

0celo7

Ha!

We should make a rating of math difficulty

Slereah

Which one will be on top

0celo7

12:15 AM

1-4, from Hartle to BEE

Kobayashi?

Is that a GR book?

diff geo

Oh, would we make that a "related" book?

Slereah

That's gonna be a lot of 'em

0celo7

12:16 AM

Yeah, do we have to list ALL of the geometry books?

Because that would be insane.

Slereah

What about the math books on Lorentzian manifolds

I guess we should include like 2 or 3 diff geo books

Just the most referenced ones

0celo7

I put those that I know of in the list above.

BEE and O'Neil.

Are there any more?

That surface book but that's not really GR.

Slereah

amazon.com/Foundations-Differential-Geometry-Classics-Library/…

I often see that one referenced

I like Poplawski for GR + torsion, although currently it's not a book

Just a book draft

0celo7

I'm probably going to buy that one day

The Asian version is cheap.

@Slereah 4 levels of difficulty:

1: Hartle, Schutz

2: Zee, Weinberg

3: Wald

4: HE, BEE

Slereah

sounds aight

0celo7

12:24 AM

Now where to put stuff like Poisson...

FenderLesPaul

12:44 AM

@0celo7 Well I guess Danu's research interests are closer to mine than anyone else's here

@0celo7 UCSB is closer to LA

@ACuriousMind I have tried that haha but I end up picking a school for non-academic reasons (more personal reasons) which may not be the best mode of thought

ACuriousMind

@FenderLesPaul Well, given that academically both are quite good for you, what else could you possibly go on?

And academic reasons are not everything

FenderLesPaul

It's more like, UCSB is definitely better than Berkeley for my research interests but I'd rather be at Berkeley so I can be close to someone

0celo7

...close to someone?

is there someone else

FenderLesPaul

sorry you had to find out this way

0celo7

the joke's on you

I've cheated on you every day for the past two months

ACuriousMind

12:52 AM

I have seen too many of such relationships break apart to recommend that to anybody. But I'm a jaded cynic in that respect :P

0celo7

@Slereah I'm going to restrict my attention to books I've actually had experience with

"On the Topology and Future Stability of the Universe" seems interesting but I have no clue what it's about

ACuriousMind

...the "clean sticky stuff of their covers" type of experience?

0celo7

also it's in some strange font that burns my eyes, so I'll never read it

@ACuriousMind I'm on my second copy of HE, baby

wtf is with that font

FenderLesPaul

@ACuriousMind oh it's not a relationship

0celo7

awk

FenderLesPaul

12:55 AM

my best friend is going there

0celo7

@FenderLesPaul I've not been cheating on you

FenderLesPaul

@0celo7 it's too late

to apologize

its too laaaaate

brb

ACuriousMind

@FenderLesPaul Ahhhhh, now that's different.

Although I still wouldn't base a decision on that, I guess

0celo7

@ACuriousMind what's the heirarchy of classical GR books

ACuriousMind

How could you possibly expect me to have an answer to that?

0celo7

12:57 AM

Osmosis.

I think MTW is the "king" but it's not a good book

ACuriousMind

My knowledge osmosis skills are great, but they do not extend to books, at all.

0celo7

What non-GR books are useful for GR? Lee, Lee, Steenrod, Kobayashi-Nomizu, Milnor, do Carmo

Lee, Lee

Throw in all the Lee books

Cahill probably.

amazon.com/Mathematical-Physics-Chicago-Lectures/dp/0226288625/…

Seriously? It's category shit.

Anuroop Kuppam

what is this chat room about? Because I have a question regarding rotations on Bloch sphere, can I ask it here?

0celo7

Yep

But be warned: this chat is mostly GR

ACuriousMind

@AnuroopKuppam It's about whatever the people here want to talk about. If you have a question, just ask it, if someone wants to answer it, they will.

@0celo7 It's only "mostly GR" because that's what you yap about all day :P

0celo7

1:08 AM

@ACuriousMind no

it's that French hooligan!

@ACuriousMind have some good music to raise your spirits

Lil Wayne - John (Explicit) ft. Rick Ross

►

I have literally no clue what that song is about

But it's amazing.

If you get in trouble that just mean you fuckin' up.

Wise words.

Anuroop Kuppam

I did however ask the question in physics.stackexchange.com/questions/244586/… , it did not garner much attention, owing to my incompetence in asking a question on stackexchange.

0celo7

@ACuriousMind Americanized German last names are the worst.

Anuroop Kuppam

@0celo7 Trump is better than Drumph, dont you think?

0celo7

What?

Anuroop Kuppam

Donald Trump's ancestors went by the name Drumph, before they arrived in America, so I am told

0celo7

1:19 AM

Ok, so?

Anuroop Kuppam

@0celo7 Drumpf is a German last name, and Trump is the Americanized version of it. I was just suggesting that Trump sounds better than Drumpf.

ACuriousMind

@AnuroopKuppam You can explicitly compute that $\exp(\theta \vec n \cdot \vec \sigma) = I\cos(\theta) + \mathrm{i}(\vec n \cdot \vec \sigma)\sin(\theta)$, showing that since the l.h.s. is the rotation generated by $\vec n \cdot \vec \sigma$, the r.h.s. is so, too.

0celo7

I have never heard of a German called that.

ACuriousMind

One explicitly computes that by expanding in a power series, and using that $\sigma_i^2 = I$.

0celo7

@ACuriousMind which idiot thought of naming a unit of a ring something that's not 1

ACuriousMind

1:25 AM

@0celo7 I don't understand that question.

Anuroop Kuppam

@ACuriousMind let me give it a try.

0celo7

@ACuriousMind $a\in R$ is a unit if there exists $b\in R$ s.t. $ab=1$

ACuriousMind

@0celo7 I know. Are you bugged by a "unit" not being the same as the multiplicative identity?

0celo7

@ACuriousMind Yes

Because we call it a unital ring

ACuriousMind

@0celo7 Well, it's a unital ring because it has units (you can't define units in the absense of the mult. identity)

Anuroop Kuppam

1:29 AM

@ACuriousMind the problem is that I simply cannot apply the LHS to a vector, because the operator matrices are still in the exponent. I have to expand it using the power series and I will arrive at RHS anyway.

ACuriousMind

And when looking at prime factors and such, "units" are a more natural class of "do nothing" objects than the identity.

@AnuroopKuppam You can arrive at the r.h.s. without applying it to any specific vector, see Wikipedia.

And why would that be a "problem", anyway?

Anuroop Kuppam

@ACuriousMind now I have to prove that the LHS is infact a rotation about the axis $\hat{n}$, how do I do that.? I convinced myself that $R_x(\theta)$ is infact a rotation about X by applying it on a vector and checking that it infact is rotated by theta about X, and the same for Y and Z.

0celo7

@ACuriousMind is it nontrivial to prove that if $ua=1$, then $au=1$? (u is a unit)

ACuriousMind

@AnuroopKuppam How do you define a "rotation about $n$"?

@0celo7 It's pretty trivial for someone who's used to algebra, but it is good to work it out yourself.

Anuroop Kuppam

1:48 AM

@ACuriousMind I am not sure but I think one needs to show how the components of a vector change.

ACuriousMind

@AnuroopKuppam Here's a straightofrward way: If you're convinced that $\exp(\theta\sigma_i)$ are rotations about the $i$-th axis, just rotate your coordinate system such that $n$ is aligned with one of the corrdinate axes, so that the case reduces to the one you've already proven.

0celo7

@ACuriousMind Ok, here's my attempt (not homework): Note, I proved for homework that $u$ is never a zero div. Some algebra: $ua=1,aua=a,(au-1)a=0$. Now I wanted to show that $au-1$ is not a zero div, but got stuck. A proof by contradiction failed.

Actually I showed that $u(au-1)=uau-u=u-u=0$, but since $u$ is not a zero div...

Is that correct?

ACuriousMind

Wait a moment...

In a non-commutative ring, you can have that $ab=1$, but $ba\neq 1$.

The thing you're trying to prove is either trivial or false.

and "unit" is usually only use in the commutative context

0celo7

Hmm

Actually what I did is false

I used $au=1$ in my proof that a unit is not a zero div

ACuriousMind

Your ring must be assumed commutative, what is there even to prove? $au=ua$ by definition.

0celo7

1:58 AM

:P

Lemme ask the prof

He said something about it being nontrivial and he didn't want to get into it

ACuriousMind

Just to be clear, what is your exact setting?

I.e. what are $u$ and $a$ elements of?

0celo7

From my notes:

Def. $a\in R$, $R$ a ring, is a unit if $\exists b\in R$ s.t. $ab=ba=1$.

Upon a closer inspection, the textbook requires $R$ to be commutative.

At this point, the prof usually specifics "ring" vs. "commutative ring".

Anuroop Kuppam

@ACuriousMind rotating the entire co-ordinate system, will actually change the angles $\theta$ and $\phi$ of a vector and figuring them is not so easy.

ACuriousMind

2:18 AM

@AnuroopKuppam Well, indeed, any explicit calculation here is not going to be "easy", it's going to get a bit ugly at some point either way. This is one of the computations one does once and then never does again.

Anuroop Kuppam

@ACuriousMind Will give it a try and let you know.

0celo7

2:38 AM

S.W. Hawking and G.F.R. Ellis (1973), *The Large Scale Structure of Space-Time*.

R.M. Wald (1984), *General Relativity*.

J.K. Beem, P.E. Ehrlich, and K.L. Easily (1996), *Global Lorentzian Geometry*.

Y. Choquet-Bruhat (2009), *General Relativity and the Einstein Equations*.

A. Zee (2013), *Einstein Gravity in a Nutshell*.

S. Weinberg (1972), *Gravitation and Cosmology*.

S. Carroll (2004), *Spacetime and Geometry*.

C.W. Misner, K.S. Thorne, and J.A. Wheeler (1973), *Gravitation*.

N. Straumann (2013), *General Relativity*.

@Slereah

That's a little ridiculous :P

It's also crazy how many of those I knew off the top of my head

user54412

4:21 AM

@JohnRennie If it's any consolation that's no more wrong than the other 10 answers on the page. Really I think everyone just missed the simple explanation that the original statement makes sense in some form of non-relativistic QM, so one cannot introduce the speed of light and expect anything good to happen. For some reason this one statement of Cox's gets a lot of flak by people who want to claim he's stupid. It brings out misdirected pedantry more than anything else.

user54412

@FenderLesPaul You know, everyone always says to ignore non-academic issues (short-term significant others, friends, weather, entertainment, etc.), but I think that's just foolish. You're going to spend more time in grad school than any stage of your life so far, and you have every right to aim for something enjoyable.

3

user54412

Sure, there's a danger of overvaluing non-academic stuff. I know Californians who never even considered moving out of state because they don't believe the sun shines anywhere else in the world.

user54412

But appropriate weighting of all factors is necessary to making a fully rational decision.

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

4:58 AM

Well said^

Sidarth

5:58 AM

hey is anybody active?

My professor just told me one of the weirdest things and i can make no sense of it

@ACuriousMind

@ChrisWhite

its about gravitation

@0celo7

He said something about "gravitational waves in a "digital background" "

does that mean anything?

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

6:13 AM

Is he a philosophy professor?

Sidarth

nono......a person who studies GR

a good one as well/....

so....any thoughts?

Danu

7:50 AM

@FenderLesPaul So, can you make a case for both choices?

Danu

8:04 AM

@Sidarth You'll need to expand on that.

Slereah

8:39 AM

@0celo7 looks okay

JM97

9:22 AM

Could anybody answer this:physics.stackexchange.com/questions/227121/…

Slereah

10:10 AM

@0celo7 physics.stackexchange.com/questions/245070/…

user116211

11:07 AM

14

Q: Uncertainty in Uncertainty?

I was reading about how the Planck's Constant can be measured with LEDs, which made me think about this question. The Heisenberg Uncertainty Principle states that: $$\Delta x \Delta p \ge {\hbar\over2}$$ a.k.a, there is always some uncertainty while measuring things. This is a fundamental law. N...

user116211

::Facepalm::

user116211

From now, anyone who wants to build up rep.....

user116211

Just ask such old wine in new bottle sort of uncertainty questions even though without searching a bit of the otherwise gazillions of questions lying in PSE.

user116211

You'd be rep-rich.

Danu

Answering them is also fun business ;)

user116211

11:14 AM

@Danu ;P

user116211

ACM is always at the rescue.

Danu

While checking out what badges I could next obtain, I got so annoyed that this answer is still stuck at 19 :P

user116211

@Danu 20 is okay?

yuggib

@user36790 people may be completely amazed to know that there are states for which the uncertainty principle do not hold :-D

user116211

@Mehrdad: Indeed, thanks! 19 upvotes and you're the first to notice that... — ACuriousMind 23 mins ago

user116211

11:16 AM

That's epic absence of mind ;P

yuggib

think how many upvotes for that

user116211

@yuggib oh.

user116211

@Danu: WTF!

ACuriousMind

@yuggib Domain issues (that's what you're referring to, right?) don't usually tend to amaze people, in my experience...

user116211

-8 ;(

yuggib

11:19 AM

@ACuriousMind no, I mean this

it has also experimentally realized...let me search it

ACuriousMind

@yuggib Oh, but that's about measurements.

Danu

> Reformulation of the Heisenberg uncertainty principle

And you're saying the uncertainty principle doesn't hold?

yuggib

@ACuriousMind the Heisenberg principle is all about measurements

@Danu I am saying it doesn't hold as stated

not that QM is wrong, or anything

nature.com/articles/srep02221

ACuriousMind

@yuggib No, when I write down $\sigma(A,\psi)\sigma(B,\psi)\geq 0.5\langle [A,B]\rangle_\psi$, I do not refer to any measurement at all.

Danu

@ACuriousMind $0.5$ ewwwww

ACuriousMind

11:22 AM

@Danu I hate the inline spacing for fractions :P

Danu

$1/2$?

ACuriousMind

@Danu Then there's always the ambiguity if what follows is still under the fraction or multiplied to it, so I have to use more brackets...

Danu

No, without brackets there is no ambiguity

yuggib

@ACuriousMind well, you are assuming that these operations are yielded by a measuring process

if else everything is moot

ACuriousMind

@yuggib Well, $A$ and $B$ correspond to observables I could in principle measure, but to me, the uncertainty principle is not about what happens if I actually do measure them. It's about the "widths" of wavefunctions, how "smeared out" the state is with respect to these observables, not about what experimental noise I get when using a particular apparatus to actually measure them.

yuggib

11:27 AM

ok, I see your point

and probably this is also what people mostly refer to when arguing over uncertainty principle

ACuriousMind

Nevertheless, that paper is interesting because it shows you cannot transport this abstract uncertainty relation over to measurements straightforwardly. Nice reference to have

yuggib

yeah, I think so

that damn Ozawa does a lot of interesting stuff

(he's the one that have proved existence of a measuring apparatus for any observable)

(and also the one who has done the quantum set theory, where the self-adjoint operators are real numbers of this new ZFC-type set theory)

0celo7

@Slereah dammit I can't answer that right now

Someone else will steal MY POINTS

@Slereah Why hasn't some math person written a tome on black holes

There's plenty of interesting geometry there

Slereah

Have you ever seen a black hole in the sky

0celo7

No, and I don't give a shit.

Einstein was wrong, deal with it.

Did you know that Eimstime failed the driving test a whole bunch of times

ACuriousMind

11:39 AM

@yuggib He's the one who wrote that paper on measurements that you had a bit of difficulty to obtain, right?

0celo7

And constantly shit all over the place

yuggib

@ACuriousMind yeah exactly

because many universities do not pay for the old issues of J. Math. Phys.

only for the ones of the last 5 or 10 years

(I have no idea why)

Slereah

Hint : It's money

yuggib

yeah, but then I suppose they would not have a subscription at all...

why just a subscription for recent papers (that are 97% of the time available on arXiv)?

Slereah

For the 3% I guess

And I suppose the old papers come up less often

0celo7

12:11 PM

@Slereah anything back from Ellis?

Slereah

As I said

He basically said WOOPS I'M A BIT BUSY

Where are the famous Kerr CTCs in the Penrose diagram, anyway

0celo7

Huh?

Slereah

None of them seem to show any bit where a timelike curve would loop back

Aren't Penrose diagrams supposed to preserve the causal structure

0celo7

Are there CTCs?

Proof?

Or the HE page and I'll take a look at it later

Slereah

0celo7

12:19 PM

What book is that

Slereah

Some rando paper

0celo7

Ok I'm eating right now and doin homework, I'll look at it later

Dammit phone why won't you autocorrect doin

It's doinG

@Slereah Uh, I think the Sanchez metric is the one I have.

So you're fucked.

Slereah

Unless someone else finds it!

0celo7

I ordered a MyCopy of the book it's in.

I'll write the thing when I have it.

Slereah

What book

0celo7

12:30 PM

Not telling you.

How many GR books are on Spriner though

Slereah

Hundreds, probably

You never solved that metric at all, you fraud

it was all someone else!

Secret

> postulate 2 is required by postulate 1: if the speed of light were not the same in all inertial frames, measurements of different speeds would make it possible to distinguish between inertial frames.As a result,a preferred,absolute frame could be identified.

I don't quite get it, I know that the constancy of speed of light is the reason why we have a (-+++) metric, and hence things like time dilation. But I am not sure how to understand how if we measuring the speed of light being different will aloow everything to be modelled in just one type of inertial frame?

Slereah

The speed of light stems from the laws of physics

The Maxwell equation gives you a propagation speed for EM waves

If it varied between frames, the Maxwell equations would vary between frames

Secret

Ah I see, then postulate will be invalid

postulate 1*

Slereah

Hence you could pick a frame where the Maxwell equation is in a particular form

0celo7

12:39 PM

@Slereah There are not hundreds of dedicated GR books.

Slereah

Are there not

0celo7

No

Slereah

14580 results on Springer for english books physics with "general relativity"

0celo7

Those are not dedicated

Actually there's 138

Slereah

Not bad

0celo7

12:53 PM

But even then

A lot are bullshit.

Like the matrix one, or the other without calculus.

And there's some SR books in there too

Is Callahan any good?

Slereah

Without calculus?

Callahan is a good intro

I wouldn't recommend it to a seasoned GR man tho

Callahan is basically

SR, SR in accelerating frames, SR in rotating frames, curved imbedded manifolds

Then curved manifolds

Then GR

0celo7

Penrose coming today

Slereah

and then some Schwartzschild with the remaining time

It doesn't do a lot of GR proper but it was one of my first GR book and I think it was a good thing

0celo7

Holy fuck is Visser coming from like China by boat

It's still "in transit"

Slereah

in a rickshaw

0celo7

1:00 PM

Amazon wants me to buy HE again

Slereah

Can't have too many HE

Was there ever a reedition of HE

Seems weird that such a classic was only published in the 70's

0celo7

The paperback I have is a 90s reprint

The Original was hardback

Random capitalization GG iPad

Slereah

I had to buy the old hardback Feynmann Gibbs

Then the next year, it was reedited

0celo7

2:00 PM

Don't you mean Hibbs

Slereah

Pibbs

It was written by Mister Pibbs

0celo7

Ah, Dibbs

Secret

http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3700.html

Multiparticle systems

0celo7

@Slereah Penrose is on the truck and out for delivery!!!

Oh wait I misread your post in my haste this morning.

Shit, I don't have my laptop with me, won't be able to answer it until tonight!

DeNiSkA

2:53 PM

guys on SO chat are really weird

David Z

@DeNiSkA what do you mean?

I mean, it's probably true, we're all kind of weird, but chat demands stories

DeNiSkA

@DavidZ guys there are quite undisciplned compared to this chat room

in Lounge<C++> on Stack Overflow Chat, 14 mins ago, by Rerito

@DeNiSkA Hang yourself

@DavidZ you are also SO user with high rep. woah O.O

David Z

@DeNiSkA Hmm... yeah. Seems so.

The C++ chat room does have somewhat of a bad reputation

DeNiSkA

@DavidZ even python!

whatever i post, they delete it

David Z

Well, that doesn't necessarily make them undisciplined! It depends on what you're posting, and what the culture of the room is.

It does raise some eyebrows though.

DeNiSkA

3:05 PM

@DavidZ yeah ;)

0celo7

@Slereah you around

Slereah

mb

Maybe I went with the metric all wrong

Maybe I should just take the metric in the $X_1 X_2$ basis

And do a good ol diffeomorphism

DeNiSkA

3:46 PM

@ACuriousMind ?

Slereah

What would be $x,t$ in this basis, tho

Hm

DeNiSkA

This account is temporarily suspended to cool down
what does this mean

Slereah

wolframalpha.com/input/…

Well WA doesn't know

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