The h Bar

ACuriousMind

11:38

@DanielSank Algebras, never algebrae - it's not a Latin word.

Slereah

@ACuriousMind

What is the difference between an analytic function and a regular function

ACuriousMind

That depends on what your definition of "regular" is

Slereah

What can it be?

ACuriousMind

I think it has something to do with branch points in complex analysis, but I'm not sure, and I don't think there's a definition widely used

Slereah

Quite unfortunate

I often see it thrown around but I never see any definition

ACuriousMind

11:44

In what context exactly did you find is?

Slereah

And when I go see it, it seems to just mean analytic

A few contexts

usually I see it as "It's all cool because the solution is regular"

Example :

ACuriousMind

I think "regular" might just mean "not singular" there

Slereah

It seems to sometimes mean analytic, sometimes $C^r$ and sometimes non-singular

blah

Basically it's a word that just means "the function is not bad"

for varying degrees of bad

John Rennie

0

A: How can we combat arrogance and ignorance on physics stack exchange?

The question of how to decide what is right and wrong in science is a vexed one and always has been. The current approach is peer review, but of course the problem is how to select the peers. Eminent scientists have been wrong in the past and will be wrong again, so ultimately no-one’s judgement ...

That is at least an hours work trying to be as objective as possible and resist the temptation to ad hominem comments.

I think I've done pretty well.

Bearing mind that the original post is a thinly veiled attack on me.

Slereah

lol Duffield

I'd say that since we banned him arrogance and ignorance have gone down a fair amount

John Rennie

11:56

@Slereah now don't you go spoiling my good work in avoiding the personal attacks!!

Slereah

(John Duffield smells)

AccidentalFourierTransform

I'll leave this here

Physics Meta

0

Q: Encyclopedia of the best questions and answers

I see sometimes that some interesting questions that appear on the site have already been asked in the past and are flagged as duplicates. I thought it could be interesting to have a collection of the most asked, important and/or well-answered questions. It's still a vague idea, also because I do...

AccidentalFourierTransform

BTW I love British accent

I see. I don't like you people chatting when I'm not around...

BTW whose the man in JR's profile picture?

ACuriousMind

@JohnRennie "If I disagree with an answer to the extent that I want to downvote it I will look to see if there is a better answer, and if there is no better answer I will post one." - but one can disagree with an answer for missing the point of the question, or for presenting a clearly fallacious argument, or for just making no sense at all without knowing what the correct answer is

AccidentalFourierTransform

12:09

and what happened to CW?

Ah, so many questions...

ACuriousMind

@AccidentalFourierTransform It's JR

@AccidentalFourierTransform He voluntarily deleted his account without telling anyone why (although there's some speculation in the chat log which I would ask everyone not to re-hash now)

AccidentalFourierTransform

May 25 at 19:16, by AccidentalFourierTransform

eg, @JohnRennie may I ask you whos the handsome gentleman from your profile picture?

ACuriousMind

Sigh...my ironymeter isn't well-calibrated today, it seems :/

Jorge B.

@AccidentalFourierTransform if you don't want stuff here don't put here is first place.

AccidentalFourierTransform

oh no I got in troubles

apologies to all moderators for wasting their time

(I should definitely flag my comment above, asking the moderators to delete it for me)

Jorge B.

12:20

@AccidentalFourierTransform no problem have a nice day.

AccidentalFourierTransform

@JorgeB. same to you. Happy holidays.

Secret

12:50

scmp.com/news/china/article/2054501/…

Jim

13:07

ah, last day of work before my holiday vacation starts

Working in academia is the best

David Z

If you get holiday vacations it's not really academia :-P

Emilio Pisanty

Hey @ACuriousMind that's a lot of close-queue reviews with unilateral votes.

2

Anything specific going on?

With, say, this one, I would say it's better to let the queue take care of it. The bulk of closures are meant to be handled there.

ACuriousMind

13:39

The queue had around 40 items in it, which is unusually large, so I thought I'd reduce it to the usual level by voting on the clear cut cases or those where I was the fourth or fifth vote.

If this size turns out not to have been a fluke, I won't do that regularly

Mew

13:51

@koolman @heather users can now edit closed questions

Slereah

14:01

Montgomery Burns Award for outstanding achievement

►

Jim

@DavidZ The university closes for two weeks around christmas. I get those weeks off as a result

So do the professors

John Rennie

14:53

@MAFIA36790: you need to remove your comment to my answer in the meta. Your comment doesn't contribute anything useful and it is just going to inflame things.

@ACuriousMind yes I agree (I'm sure you didn't think I wouldn't). What I describe is an ideal situation in which we all have unlimited time and, perhaps more importantly, unlimited patience to write answers.

user116211

15:06

Sorry @JohnR; he is already pissed off, I think.

user116211

Hey @AccidentalFourierTransform; long time, no see in the chat; anyway welcome again.

David Z

15:25

@Jim ah, nice. For me, this was not taken for granted.

AccidentalFourierTransform

@MAFIA36790 Hi :-)

what have you been up to?

Physics Meta

15:44

0

Q: Awarding Informed Badge

I think the " Informed " Badge must not be given so easily . Before giving the informed badge , newcomers should not only be briefed about basic rules and regulations of Physics SE , but also :- Be given more information about the system of badges and reputation . Be given a short article on u...

discussion feature-request

Emilio Pisanty

16:00

speaking of badges

stackoverflow.com/help/badges/6381/not-a-robot

60

Q: A New Silver Badge That Robots Simply Can't Win

We don't do a lot of socialization on Stack Overflow, or even Meta Stack Overflow. In fact, we really don't do any socializing. But, that doesn't mean being social and having informal conversations is bad in any way, we'd just rather that folks do it somewhere else. Somewhere else turns out to ...

discussion badges events

Ramanujan

16:14

Hi nerds

John Rennie

16:56

@AccidentalFourierTransform: are you around?

AccidentalFourierTransform

@JohnRennie yes

John Rennie

@AccidentalFourierTransform thanks. Equation (3) in your answer here:

5

Q: How does the inclusion of vacuum energy modify Newtonian gravity equation of motion?

The equation of motion (in the center of mass frame) due only to gravitational forces between two point masses is: $$\frac{d^2r}{dt^2} = -\frac{GM}{r^2}$$ How does the equation get modified when a repulsive force due to vacuum energy/dark energy is included?

gravity cosmology astrophysics dark-energy

What are the dimensions of $\Lambda$?

Danu

You can tell from the definition... It's an energy density, once you divide by $G$

John Rennie

I though the cc had dimensions of $m^{-2}$ but your equation wouldn't be dimensionally consistent if that were the case.

Your equation requires the dimensions be $t^{-2}$

AccidentalFourierTransform

Ah, I don't remember... let me think about it

Well, from the first equation $[\Lambda]=[G\rho]$, as Danu says

John Rennie

17:02

I wonder if what you have there is $c^2\Lambda$

Danu

My analysis tells me it's got to be $[L]^2/[T]^4$ @JohnRennie

Since $\rho$ has units $[M]/([L][T]^2)$ and $G$ has units $[L]^3/([M][T]^2)$

AccidentalFourierTransform

@JohnRennie at least, here: arxiv.org/abs/gr-qc/0004037v2

eq. 2.6 agrees with my second equation

Danu

There have to be some suppressed constants

$GM/r$ cannot equal $\Lambda r$ without suppressed constants

There is a $c^2$ missing

In one of the two

AccidentalFourierTransform

Wait, $\Lambda=G\rho/c^2$

Danu

okay

that solves it

I have to say that setting $c=1$ when taking the Newtonian limit is bad form :P

John Rennie

17:08

@Danu That was my thought.

Aha!

AccidentalFourierTransform

my bad, sorry :-P

John Rennie

In that case re this question:

0

Q: Orbits in an universal expansion?

Has anyone worked out the math for the motion of objects in distant orbits accounting for both gravity and universal expansion? Objects in very distant orbits in expanding space-time should orbit more slowly than when accounting for gravity alone. Eventually at some great distance an orbit will...

orbital-motion universe

Danu

Wtf?

John Rennie

I make the point where the CC balances the Sun's gravity at about 10,000 light years, not the Kuiper belt!

Danu

I assume OP made a calculational error

AccidentalFourierTransform

17:11

Always assume OP made a calculational error

Especially when I am OP

John Rennie

17:55

The cosmological constant is quoted in all sorts of different units. Wikipedia quotes is as $1.19 \times 10^{-52}$ m$^{-2}$, or as $10^{-35}$ s$^{-2}$ or as $10^{-29}$ g/cm$^{-3}$. All the same number but with various factors of $c^2$ and $8\pi G$ thrown in.

AccidentalFourierTransform

I like to work in the metric convention where $\Lambda$ is imaginary.

Also, in imaginary $y$ axis so that $\eta=(-1,+1,-1,+1)$.

bolbteppa

18:17

Ising model anyone

gandhiviswanathan.wordpress.com/2015/01/09/…

Emilio Pisanty

18:50

folks seen this notice?

AccidentalFourierTransform

huh, that's new, isn't it?

Emilio Pisanty

@AccidentalFourierTransform yeah

John Rennie

20:04

@EmilioPisanty yes, one of my old answers got bumped with that message a few days ago. I got a couple of upvotes out of it :-) I must admit I didn't realise it was new. I just assumed that feature had always been there.

DanielSank

22:01

@EmilioPisanty I like it.

John Rennie

There. Take that!

0

A: How can we combat arrogance and ignorance on physics stack exchange?

I’m going to post this as a separate answer because it’s not a direct answer to the question. However I think, or at least I hope, it addresses the underlying problem that has led to your post. The crux of the matter is that the theory of relativity taught to today’s physics students is not the ...

HDE 226868

@JohnRennie Wow, that's . . . fairly polite. Nicely put.

Emilio Pisanty

22:21

@JohnRennie the bumping's always been there. it now tells you it's doing it, instead of leaving you to wonder why it's on the front page

@JohnRennie nice answer. Unfortunately the question is now at score < -8 which means that it doesn't show on the front page of meta, which I don't think is a good thing.

I don't think mods have the power to undo the visibility thing? It would be nice if they did. This isn't a nice conversation to have but it doesn't serve anyone to hide it from view.

Emilio Pisanty

22:50

...apparently not.

David Z

23:55

@EmilioPisanty No, we do not. Visibility is based on votes. And stuff that's been so heavily downvoted generally is not worth showing off. (Note the difference between "not showing off" and actually hiding in the sense that deleted posts are hidden.) There are of course exceptions, more frequently on meta, but still they're rare enough that I don't think it's worth adjusting the system to allow for them.

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