The h Bar

@JaimeGallego I was going to say that it ain't so bad, at least you're not trying to become a regional governor while in exile in Brussels, but it's probably not a great idea to go there

Jaime Gallego

@EmilioPisanty Puigdemont?

Emilio Pisanty

that's what I meant, yes

but I should probably drop that and go to bed

Bernardo Meurer

Meh I was pretty crushed when the rejections started coming in

Jaime Gallego

@BernardoMeurer Still have a few shots left, we'll see how this goes on the end of March

Bernardo Meurer

@JaimeGallego Who's left / who's gone?

Jaime Gallego

12:23 AM

A few ivies

I cannot apply for anything more realistic

No $$$ aid

Bernardo Meurer

@JaimeGallego I was mostly curious to know where you applied to

Jaime Gallego

UChicago, Rice, Princeton, NW, and others

Ungodly amount of money on fees

They're like 10 or so

NW?

Northwestern

Ah

12:25 AM

On Evanston IL

Bernardo Meurer

Princeton has always been my dream school

Jaime Gallego

Turing and IAS of course

Bernardo Meurer

I hope you get in :)

Jaime Gallego

@BernardoMeurer Shall we create a fictional African tribe and then submit requests to Unicode

Apple vulns on demand

Bernardo Meurer

Lol

\me thinks people just just use extended ASCII and give up on their native languages and symbols

Jaime Gallego

12:30 AM

You misspelled EBCDIC

Bernardo Meurer

No, IIRC Unix did not support EBCDIC

Therefore I do not want it

uhoh

12:56 AM

bbc.com/news/world-asia-china-43395650

vzn

3:43 AM

time.com/3531/hawking-myth-or-legend archives.cjr.org/the_observatory/media_made_hawking_famous.php medium.com/astronomy-cosmology-space-exploration/…

Tanuj

5:36 AM

@JohnRennie Hi ! Good morning :)

DanielSank

6:52 AM

How do I tell gpg to stop storing my keys locally?

Slereah

7:15 AM

entangle the qubits of your keys to a remote location

Slereah

10:06 AM

hey @JohnRennie

John Rennie

Morning :-)

Captain Bohemian

11:48 AM

good night

Slereah

12:21 PM

arxiv.org/pdf/1009.1136.pdf

The counterpart to Hawking-Ellis

John Duffield

1:19 PM

Carlip said "several lines of evidence hint that quantum gravity at very small distances may be effectively two-dimensional." But there isn't any evidence.

0celo7

1:40 PM

@BernardoMeurer @BalarkaSen Lil Boat 2 got a light 7

John Duffield

I've been reading a lot of old papers in the past year.

IMHO it's amazing what's out there. See for example Arthur Compton's 1921 paper the magnetic electron. He referred to the Parson electron or magneton which featured a rotation with a "peripheral velocity of the order of that of light". Compton said "we may suppose with Nicholson that instead of being a ring of electricity, the electron has a more nearly isotropic form".

bolbteppa

@JohnDuffield speaking of old big papers, skipping section 1, can you read math.ucsd.edu/~nwallach/Dirac1928.pdf despite the math? Do you not want to know how he was doing what he was doing (which involves learning the math)?

John Duffield

Well, I've read it, but I got lost in the maths and didn't end up with any picture of what the electron is. To be honest I don't think Dirac did either. Did you?

Slereah

So as a way to honor Stephen Hawking, can they republish Hawking-Ellis

I'd like a decent version

John Duffield

1:56 PM

@bolbteppa : in 1962 Dirac wrote an extensible model of the electron which depicted the electron as a charged conducting sphere with a surface tension. I'm confident that it isn't anything like that.

Semiclassical

@JohnDuffield something something entropy of a black hole? That scales with the area of the event horizon, so that does seem to encourage a 2D mindset. (Whether that rises to the level of evidence is another matter...)

John Duffield

@Semiclassical : IMHO there's a lot of speculation about the nature of black holes. I'm confident that they exist, but having read a lot of old papers, I'm not confident that they're correctly described in contemporary literature.

Semiclassical

I haven’t tried to read that stuff period so I can’t say either way

But that’s my guess for what Carlip has in mind

John Duffield

Penrose wrote his “epoch-making” paper gravitational collapse and space-time singularities_ in 1964. I don't like it because it doesn't square with what I call "Einstein and the evidence". There are other papers I have similar feelings about.

@Semiclassical : I've read an awful lot of old quantum mechanics/electrodynamics/field theory papers recently. IMHO the quantum gravity issues Carlip is referring to go back a long way.

bolbteppa

2:16 PM

@JohnDuffield in that paper he derived an imaginary electric moment, using math, and says it being imaginary means it might not have physical meaning, why do you think his math derived such a thing, how will you know whether that's the flaw in all of this theory or not without knowing the math

I mean he took the negative energy seriously from the same theory and predicted positrons from this, why not imaginary moments

John Duffield

@bolbteppa : I know some maths. Only to A-level so I'm not fluent like some of the guys here. But I can look things up and pick my way through it. I can't explain why his maths derived an imaginary electric moment, but I am reminded of something a professor told me years back: whenever you see an imaginary term in the maths, there's always a real rotation in the physics.

@bolbteppa : In 1931 Dirac wrote his quantised singularities in the electromagnetic field. This is where he’s said to have predicted the positron. However it's a bit of a leap from holes to positrons. Somebody told me Dirac was moving the goalposts after Oppenheimer’s paper on the theory of electrons and protons.

Graham Farmelo talks about it in his 2010 article did Dirac predict the positron? He says Dirac’s "close friend Patrick Blackett, one of the leading players in the story’s denouement, denied it”. And that "very few physicists took Dirac’s hole theory seriously" and "Victor Weisskopf later recalled the idea ‘seemed incredible and unnatural to everybody’".

IMHO there's some real interesting stuff tucked away in the old papers and articles. OK, I must go. Bye.

vzn

3:11 PM

@JohnDuffield hey this (clifford ref) is really wild, a rabbit out of the hat. do you have any more info on clifford? a very obscure ref that seems to mostly have been lost in the sands of time & almost zero )( ref to him even in physics history literature. fyi am (long) pursuing some ideas along similar lines as those youve espoused wrt a fluid theory of space... collecting many refs myself & am gonna blog again soon on connections with astrophysical hydrodynamics, madelung fluid etc...

Slereah

@0celo7 Hawking says that $\chi = 0$ for a compact spacetimes implied $\pi_1 \neq 0$

But $S^3$ is a spacetime

and it is still simply connected

Tanuj

@JohnRennie Hi ! Good afternoon :)

John Rennie

Hi :-)

Tanuj

@JohnRennie

@JohnRennie how did they get $f'(1)=4$ and $g'(1)=2$ ?

Semiclassical

3:26 PM

@Tanuj Doesn't the problem states that $f'(1)=2g'(1)=9$?

Tanuj

@Semiclassical yea

Semiclassical

in which case $f'(1)-g'(1)=2g'(1)-g'(1)=g'(1)=5/2$ not 2...

:/

Tanuj

yea

John Rennie

@Semiclassical yes, that's what I thought as well ...

Semiclassical

So yeah, I don't buy it

it'd work if it were f'(1)=2g'(1)=4. but as written I think it's simply wrong.

Tanuj

3:30 PM

yea

Tanuj

3:42 PM

Okay guys , I have $y=|x-2|+|x-5|$ and I have to find if $f^{-1}(4)=0$ is true or not

I think it will be false , but its given to be true

the three definitions of $y$ when $x<2 , 2<x<5 , x>5$ are respectively $y=7-2x , y=3$ and $y=2x-7$

And $f^{-1}(4)$ is not equal to $0$ for any of the case. Then how is it true ?

Semiclassical

Do they mean $f^{-1}(4)=0$ or $f'(4)=0$?

the latter will be true.

Slereah

4:42 PM

Help

Computing the Cauchy horizon of a wormhole is awful

Tanuj

@Semiclassical How would even $f'(4)=0$ be true ?

@Semiclassical isn't $f'(x)=2$ and $-2$ respectively for $x>5$ and $x<2$ ?

Semiclassical

@Tanuj sure, but 4 is between 5 and 2

Tanuj

Ah @Semiclassical Got you ! Yea it must be a misprint then . Thanks :)

Semiclassical

kk

Slereah

4:57 PM

I don't even know what the Cauchy horizon looks like if the wormholes are rotated

There doesn't seem to be any closed null geodesics

although I do need to check the geodesic equation at the boundary

it is not trivial

John Duffield

5:16 PM

@vzn : no, sorry, I don't have much on Clifford. But check out David Hestenes and Christoph Schiller plus Robert Close. IMHO we're talking about a solid analogy rather than fluid.

vzn

5:32 PM

@JohnDuffield there are various similarities between a solid and a fluid wrt some of these metaphors/ relationships. re that, reminds me, did you ever see this? think youll like it, a big fan myself... cited it a lot in here long time ago but got little )( response, am sure you can relate :(

Aug 9 '16 at 14:37, by Secret

https://arxiv.org/pdf/1603.07655.pdf

For all you GR guys to ponder about

NB I suspect it fails for CTC and the pp wave spacetime that slereah mentioned

ACuriousMind

6:02 PM

@BernardoMeurer Weren't you coming to Germany some time this summer or did I hallucinate that?

Cows

6:31 PM

@ACuriousMind what is your general instinct for computing $$\int dt (vt^6 - w t^5 + x t^4 - y t^3 + z t^2)^\frac{1}{2}$$

@ACuriousMind I have used my signature techniques and have some humiliating news to share. At any rate all i can say about this is that it came from some trivial things I am also ashamed to mention

@ACuriousMind stantad elliptic voodoo fail as we are P degree != 3 or 4, I was going to roast the problem in taylor expansion soup and pray for a series that conv. or hit that cow with padde and drop bounds the int it

@ACuriousMind lmk what you'd do. v;w;x;y;z are just some special constants, none the less constants.

I mean I can just drop this donkey into the computer and slap it, but I want to be clever.

I am ashamed I can't see how to immediately do this

please help

@ACuriousMind Also I can live attack it on youtube Saturday too if you prefer we hack it that way

Anonymous

@Cows Can you deal with something like $\int(vt^4-wt^3+xt^2-yt+z)^{1/2}dt$ ?

Cows

@Blue kinda. . . . but not sure hehe, how would you attack it

bolbteppa

$$I = \int dt (vt^6 - w t^5 + x t^4 - y t^3 + z t^2)^\frac{1}{2} = \int dt \, t (vt^4 - w t^3 + x t^2 - y t + z) = \int dt \ t \dfrac{vt^4 - w t^3 + x t^2 - y t + z}{(vt^4 - w t^3 + x t^2 - y t + z)^\frac{1}{2}}$$

Pretty sure you can reduce this to a sum of elliptic integrals

Cows

@bolbteppa interesting

bolbteppa

Something like this explains it

planetmath.org/reductionofellipticintegralstostandardform

ACuriousMind

6:40 PM

@Cows I am afraid that I never cared much about being able to pull silly integration tricks out of my hat, so I wouldn't try to solve that integral by hand unless someone pointed a gun at me :P

Cows

@bolbteppa I attempted factoring then beating it to an elliptic donkey

@ACuriousMind no worries, yeah I kinda have a gun to my head, so I need to hit this hard lol

@ACuriousMind I will work on it a bit, I think I should be able to do it

@bolbteppa looking at the link now

Anonymous

Maybe ask on Math SE...

Anonymous

Bolbteppa's hint looks good

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