The h Bar

user54412

12:15 AM

@ManishEarth Looking for a challenge, eh?

user54412

I'm actually spending the next week visiting a collaborator to hash out GR in new and crazy ways

tpg2114

What does new and crazy mean?

user54412

or, to the extent that what we're doing is not new, it's the sort of technical thing no one ever bothers publishing, so off we go to rederive it once again

ManishEarth

@ChrisWhite yeah :)

user54412

@tpg2114 adding MHD :P

user54412

12:20 AM

which to be fair has been done by a lot of people, but everyone's published methods are very situtational and not generalizable to other cases

tpg2114

I don't know enough about GR, or MHD, to know how either one changes the other

ManishEarth

I sorta did some GR on my own a couple of years ago, so what looks trivial to me isn't always trivial to everyone else. So.... I expect a bit more from the course (I know that it will speed up soon though)

MHD = hydrodynamics?

tpg2114

magneto-HD

ManishEarth

ah

I actually drew a Christoffel symbol in matrix form (drew it as a matrix of vectors, and tried but failed to draw it as a 3D matrix) because I got bored

tpg2114

All I know about MHD is that it can stabilize fluid instability like the RMI problem or turbulence... but that's the extent of what I know

user54412

12:22 AM

@tpg2114 Neither do I :P

tpg2114

There's a poster about that from our lab outside my boss's office... so I've read it many times while waiting

user54412

The equations of ideal MHD (in covariant form): $\nabla_\mu J^\mu = \nabla_\mu T^{\mu\nu} = \nabla_\mu {}^*F^{\mu\nu} = 0$

user54412

written like that, they don't seem all that bad

tpg2114

Navier-Stokes written as F = ma don't look so bad either :)

ManishEarth

@tpg2114 lol

@ChrisWhite Why do we specify "MHD equations in covariant form" or "EM equations in covariant form"? Is there a contravariant form? And if so, what's the difference -- it would be just a transformation away, right?

user54412

12:33 AM

@ManishEarth sometimes "covariant" means "opposite of coordinate-dependent" rather than "opposite of contravariant"

user54412

sure, you can raise and lower indices to your heart's content

ManishEarth

@ChrisWhite ah, I see.

user54412

(or at least that's my usage of the word)

Terry Bollinger

1:00 AM

"Hello world"

(my programming side coming out there...)

user54412

printf("Hello @Terry Bollinger\n");

David Z

tempted to do the same in brainf*ck but I will resist

Terry Bollinger

:)

Great googly mooglies, is that the name of some real programming language?

Hi Chris. It always amuses me that the C family of languages stole the printf formatting from ancient Fortran. And that Fortran and Lisp were the first...

user54412

there is no higher compliment than imitation :)

user54412

(and that's about the only compliment I have for Fortran - sorry @Kyle Kanos ;-)

user54412

1:13 AM

@TerryBollinger not only is it real, it's currently featured on the esoteric programming languages wiki

Terry Bollinger

Chris, so I see, I just looked it up on Wikipedia! That is a delightful syntax, and at least an order of magnitude more meaningful than string theory (hey, this is a physics chat, I had to say something physics-ish...)

user54412

wow, there are hundreds of them cataloged, and that's excluding things they deem "jokes"

user54412

@TerryBollinger It is rather Turing-machine like

Terry Bollinger

That list says something very scary about programming and programmers I fear...

David Z, how's the snow situation up there? We're getting good melting here a bit farther south, glad to see it go.

user54412

btw @Terry since I remember you being associated with language and such, you might find ~English interesting

Terry Bollinger

1:29 AM

@Chris, that is interesting... Dr Nicholas Cassimatis, creator of Polyscheme and now working at Yahoo, has created some of the best low-processing-overhead English comprehending software I've seen.

My son just showed me LOLCODE and I could not stop laughing.

Later, my wife just arrived also...

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