@Phonon I will!

@alarge yeah but it s usually either about solid state or DFTs...

@ACuriousMind Lol @ Danu's QM stroke earlier

@Phonon Those are represented, too, but if you look at CECAM's front page, most of the highlighted workshops are not about either. I went to couple when I was doing my PhD and those were also not in DFT nor in solid state (to be fair, the multiscale or whatever one I went to did also cover aspects of DFT, but I wouldn't say it was the main focus).

@0celo7 We all have our pet peeves :D

@ACuriousMind Mine is slow internet when away from home.

I also don't like when people have terrible posture. On the flipside, I hate when people have impeccible posture.

@0celo7 I think that one is universal

So, are you back home now?

@ACuriousMind This hotel internet is roughly 200 times slower than at home.

That's only a 50% exaggeration.

@ACuriousMind Orientation ended today at 3 PM.

I have a nice 8.5 hour drive home tomorrow.

Sounds...fun.

I know, right? Who doesn't love that!

@ACuriousMind You mentioned something about non-Hausdorff manifolds having very little relevance in physics the other day. I'm currently reading about the Taub-NUT space in HE and some interesting non-Hausdorff properties arise. Further discussion is found in: Hajiek, P. (1971), 'Causality in non-Hausdorff space-times', Comm. Math. Phys. 21, 75-84.

I think the Hausdorff property of Einstein's space-time is relevant to the singularity theorems.

Otherwise, I see no reason for HE to bring it up.

@0celo7 If it is not Hausdorff, then the Wiki entry is wrong in claiming it has topology $\mathbb{R}\times S^3$.

@ACuriousMind The space itself is not non-Hausdorff. The covering space has interesting non-Hausdorff properties. Cf. Sect. 5.8 in HE.

In fact, the maximal covering space is not a manifold at all.

From string theory I know it is an orbifold.

@0celo7 Usually, manifolds are defined to be Hausdorff, anyway, but I guess you're saying it is not locally $\mathbb{R}^n$ for fixed $n$.

@ACuriousMind HE drops this requirement.

@ACuriousMind Maybe you should read the section. I'm likely butchering it and will re-read.

anyone remember this?

pingu!

Hotel internet can't handle it

search for pingu.

@0celo7 Maybe I will. Non-Hausdorff manifolds don't sound all that useful to me right now

@ACuriousMind I don't know of the use, but since they introduce the concept randomly in Ch. 5, I think it might have use later. (Ch. 5 analyzes solutions and general trends for use in the proofs of the singularity theorems.)

@ACuriousMind I don't know how they can manage to talk about stuff like Hausdorfficity (?) and fiber bundles, yet still write $\mathrm{d} s^2$ for the metric.

That ds^2 looks a bit funny.

@0celo7 I've seen plenty of mathematicians write metrics in that form, too, it's not that weird

@0celo7 I think it's a perfectly fine little ds^2.

@ACuriousMind Are you saying HE aren't mathematicians?

Hawking is a Professor of Mathematics at Cambridge.

@0celo7 I thought they were mathematical physicists

Ellis a Professor of Applied Mathematics at Cape Town.

@ACuriousMind I think Wiki has him (Hawking) as Cosmologist.

Ah, well then, add an "other" in front of "mathematicians" in my statement.

@ACuriousMind Is your soul bear a mathematician or physicist?

@0celo7 Actually, I don't know.

His Ph.D. was in physics, but he's a math prof. (The Bear.)

A hybrid, then :D

It's called mathematical physicist.

@Icosahedron Only Dutch people may attain that title.

Elite Dutch people.

Though wikipedia names a lot of physicsts/mathematicians mathematical physicsts.

i.e. roger penrose.

@0celo7 lol, I can imagine Danu rolling his eyes at that.

Penrose is a hippie

penrose is cool.

Hawking radiation in a nutshell:

aw why didn't he throw in a d20.

@0celo7 lol.

Quote from Hawking & Penrose: Consideration of black holes suggests, not only that God does play dice, but that He sometimes confuses us by throwing them where they can’t be seen.

from the space time book?

@Icosahedron arxiv.org/abs/hep-th/9409195

@0celo7 That's one of these statements that sound witty/profound but make less and less sense the more you think about it.

Those lectures are hilarious.

that looks like it came straight out of zee.

I know, fantastic book.

it needs more 1 stars on amazon.

The Boundary Condition Of The Universe Is That It Has No Boundary.

Sounds like a Jason Smith tweet.

@ACuriousMind How so?

boundary $\neq$ boundary condition though?

@Icosahedron Huh? Take it up with Hawking.

@0celo7 Can you tell me what it's actually supposed to mean?

@ACuriousMind I'm not the one in the QTF in curved spacetime seminar :)

@Icosahedron No, pretty sure a boundary condition is called so because it is a constraint for the solution on the boundary of the domain, so they are pretty closely related, though not the same

If the domain doesn't have a boundary, you can't give boundary conditions.

@0celo7 Nice dodge :P

Anyone care to tell me why my lame theory for creating energy isn't possible?

I've warned the guy with the Hawking effect talk already that I tend to ask very annoying questions as soon as someone talks about virtual particles.

@ACuriousMind Like?

@shader2199 Give it a go.