From: Anders Sandberg (asa@nada.kth.se)
Date: Sun Dec 08 2002 - 17:28:44 MST
On Sun, Dec 08, 2002 at 09:40:33PM +0100, Eugen Leitl wrote:
> On Sun, 8 Dec 2002, Robert J. Bradbury wrote:
>
> > > There is also apparently a theorem somewhere (I think it also easily
> > > follows from the third law of black hole thermodynamics) that says you
> > > cannot break a black hole by spinning it up with external fields. A
> > > pity.
>
> But I seem to remember that solutions which are ring black holes are
> possible. If one can spin up one to become a ring, then one can surely
> keep this up until the ring is very thin? Or is there going to be some
> instabilities, like event horizont turbulence?
I think there is a lot of weird turbulence-like instabilities here
(just look at the animations of Brill waves
http://jean-luc.ncsa.uiuc.edu/Movies/NCSA1999/BrillWaves/).
But the real problem seems to be a topology theorem I have heard about
but not yet read up on, which (according to the GR theorist brother of a
colleague I asked) means that unless some energy conditions are broken
spacetime is locally connected - ring-shaped black holes are not
allowed. The way around this, since I can always arrange some stars into
a ring and compress them into a ring shaped black hole with my Stellar
Melasmifyer, is that the event horizon of the ring rushes inwards very
fast (it can move superluminally, since it is not really a signal or an
object, merely the region from which nothing can emerge) so that no
signal can get through the hole. So the ring collapses into an oblate
black hole which then "rings" away the anisotropy with gravity waves. I
promise to check this theorem when I get the time, because I honestly
don't understand how that works if the matter of the ring was originally
rotating faster than allowed by an extremal black hole.
> > ROTFL. Only from the mind of Anders.
> >
> > It should be the goal of every adventuresome extropian to live in
> > an Anders Sandberg(tm) universe. They are likely to be far more
> > interesting (as in "may you live in interesting times") than the
> > vanilla universe(s) we are stuck with now-a-days.
Thanks! :-) I promise that once I get a good production line up and
running for my universes this list will get priority for them.
I'm thinking of those Brill waves. Maybe we should base matter on them
instead of particles...
-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y
This archive was generated by hypermail 2.1.5 : Wed Jan 15 2003 - 17:58:37 MST