From: Anders Sandberg (asa@nada.kth.se)
Date: Thu Dec 12 2002 - 14:28:14 MST
On Wed, Dec 11, 2002 at 12:17:28AM +0100, scerir wrote:
> [Anders]
> > I thought it ended up with a boring Schwarzschild hole
> > after the charges had been neutralized.
>
> The pair creation process requires an electric field strengh
> like (m^2 c^3) / (hbar e) where m and e are the mass and the
> charge of an electron. But the key factor is that the number
> of pairs (e+ e-) created is very high, something like
> (Q x radius of the dyadosphere)/(e x Compton el. wavelenght).
> This means that the density of pairs created, as a function
> of the radial coordinate is so high (and the time so short) that
> these pairs will leave the EMBH by creating an enormous pulse,
> which expands relativistically out to infinity. Or, in a different
> picture, the e+ e- plasma fluid expands, cools, and the pairs
> recombine.
>
> Is it possible to sketch a perfect EMBH engine based on
> creation of pairs - expansion of plasma - compression -
> annihilation? I do not think so because, imo, the EMBH must
> lose some mass-energy, sooner or later.
Hmm, let's see. Charged black hole blasts out e+/e- pairs until its
charge has been neutralized. The pairs mostly recombine into gamma rays,
which are absorbed by a standard Dyson and used for useful work. The
excess charge ends up on the dyson shell which now has the same charge
as the black hole did. The now neutral hole does not notice anything
since it is inside a equipotential Faraday cage. The Dyson engineers now
start to throw charges into the black hole using an electron gun. The
first electron is easy - no resistance. The second has to be thrown
against a one electron charge potential, so now a bit of extra energy
has to be added. And so on; the final electron has to be given a huge
energy to overcome the dyadosphere before it ends up in the hole. The
total amount of energy used is equivalent to the one gained by having
the dyadosphere release the charge as pairs, so this is just a
reversible operation (leaving out that the hole would like to flash as
soon as we get enough charge on it). Seems pretty useless, but might be
useful if we have charge in other stable particles than electrons - drop
a proton into the hole, get back an electron in the end.
> Got the unpleasant feeling that all the above was 'murkily
> written and murkily thought' :-)
Not really. I understood it. Which might imply I am correspondingly
murky :-)
-- ----------------------------------------------------------------------- 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
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