Re: New Theories Dispute the Existence of Black Holes

[Jack Uretsky <jlu@HEP.ANL.GOV>]

Well, let's be a little more careful.  The only singularity at the
Schwarzchild radius is a coordinate singularity.  It's importance is that
anything inside that radius cannot come out again.

Now this model, which I shall persist in calling the "Shell game model"
works like this:
        Take mass M which has a Schwarzchild Radius R, concentrated
into a thin spherical shell at radius R'>R.  For any radius r>R' the
metric is identical to that of a black hole of mass M.
        Inside the shell, a la Newton, there is zero gravitational field.
If the R' is close to R, then the value of g at R' is huge, so
any infalling matter will strike the shell with wopping-big (a technical
term) momentum, and before you have eaten your supper there will be matter
inside of the spherical shell.  Now there are gravitational fields inside
the shell and, without more, the matter in the shell will begin to
collapse.
        How to prevent this collapse?  Simple.  We turn on our antigravity
machine so that instead of zero field inside of the original spherical
shell we have a repulsive field. Then the infalling matter will be pushed
back into the shell. An easy solution, but it leaves questions.
        Where do the field lines of the the repulsive field originate and
terminate?  The answer seems to be: on dark matter. Dark matter, in this
context, is a euphemism for Einstein's cosmological constant, which is not
related to the matter distribution.  So where do the outgoing antigravity
field lines terminate?  They had better terminate inside the shell;
otherwise the shell will no longer simulate a black hole.
        What all this amounts to, I think, is that the authors are dealing
with a model that no longer presents a solution of the Einstein field
equations.  And, in any event, there is always the possibility of an
algebraic error in their work.
                                        Regards,
                                                Jack


On Sun, 20 Jan 2002, Robert B Zannelli wrote:

> In a message dated 1/20/02 7:55:19 PM Eastern Standard Time, jlu@HEP.ANL.GOV
> writes:
>
> << But the paper does not claim the non-existence of Black holes.
>  What it does do is claim another solution to the Einstein
>  equations that can simulate some of the effects of a black hole.  What
>  the authors seem to be doing is making a model where a collapsing star
>  collapses into a spherical shell rather than simply shriveling into a
>  volume that eventually recedes inside an event horizon.  The spherical
>  shell is located at the radius that would correspond to the event horizon
>  for the star's mass.  Their claim seems to be that this mode of collapse
>  evades the Chandrasekhar limit. >>
>
>
> Jack as I read this paper in the so called Gravastar model there would be no
> event horizon and no singularity. They are proposing that rather than
> complete collapse of a massive dying star, a region of strong "anti gravity"
> ( for want of a better word). would cause all the collapsing matter to be
> confined to a thin membrane where the Schwarzchild classical event horizon is
> predicted to be by black hole theory. This opposing force inside the membrane
> prevents further collapse and any possibility of a singularity. Most
> importantly, there is no information paradox, as predicted by the Bekenstein
> equation. This would, I believe, invalidate Hawking's theory of black hole
> radiation and t'Hooft's holographic theory. In the paper the interior inside
> the Gravastar would have a negative energy density (effectively the same as
> positive cosmological constant in that region of space). generating the anti
> gravity force preventing further collapse. The membrane would a have a
> positive energy density and the exterior energy density would be zero. The
> Bekenstein equation for entropy is:
>
>                       S_BH=4*Pi*K_b*M^2/hbar*C ( which equals
> (Pi/2)*(K*C^3/Gh)*A_eh ) while in the gravastar model S= K_b*L*M*C/hbar
> where L is the membrane thickness. Considering how much is invested in the
> idea of the Berkenstein Bound, in membrane theory (Superstring theory) and
> loop Quantum gravity for example, this paper is suggesting a serious change
> of direction in physical theory. BTW personally I am very skeptical about
> this proposal but I think it deserves serious consideration. As pointed out
> by another Physicist on a different physics list measurements of stellar
> black holes, like Cygnus X-1,demonstrated that there was no signature of a
> "splash" of accreted matter impacting a hard surface. This result is
> predicted to occur if this idea is valid.
>
> Bob Zannelli

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