|Oct12-06, 04:43 AM||#324|
[SOLVED] Is there a true singularity in nature?
"MP" <firstname.lastname@example.org> wrote in message
> "the softrat" wrote
> > I am well aware that a number of physical models contain or predict
> > singularities. My question is: Is there any experimental evidence that
> > any singularity actually exists
> > or are they all artifacts of the models?
> Not artifacts, mathematical properties of a certain class of exact
> solutions of the Einstein field equations.
> > Lest someone jump right in with the singularity at the center of a
> > black hole, let me say that, although the various solutions of
> > Einstein's Equation have provided much useful guidance in
> > understanding the structure of the universe, as far as I know, the
> > center of a star or BH is outside of the range (or is it domain) of
> > applicability of the various solutions because they presume a non-zero
> > stress-energy tensor.
> For the Schwarzschild and Kerr solutions the stress-energy
> tensor is identical zero throughout the whole space-time.
> The singularity, technically spoken, is not part of the space-time.
> Of course one can ask whether a stress-energy tensor identical
> to zero is physically realistic, in particular if there is Hawking
> radiation, which clearly produces a non-zero energy-density
> in the exterior space-time. The question of self-consistency
> arises naturally in this context. The problem that the (classical)
> solution we study has zero energy-density, whereas the (quantum)
> physics demands non-zero energy-density, is closely related to
> the highly non-trivial problem of back-reaction of Hawking
Yes, and some theorists has adressed this issue. Johan Masreliez
does it by i.a.keeping Too + T11 + T22 + T33 =0, leaving the
event horizon as sole singularity.
> > It is my belief that there are no singularities in nature. I am
> > looking for evidence that I am wrong.
> Evidence that you are wrong would be the direct observation
> of a singularity. It is quite unlikely, that this will ever happen. If
> the cosmic censorship hypothesis is correct, you will never
> observe a singularity directly. In this case the observational
> proof of an event horizon or a trapped surface would be
> indirect evidence for a singularity.
> maybe the model is incomplete. Maybe the solutions we
> study are not the physically realistic or relevant ones...
Johan Masreliez´ approach to non identically zero stress-energy
tensors and the other implications from his scale expanding FRW
model for what is generally attributed to "black holes" is treated
in his Gravitation article for the October 2004 issue of Apeiron:
If he is right we should rather be observing bubbles than BHs.