Re: Symmetry

Barry <Sirdry@xxxxxxxxxxx> wrote:
carlip-nospam@xxxxxxxxxxxxxxxxxxx wrote:

Barry wrote:

carlip-nospam@xxxxxxxxxxxxxxxxxxx wrote:

Then can we say that, the mathematics of GR allows for them,

We do *not* know whether "the mathematics of GR" allows naked singularities
to form from physically reasonable configurations of matter.

But the Cosmic Censorship Conjecture says that naked singularities
can't form, And if that's part of GR, then GR does not allow naked
singularities to form from physically reasonable configurations of
matter.

And, as you said earlier, about whether there is anything in GR, per
se, that predicts that `singularities will not be observed' - "it is
highly premature -- we don't know whether this is correct or not".

If the CCC is part of GR, then we do know that it's correct. If it's
not, then we don't.

This is getting a little silly.

The cosmic censorship conjecture is a conjecture -- "a mathematical
statement which has been proposed as a true statement, but which no
one has yet been able to prove or disprove" (wikipedia). Specifically,
it is a conjecture that general relativity has the property of cosmic
censorship, that is, that physically reasonable initial conditions
don't lead to naked singularities.

If the *cosmic censorship conjecture* is correct, then *cosmic censorship*
is part of GR. If the conjecture is incorrect, then cosmic censorship is
not part of GR.

We don't know whether the cosmic censorship conjecture is correct. That
is, we don't know whether general relativity has the property of conmic
censorship. That is, we don't know whether physically reasonable initial
conditions in GR can lead to naked singularities.

Clear?

[...]
I suppose your answer for Closed Timelike Curves would be similar.

In classical GR, Hawking has proven that, as a feature of classical GR
(NOT something "grafted on" from the outside), if energies are positive,
closed timelike curves cannot form in a finite region that initially
does not contain them. There are arguments that in quantum field theory
the assumption of positive energy may not be justified, and continuing
deates on the implications, but classically the issue is settled.

Did he make use of his Chronology Protection Conjecture?

No, of course not! That would be circular. He *proved* a particular
version of the Chronology Protection Conjecture.

Steve Carlip
.

Relevant Pages

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  • Re: Symmetry
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    (sci.physics.relativity)