Hi Edward and all.

On Feb 14, 7:11 pm, Edward Green wrote:
On Feb 14, 1:38 am, Eric Gisse wrote, in part:

There are NO interior solutions to Kerr in general relativity to my
knowledge. That raises a red flag - I don't believe it is proven they
don't exist, but it's suggestive to me.

Yes, to me too.

I had intended to ask whether "interior solution" means interior to
the event horizon or interior to a surface within which the vacuum is
replaced with a mass density. It turns out, on some investigation,
both!

The vacuum solution inside the event horizon is said to be "unstable",
whatever that means, or else "unphysical" (that part of a respectable
theory which in lesser theories might be described as "wrong"). I also
learned, as you say, that there is no known solution including mass
density which can be smoothly joined to the outer Kerr solution
(although some treatment of a spinning dust disk reduces to Kerr
solution in a limiting case).

The evidence is firmly ambiguous: if we could show no non-vacuum
extension of the solution were possible inward, then I think we could
safely say that the hope that Kerr describes the exterior field of a
massive spinning body is doomed; however, the language is "not known"
-- and there is the tantalizing datum of a single known solution is a
single special case.

I am tempted to claim that the exterior vacuum Kerr solution, while a
valid solution of the field equations, cannot represent the external
field of a spinning body. As I mentioned, a rotating massive object
seems to transmit no intelligence of its sense of rotation to the GR
source term. If we are in fact able to tell from purely gravitational
observation which way a spheroid is spinning, then there must be some
additional factor which breaks the symmetry.

I agree, because the Guv=Tuv is symmetrical,
furthermore I think AE made a mistake in Ch2
of this ref,
http://www.alberteinstein.info/galle...lish_pp146-200...

AE has S1 a as sphere and S2 as an ellipsoid,
then he relies on Mach's *principle* to
justify the differing shapes, (something
about rotation) but it's unnecessary in GR.
The internal "stress-energy" tensor shapes
differences work quite well, for example see,
http://en.wikipedia.org/wiki/Piezoelectricity

If S1 is composed of a Piezoelectrical
crystal, with no interior voltage diffs,
but S2 has interior voltage diffs to
force the sphere into a ellpsoidal shape,
as in the wiki ref, where the North and
South Pole are pushed together, the
reciprocal effect is to apply a voltage
and vary the geometry, as a smoke detector
squeaker does.

As Edward points out,(and I agree),the
fact of an ellpsoidal shape does NOT
provide any direction of rotation into
the g-field, and there is no need to
presume rotation is the cause of the
ellipsoid.
Regards
Ken S. Tucker
[snip]