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The Weyl tensor hypothesis of Penrose excludes Einstein-Rosen wormholes in
the matter-free Schwarzschild solution continued into the interior of the
2M surface because the singularity would be in the Weyl tensor giving an
initial infinite entropy rather than the initial zero entropy required for
the arrow of time according to Zeh p.115.

The black hole formed from gravitational collapse of matter "possesses only
a future horizon and a future singularity, it specifies a direction in
time.... the time-reverse of a black hole ... a white hole - is also a
solution... it would descrive a star (perhaps with planets carrying life)
emerging from a past horizon. This would ... contradict the intuitive
notion of causality .. this woud lead to a clash between opposite arrows of
time. Such a clash is avoided by the Weyl tensor hypothesis. p.117

In addition to past [timelike] singularities - so-called naked
singularities could be 'visible' to us. They were excluded by what Penrose
called his cosmic censorship postulate.

...the Kerr-Newmann solution ... describes axially symmetric black holes
with angular momentum J and charge Q lll every black hole may therefore, to
within Lorentz transformations and translations, be characterized by no
more than the three parameters M,J and Q. This is called the no-hair
theorem ...  the collapsing matter must radiate away all its higher
multipoles of matter and charge, while conserved quantities associated with
short-range forces, such as lepton or baryon number cannot be practically
observed beyond some small distance from the horizon p.117 ... In the
presence of incoming (advanced) radiation, a hole could 'grow hair' and
thus form a white hole.

Spacetime singularities which have been shown to occur necessarily if
future horizons form in black holes... would be of fundamental importance
for quantum theory because of the latter's kinematical nonlocality. p.118
...If the space-like hypersurfaces forming a foliation of spacetime and
defining a time coordinate t somewhere hit a future singularity, not only
the state on this singularity but also its quantum correlations with the
rest of the universe would become undefined. .... there would no longer
exist a pure state [with zero entropy JS] for the non-singular rest of the
universe ... unless all correlations vanishe conspiratively ... the non-
singular part of the universe for objective reasons afterwads have to by
characterized by a density matrix [with finite positive entropy JS] >>>Wald
(1980) has therefore concluded that quantum gravity must violate unitarity
[ remember it is now believe falsely I say that it is unitarity that
prevents faster than light communication by nonlocal quantum correlations.
My gendanken experiment shows this belief to be false in that clever design
of the apparatus premits us to tunnel through the unitarity barrier. But
certainly on quantum gravity level there is superluminal communication
since there is no unitarity barrier. JS] ... Penrose (1986) ...suggested
that the collapse of the state vector might also be traced back to an
effect of gravity [ I said this in first edition of SPACE TIME AND BEYOND
Dutton 1974 - but I had been influenced by Penrose at Birkbeck College in
1971].   ... The nonunitarity of these non-global density matrices is the
same as that arising in general from the quantum mechanical nonlocality by
using the relevance concept of locality [for example, this is why first
order fringes are not seen locally at the transmitter end of my FTL
communicator gedanken experiment but are seen indirectly at the receiver
end!] ... In a universe that contains only future singularities, this
'phenomenological non-unitarity' connected with black holes produces a
quantum/thermodynamical arrow of time. It has been proposed to be of
further importance because of the interaction of matter with virtual mini-
holes expected to occur in a quantum field theory that includes gravity
(Hawking, 19870." p.119 Zeh , The Direction of Time, Springer-Verlag 1992.