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Stardrive

Ray

The escaping member of the photon pair, which has torn apart by the strong gravitational tidal forces near the event horizon

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The escaping member of the photon pair, which has been torn apart by the strong gravitational tidal forces near the event horizon

:-)

So, now I need to understand Ibison's argument in detail as part of the question of how to apply the thermodynamics to our future cosmological horizon.

Ray Chiao writes:

"“Black holes” are “black,” in the sense that they are perfect absorbers of
every kind of particle, including photons at all frequencies [1]. Once particles
have passed through the event horizon of a BH, they can never get out again,
at a classical level of description. For in order for a particle to be able to escape
from the black hole, it would need somehow to acquire an escape velocity which
effectively exceeds the speed of light at the event horizon."

My basic idea that I tried to explain to Roger Penrose at Castiglioncello in 2008 is simply to apply the above idea for the black hole, to our future cosmological horizon. Therefore, trivially we have the Wheeler-Feynman total absorber final boundary condition in our accelerating universe that is heading for the de Sitter solution. We are not de Sitter in the past - an important Arrow of Time asymmetry there.

The only Hawking radiation we can see back-from-the-future is Wheeler-Feynman advanced thermal radiation that may well be the dark energy,

I also tried to explain this to Bernard Carr at King's College London - I think he got it, but Penrose did not because it contradicts his current idea of cyclic big bangs.

We are outside a black hole horizon, but inside our future horizon which is also observer dependent.

I don't yet understand Ibison's

"There is no conflict however if electromagnetic interactions on the advanced cone are principally negative rather
than positive energy interactions. If indeed they were, then the emission of positive energy radiation on the retarded
cone of a local source can be re-interpreted as an increment in the magnitude of negative binding energy propagating
(in forwards time) along the (here, necessarily) advanced cone of that source. No future sinks or sources are then
required. The predominance of retarded radiation as commonly understood then follows from the asymmetry of
advanced Greens functions which are the consequence of the boundary condition associated with a future time-like
mirror."

Ibison has this idea of a "time mirror" to replace the Wheeler-Feynman total absorber future boundary condition.

My original idea was simply this

1) No thermodynamic difference between a black hole horizon and our future cosmological horizon - other differences of course.

2) In both cases the static LNIF near the horizon sees infinite blue shift/Unruh temperature

3) i.e. for black hole

g(r) = (rs/r^2)(1 - 2rs/r)^-1/2

horizon at r = 2rs

4) for cosmological future horizon we are at  r = 0 and

g(r) = c^2/\^1/2(1 - /\r^2)^-1/2

horizon at r = /\^-1/2