Cosmological Redshift in Simulated Universe

[PeterDonis]

Can the equivalence principle really be used in the situation I described

Yes, because, as @Ibix has already pointed out, the size of the cloud is small enough compared to the size of the hole that tidal gravity due to the hole can be ignored in the region occupied by the cloud.

 

[Ibix]

in the frame of the “cloud” a photon is traveling 46 Gly from edge to center, but in the frame of the “hole” the photon is traveling much farther because the cloud moves very close to the speed of light

As already answered, yes. If you want to think about changing gravitational time dilation you also need to think of the changing speed of the cloud and the effects this has on clock rates and time taken to absorb a cycle of a light wave. You seem to be consistently ignoring this in your thinking.

Again as already stated, sufficiently precise experiments could detect the failure of spacetime to be flat, which would yield anisotropies, but no global redshift. However, tidal effects are weaker the larger the black hole, so these are very small for this scenario.

 

[Devin-M]

Is a growing event horizon constrained to the speed of light relative to an observer hovering at fixed altitude above the center of the hole?

If the hole wasn’t growing, the clocks in the cloud would be ticking faster as they coasted away from the hole. But if the event horizon was growing fast enough to move towards them, would the “cloud clocks” be slowing down and would this have any effect on their observations of flashes of light in the cloud? The flashes of light are losing gravitational potential energy as they coast upwards, but the observers clocks would be slowing down rather than speeding up as the event horizon approaches them.

 

[Ibix]

Is a growing event horizon constrained to the speed of light relative to an observer hovering at fixed altitude above the center of the hole?

An event horizon is a null surface. To the extent it has a speed, it is always $c$ whether it is growing, shrinking, or static.

But if the event horizon was growing fast enough to move towards them, would the “cloud clocks” be slowing down and would this have any effect on their observations of flashes of light in the cloud?

The equivalence principle is a foundational principle of general relativity. You cannot get round it by adding bells and whistles to a scenario. You can just make your scenario so complicated that you don't understand how to connect your thinking to that foundation. This is especially true with your maths-free approach.

So I refer you to my previous answer.

 

[PeterDonis]

I refer you to my previous answer.

And with that, the OP question has been more than sufficiently answered, and this thread is closed.