[AnotherGoodName]

The 1.7second difference isn't from any actual speed difference. It's from light hitting things on its way here that gravity interacts weakly with and thus doesn't hit. So that wouldn't explain no light at all escaping while 100% of gravity does from a black hole.

Instead since light is redshifted as it exits a gravity well a better thought would be "is the almost but not quite black hole red-shifting light to the point of being impossible to detect?". After all light with almost 0hz frequency is basically non-interactive. It has a similar outcome. You could then have an 'almost black hole' that looks just like a real black hole but allows gravity to escape. https://arxiv.org/abs/2102.07769

[tsegratis]

Thanks, that was the question:

> You could then have an 'almost black hole' that looks just like a real black hole but allows gravity to escape

I wondered if that answer to the conundrum could apply to all black holes. I suppose not

For real black holes, I suppose we should say they are not true singularities where the event horizon curvature goes vertical, but simply that curvature goes beyond the speed of light, so the maths still makes sense

Thanks that is a lot more logical

So then the effect of gravity from a real black hole would be like the effect of a messy person after they've left the room, and the reason why the effect of a black hole is felt for much longer is because of time dilation, and gravity doesn't experience redshift?

[raattgift]

How did you come across these two arxiv preprints? Both are far from astrophysics. One is highly speculative theoretical physics. The other shoots down previous work that was highly speculative theoretical physics.

> astro-ph/2102.07769

This is about a particular model of dark matter that unlike in the standard cosmology is hot and has a particular radial profile within galaxies and outside galaxies undergoes a phase change to a uniformly distributed cold dark matter.

Tracing the gravitational collapse consequences of a theory whose characteristic matter distribution does not concord with observation (it breaks when the radial symmetry breaks, as in galaxy-galaxy mergers, lumpy galaxy clusters, and so on) is interesting but doesn't say much about astrophysics.

The preprint itself was the basis of a workshop talk on speculative physics, and the workship was literally titled in the form of a question ("What Comes Beyond Standard Models?")

FWIW, I had never before this heard of Bled Workshops in Physics, and I still don't know (after poking around in citeseer and the like) whether it is an event in Slovenia, or just named after Bled, Slovenia.

> hep-th/0710.1735

I don't understand why this is in hep-th rather than gr-qc as it is manifestly about a semiclassical model, with a peculiar form of quantum matter used to study gravitational collapse.

The paper is essentially an obituary for an idea for a toy quantum field on a classical curved spacetime that might work better than the simplest toy quantum field that has been in use since at least Hawking's 1974 work. The original work [hep-th/0205.319] introduces this toy model containing analogue to electromagnetism, and found that they could only form black holes under certain conditions. These additional complications, your linked paper's authors argue, aren't helpful even under those certain conditions, leading to things like naked singularities away from the horizon (p.20).

The paper's central purpose is to narrow the viability of this family of toy matter; in the authors' words (p.2.), "In this work we address the following question: Are there other static, spherically symmetric black hole solutions for the MTZ model, satisfying the dominant and strong energy condition between the event and cosmological horizon, besides MTZ1 and MTZ2? Using a combination of analytical and numerical methods we conclude that the answer to this question is negative." (In the very next paragraph they point out that MTZ2 has already been shown to be unstable with the addition of spherically symmetric masses, and that they will show that MTZ1 has the same problem).

The final paragraph of p.20 is pretty damning, and declares the low-energy-string-theory MTZ idea dead. ("M" is also one of the authors of the obituary). And so this raises my second question:

Why did you link this paper?

In my view does not support your statement that there is "a huge hole in black hole theory right now", but am certainly interested on what motivated your choice of that paper in the context of the questions tsegratis asked. Neither paper seems to go anywhere near answering those questions.