Black hole questions continue

The speculations as to the fate of black holes continue over at arxiv.org. Why should you care? Because it's possible that the LHC at CERN will start creating very tiny ones within a year or so, and they may have such low velocity that they end up hanging around (or in) the Earth. Would be nice if scientists had a real handle on how they were going to behave, don't you think?

The latest paper to be seen about this is here. The title: "Moduli Vacuum Bubbles Produced by Evaporating Black Holes". The main idea: black holes may have "vacuum bubbles" around them which will make their appearance somewhat different from what Hawking radiation would indicate. The article notes that:

Smaller mass black holes that have already evaporated away could have left vacuum bubbles behind that contribute to the dark matter.

To be fair, the article only talks about larger black holes, and "primordial" ones in particular, but I am curious to know if this is relevant to the evaporation of micro black holes of the type that may be created at CERN.

Another recent paper, which is again hard for the lay person to follow, suggests that maybe the LHC won't produce black holes whether or not large extra dimensions exist. This is due to the effect of what the article calls RG (renormalisation group.) The conclusions:

We have applied the RG to the black hole production scenario in the context of large extra dimensions. This has two surprising effects:
• First, the area of the black hole (which is of the same order as the production cross-section) does not only inherit the UV safety as it was observed for standard
scattering cross-section, but it even gets damped so strongly that it goes to zero.
• Second, the truncation parameter t, which does not play an important role in the
qualitative standard scattering cross-section picture, gets central importance for
the BH threshold. Even more, BH production could be completely forbidden3 for values of t ≤ 1, which according to [6] are perfectly possible.

In the light of such dramatic consequences of the application of RG to the simplest
picture of BH production, we conclude that more detailed studies have to be made
on both sides of the problem. It would be of great interest to see whether the straight forward statements, which were made here, would survive an improved formulation of the BH production threshold, of the RG solutions, and of the determination of the truncation parameter t. If the results persist and t can be determined to be ≤ 1, no black holes will be produced at the LHC whether large extra dimensions exist or not.

The paper notes that this RG stuff had previously been used to predict that the final outcome of black hole evaporation is a remnant which is a "mini black hole of Planckian size". The article which discusses this notes that:

It would be interesting to investigate the possible astrophysical implications of a population of stable Planck size mini-black holes produced in the Early Universe or by the interaction of cosmic rays with the interstellar medium

The suggestion being, I assume, that some of the dark matter in the universe may be very tiny black holes swarming around the place.

As far as black hole remnants are concerned, I noted in a post last year that an arxiv paper suggested they could be a useful source of energy:

If BHRs (Stable Remnants) are made available by the LHC or the
NLC and can be used to convert mass in energy, then the total 2050 yearly world energy consumption of roughly 1021 Joule can be covered by just ∼ 10 tons of arbitrary material, converted to radiation by the Hawking process via m = E/c2 = 1021J/(3·108m/s)2 = 10 4kg.

But how do you actually make it into an energy generator? Shot particles at it in an accelerator? Would it be easy to hit? And more importantly, what does it mean if you drop one, or thousands, into the centre of the earth? Here's some speculation: are some planet interiors already partially heated by captured black hole remnants? Would adding thousands of human made ones be a bad idea?

All questions I am waiting to see answers to.